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Ames, Carsyn Jean. "Insights for provenance analysis of modern watersheds from detrital apatite and detrital zircon U-PB geochronology- Talkeetna Mountains, southcentral Alaska." Thesis, University of Iowa, 2018. https://ir.uiowa.edu/etd/3244.
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Detrital zircon U-Pb geochronology is a useful tool for analyzing provenance in the sedimentary record. Differentiating recycled and first cycle populations in the detrital record, however, is not a straightforward process. A second potential problem in using detrital signatures to determine provenance of sediment lies in the assumption that detrital signatures of modern rivers reflect input from each exposed unit in the catchment boundaries. To investigate each of these problems, I present U-Pb analysis of detrital zircon (DZ) from modern river sand collected from 20 watersheds, 6 detrital apatite (DA) signatures from modern river sand, and 6 DA signatures from exposed strata, all within the Talkeetna Mountains (south-central Alaska). DA rarely survives past the first cycle of erosion and deposition due to its inability to survive chemical weathering, and thus dominantly represent igneous input in detrital signatures, whereas zircon can be of igneous origin or can survive multiple cycles of erosion and deposition. By comparing the DA signatures with the DZ signatures, I present a method to better differentiate first cycle, igneous sediment contributions from recycled populations within a detrital signature. The results of these comparisons show that DA signatures provide ages of igneous input into the detrital record; these ages are also reflected in the DZ signature, thus signaling these DZ populations as igneous in origin. This study also investigates the potential for DA recycling and DA input from recycled strata. To address the second problem, I present a method using GIS software and the most recent map of Alaska to create simulated signatures that records input on a scale proportionate to the exposed surface area of each bedrock unit. In ~35% of the watersheds tested, the simulated signatures predict trends similar to the DZ signatures from the modern river sands, in 55% of the watersheds tested the simulated signatures missed one or more populations present in the DZ signature, and in 10% of watersheds tested, the simulated signature predicted trends very different from the DZ signatures. In cases where the DZ and simulated signatures do not match, I believe this represents influences of climate and relief and zircon fertility.
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Sorota, Kristin Joy. "Age and Origin of the Merrimack Terrane, Southeastern New England: A Detrital Zircon U-Pb Geochronology Study." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3043.
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Thesis advisor: J C. HepburnThesis advisor: Yvette D. Kuiper
Metasedimentary rocks of the Merrimack terrane (MT) originated as a thick cover sequence on Ganderia consisting of sandstones, calcareous sandstones, pelitic rocks and turbidites. In order to investigate the age, provenance and stratigraphic order of these rocks and correlations with adjoining terranes, detrital zircon suites from 7 formations across the MT along a NNE-trending transect from east-central Massachusetts to SE New Hampshire were analyzed by U-Pb LA-ICP-MS methods on 90-140 grains per sample. The youngest detrital zircons in the western units, the Worcester, Oakdale and Paxton Formations, are ca. 438 Ma while those in the Kittery, Eliot and Berwick Formations in the northeast are ca. 426 Ma. The Tower Hill Formation previously interpreted to form the easternmost unit of the MT in MA, has a distinctly different zircon distribution with its youngest zircon population in the Cambrian. All samples except for the Tower Hill Formation have detrital zircon age distributions with significant peaks in the mid-to late Ordovician, similar abundances of early Paleozoic and late Neoproterozoic zircons, significant input from ~1.0 to ~1.8 Ga sources and limited Archean grains. The similarities in zircon provenance suggest that all units across the terrane, except for the Tower Hill Formation, belong to a single sequence of rocks, with similar sources and with the units in the NE possibly being somewhat younger than those in east-central Massachusetts. The continuous zircon age distributions observed throughout the Mesoproterozoic and late Paleoproterozoic are consistent with an Amazonian source. All samples, except the Tower Hill Formation, show sedimentary input from both Ganderian and Laurentian sources and suggest that Laurentian input increases as the maximum depositional age decreases
Thesis (MS) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Geology and Geophysics
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Pepper, Martin Bailey. "Magmatic History and Crustal Genesis of South America: Constraints from U-Pb Ages and Hf Isotopes of Detrital Zircons in Modern Rivers." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/347220.
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South America provides an outstanding laboratory for studies of magmatism and crustal evolution because it contains older Archean-Paleoproterozoic cratons that amalgamated during Mesoproterozoic and Neoproterozoic supercontinent assembly, as well as a long history of Andean magmatism that records crustal growth and reworking in an accretionary orogen. We have attempted to reconstruct the growth and evolution of South America through U-Pb geochronology and Hf isotope analyses of detrital zircons from 59 samples of sand from modern rivers and shorelines. Results from 5,524 new U-Pb ages and 1,199 new Hf isotope determinations are reported. We have also integrated our data into a compilation of all previously published zircon geochronologic and Hf isotopic information, yielding a record that includes>42,000 ages and>1,600 Hf isotope analyses. These data yield five main conclusions: (1) South America has an age distribution that is similar to most other continents, presumably reflecting the supercontinent cycle, with maxima at 2.2-1.8 Ga, 1.6-0.9 Ga, 700-400 Ma, and 360-200 Ma; (2)<200 Ma magmatism along the western margin of South America has age maxima at 183 Ma (191-175 Ma), 151 Ma (159-143 Ma), 126 Ma (131-121 Ma), 109 Ma (114-105 Ma), 87 Ma (95-79 Ma), 62 Ma (71-53 Ma), 39 Ma (43-35 Ma), 19 Ma (23-15 Ma), and 6 Ma (10-2 Ma); (3) for the past 200 Ma, there appears to be a positive correlation between magmatism and the velocity of convergence between central South America and Pacific oceanic plates; (4) Hf isotopes record reworking of older crustal materials during most time periods, with incorporation of juvenile crustal materials at ~1.6-1.0 Ga, 500-400 Ma and ~200-100 Ma; and (5) the Hf isotopic signature of<200 Ma magmatism is apparently controlled by the generation of juvenile magmas during extensional tectonism and reworking of juvenile versus evolved crustal materials during crustal thickening and arc migration.
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Reid, Mattie Morgan. "Forearc basin detrital zircon provenance of Mesozoic terrane accretion and translation, Talkeetna Mountains-Matanuska Valley, south-central Alaska." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5611.
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The Wrangellia composite terrane is one of the largest fragments of juvenile crust added to the North American continent since Mesozoic time, and refining its accretionary history has important implications for understanding how continents grow. New U-Pb geochronology and Hf isotopes of detrital zircons from Late Jurassic-Late Cretaceous strata from the forearc of the Wrangellia composite terrane allows more insight on the tectonic and paleogeographic history of the terrane.
Our stratigraphically oldest samples from the Late Jurassic Naknek Formation have a detrital zircon U-Pb signature dominated by Early and Late Jurassic grains (195-190 Ma; 153-147 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Disconformably above the Naknek Formation are two poorly understood units Ks and Kc. The Ks unit is dominated by Early to Late Jurassic grains (159-154 Ma) with a few Paleozoic grains (347-340 Ma). Hf isotopic compositions of Carboniferous-Jurassic grains are juvenile to intermediate (εHf(t)=6.0-18.8). The overlying Kc unit has Late to Early Jurassic zircons (198-161 Ma), and an increase in Paleozoic ages (374-323 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Samples from the Matanuska Formation have major Late Cretaceous grains (90-71 Ma), and minor Early Cretaceous (137-106 Ma), Late to Early Jurassic (200-153 Ma), Paleozoic (367-277 Ma), and Precambrian grains (2597-1037 Ma). Hf compositions have a wider range from both the Late Cretaceous grains (εHf(t)=-1.5-14.9) and Paleozoic-Precambrian grains (εHf(t)=-23.7-16.3).
Our results suggest an evolving provenance from Late Jurassic to Late Cretaceous time for the Wrangellia composite terrane forearc basin. The Late Jurassic Naknek Formation samples were dominantly derived from a juvenile to intermediate Jurassic igneous sediment source. During Early Cretaceous time, there is a slight increase in the number of Paleozoic grains in the Ks and Kc unit samples. The Early Cretaceous sediments have a mostly positive Hf isotopic compositions suggesting exhumation of Jurassic and Paleozoic juvenile igneous sediment sources. By Late Cretaceous time, our data illustrates another increase in Paleozoic grain abundances, in addition to the introduction of Precambrian grains, all with widely variable Hf isotopic compositions. We interpret this to reflect a larger sediment flux from the interior of Alaska where more evolved igneous rocks of that age are found.
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Barbeau, David Longfellow Jr. "Application of Growth Strata and Detrital-Zircon Geochronology to Stratigraphic Architecture and Kinematic History." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/244092.
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Growth strata analysis and detrital-zircon geochronology are useful applications of stratigraphy to tectonic problems. Whereas both tools can contribute to kinematic analyses of supracrustal rock bodies, growth strata are also useful for analyzing the influence of tectonics on stratigraphic architecture. This study reports: 1) a conceptual model for growth strata development; 2) stratigraphic and kinematic analyses of growth strata architectures from growth structures in southeastern Utah, the Gulf of Mexico, and northeastern Spain; and 3) the detrital-zircon geochronology of the Salinian block of central coastal California. Kinematic sequence stratigraphy subdivides growth strata into kinematic sequences that are separated by kinematic sequence boundaries. Kinematic sequences can be further partitioned into kinematic domains based on the termination patterns of strata within a kinematic sequence. Salt- related fluvial growth strata from the Gulf of Mexico and southeastern Utah contain stratigraphic architectures that are unique to different kinematic domains. Offlap kinematic domains contain fluvial strata indicative of high slopes, low accommodation rates, and strong structural influence on paleocurrent direction. Onlap kinematic domains contain fluvial strata indicative of moderate slopes, high accommodation rates, and decreased structural influence on paleocurrent direction. The stratigraphic architecture of alluvial -fan thrust -belt growth strata in northeastern Spain does not display a marked correlation with kinematic domain, and is most easily interpreted using existing models for autocyclic alluvial -fan evolution. Detrital- zircon (U -Pb) geochronologic data from basement and cover rocks of Salinia suggest that Salinia originated along the southwestern margin of North America, likely in the vicinity of the Mojave Desert. The presence of Neoproterozoic and Late Archean detrital zircons in Salinian basement rocks also suggest that Salinian sediments were recycled from miogeoclinal sediments of the western margin of North America.
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Midwinter, Derrick. "Using Detrital-Zircon Geochronology and (U-Th)/He Thermochronology to Re-evaluate the Triassic-Jurassic Tectonic Setting of Northern Laurentia, Canadian Arctic." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35326.
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New geochronological and field data were examined from Triassic-Jurassic strata in the Sverdrup Basin, Arctic Canada. Detailed analysis of detrital-zircon data identified a pronounced near-syndepositional age-fraction in Triassic strata, which significantly is absent in Jurassic strata of the Sverdrup Basin suggesting a protracted history of magmatism and sediment dispersal from areas north of the basin during the Triassic. However, as a result of rifting, during the Early Jurassic, the northern source region became disconnected from the Sverdrup Basin, and opened the precursor basin (Amerasia Basin) to the Arctic Ocean.
Jurassic rifting of the Amerasia Basin would have had associated rift-flank uplift. Time-temperature models produced from zircon (U-Th)/He thermochronological data elucidate the unknown thermal history between the regional Devonian-Cretaceous unconformity in the southwestern Canadian Arctic suggesting ~4 km of addition deposition on Banks Island and ≤1 km of deposition towards the craton interior.
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Linde, G. M., J. H. Trexler, P. H. Cashman, G. Gehrels, and W. R. Dickinson. "Three-Dimensional Evolution of the Early Paleozoic Western Laurentian Margin: New Insights From Detrital Zircon U-Pb Geochronology and Hf Isotope Geochemistry of the Harmony Formation of Nevada." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626478.
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Uranium-lead (U-Pb) geochronology and Hafnium (Hf) isotope geochemistry of detrital zircons of the Harmony Formation of north central Nevada provide new insights into the tectonic evolution of the Late Paleozoic western Laurentian margin. Using laser-ablation inductively coupled plasma mass spectrometry, 10 arenite samples were analyzed for U-Pb ages, and 8 of these samples were further analyzed for Hf isotope ratios. Three of the sampled units have similar U-Pb age peaks and Hf isotope ratios, including a 1.0-1.4Ga peak with epsilon Hf values of +12 to -3 and a 2.5-2.7Ga peak with epsilon Hf values of +7 to -5. The remaining seven samples differ significantly from these three, but are similar to one another; having age peaks of 1.7-1.9Ga with epsilon Hf of +10 to -20 and age peaks of 2.3-2.7Ga with epsilon Hf of +6 to -8. The data confirm the subdivision of the Harmony Formation into two petrofacies: quartzose (Harmony A) and feldspathic (Harmony B). The three samples with 1.0-1.4 and 2.5-2.7Ga peaks are the Harmony A, which originated in the central Laurentian craton. The other seven samples are the Harmony B, which originated in eastern Alberta-western Saskatchewan, north of the Harmony A source. We propose that all Harmony Formation strata were deposited near eastern Alberta and subsequently tectonically interleaved with Roberts Mountains allochthon strata. We interpret that the entire package was tectonically transported south along the western Laurentian margin and then emplaced eastward onto the craton during the Late Devonian-Early Mississippian Antler orogeny.
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Ely, Kim Susan. "Geochronology of Timor-Leste and seismo-tectonics of the southern Banda Arc." Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/7063.
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Arc–continent collision is a significant plate boundary process that results in crustal growth. Since the early stages of evolution are often obscured in mature orogens, more complete understanding of the processes involved in arc–continent collision require study of young, active collision settings. The Banda Arc presents an exceptional opportunity to study a young arc–continent collision zone. This thesis presents aspects of the geology and geochronology of Ataúro and the Aileu Complex of Timor-Leste, and the tectonics of the Banda Arc.U–Pb dating of detrital zircons from the Aileu Complex by LA-ICPMS show major age modes at 270–440 Ma, 860–1240 Ma and 1460–1870 Ma. The youngest zircon populations indicate a maximum depositional age of 270 Ma. The detrital zircon age populations and evidence for juvenile sediments within the sequence favours a synorogenic setting of deposition of sediments sourced from an East Malaya – Indochina terrane.
Previous uncertainty in aspects of the cooling history for the Aileu Complex is resolved with 39Ar/40Ar geochronology of hornblende. Cooling ages of 6–10 Ma are established, with the highest metamorphic grade parts of the Complex yielding the older ages. Cooling ages of 10 Ma imply that metamorphism of the Aileu Complex must have commenced by at least ~12 Ma. Metamorphism at this time is attributed to an arc setting rather than the direct result of collision of the Australian continent with the Banda Arc, an interpretation consistent with the new provenance data.
Geological mapping of Ataúro, an island in the volcanic Banda Arc north of Timor, reveals a volcanic history of bi-modal subaqueous volcanism. 39Ar/40Ar geochronology of hornblende from dacitic lavas confirms that volcanism ceased by ~3 Ma. Following the cessation of volcanism, coral reef marine terraces have been uplifted to elevations of 700 m above sea level. Continuity of the terraces at constant elevations around the island reflects regional-scale uplift most likely linked to sublithospheric processes such as slab detachment.
North of Timor, the near complete absence of intermediate depth seismicity beneath the inactive segment of the arc is attributed to a slab window that has opened in the collision zone and extends to 350 km below the surface. Differences in seismic moment release around this slab window indicate asymmetric rupture, propagating to the east at a much faster rate than to the west. If the lower boundary of this seismic gap signifies the original slab rupture then the slab window represents ~4 m.y. of subsequent subduction and implies that collision preceded the end of volcanism by at least 1 m.y.
Variations in seismic moment release and stress state across the transition from subduction of oceanic crust to arc–continent collision in the Banda Arc are investigated using earthquake catalogues. It is shown that the slab under the western Savu Sea is unusual in that intermediate depth (70–300 km) events indicate that the slab is largely in down-dip compression at this depth range, beneath a region of the arc that has the closest spacing of volcanoes in the Sunda–Banda arc system. This unusual state of stress is attributed to subduction of a northern extension of the Scott Plateau. Present day deformation in the Savu Sea region may be analogous with the earliest stages of collision north of Timor.
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Neace, Erika R. "Zircon LA-ICPMS Geochronology of the Cornubian Batholith, SW England." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1448912006.
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Voice, Peter James. "The Global Detrital Zircon Database: Quantifying the Timing and Rate of Crustal Growth." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/27785.
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Published detrital zircon geochronological data was compiled to form the Global Detrital Zircon Database (GDZDb). This database provides a reference block for provenance analysis by future detrital zircon geochronological studies. This project entailed three subprojects: 1. crustal growth/crustal recycling patterns, 2. a provenance study of the Triassic Dry Fork Formation of the Danville-Dan River Rift basin of Virginia and North Carolina, and 3. sample size issues in detrital zircon studies.
The global detrital zircon age frequency distribution exhibits six prominent, statistically significant peaks: 3.2-3.0, 2.7-2.5, 2.0-1.7, 1.2-1.0, 0.7-0.5, and 0.3-0.1 Ga. These peaks are also observed when the data is sorted for continent of origin, the tectonic setting of the host sediment and for modern river sediments. Hf isotope model ages were also incorporated into the database where grains were dated with both U-Pb and Hf isotopes. The Hf isotope model ages suggest that the majority of detrital zircons U-Pb ages reflect crustal recycling events that generated granitic magmatism, as most grains exhibited Hf isotope ages that are much older than the corresponding U-Pb age.
The Triassic Dry Fork Formation was sampled from a site in southern Virginia in the Danville-Dan River Basin. The detrital zircon age frequency distribution for this formation was strongly unimodal with a peak at 400-450 Ma and a paucity of Grenville-age zircons. Comparison of the Dry Fork sample to published east coast data and to the North American record (from the GDZDb) illustrate the unusual nature of the Dry Fork Formation sample. It is probable that older Grenville zircons were blocked from the rift valley by the rift shoulder.
Using the GDZDb a study of sample size was conducted in order to estimate the best sample size to use when trying to constrain the maximum age of sedimentation of the host sediment. Rift basins and active margins exhibited smaller offsets from the youngest zircon grain age to host sediment maximum age than observed in samples from passive margins. This study recommends that at least 50 grains need to be age dated on average in order to best constrain the age of the host sediment.Ph. D.
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Bootes, Nathaniel R. "Late Cenozoic Offshore Record of Exhumation and Sediment Routing in Southeast Alaska from Detrital Zircon U/Pb and FT double-dating." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592169111121451.
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Painter, Clayton S. "Sequence Stratigraphy, Geodynamics, and Detrital Geo-Thermochronology of Cretaceous Foreland Basin Deposits, Western Interior U.S.A." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/307071.
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Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_UPb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf). Appendix A. Subsidence in the retroarc foreland of the North American Cordillera in the western U.S.A. has been the focus of a great deal of research, and its transition from a flexural foreland basin, during the Late Jurassic and Early Cretaceous, to a dynamically subsided basin during the Late Cretaceous has been well documented. However, the exact timing of the flexural to dynamic transition is not well constrained, and the mechanism has been consistently debated. In order to address the timing, I produced new isopach maps from ~130 well log data points that cover much of Utah, Colorado, Wyoming and northern New Mexico, producing in the process, the most detailed isopach maps of the area. These isopach maps span the Turonian to mid-Campanian during the Late Cretaceous (~93–76 Ma). In conjunction with the isopach maps I flexurally modeled the Cordilleran foreland basin to identify when flexure can no longer account for the basin geometry and identified the flexural to dynamic transition to have occurred at 81 Ma. In addition, the dynamic subsidence at 81 Ma is compared to the position of the hypothesized Shatsky Oceanic Plateau and other proposed drivers of dynamic subsidence. I concluded that dynamic subsidence is likely caused by convection over the plunging nose of the Shatsky Oceanic Plateau. Appendix B. The second study is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation. Its equivalent in the Book Cliffs area in eastern Utah has been rigorously documented and its distal progradation has been contrastingly interpreted as a result of active tectonism and shortening in the Cordilleran orogenic belt ~250 km to the west and to tectonic quiescence, flexural rebound in the thrust belt and reworking of proximal coarse grained deposits. I documented ~17 km of along depositional dip outcrops of the Sego Sandstone Member north of Rangely, Colorado. This documentation includes measured sections, paleocurrent analysis, a stratigraphic cross section, block diagrams outlining the evolution of environments of deposition through time, and paleogeographic maps correlating northwest Colorado with the Book Cliffs, Utah. The sequence stratigraphy of the Sego Sandstone Member in northwest Colorado is similar to that documented in the Book Cliffs area to the south-southwest, sharing three sequence boundaries. However, flood-tidal delta assemblages between fluvio-deltaic deposits that are present north of Rangely, Colorado are absent from the Book Cliffs area. These flood-tidal-delta assemblages are likely caused by a large scale avulsion event in the Rangely area that did not occur or was not preserved in the Book Cliffs area. In regards to tectonic models that explain distal progradation of the 76 Ma Sego Sandstone Member to be caused by tectonic quiescence and flexural rebound in the thrust belt, the first study shows that at 76 Ma, flexural processes were no longer dominant in the Cordilleran foreland, so it is inappropriate to apply models driven by flexure to the Sego Sandstone Member. Dynamic processes dominated the western U.S.A. during the Campanian, and flexural processes were subordinate. Appendix C. In order to test the tectonic vs. anti-tectonic basin-filling models for distal coarse foreland deposits mentioned above, the third study involves estimating lag times of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. Measuring lag time requires a good understanding of both the stratigraphic age of a deposit and the thermal history of sedimentary basin. To further constrain depositional age, I present twenty-two new detrital zircon U-Pb (DZ U-Pb) sample analyses, spanning Upper Jurassic to Upper Cretaceous stratigraphy in Utah, Colorado, Wyoming and South Dakota. Source exhumation ages can be measured using thermochronology. To identify a thermochronometer that measures source exhumation in the North America Cordillera, both zircon (U-Th)/He, on eleven samples, and apatite fission track (AFT) thermochronology, on eleven samples was performed. Typically, the youngest cooling age population in detrital thermochronologic analyses is considered to be a source exhumation signal; however, whether or not these apatites are exhumed apatites or derived from young magmatic and volcanic sources has been debated. To test this, I double dated the detrital AFT samples, targeting apatites with a young cooling age, using U-Pb thermochronology. Key findings are that the maximum depositional ages using DZ U-Pb match existing biostratigraphic and geochronologic age controls on basin stratigraphy. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4–5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed from <8–9 km depth. Double dating apatites (with AFT and U-Pb) indicate that volcanic contamination is a significant issue; without having UPb dating of the same apatite grains, one cannot exclude the possibility that the youngest detrital AFT population is contaminated with significant amounts of volcanogenic apatite and does not represent source exhumation. AFT lag-times are 0 to 5 Myr with relatively steady-state to slightly increasing exhumation rates. We compare our data to orogenic wedge dynamics and subsidence histories; all data shows active shortening and rapid exhumation throughout the Cretaceous. Our lag-time measurements indicate exhumation rates of ~.9–>>1 km/Myr.
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Quinn, Ryan Joel. "THE EVOLUTION OF GRENVILLE BASEMENT IN THE EASTERN GREAT SMOKY MOUNTAINS; CONSTRAINTS FROM U-PB ZIRCON GEOCHRONOLOGY, WHOLE ROCK SM-ND, AND FELDSPAR PB GEOCHEMISTRY." UKnowledge, 2012. http://uknowledge.uky.edu/ees_etds/7.
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Identifying the crustal affinity of Grenville basement rocks in the Dellwood quadrangle, western NC, provides insight into the tectonic evolution of eastern Laurentia during Grenville orogenesis. U-Pb zircon geochronology of orthogneiss, augen gneiss, and mafic xenoliths in orthogneiss reveal magmatic pulses at 1130, 1180, and 1330 Ma and metamorphic episodes at 450 and 1040 Ma. Xenoliths in 1330 Ma orthogneiss are as old as 1382 Ma and represent the oldest component of Blue Ridge basement identified to-date. Feldspar Pb isotope values span a range between juvenile-Laurentian and southern-central Appalachian basement/Amazonia. Most Pb isotope data define an array consistent with crustal mixing between Laurentia and Amazonia, however, one xenolith has a unique Pb isotopic composition interpreted as Laurentian crust. Sm-Nd isotope data yield depleted mantle model ages ranging from 1.52 to 1.79 Ga (200 to 650 Ma older than their crystallization ages) indicating a broadly non-juvenile heritage for Dellwood basement. Three biotite gneiss samples contain detrital zircon grains derived from 1060, 1160, 1330, and 1750 Ma sources. Multiple magmatic zircon age populations, variable depleted mantle modelages, and regionally unique isotopic Pb signatures are evidence of protracted Grenville magmatism in the southern Appalachians involving both Laurentian and Amazonian crustal components.
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Loan, MaryEllen Louise. "New Constraints on the Age of Deposition and Provenance of the Metasedimentary Rocks in the Nashoba Terrane, SE New England." Thesis, Boston College, 2011. http://hdl.handle.net/2345/2422.
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Thesis advisor: J. Christopher HepburnThe Nashoba terrane of SE New England is one of three peri-Gondwanan tectonic blocks caught between Laurentia and Gondwana during the closure of the Iapetus Ocean in the early to mid- Paleozoic. U-Pb analyses (LA-ICP-MS) were carried out on zircon suites from the meta-sedimentary rocks of the Nashoba terrane. The youngest detrital zircons in the meta-sedimentary rocks of the Nashoba terrane are Ordovician in age. There is no significant difference in age between meta-sedimentary units of the Nashoba terrane across the Assabet River Fault Zone, a major fault zone that bisects the NT in a SE and a NW par. Zircon in meta-sedimentary rocks in the Marlboro Fm., the oldest unit of the Nashoba terrane, is rare, which may reflect the basaltic nature of the source material, and is commonly metamict. The Marlboro Fm. contained the oldest detrital grain of all the analyzed samples, with a core of ~3.3 Ga and rim of ~2.6 Ga indicating that it was sourced from Archaen crustal material. Detrital zircons from the Nashoba terrane show a complete age record between the Paleoproterozoic and Paleozoic that strongly supports a provenance from the Oaxiqua margin of Amazonia. The detrital zircon suite of the Nashoba terrane is distinct from both Avalonia and the Merrimack belt; however, they resemble zircon suites from Ganderia. This study proposes that the Nashoba terrane of Massachusetts correlates with the passive trailing edge of Ganderia. Finally, metamorphic zircon analyses of the terrane show that the Nashoba terrane experienced a peak in hydrothermal fluid infiltration during the Neoacadian orogeny
Thesis (MS) — Boston College, 2011
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences
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Ng, Wai Pan. "Petrogenesis, U-Pb zircon geochronology and tectonic evolution of the Malaysian granite provinces in the Southeast Asian tin belt." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:0f2f3942-6d64-4a17-b194-08672107aeb2.
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The Malaysian granitoids form the backbone of the Malay Peninsula and have long been recognized as composed of two distinct granitic provinces separated by the Bentong-Raub suture zone:
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Perkes, Tyson L. "Integrating Facies Analysis, Terrestrial Sequence Stratigraphy, and the First Detrital Zircon (U-Pb) Ages of the Twist Gulch Formation, Utah, USA: Constraining Paleogeography and Chronostratigraphy." Diss., CLICK HERE for online access, 2010. http://contentdm.lib.byu.edu/ETD/image/etd3409.pdf.
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Loughry, Donald Franklin Jr. "ORIGIN OF BLUE RIDGE BASEMENT ROCKS, DELLWOOD QUAD, WESTERN NC: NEW EVIDENCE FROM U-PB ZIRCON GEOCHRONOLOGY AND WHOLE ROCK GEOCHEMISTRY." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/11.
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Terrane discrimination in polycyclic continental basement rocks is challenging due to high-grade metamorphism and intense deformation. Based on early USGS mapping the Blue Ridge basement in the Dellwood quadrangle of the eastern Great Smoky Mountains was proposed to consist of augen orthogneisses of Laurentian (Grenvillian) affinity interfolded with migmatitic hornblende and biotite paragneisses (“Carolina Gneiss”) and amphibolites of uncertain affinity. However, detailed study reveals that the hornblende gneiss of Hadley and Goldsmith (1963) is a heterogeneous map unit consisting of (1)metaplutonic rocks; (2) variably foliated and folded felsic orthogneisses; (3) strongly migmatitic, folded Hbl+Bt-bearing gneisses; (4) foliated and lineated garnet amphibolites Field relations, petrology, and geochemistry demonstrate that felsic orthogneisses are related to metaplutonic rocks via (post-Taconian) progressive deformation and reconstitution. Whole rock XRF geochemistry reveals likely protoliths of Hbl gneiss and Bt gneiss are geochemically similar and have common sources. U-Pb zircon geochronology and field relationships suggest felsic orthogneisses (1050 Ma,1150-1190 Ma, 1250-1300 Ma) are components of the Mesoproterozoic Grenville basement, and not part of a metamorphosed Neoproterozoic syn-rift Laurentian margin cover sequence. A previously unknown age mode for Mesoproterozoic plutonism in the southern Appalachians was discovered (~1250-1300 Ma) suggesting the presence of a component exotic to pre-Grenvillian Laurentia (Amazonia?).
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Asmussen, Pascal. "Insights from the Devonian Adavale Basin on the tectonic history of the Thomson Orogen." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/200906/1/Pascal_Asmussen_Thesis.pdf.
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This research aims to advance our understanding of the expansion of the Australian continent during the Palaeozoic. Geological remnants of specific sedimentary basins in southwest Queensland and north-western NSW were used as focus sites. A novel multi-method approach used sediment compositional information and Uranium-Lead mineral dating in combination with novel statistical methods to constrain the relative timing, sediment pathways and connectivity of these basins. The research showed that although a major period of stabilisation of the Australian continent had occurred by the beginning of the Devonian, approximately 400 million years ago, the new sedimentary basins were not yet directly connected.
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Nasdala, Lutz, Fernando Corfu, John W. Valley, Michael J. Spicuzza, Fu-Yuan Wu, Qiu-Li Li, Yue-Heng Yang, et al. "Zircon M127 - A Homogeneous Reference Material for SIMS U-Pb Geochronology Combined with Hafnium, Oxygen and, Potentially, Lithium Isotope Analysis." WILEY-BLACKWELL, 2016. http://hdl.handle.net/10150/621937.
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In this article, we document a detailed analytical characterisation of zircon M127, a homogeneous 12.7 carat gemstone from Ratnapura, Sri Lanka. Zircon M127 has TIMS-determined mean U-Pb radiogenic isotopic ratios of 0.084743 +/- 0.000027 for Pb-206/U-238 and 0.67676 +/- 0.00023 for Pb-207/U-235 (weighted means, 2s uncertainties). Its Pb-206/U-238 age of 524.36 +/- 0.16 Ma (95% confidence uncertainty) is concordant within the uncertainties of decay constants. The delta O-18 value (determined by laser fluorination) is 8.26 +/- 0.06 parts per thousand VSMOW (2s), and the mean Hf-176/Hf-177 ratio (determined by solution ICP-MS) is 0.282396 +/- 0.000004 (2s). The SIMS-determined delta Li-7 value is -0.6 +/- 0.9 parts per thousand (2s), with a mean mass fraction of 1.0 +/- 0.1 mu g g(-1) Li (2s). Zircon M127 contains similar to 923 mu g g(-1) U. The moderate degree of radiation damage corresponds well with the time-integrated self-irradiation dose of 1.82 x 10(18) alpha events per gram. This observation, and the (U-Th)/He age of 426 +/- 7 Ma (2s), which is typical of unheated Sri Lankan zircon, enable us to exclude any thermal treatment. Zircon M127 is proposed as a reference material for the determination of zircon U-Pb ages by means of SIMS in combination with hafnium and stable isotope (oxygen and potentially also lithium) determination.
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Luo, Yan. "U-Pb age and Hf isotopic study of detrital zircons from the Liaohe Group constraints on the evolution of the Jiao-Liao-Ji Belt, North China craton /." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36639242.
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Luo, Yan, and 羅彥. "U-Pb age and Hf isotopic study of detrital zircons from the Liaohe Group: constraints on the evolution of theJiao-Liao-Ji Belt, North China craton." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36639242.
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Laurent, Antonin. "Etude pétrologique et chronométrique (U-Th-Pb) de la monazite et du zircon dans les granulites de ultra-haute température du Rogaland, Norvège." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30290/document.
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La compréhension des processus orogéniques nécessite un couplage toujours plus étroit entre données pétrologiques visant à contraindre le trajet pression-température des roches et les données géochronologiques donnant accès aux âges et durées absolues. Cette thèse vise en premier lieu à étudier le comportement des monazites et des zircons, utilisés en géochronométrie U-Th-Pb dans les granulites de ultra-haute température (UHT) du Rogaland (sud de la Norvège). Nous montrons que la datation ponctuelle in-situ U-Th-Pb, combinée à l'analyse des éléments majeurs et traces contenus dans la monazite permet d'identifier et de quantifier deux incursions à ultra-haute température du Rogaland à 1030-1005 Ma et à 940-930 Ma. En effet, l'examen des relations de phases à l'équilibre entre monazite, xénotime et huttonite a permis de démontrer que les monazites étaient capables de cristalliser et d'enregistrer des températures supérieures à 880 °C. D'autre part, la caractérisation chimique et isotopique U-Th-Pb-O des néocristallisations et surcroissances des zircons permet de définir un intervalle de temps de 60 Ma entre les deux pics de métamorphisme, au cours duquel la croûte moyenne était partiellement fondue à des températures supérieures à 800°C et à basse pression (0.7-0.4 GPa). Ces travaux de thèse soulignent par ailleurs la variété des facteurs susceptibles de conduire à la remise à zéro, partielle ou non, des âges U-Th-Pb dans les monazites et les zircons. Nous montrons que compte tenu de l'histoire T-t du domaine étudié, le système chronométrique U-Th-Pb est largement contrôlé dans le zircon par le degré d'amorphisation de ce dernier lié à son auto-irradiation, alors que dans la monazite, ce sont les processus de dissolution-recristallisation en présence de fluides silicatés ou aqueux qui sont prépondérants. Nous montrons également qualitativement l'influence des conditions d'oxydo-réduction dans l'incorporation du S comme sulfate dans le réseau cristallin de la monazite et par conséquent le potentiel que représente la monazite pour sonder l'état d'oxydo-réduction lié aux différents évènements géologiques, dans les roches métamorphiques. Finalement, nous mettons en évidence une corrélation spatiale et temporelle entre magmatisme mantellique et métamorphisme de ultra-haute température qui ne peut être expliquée avec les modèles actuellement acceptés pour la genèse du métamorphisme de UHT. Ces observations peuvent néanmoins être expliquées en prenant en compte la différence de composition et de température du manteau Protérozoïque comparé à l'actuel, favorisant le développement d'orogènes ultra-chauds et de phénomènes gravitairesUnderstanding mountain building processes requires a better integration of petrological and peochronological data in order to link pressure-temperature paths to absolute ages. This work focuses on the behaviour of monazite and zircon, which are used as geochronometers, in ultra-high temperature granulites of Rogaland (South Norway). We show that linking in-situ U-Th-Pb dating of monazite with its major- and trace-element composition lead to the recognition of two ultra-high temperature (UHT) metamorphic events in Rogaland at c.1030-1005 Ma and c. 940-930 Ma. Indeed, the examination of monazite-xenotime-huttonite phase relationships suggests that monazite may record crystallization age at or near ultra-high temperature. Besides, the chemical and U-Th-Pb-O isotopic characterization of zircon neo-crystallization or overgrowths indicates that the Rogaland crust remains molten (> 800 °C at 0.7-0.4 GPa) at least during 60 My between the two identified UHT excursions. This manuscript also highlights the various factors responsible for U-Th-Pb (partial) resetting in the course of granulite facies metamorphism. Zircon behaviour is mostly controlled its level of amorphization, enhancing Pb loss during annealing, whereas monazite resetting is dominated by dissolution-precipitation processes in the presence of a melt or fluid phase. More specifically, we point out that monazite may be used to monitor the redox conditions of its crystallizing medium since monazite may incorporate the redox-sensitive element S in its lattice as sulphate. Finally, we demonstrate a spatial and temporal correlation between magmatism and UHT metamorphism in Rogaland. The timescale, P-T path and tectono-magmatic history however cannot be explained by currently accepted models for UHT. We suggest that physical and thermal specificities of Proterozoic mantle may explain the observed ultra-hot orogen style and the occurrence of gravity driven processes during orogeny
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Jones, Carson L. "U-Pb geochronology of monazite and zircon in Precambrian metamorphic rocks from the Ruby Range, SW Montana deciphering geological events that shaped the NW Wyoming province /." [Kent, Ohio] : Kent State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1214308001.
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Thesis (M.S.)--Kent State University, 2008.Title from PDF t.p. (viewed Oct. 5, 2009). Advisor: Peter Dahl. Keywords: Geochronology; Radiometric Dating; Plate Tectonics. Includes bibliographical references (p. 106-109).
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Sakata, Shuhei. "Development of analytical technique for precise age determination of Quaternary zircons with the correction of the initial disequilibrium on U-Th-Pb decay series using a laser ablation-ICP-mass spectrometry." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199112.
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Ghosh, Amiya Kumar. "Reconnaissance U-Pb geochronology of Precambrian crystalline rocks from the northern Black Hills, South Dakota: Implications for regional thermotectonic history." [Kent, Ohio] : Kent State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1240007954.
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Thesis (M.S.)--Kent State University, 2009.Title from PDF t.p. (viewed Feb. 12, 2010). Advisor: Peter Dahl. Keywords: Black Hills; Crook Mountain granite; Homestake gold mine; gold mineralization; magmatism; metamorphism; metapelite; g monazite; zircon; titanite; geochronology; thermotectonism Includes bibliographical references (p. 97-106).
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Borgo, Ariadne. "Le gisement d’or du Tocantinzinho (province aurifère du Tapajós) relations entre déformation, hydrothermalisme et minéralisation." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT078/document.
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Le gisement de Tocantinzinho est situé sur la province aurifère de Tapajós et est le plus grand gisement d'or de la province, avec 53,9 tonnes d'or estimées. Sa formation commence par un magmatisme granodioritique autour de 2005 Ma, suivi d'un magmatisme granitique. Le granite Tocantinzinho est composé de deux faciès principaux (syenogranite - 1996± 2Ma; monzogranite 1989±1 Ma), des corps d’aplite et de pegmatite, qui suggère un magmatisme enrichie en fluide et mis en place à faible profondeur. Intrusifs dans ces roches, des dykes d'andésite (1998±8Ma) ont des fragments de granite et des mélanges entre les 2 magmas suggèrent un magmatisme à la fois continu et polyphasé. Il est proposé que les premiers dykes d’andésite se sont mis en place alors que le granite n’était pas entièrement cristallisé (mingling) et les derniers lors des stades de déformation à l’état solide du granite. Utilisant la courbe de refroidissement, un âge minimum de 1975 Ma a été estimé pour l’andésite. Les taux de refroidissement des roches plutoniques varient de 3,6 à 14,7°C/Ma, avec une moyenne de 7,5°C/Ma, suggérant que les processus d'exhumation verticale sont faibles. La géométrie allongée du granite ainsi que la tectonique syn-magmatique de l'andésite corroborent la prédominance des mouvements horizontaux. L’affinité calc-alcaline fortement potassique et des anomalies en niobium définissent deux configurations possibles pour le cadre géotectonique: arc continental de type Andin ou Post-collisionnel. Compte tenue la relation génétique entre magmatisme, cisaillement décrochant et les faibles taux de refroidissement, l’environnement post-collisionnel est plus probable. Cela ensemble avec les âges nous permettent de comparer ces roches avec celles de la Suite Intrusive Creporizão (1997-1957Ma). La dacite (1992 ± 2 Ma) recoupe les autres roches, cependant, la signature géochimique comparable aux roches anorogéniques suggère qu’elle appartient à une série magmatique distinct. La zone minéralisée est limitée par deux failles majeures senestres de direction N100°-130E°. Le granite Tocantinzinho et les roches hypo-volcaniques déformées sont dans ce couloir, altérées par de fluides hydrothermaux et minéralisées pendant deux phases tectoniques distinctes. La première est caractérisée par des brèches et des microfractures remplies par muscovite (1864±5Ma) et pyrite, associées à de faibles teneur d’or (<1,5ppm) restreintes au granite. La deuxième phase a été contrôlée par le cisaillement décrochant senestre normal générant des fentes de tension et des brèches remplies par quartz, chlorite, calcite, albite, rutile, pyrite, galène, sphalérite, chalcopyrite et or. La teneur en or peut atteindre jusqu'à 70 ppm dans les veines riches en sulfures. Ces structures de remplissage syntectonique sont parallèles entre elles et orientées N30-60°E. Deux hypothèses ont été proposées pour expliquer la genèse du gisement: la première considère une relation génétique entre magmatisme et minéralisation au moins pour le premier stage de minéralisation selon un modèle porphyrique et la seconde alternative considère une réactivation des failles préexistantes par une tectonique transtensive liée au magmatisme Maloquinha (ca. 1880Ma) pour les deux stades minéralisateurs. Les deux phases dans les deux hypothèses, ont été classées comme des minéralisations de type magmato-hydrothermale qui pourraient être classées soit comme des systèmes d'or liés à l'intrusion. De nouveaux travaux sur le terrain et en laboratoire seraient nécessaires pour identifier et caractériser la nature et la source des fluides hydrothermaux, pour dater la minéralisation et mieux comprendre le rôle des roches hypo-volcaniques. Toutefois, les premiers résultats, et notamment le rôle fondamental du contrôle tectonique pour la minéralisation sont très significatifs et peuvent aider de manière conséquente à l'établissement des programmes d'exploration et d'exploitation futursThe Tocantinzinho deposit is located on the Tapajós Gold Province and is the largest gold deposit within Province, with 53,9 tons of gold. Its formation begins with a granodioritic magmatism around 2005Ma, followed by a granitic magmatism 10 Ma latter. The Tocantinzinho granite is composed by two main facies, syenogranite (1996±2Ma) and monzogranite (1989±1Ma), and by aplite and pegmatite bodies, suggesting a fluid-rich magmatism at shallow depth. Andesite dikes (1998±8Ma) are intrusive in both rocks. Sharp fragments of those rocks along contacts and minor mingling with granitic magma suggest a multiphase magmatism at distinct timing. The first dikes have intruded within granite when it was crystalizing, thus a minimum age of 1975Ma was estimated. Cooling rates of plutonic rocks vary from 3.6 to 14.7°C/Ma, with an average of 7.5°C/Ma, suggesting vertical exhumation processes were minor. The elongated geometry of granite along with sin-magmatic strike-slip tectonics of andesite corroborate the predominance of horizontal movements. Geochemical analysis show high-K calk-alkaline affinity and niobium anomaly indicator of two possible geotectonic settings for these rocks: Andean-type continental arc or post-collisional one. Considering the genetic relationship between magmatism, strike-slip faults, and low cooling rates, a post-collisional setting is more likely. The geochemical signature, ages and style of tectonism allow us to compare those rocks with the ones from Creporizão Intrusive Suite (1997-1957Ma). Dacite dikes (1992±2Ma) cut across all other rocks, but the temporal relationship among them remains misunderstood, due to the geochemical signature similar to the anorogenic rocks, suggesting it belongs to a distinct and latter magmatic series. Indeed, the dated zircons were probably inherited from host rocks. The mineralized area is restricted to a domain constrained by two major sinistral strike-slip N100°-130E°E faults that comprises the Tocantinzinho granite and sub-volcanic rocks, which were hydrothermally altered, brittle deformed and mineralized during two phases. The first one is characterized by breccias and microfractures infilled with muscovite (1864±5Ma) and pyrite, which contains low gold grades and are restricted to the Tocantinzinho granite. The second phase was controlled by strike-slip and normal tectonics generating tension gashes veins and pull apart breccias infilled with quartz, chlorite, calcite, albite, rutile, pyrite, galena, sphalerite, chalcopyrite, and gold. The gold grade can reach up to 70 ppm in some sulfide-rich veins. These structures are parallel and mainly trends N30-60°E, showing textures and orientated minerals typical of syn-tectonic infilling. Based on petrographical features and argon ages two hypothesis were proposed for the ore genesis: the first one consider a genetic relationship between magmatism and ore fluids for first mineralization stage and the second hypothesis consider a reactivation of pre-existing faults by an extensional tectonism related to the Maloquinha Intrusive Suite magmatism (ca.1880Ma) for this phase. The second mineralization phase is considered as formed as consequence of tectonic reactivation at ca. 1880Ma, in both hypothesis. Both phases in both hypothesis were classified as magmatic-hydrothermal ore mineralization and might be classified as intrusion-related gold systems. However, new field works are important in order to identify and characterize the nature and source of hydrothermal fluids, as well as ore dating and new geochemical and geochronological data of sub-volcanic rocks are imperative to better understand the genesis and evolution of the Tocantinzinho gold deposit. Such results, strongly linked to the fact that the tectonic control seem significant, may help for future exploration and exploitation programs
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Sanchez, Lohff Sonia K. "Upper plate response to varying subduction styles in the forearc Cook Inlet basin, south-central Alaska." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530270586819066.
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Harrison, Bianca. "Palaeoenvironments and position of the Precambrian–Cambrian boundary within the lower Vanrhynsdorp Group of South Africa: sedimentary facies analysis, U-Pb series zircon geochronology and micropalaeontology." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29450.
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The Vanrhynsdorp Group is a mainly fluvio-marine siliclastic succession that outcrops in the northwestern part of South Africa. The critical Precambrian-Cambrian boundary falls within the group, however the depositional environments across the boundary, its exact stratigraphic position and nature are unresolved. The group was deposited in the Vanrhynsdorp Basin, which has been shown to be the southernmost extension of the Nama Foreland Basin. Consequently, the Vanrhynsdorp Group has been correlated with the world-famous Nama Group, which features diverse Ediacaran-Cambrian fossils. To date, no body fossils have been discovered in the Vanrhynsdorp Group. Through U-Pb dating of detrital zircons using LA-ICP-MS, radiometric ages for the middle part of the Vanrhynsdorp Group (Besonderheid Formation) were obtained in a preliminary study of this project. The radiometric data, yielding a maximum depositional age of 524 to 528 Ma from the youngest zircon grain population, indicated that the Precambrian-Cambrian boundary is stratigraphically lower in the group than it was thought before. To further constrain the age of the lower Vanrhynsdorp Group, and by extension the position of the Precambrian-Cambrian boundary, several detrital zircon samples were processed for age determination from the succession in this study. In addition, using sedimentary facies analysis, the lateral and vertical facies variation in this lower part of the group were (re)documented in order to refine the palaeoenvironmental setting. The current results suggest a dominantly shallow marine, partly storm-dominated depositional environment for the lowermost units as opposed to the previous interpretations of dominantly alluvial settings. Because of the global importance of the Ediacaran-Cambrian transition for diversification of marine biota in the Cambrian, addressing these palaeoenvironmental inconsistencies is the vital outcome of this study. By integrating our sedimentological and geochronological results, the project presents an improved understanding of the depositional history of the Vanrhynsdorp Group during the critical Ediacaran-Cambrian transition.
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Albardeiro, Luís José de Sousa. "Aplicação da geocronologia U-Pb em zircão a areias e rochas do substrato do litoral do sudoeste de Portugal: implicações para a proveniência, dinâmica sedimentar e história geológica da região." Doctoral thesis, Universidade de Évora, 2015. http://hdl.handle.net/10174/18275.
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O presente estudo de proveniência sedimentar baseia-se na geocronologia U-Pb em zircão da areia de praia (Areias Brancas, Aberta Nova e São Torpes) e, das rochas que constituem as arribas adjacentes, junto ao Cabo de Sines (grauvaques do Grupo do Flysch do Baixo Alentejo, areias da Bacia de Alvalade e sienitos do Maciço de Sines). As populações de zircão detrítico dos grauvaques carbónicos amostrados neste estudo distribuem-se principalmente pelo Neoproterozoico (ca. 844-548 Ma), derivando de fontes localizadas no bloco continental de Gondwana (Zona de Ossa-Morena). O restante flysch inclui outras fontes que podem ser atribuídas à Laurússia e a um suposto arco insular devónico; estas fontes estão relacionadas com a formação do supercontinente Pangeia (Orogenia Varisca). As idades dos zircões ígneos dos sienitos do Maciço de Sines (ca. 87-74 Ma) indicam a presença de três episódios de cristalização durante ca. 13 Ma no Cretácico Superior e as idades obtidas indicam que este Maciço é contemporâneo do magmatismo alcalino intraplaca representado pelo Maciço de Sintra. Nas areias das arribas plio-pleistocénicas da Bacia de Alvalade predominam zircões paleozoicos (ca. 541-277 Ma); são provenientes de fontes localizadas a norte (soco pré-Mesozoico da Zona Centro-Ibérica e do Eocénico-Miocénico da Bacia do Baixo Tejo), a leste (zonas de Ossa- Morena e Sul Portuguesa) e a oeste (Zona Sul Portuguesa, Triásico da Bacia do Alentejo e Maciço de Sines). Estas fontes foram expostas em resultado do rejuvenescimento do relevo por efeito da tectónica Alpina. A areia holocénica de praia, amostrada a norte do Cabo de Sines, é caracterizada pela predominância de zircões paleozoicos tal como acontece na areia plio-pleistocénica das arribas adjacentes. Na areia holocénica de praia colhida a sul do Cabo de Sines predominam os zircões cretácicos (ca. 95-73 Ma) provenientes do Maciço de Sines; esta diferenciação de fontes está relacionada com a dinâmica litoral atual;
ABSTRACT: This sedimentary provenance study is based on U-Pb geochronology of zircon extracted from beach sand (Areias Brancas, Aberta Nova and São Torpes) and sea cliffs rocks around Sines Cape (Baixo Alentejo Flysch Group greywacke, Alvalade Basin sands and Sines Massif syenites). The populations of detrital zircon from the Carboniferous greywackes (this study) are mainly distributed over the interval ca. 844-548 Ma (Neoproterozoic); they derived from sources located in Gondwana (Ossa-Morena Zone). The rest of the flysch deposits include other sources that can be attributed to Laurussia and to a supposed Devonian island arc. These sources are related to the formation of the supercontinent Pangaea (Variscan Orogeny). The ages of igneous zircons from Sines syenites (ca. 87-74 Ma) reveal three crystallization episodes during a period of ca. 13 Ma in the Upper Cretaceous; the ages obtained indicate that the Sines Massif is coeval with the Sintra Massif representing a major event of intra-plate alkaline magmatism in Iberia. Paleozoic detrital zircons (ca. 541-277 Ma) are dominant on the Plio-Pleistocene sands (Alvalade Basin) forming the sea cliffs; they derived from sources located in the north (the pre- Mesozoic basement of the Central-Iberian Zone and the Eocene-Miocene of the Lower Tagus Basin), east (areas of Ossa-Morena and South Portuguese zones) and west (South Portuguese Zone, Triassic Alentejo Basin and Sines Massif). These sources were exposed as a result of landscape rejuvenation during Alpine tectonics. The population of detrital zircons from the Holocene beach sand sampled north of the Sines Cape is dominated by Paleozoic grains as in Plio-Pleistocene sand forming the adjacent sea- cliffs. In the beach sand sampled south of the Sines Cape, Cretaceous zircons are dominant (ca. 95-73 Ma) and probably derived from the Sines Massif; this variation in sources is related to modern littoral dynamics.
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Canile, Fernanda Maciel. "Geologia isotópica em zircões detríticos (U-Pb, Hf e O) e em rocha total (Sm-Nd e Pb-Pb) das rochas da Bacia do Paraná em Santa Catarina." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-24022016-140417/.
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Dados isotópicos U-Pb, Hf e de O foram obtidos em zircões detríticos das unidades do final do Paleozoico e início do Mesozoico da Bacia do Paraná, sudeste do Brasil, com o objetivo de determinar a proveniência dos sedimentos, assim como contribuir para o entendimento da evolução tectônica da bacia. Assinaturas isotópicas Sm-Nd e Pb-Pb em amostras de rocha-total também foram obtidas com o intuito de auxiliar na interpretação sobre as áreas fontes. A seção estudada, Coluna White em Santa Catarina, inclui rochas de 11 unidades estratigráficas (da base para o topo): Formação Rio do Sul, Formação Rio Bonito, incluindo os membros Triunfo, Paraguaçu e Siderópolis, Formação Palermo, Formação Irati, Formação Serra Alta, Formação Teresina, Formação Rio do Rasto, subdividida nos membros Serrinha e Morro Pelado, e Formação Botucatu, Idades U-Pb foram obtidas em 1941 grãos de zircão detrítico e variam de 242 Ma a 3,4 Ga. Todas as unidades sedimentares apresentam quatro grupos principais de zircões detríticos, Neoarqueano (2,7-2.5 Ga), Paleoproterozoico Médio (2,0-1,8 Ga), Grenviliano (1,1-0,9 Ga) e Brasiliano (850-490 Ma), refletindo a importância do embasamento Pr-e-Cambriano que bordeja a parte leste da bacia como áreas fontes, tais como as Faixas Dom Feliciano, Kaoko e Namaqua-Natal, incluindo o embasamento local datado em 584 Ma. O Membro Siderópolis apresenta uma importante mudança nas fontes dos sedimentos que preencheram a Bacia do Paraná, pois é a partir dessa unidade que o pico de idade permiana (266 a 290 Ma) é observado. Esse pico persiste até o topo da seção, a Formação Botucatu. As assinaturas isotópicas de O e Hf dos zircões detríticos mostram que parte dos grãos do Paleoproterozoico Médio é provavelmente de rochas do embasamento atualmente recoberto, que estava exposto até a deposição da Formação Rio Bonito. Os isotópos de Hf e O também mostram que parte dos zircões com idade grenviliana é proveniente de rochas argentinas, o que implica em longas distâncias de transporte. As assinaturas isotópicas de parte dos grãos permianos os ligam a fontes da Argentina e Chile, sendo que parte desses grãos possui forma mais arredondada, o que sugere que eles alcançaram a bacia pelo transporte em ambientes subaquáticos e não somente pelo ar (quedas de cinzas vulcânicas) como é comumente apontado. Outros picos de idade mais jovens (Ordoviciano ao Carbonífero), observados a partir da Formação Palermo e nas unidades superiores, também são provenientes de fontes argentinas e chilenas, mostrando a importância dos detritos de fontes distantes durante o preenchimento da bacia. Os dados Sm-Nd e Pb-Pb em rocha total mostram que os sedimentos da Bacia do Paraná apresentam predominância de fontes de origem crustal. As assinaturas são semelhantes aos granitoides de Santa Catarina, rochas da Faixa Ribeira, do Escufo Brasileiro, das Faixas Namaqua-Natal e Kaoko, Terreno Arequipa-Antofalla (embasamento dos Andes) e granitoides do Norte da Patagônia. Esses dados corroboram os padrões de zircões detríticos observados, que apontam para áreas fontes tanto proximais quanto distais. Além disso, as idades modelo Sm-Nd (\'T IND. DM\') obtidas são mais antigas que 1,4 Ga e mais negativas (-10 a -15) nas unidades inferiores (Formação Rio do Sul até o Membro Paraguaçu), enquanto que as unidades superiores apresentam valores de \'\'épsilon\' IND.Nd(0) entre -6 a -12 e idades modelo \'T IND.DM\' mais jovens que 1,5 Ga, sugerindo a participação de uma fonte mais jovem a partir da deposição do Membro Siderópolis, conforme foi observado pelos dados de zircão detrítico (pico de idade permiana)U-Pb, Hf and O isotope data were obtained from detrital zircons from late Paleozoic-early Mesozoic units from Paraná Basin, southeastern Brazil, in order to constain the provenance of the sediments, as well as to contribute to the understanding of the tectonic evolution of the basin. Whole rock Sm-Nd and Pb-Pb isotopic signatures were also taken in order to help the interpretation. The studied section, White Column in Santa Catarina state, includes rocks from 11 stratigraphic units (from base to top): Rio do Sul Formation, Rio Bonito Formation (Triunfo, Paraguaçu and Siderópolis members), Palermo Formation, Irati Formation, Serra Alta Formation, Teresina Formation, and Rio do Rasto Formation (Serrinha and Morro Pelado members) and Botucatu Formation. U-Pb ages were obtained on 1941 detrital zircons and range from 242 Ma to 3400 Ma. All sedimentary units show four main detrital age groups, Neoarchean (2700-2500 Ma), mid-Paleoproterozoic (2000-1800 Ma), Grenvillian (1100-900 Ma) and Brasiliano (850-490 Ma), reflecting the importance of the Precambrian basement bordering the east side of the basin, such as Dom Feliciano, Kaoko and Namaque-Natal Belts as source areas, including the local basement that was dated at 584 Ma. The Siderópolis Member shows an important change in the source of sediments with a Permian age-peak (266 to 290 Ma). This age-peak persists towards the top of the section until the Botucatu Formation. O and Hf isotopic signatures from the detrital zircons show that a portion of the mid-Paleoproterozoic grains is probably from rocks of the presently covered basement, which was exposed until the deposition of the Rio Bonito Formation. O and Hf isotopes also show that some Grenvillian aged zircons are from Argentinian rocks, which implies a long transport distance. Isotopic signatures of part of the Permian grains also link them to sources from Argentina and Chile, and part of these grains has more rounded shapes, suggesting that they reached the basin after long distance traveling on subaquatic environment and nor only through the air (ash falls) as it is commonly accepted. Other younger age peaks (Ordovician to Carboniferous) found from Palermo Formation upsection are also linked to Argentinian and Chilean sources, showing the importance of distant sources during the filling of the basin. The Sm-Nd and Pb-Pb data on whole rocks show that the sediments from the Paraná Basin present predominance of sources with crustal origin. Osotopic signatures are similar to granitoid rocks from Santa Catarina, Ribeira Belt, Brazilian Shield, Namaqua-Natal and Kaoko Belts, as well as the Arequipa-Antofalla terranes (Andes basement) and granitoids from North Patagonia. These data corroborate the observed detrital zircon patterns thar point to both proximal and distal source areas. \'T IND.DM\' model ages older than 1.4 Ga and more negative (-10 to -15) epsilon values were observed in the lower units (Rio do Sul Formation to Paraguaçu Member), while the upper units show \'\'épsilos\' IND.Nd(0)\' values ranging from -6 to -12 and \'T IND. DM\' model ages younger than 1.5 Ga, corroborating the addition of a younger source starting from the Siderópolis Member deposition upwards, as noted by detrital zircon data (Permian age-peak).
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Caquineau, Tom. "Etude géochronologique U-Pb et isotopique Lu-Hf sur zircon du groupe de Turee Creek : implications sur l’événement de grande oxygénation et les glaciations paléoprotérozoïques." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC236/document.
Full textAbstract:
La transition Archéen – Protérozoïque (~2,45 Ga) est marquée par des bouleversements environnementaux majeurs dans l’histoire de la Terre (oxygénation de l’atmosphère et glaciations globales). Les séquences sédimentaires qui enregistrent ces événements ont été très étudiées en Amérique du Nord (séquence Huronienne) et en Afrique du Sud (Transvaal). Une séquence analogue sur le craton de Pilbara en Australie Occidentale (groupe de Turee Creek, TCG) contient 3 niveaux de diamictites glaciaires. 3 forages continentaux (Turee Creek Drilling Project, TCDP) ont été réalisés pour étudier la séquence. La géochronologie U-Pb de monazite et zircon dans des échantillons de forage et de surface a daté la première glaciation à 2,45 Ga et la seconde à ~2,34 Ga. Des analyses Re-Os de pyrites de la seconde diamictite ont donné une isochrone à 2,31 Ga. Ces résultats ont permis de proposer un scenario de corrélation des glaciations paléoprotérozoïques enregistrées sur différents continents. Une ‘Snowball Earth’ aurait eu lieu à ~2,45 Ga sur au moins 5 cratons (Pilbara, Kaapvaal, Supérieur, Wyoming, Karélia). Une seconde glaciation aurait pu avoir lieu à ~2,31 Ga sur 4 cratons. L’ensemble des zircons détritiques du TCG ont une distribution d’âge avec des pics à 2,45, 2,54, 2,68, 2,82, 2,95 et 3,2 Ga. Un cristal de zircon Hadéen a été découvert et indique la présence d’une probable croûte différenciée dans le craton de Pilbara à 4,0 Ga. 70% des zircons ont des compositions isotopiques en Hf juvéniles, suggérant que le TCG a incorporé du matériel volcanique provenant de larges provinces ignées continentales à travers l’érosion des groupes sous jacents de Hamersley et FortescueThe Archean – Proterozoic transition at 2.45 Ga is marked by major environmental changes in Earth’s history (atmosphere oxygenation and global glaciations). The origin and the relationships between these events are debated. Sedimentary sequences that record these events have been widely studied in North America (Huronian sequence) and South Africa (Transvaal). An analog sequence in the Pilbara craton in Western Australia (Turee Creek Group, TCG) contains 3 glacial horizons. 3 continental drill cores (Turee Creek Drilling Project, TCDP) were performed in order to investigate the sequence. U-Pb geochronology of monazite and zircon from drill core and surface samples allows to date the first paleoproterozoic glaciation at 2.45 Ga and a second glacial event at ~2.34 Ga. Re-Os analyses of pyrites from the second diamictite yielded an isochron at 2.31 Ga. These results enable to propose a correlation scenario of the paleoproterozoic glacial events recorded on different continents. A ‘Snowball Earth’ would have occured at 2.45 Ga at least on 5 cratons. A second glaciation could have occured at ~2.31 Ga on 4 cratons. Detrital zircons age spectrum highlights age peaks at 2.45, 2.54, 2.68, 2.82, 2.95 and 3.2 Ga. A crystal of Hadean zircon was discovered and indicate the existence of a probable differentiated crust within the Pilbara craton at 4.0 Ga. 70% of the analyzed zircons have juvenile Hf isotope composition, suggesting that the TCG incorporated volcanic material from continental large igneous provinces through the erosion of the underlying Hamersley and Fortescue groups
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Ver, Hoeve Thomas James. "Applications of LA-ICP-MS analysis to zircon : assessing downhole fractionation and pre-treatment effects for U-Pb geochronology and trace element variations in accessory minerals from the Bushveld Complex." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60201.
Full textAbstract:
Zircon and other U-Th-Pb-bearing minerals are now recognized as key geochemical and geochronological tracers of the evolution of late-stage fractionated interstitial melt in mafic layered intrusions. Two separate, yet complementary, applications of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) on zircon from layered intrusions are presented with the goals of advancing the analytical capabilities of LA-ICP-MS and showcasing the powerful geochemical fingerprinting of zircon. The effects of downhole fractionation, the time-dependent evolution of Pb-U ratios during laser ablation, represents a significant limitation on the accuracy of U-Th-Pb zircon geochronology by LA-ICP-MS. Exponential downhole correction models developed from the analyses of three common zircon reference materials (Plešovice, Temora-2, 91500) and applied to low-U zircon from Precambrian mafic intrusions (Laramie, Bushveld, Stillwater) indicate that successful correction requires careful matrix-matching the reference zircon to the unknowns. Pre-treatment protocols, including annealing and leaching, applied to all analyzed zircon produces strong effects on downhole fractionation with correlative impact on the relative accuracy of the calculated ages as a function of the downhole behaviour in the reference material used. In the Paleoproterozoic Bushveld Complex, the world’s largest layered intrusion, the trace element systematics of zircon provide temperature-composition constraints on the near-solidus crystallization of mafic-ultramafic cumulates and overlying granitic rocks. Zircon occurs with other late-stage interstitial minerals (e.g., quartz, biotite, Na-plagioclase) and crystallized at temperatures ranging from 950°C down to 690°C based on Ti-in-zircon thermometry. Forward modeling using rhyolite-MELTS of proposed Bushveld parental magmas yields similar zircon saturation temperatures from melts of intermediate-silicic composition, representing less than ~15% remaining melt, and reproduces the observed mineral assemblages. Anomalously high and variable Th/U in zircon from the Critical Zone (e.g., UG2 chromitite, Merensky Reef) reflects U loss to late, oxidized Cl-rich fluids that exsolved from the fractionated interstitial melt, a process that may be a characteristic feature of large open-system layered intrusions (e.g., Neoarchean Stillwater Complex). The presence of late-stage interstitial zircon and other accessory minerals in layered intrusions provides new in situ geochemical and geochronological tools for evaluating the origin and evolution of mafic-ultramafic magmatism in the Earth’s crust throughout geological time.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Teixeira, Alice Westin. "O Grupo Carrancas e a frente da Nappe Andrelândia na borda sul do Cráton do São Francisco: Proveniência sedimentar e implicações tectônicas." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/44/44143/tde-26092012-150855/.
Full textAbstract:
O Sistema de Nappes Carrancas compõe um sistema de nappes que circunda ao sul o Cráton do São Francisco e é formado pela Unidade Biotita Xisto e pelas formações Campestre e São Tomé das Letras do Grupo Carrancas. A Unidade Biotita Xisto contém veios de quartzo e xistosidade anastomosada e é formada por quartzo, biotita, muscovita, clorita e, localmente plagioclásio, carbonato e granada. A Formação Campestre é formada por quartzitos intercalados a filitos/xistos que variam de cloritóide filitos grafitosos, com muscovita, quartzo e turmalina e, localmente, granada a xistos com granada, estaurolita e cianita. A investigação da Unidade Biotita Xisto como autóctone em relação ao Cráton do São Francisco, seu potencial agrupamento com o Grupo Carrancas em uma megassequência deposicional, bem como sua comparação com a unidadealóctone Xisto Santo Antônio (Nappe Andrelândia) constituem parte dos objetivos deste estudo. Para tal, foram feitas análises químicas e isotópicas (Sr e Nd) em rocha total e geocronologia U-Pb em cristais de zircão detríticos, tanto na Unidade Biotita Xisto como na Formação Campestre, com intuito de elucidar a relação entre as mesmas e compará-las com dados da literatura disponíveis para o Xisto Santo Antônio. A Unidade Biotita Xisto apresenta características químicas compatíveis com sedimentos que sofreram intemperismo químico de intensidade e período de tempo moderados, depositados em ambientes de colisão continental, com área-fontecomposta essencialmente por rochas félsicas. Assinaturas de elementos traço e isotópicas de Sr ( \'ANTPOT.87 Sr\'/\'ANTPOT. 86 Sr\' entre 0,713 e 0,715) e Nd (\'\'épsilon\' IND.Nd\' entre -6 e -5) indicam contribuição de arco magmático e crosta continental e diferem, portanto, daquelas esperadas em ambientes de margempassiva. A mesma contribuição é observada para o Xisto Santo Antônio, cuja área fonte registra importante assinatura de material juvenil. As idades U-Pb LA-MC-ICP MS obtidas em cristais de zircão mostram contribuição principal de rochas do final do Criogeniano e contribuição secundária do Riaciano. A classe modal ao redor de 665 Ma é comparável com a idade cristais de zircão detrítico do Xisto Santo Antônio, o que aponta parauma mesma área-fonte principal para ambas unidades. A deposição dos sedimentos precursores da Unidade Biotita Xisto ocorreu entre 630-611 Ma, sendo as fontes principais os granulitos cálcio-alcalinos e rochas vulcânicas co-genéticas, além de granitos sin-colisionais da Nappe Socorro-Guaxupé. A pouca representatividade de idades paleoproterozóicas e a ausência de assinaturas químicas de margem passiva, inviabilizam as rochas do Cráton doSão Francisco como parte da área-fonte. Desta forma, a Unidade Biotita Xisto não é autóctone em relação ao Cráton do São Francisco, sendo, potencialmente, a unidade que compõe a frente da Nappe Andrelândia. Por outro lado, a Formação Campestre possui assinatura geoquímica de sedimentos que sofreram uma intensa reciclagem e alteração da composição do sedimento original. As assinaturas químicas de elementos traço e isotópicas Sr e Nd indicam contribuição de crosta continental superior, com componente de crosta antiga e sem afinidade com sedimentos depositados em margem passiva (\'ANTPOT.87 Sr\'/\'ANTPOT. 86 Sr\' entre 0,74 e 0,76; \'\'épsilon IND.Nd\' entre -18 e -15). Os zircões detríticos analisados forneceram idades U-Pb LA-MC-ICP-MS variadas, do Toniano ao Mesoarqueano, correlacionáveis com rochas vulcânicas e plutônicas do Cráton do São Francisco, com as faixas marginais do Cráton de Angola e/ou faixas orogênicas do Cráton Amazônico e com rochas dos arcos Mara Rosa e Goiás.A abrangência das idades U-Pb da Formação Campestre e das formações Chapada dos Pilões e Paracatu, permite a correlação, no Orógeno Brasília, entre os Grupos Carrancas e Canastra. A paleogeografia mais provável é a de um ambiente de rifte, antecessor à deriva e aoestabelecimento de uma margem continental passiva.The Carrancas Nappe System composes a system of nappes that surround the southern margin of the São Francisco Craton and is formed by the Biotite Schist Unit and by the Campestre and São Tomé das Letras formations of the CarrancasGroup. The Biotite Schist Unit encompass quartz veins and anastomosed schistosity and is formed by quartz, biotite, muscovite, chlorite and, locally plagioclase, carbonate and garnet. The Campestre Formation is composed by interleaved quartzites and phyllite/schist that varies from graphite-chloritoid phyllites, with muscovite, quartz, tourmaline and garnet, and locally garnet schists and schists with garnet, staurolite and kyanite. The investigation of the Biotite Schist Unit as authochtonous in relation to the São Francisco Craton, it´s potencial grouping with the Carrancas Group in a deposicional megassequence, as well as it´s comparison with the allochthonous Santo Antônio Schist (Andrelândia Nappe) is part of the goals of this study. For this purpose, chemical and isotopic (Sr and Nd) whole rock analysis were obtained, along with U-Pb detrital zircon data, in the Biotite Schist Unit and also in the Campestre Formation, in order to elucidate the relationship between these units and compare them with literature data available for theSanto Antônio Schist. The Biotite Schist Unit show chemical characteristics compatible with sediments that underwent chemical weathering of moderate intensityand time, deposited in continental collision setting, with source region composed essentially by felsic rocks. Trace elements and Sr isotopic signatures ( \'ANTPOT.87 Sr\'/\'ANTPOT. 86 Sr\' between 0,713 and 0,715) and Nd (\'\'épsilon IND.Nd\' between -6 and -5) points to contribution from magmatic arc and continental crust, and are different from the expected for passive margin settings. The same contribution is observed in the Santo Antônio Schist, which source area registers an important juvenile material signature. The U-Pb LA-MC-ICP MS zircon data show major contribution from rocks of the later Cryogenian and minor contribution from the Ryacian. The modal class around 655 Ma is comparable with the U-Pb detrital zircon data from the Santo Antônio Schist, pointing to the same source area for both units. The deposition of the precursors sediment of the Biotite Schist Unit occurred between 630 - 611 Ma, and the main sources were the calk-alcaline granulites and co-genetic volcanic rocks, besides the Socorro-Guaxupé Nappe sin-collisional granites. The low representation of Paleoproterozoic ages and the absence of passive margin chemical signatures preclude the rocks of the São Francisco Craton as part of the source area. Thus, Biotite Schist Unit is not an autochthonous unit in relation to the São Francisco Craton, and is, potentially, the unit that composes the Andrelândia Nappe front. On the other hand, the Campestre Formation has geochemical signatures of sediments that underwent intense recycling and alteration of the original sediment. The trace element and Sr and Nd isotopic signatures indicates upper continental crust contribution, with older crust component and no affinity with passive margin sediments ( \'ANTPOT.87 Sr\'/\'ANTPOT. 86 Sr\' between 0,74 and 0,76; \'épsilon\' IND.Nd\' between -18 and -15). The U-Pb LA-MC-ICP MS detrital zircon data provide varied ages, from the Tonian to the Mesoarchean, correlated withvolcanic and plutonic rocks of the São Francisco Craton, with the marginal belts of the Angola Craton, and/or orogenic belts of the Amazonian Craton and with the Mara Rosa and Goiás magmatic arcs. The range of the U-Pb ages of the Campestre Formation and the Chapada dosPilões and Paracatu formations, allows the correlation, in the Brasília Orogen, of the Campestre and Canastra groups. The most likely paleogeography is that of a rift setting, before the continental drift and the establishment of a passive continental margin.
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Brezina, Cynthia A. "The detrital mineral record of Cenozoic sedimentary rocks in the Central Burma Basin : implications for the evolution of the eastern Himalayan orogen and timing of large scale river capture." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6730.
Full textAbstract:
This study contributes to the understanding of major river evolution in Southeast Asia during the Cenozoic. In order to trace the evolution of a hypothesized palaeo-Yarlung Tsangpo-Irrawaddy River, this work undertakes the first systematic provenance study of detrital minerals from Cenozoic synorogenic fluvial and deltaic sedimentary rocks of the Central Burma Basin, employing a combination of high precision geochronology, thermochronology, and geochemistry analytical techniques on single grain detrital zircon and white mica. The dataset is compared to published isotopic data from potential source terranes in order to determine source provenance and exhumation history from source to sink. A Yarlung Tsangpo-Irrawaddy connection existed as far back as ca. 42 Ma and disconnection occurred at 18–20 Ma, based on provenance changes detected using a combination of U-Pb ages and εHf(t) values on detrital zircons, and ⁴ºAr/³⁹Ar dating on detrital micas. During the Eocene and Oligocene, units are dominated by U-Pb age and high positive εHf(t) values, characteristic of a southern Lhasa Gangdese magmatic arc source. An antecedent Yarlung Tsangpo-Irrawaddy River system formed the major river draining the eastern Himalaya at this time. A significant change in provenance is seen in the early Miocene, where detritus is predominantly derived from bedrock of the eastern Himalayan syntaxis, western Yunnan and Burma, a region drained by the modern Irrawaddy-Chindwin river system characterized by Cenozoic U-Pb ages and negative εHf(t) values. This is attributed to the disconnection of the Yarlung-Irrawaddy River and capture by the proto-Brahmaputra River, re-routing Tibetan Transhimalayan detritus to the eastern Himalayan foreland basin. Re-set zircon fission track ages of 14-8 Ma present in all units is used to infer post-depositional basin evolution related to changes in the stress regime accommodating the continued northward migration of India. The early Miocene initiation of the Jiali-Parlung-Gaoligong-Sagaing dextral shear zone and the continued northward movement of the coupled India-Burma plate aided in focusing deformation inside the syntaxis contributing to the disconnection of the Yarlung Tsangpo-Irrawaddy system, linking surface deformation and denudation with processes occurring at deeper crustal levels.
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Kuiper, Yvette Dominique. "Isotopic constraints on timing of deformation and metamorphism in the Thor–Odin dome, Monashee Complex, southeastern British Columbia." Thesis, Department of Geology, University of New Brunswick, 2003. http://hdl.handle.net/1882/46.
Full textAbstract:
New and existing U–Pb and 40Ar/39Ar geochronological data, and oxygen and
hydrogen stable isotope data, are combined with structural and metamorphic data from Thor–Odin, the southern culmination of the Monashee Complex. This leads to a new interpretation of the timing of deformation and metamorphism. Amphibolites in Thor–Odin with hornblende 40Ar/39Ar dates between ~75–70 and ~51 Ma experienced more 18O- and D-depletion than amphibolites with older dates. The younger dates that were previously interpreted as cooling ages, may have resulted from complete or partial Ar loss in the presence of meteoric fluids that were introduced into the rock during extension.
Monazite crystals in pelitic schist, quartzite and orthogneiss, which have U–Pb ages younger than 40Ar/39Ar hornblende ages in amphibolite in northwest Thor–Odin, may have grown during tension in the presence of fluids. Titanite, xenotime and zircon dates may be interpreted in the same way. Thus, the U–Pb dates that were previously interpreted as representing peak of metamorphism and the hornblende 40Ar/39Ar dates that were previously interpreted as representing cooling ages, may be interpreted as reflecting meteoric fluid penetration of the crust during regional extension. This implies that the age of the thermal peak of metamorphism is older than ~75–70 Ma. Migmatisation in a basement orthogneiss in Thor–Odin occurred at ~1.8 Ga. Dissolution rims are preserved in zircon between ~1.8 Ga domains and 52 Ma overgrowths. Because growth of new zircon (and possibly other U–Pb accessory phases) did not take place, any geological event that occurred during the ~1.8 Ga to 52 Ma time interval is not recorded. Cordilleran deformation and metamorphism may have taken place within that time interval, e.g. in the Middle Jurassic and/or mid- to Late Cretaceous, the time of Cordilleran deformation and metamorphism in the rocks overlying the Monashee Complex.
The Joss Mountain orthogneiss, west of the Monashee Complex in the Selkirk Allochthon, is dated at 362 +/– 13 Ma. F3 folding in pelitic schist at Joss Mountain is constrained between ~73 and ~70 Ma. Existing structural, metamorphic and geochronological data in, and close to, the Shuswap Metamorphic Complex in the southern Canadian Cordillera are shown to be consistent with a channel flow model.
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Andersson, Barbro. "Metamorphic Evolution of the Tjeliken Garnet-Phengite Gneiss, Northern Jämtland, Swedish Caledonides." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-276515.
Full textAbstract:
The Tjeliken Mountain in northern Jämtland, central Scandinavian Caledonides is by most authors considered to belong to the Lower Seve Nappe Complex (SNC). However, recently P-T conditions similar to the Middle Seve have been constrained for the eclogite at the top of the mountain, revitalizing the tectonic debate about Tjeliken. Also the timing of high-pressure metamorphism is debated. Two earlier studies of the eclogite yield ages between 464 Ma and 446 Ma. This study focuses on the garnet-phengite gneiss hosting the eclogite. By construction of P-T conditions and dating the two discrepancies above are investigated. U/Pb zircon dating by secondary ion mass spectrometry technique (SIMS) targeted on metamorphic rims yield a concordia age of 460.2 ± 2.7 Ma corresponding well to earlier c. 463.7 ± 8.9 Ma Sm/Nd dating of the eclogite. The inferred peak mineral assemblage of the gneiss is garnet + phengite + quartz + K-feldspar + titanite ± H2O. Thermodynamic modelling reveal that garnet cores equilibrated within 1.9 - 2.6 GPa and 600 - 700 oC. Fe2+-Mg garnet-phengite thermometry involving garnet rims yields temperatures of c. 650 - 715 oC revealing relatively similar temperatures during growth of garnet core and rim, respectively. Garnet chemistry is characterised by oscillatory zoning with an antithetic pattern of Ca and Fe. The former decreases from core to rim, whereas the latter increases. The opposite trend is observed in epidote-group minerals suggesting exchange between the two minerals during garnet growth. Skeletal textures and atoll textures together with observed chemical pattern may indicate multiple garnet growth episodes. The results of the study points toward similar P-T history of the Tjeliken eclogite and gneiss in favour of the interpretation of considering the whole Tjeliken to belong to the Lower Seve. The obtained U/Pb age support other age constraints in the area suggesting high-pressure metamorphism at c. 460 Ma related to a subduction event affecting the central Scandinavian Caledonides at c. 460 - 450 Ma.Den skandinaviska fjällkedjan, vetenskapligt benämnd de skandinaviska Kaledoniderna, har bildats på samma sätt som Himalaya och har därför liknande uppbyggnad. Från början tros fjällen ha varit av samma storlek som Himalayas berg. Deras ålder på cirka 400 miljoner år gör dock att miljontals års påverkan från vatten och vind har eroderat ner dem till dagens betydligt lägre fjäll. Den bergsyta vi ser idag utgör därför vad som från början var fjällkedjans kärna. Därför utgör de skandinaviska Kaledoniderna en unik möjlighet att studera en bergskedjas inre, vilket kan ge viktig information om bergkedjebildande processer.Forskning har visat att fjällkedjan bildades då Japetushavet mellan kontinenterna Baltika och Laurentia stängdes. Detta resulterade till slut i en kollision mellan de två kontinenterna där stora flak (skollor) av mellanliggande havsbotten och kontinentalskorpa transporterades hundratals kilometer upp på Baltika. Skollorna utgör idag våra fjäll. Känt är också att innan kontinentalkollisionen så kolliderade Baltika med öar i havet, varvid dess kontinentalkant pressades djupt ner under jordskorpan, ända ner i manteln. Bevis för detta återfinns idag i Sevesskollan ibland annat de jämtländska fjällen i form av högtrycksbergarter. Dessa har bildats under de höga tryck och temperaturer som råder på stora djup i jordens inre. Genom att studera högtrycksbergarter kan man förstå fjällkedjans bildande. Fjället Tjeliken i norra Jämtland är en av de idag kända fyndplatserna av högtrycksbergarter. Dess topp består av bergarten eklogit och dess lägre delar av gnejs, samt kvarts. Tidigare studier av eklogiten visar att den har bildats vid tryck och temperatur på cirka 2.6 GPa och 700 °C, vilket motsvarar att den varit nedpressad cirka 80 km under jordytan. Den exakta tidpunkten då detta skedde har inte kunnat fastställas då olika dateringsmetoder gett olika resultat mellan cirka 464 till 446 miljoner år sedan. I denna studie studeras tryck- och temperaturförhållanden för gnejsen som jämförelse till eklogiten, för att kunna fastställa om de båda bergarterna har genomgått samma bildningsprocesser. En ny datering genomförs också för att bättre kunna fastställa tidpunkten för högtrycksfasen.Datering baserat på radioaktivt sönderfall av uran till bly i mineralet zirkon visar att högtrycksfasen inträffade för cirka 460 miljoner år sedan. Modellering baserat på termodynamiska principer visar att kärnorna i mineralet granat bildades inom tryck- och temperaturområdet 1.9–2.6 GPa och c. 680-700 °C. En komplex kemisk zonering av granaterna indikerar att de möjligen bildades under flera tillväxtfaser, vilka inom ramen för denna studie inte kunnat modelleras, då mer avancerade metoder krävs. Denna studie visar dock att eklogiten och gnejsen sannolikt delar en gemensam tryck- och temperaturhistoria, vilken är relaterad till den djupa nedpressningen av Baltikas kontinentalkant under sen ordovicium. Dateringen stödjer även övriga åldersdateringar i området av högtrycksfasen.
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Weller, Owen M. "An integrated metamorphic and geochronological study of the south-eastern Tibetan plateau." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:f4104b43-389a-4d54-bd7b-ba3fc0e8ab95.
Full textAbstract:
The Tibetan plateau is a vast, elevated region located in central Asia, which is underlain by the thickest crust known on Earth (up to 90 km). An outstanding question of importance to many fields within geology is how and why did the Tibetan plateau form? Models attribute the growth of the plateau to a consequence of the ongoing India-Asia continental collision, but differ in the details of how the crustal thickening was accommodated: was it by underplating of Indian lower crust or by homogeneous shortening? High-grade metamorphic rocks sampled from the region potentially hold the key to answering this question, as they contain a record of past tectonic events that can discriminate between the various proposed models. This record can be decoded by integrating field, thermobarometric and geochronological techniques, to elucidate a detailed thermotectonic understanding of a region. This methodology was applied to three case studies, each of which targeted rare tectonic windows into the mid-crust of the plateau. These regions comprise Danba in eastern Tibet, Basong Tso in south-eastern Tibet and the Western Nyainqentanglha in southern Tibet. Each case study documents previously unreported metamorphic events that have allowed original interpretations to be made regarding tectonic evolution: in Danba, all metamorphism is shown to be early Jurassic; in Basong Tso, two metamorphic belts are documented that reveal a late Triassic--early Jurassic orogenic event; and in the Western Nyainqengtanglha, Cretaceous--Neogene magmatism is shown to overprint late Triassic metamorphism. Integration of the results has enabled commentary on the large scale evolution of the Tibetan plateau from the Permian until the present day, and even hinted at its future. The results indicate that the closure of the Paleotethys played an important role in the construction of the Tibetan plateau, and suggest that homogeneous crustal thickening is not a viable model for the documented exposure levels.
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Suzuki, Kazuhiro, and Mamoru Adachi. "Th, U and Pb analytical data of monazites and zircons used in the paper ”Middle Precambrian detrital monazite and zircon from the Hida gneiss on Oki-Dogo Island, Japan : their origin and implications for the correlation of basement gneiss of Southwest Japan and Korea”." Dept. of Earth and Planetary Sciences, Nagoya University, 1994. http://hdl.handle.net/2237/2821.
Full text
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Mickey, Jeremiah Lee. "Determining the Laurentide Ice Sheet and Bedrock Provenance of Midwestern Till by Applying U-Pb Geochronology to Detrital Zircons." Thesis, 2019. http://hdl.handle.net/1805/21294.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)A broad range of samples were collected from the Huron-Erie Lobe, Lake Michigan Lobe, Saginaw Lobe, and Tipton Till Plain of northern Indiana to determine the provenance of Laurentide Ice Sheet till in the Midwest U.S. during the Illinoian and Wisconsinan glaciations. U-Pb age distributions from approximately 300 detrital zircons (DZ) were used as provenance indicators for each till sample. Till from the Lake Michigan Lobe and was found to be largely homogenized. The distinct lobe DZ age distributions are the Lake Michigan Lobe till with a dominant ~1465 Ma peak, the northern Huron-Erie Lobe till with a dominant ~1060 Ma and a secondary peak at ~1450 Ma, the southern Huron-Erie Lobe till with nearly equal peaks at ~1435 Ma, ~1175 Ma, and ~1065 Ma, and the southern Saginaw Lobe till with a dominant peak at ~1095 Ma. Those four DZ age distributions were treated as endmembers in a nonlinear least-squares mixing model to calculate the contribution of each lobe to till in the Tipton Till Plain. Huron-Erie and Saginaw lobe tills were found to be the primary components of the Tipton Till Plain, and Lake Michigan Lobe till was only found in the western Tipton Till Plain. Zircons from the Saginaw Lobe till increased 39 % in the eastern Tipton Till Plain between the Illinoisan and Wisconsinan glaciations. The mixing model was also applied to relate the DZ age distributions of the lobes to bedrock within and near their flow paths. When comparing nearby bedrock to each lobe’s till, mixing model results, yield an approximate maximum transport distance between 500 and 630 kilometers for the matrix vii fraction of till in the Lake Michigan, Huron-Erie, and Saginaw lobes. Samples for the southern Huron-Erie Lobe indicate that the most of the zircon ages within the southern Huron-Erie Lobe till in Indiana were specifically entrained between Niagara County, New York and east-central Indiana. Within the model’s error, 93 – 100 % of the detrital zircons in each of the three lobes are relatable to nearby Paleozoic and Precambrian sedimentary and metamorphic bedrock formations.
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Huang, Yi-Chang, and 黃奕彰. "Detrital zircon U-Pb geochronology constraint on the formation age of the Tananao Schist and tectonic implication, Taiwan." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/70825041457560846349.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
103
The Tananao Schist, the oldest rock, exposed at the Backbone Range which consists of marble, schist, gneiss, and subordinate scattered metabasites. According to the stratigraphy and structural analysis, the Tananao Schist in the ascending order can be divided into the Chiuchu Marble, the Kuyuan Schist, the Paiyang Schist, the Tienchang marble, and the Pilu Formation. Based on previous study, depositional age of the Chiuchu Marble is closed to 250±20 Ma(Late Permian). Using zircon U-Pb dating method, magmatic age of gneiss (I-type granite) yields 90- 86 Ma. Depositional age of schist formation was difficult to define because fossils were poorly-preserved. In present study, we try to use detrital zircon U-Pb dating to yield the maximum depositional age of schist. In this study, the youngest weight mean ages of the Paiyang Schist and Pilu Formation in western part of Tailuko belt are 180-135 Ma, which are older than the Kuyuan and Paiyang Schists exposed in eastern part of the Tailuko belt. Based on macroscopic structure of straitigraphy, microscopic structure analysis, and metamorphic facies, stratigraphy in western part of the Tailuko belt is younger than that in eastern part. Source of the Tarluko belt mainly derived from ignous rock of the Mesozoic basement in Taiwan Strait. Stratigraphy in western part of the Tailuko belt lacks younger detrital zircons because of reverse exhumation. The chemical composition of the metabasites of the Tailuko belt was suggested that they were relics of oceanic crust. But in our study, 90-80 Ma metabasite intruded into Chiuchu Marble probability represts for fractions of metabasites of the Tailuko belt might form in origin of continental crust. More detail chemical analysis and examinations are necessary in the future. Results as above mentioned, we explain tectonic setting of the Tananao Schist. Taiwan region was located on passive continental margin and deposited carbonates during late Permian period. The paleo-Pacific plate westward subducted to the Cathaysia Block along continental margin, and the carbonates are metamorphosed to marble since early Jurassic. The subduction related metamorphism is called the Tailuko orogeny. Clastic sediments were unconformably deposited on the Chiuchu Marble during early Cretaceous. At the same time, the island arc migrated from southeastern China to Taiwan Strait because of the retreating arc system. And then, I-type granite and mafic igneous rock intruded into marble and clastic sediments of Taiwan during 90-86 Ma. Afterwards, clastic sediments were deeply buried caused by continuing subduction and metamorphosed. The metamorphic event is known as the Nanao orogeny.
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Trestrail, J. L. "U-Pb detrital zircon, geochemical and Nd isotope constraints on sedimentary provenance of the Chewings Range Quartzite, Warumpi Province, Arunta Region, NT." Thesis, 2010. http://hdl.handle.net/2440/106279.
Full textAbstract:
This item is only available electronically.The Chewings Range Quartzite is a meta-sedimentary cover sequence located in the Warumpi Province of the Arunta Region. U-Pb detrital Zircon analysis of the Chewings Range Quartzite indicates a minimum depositional age of ~ 1640Ma, with the main population of zircons residing within a range of 1700 – 1800Ma. Evidence from Sm-Nd isotopic data suggests that a series of Staurolite Garnet Schists, often grouped with the Chewings Range Quartzite, has a significantly more juvenile character. This suggests that it may represent a new unit with a significantly differing provenance to that of the Chewings Range Quartzite. Combined REE, geochemistry and detrital zircon dating suggests that the Chewings Range Quartzite was derived primarily off the Arunta Region and North Australian Craton, while the Stauralite Garnet Schists holds more affinity with juvenile Musgrave Province to the south.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2010
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Chou, Hsien-Yuan, and 周賢元. "Detrital zircon U-Pb geochronology of the Eocene to Pliocene Series in central Taiwan: Implications for source provenance and exhumation history." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/68841602653829555873.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
101
Detrital zircons collected from sedimentary rocks can find out exhumation history for the U-Pb dating. This study aims to reconstruct the Eocene–Miocene exhumation history of the southeast China by using U-Pb detrital zircon geochronology. The samples were collected from the Eocene-Miocene formation along the Beigang river and the upper Miocene formation from the Daan river. Each sample contains about 80-100 zircons U-Pb dating data with LA-ICPMS. Zircon formed from igneous activity or metamorphism of the source province. U-Pb dates are distributed to several groups according to the major geological movement in southeast China, (1) Wutai orogeny (2400-2600 Ma) (2) Luliang orogeny (1700-1900 Ma) (3) Sibao orogeny (930-1000 Ma) (4) Jinning orogeny (700-850 Ma) (5) Caledonian orogeny (400-450) (6) Indosinian orogeny (200-250 Ma) (7) Early Yanshanian orogeny (200-145) (8) Late Yanshanian orogeny (Ⅰ) (100-145 Ma) and (9) Late Yanshanian orogeny (Ⅱ) (100-65 Ma) (10) continental rifting period (65-8Ma). Age spectrum analyses of the Eocene formation indicates that the major proportion is the Late Yanshanian orogenyⅠgroup, about 12%－22%； the major proportion of the Oligocene formation is the Late Yanshanian orogenyⅠgroup, about 23%－36%； the major proportion of the Miocene formation is the Luliang movement group about 10%－23%. The Major proportion of Yanshanian orogeny (Ⅰ) group shows the increasing in the Eocene to the Oligocene formations, but the decreasing in the Miocene formation means that Late Yanshanian orogeny (Ⅰ) period rock eroded and reduced the exposed area during the Miocene period； The Luliang movement group proportion of Miocene formation data is increasing, and it means that the younger rocks eroded causes older rocks exposed. The youngest zircon age can be a corroboration of sedimentary age of sedimentary rock, 39.3±0.8 Ma of the Eocene formation, 27.4±0.6 Ma of the Oligocene formation, 26.7±0.6 Ma of the Miocene formation that confirms the previous reports of the age of sedimentary rocks. Keywords: Central Taiwan, detrital zircon, U-Pb datimg
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Meaney, Kieran James. "Proterozoic crustal growth in the southeastern Gawler Craton: the development of the Barossa Complex, and an assessment of the detrital zircon method." Thesis, 2017. http://hdl.handle.net/2440/114255.
Full textAbstract:
The Barossa Complex, southeast Gawler Craton, South Australia, forms the southeastern-most exposure of pre-Neoproterozoic crust in Australia. Understanding the geodynamic evolution of this area can improve paleogeographic reconstructions of the economically significant Gawler Craton, as well as global reconstructions in the Proterozoic. The first part of this thesis addresses the geological development of the Barossa Complex during the Palaeo-Mesoproterozoic.
The Barossa Complex is composed of metasedimentary and metaigneous gneisses. These include calcsilicate, quartzofeldspathic, psammopelitic, and pelitic gneisses. In the northern inliers, the protoliths to these gneisses are indicative of a progressively deepening basin. Syndepositional felsic orthogneisses and mafic amphibolites indicate a tectonically active basin.
Deposition of the metasedimentary protoliths to the Barossa Complex occurred between 1730-1655 Ma, synchronous to the onset of the Kimban Orogeny in the Gawler Craton and the deposition of the Willyama Supergroup in the Curnamona Province. U-Pb and Hf isotopic analyses from detrital zircon indicates sediment was largely derived from the Gawler Craton. Syndepositional granite intrusions occurred in the northern extent of the Barossa Complex at 1717 ±7 Ma.
Metamorphism initiated in the Barossa Complex at c. 1630 Ma with the development of a low angle metamorphic fabric. Peak granulite conditions of approximately 8-9 kbar and 800-850 °C occurred at c. 1590 Ma in the southern Barossa Complex. The northern Barossa Complex preserves lower grade metamorphic features and c. 1600 Ma zircon with hydrothermal Rare Earth Element (REE) signatures, which are potentially linked to the Hiltaba event in the Gawler Craton. Post peak metamorphism continued until c. 1550 Ma and is associated with retrograde shear zones in the southern Barossa Complex, and late pegmatites in the northern inliers.
The Barossa Complex shares a depositional and metamorphic history with the Willyama Supergroup in the Curnamona Province and Mt. Isa Inlier basin sequences, and was part of a transcontinental plate margin system during the Late Palaeo- Early Mesoproterozoic. East dipping subduction was the likely driver for extensive rift basin development across the eastern margin of Proterozoic Australia before the Isan-Olarian Orogeny inverted these basins. The Barossa Complex is the southern-most exposure of this system.
The second part of this thesis addresses the use of detrital zircon in modern sediment as a means of characterising the bedrock of a catchment area, which has been used previously in the Gawler Craton and Curnamona Province.
In the Broken Hill area of the Curnamona Province, stream sediments were sampled from drainage pathways with catchments that have stratigraphically and chronologically well characterised bedrock lithologies. Zircon ages from the modern sediment found up to 30% of the zircons were significantly younger than what expected from the bedrock sources (>1.6 Ga). Aeolian dune sands from the Strzelecki Desert to the north of the study area are found to contain zircon with U-Pb and Lu-Hf isotopic compositions matching the ‘exotic’ zircon populations in Broken Hill. Aeolian detritus is considered to have contributed zircon to the stream sediments in Broken Hill, and should be considered in any study utilising modern detritus in arid environments. Detrital zircon provenance studies of the geological record should be interpreted cautiously if aeolian input may have occurred.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 2018
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Kolesik, P. "U–Pb geochronology of volcano–sedimentary moraine sediments of the Bunger Hills: implications for Mesoproterozoic evolution of East Antarctica." Thesis, 2016. http://hdl.handle.net/2440/120941.
Full textAbstract:
This item is only available electronically.The Bunger Hills and adjacent areas of Wilkes Land and Queen Mary Land occupy the very western periphery of the Musgrave–Albany–Fraser Orogen, and represent one of the few exposures within east Antarctica with direct correlations to Australian constituent terrains of this continental-scale system. U–Pb analyses of detrital zircons from volcano–sedimentary moraine sediments of the Bunger Hills yield concordant 206Pb/238U ages ranging from ca. 1364 Ma to ca. 1040 Ma (n = 842), with a main late Mesoproterozoic magmatic zircon population clustered at ca. 1179–1161 Ma. Strong parallels with the time profile of in-situ rocks from the Stage 2 Albany–Fraser Orogen (AFO), the Bunger Hills and Windmill Islands, suggest these were the likely provenances for the associated moraine detritus. The Bunger Hills lie downstream from outcrops of the geographically inaccessible Sandow Group, which comprises clastic and mafic volcanoclastic rocks. It is interpreted that the sedimentary moraine materials of the Bunger Hills were derived from the glacial erosion of the Sandow Group supracrustal successions. The lithological character, sedimentary fill pattern and advanced diagenesis suggest that the Sandow Group formed within an active intra-continental rift-basin and represents the upper-crustal expression of extensional tectonism. Reconnaissance U–Pb geochronology of authigenic titanite suggests basin development occurred close to or within the time frame of the high-grade metamorphism recorded in the Bunger Hills. Therefore basin development was probably directly associated with the second major thermo–tectonic phase of the AFO (Stage 2; ca. 1215–1140 Ma). Due to the essentially non-metamorphosed volcano–sedimentary nature of the detritus in the sedimentary rocks, it seems likely that the evolving Mesoproterozoic orogenic system was not deeply exhumed during basin development.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016
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Li, Shih-Chuan, and 李時全. "Detrital zircon U-Pb geochronology of the Late Miocene-Pleistocene formations in the Northern Taiwan to source provenance and the unroofing history of Taiwan orogenic belt." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/qxs4s7.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
106
Lithostratigraphy, magnetostratigraphy, depositional environment and sandstone compositions of foreland basin deposits in western Taiwan, from late Miocene to Pleistocene strata, have been systematically researched. According to the petrographic studies of foreland basin deposits, sedimentary provenance originated from southeastern China (the Cathaysia Block) in Eocene-Miocene, but progressively switched to Taiwan orogenic belt due to the arc-continental collision since late Miocene (~6.0 Ma). Furthermore, the Hsuehshan Range and the Western Foothills were uplifted and eroded in sequence during Pliocene to Pleistocene. In this study, we focus on detrital zircon U-Pb dating and petrographic analysis of sandstones collected from late Miocene to Pleistocene strata, aiming to understand the origin of sedimentary provenance and the exhumation history of the western flank of Taiwan orogenic belt. The results of petrography show that sedimentary and low-grade metamorphic lithics fragments gradually increased from late Miocene to Pleistocene in sequence. In addition, the detrital zircon U-Pb age populations of late Miocene-Pleistocene strata are similar to those of Eocene-Miocene strata, suggesting that the synorogenic sediments from late Miocene to Pleistocene were derived from the orogenic belt. Based on the characteristics of U-Pb ages, lithology and metamorphic grade of Eocene-Miocene strata, we classified the provenances into Eocene, Oligocene and Miocene formations. We utilize statistical analysis to quantify the proportion of the exposed provenances of each sample, which can reveal the relation between source and sink thoroughly. In northern Taiwan, the Hsuehshan Range was uplifted during late Miocene. Foreland basin received the sediments from the Miocene strata of Hsuehshan Range since Pliocene. During early Pleistocene (2.6-2.3 Ma), Oligocene strata of Hsuehshan Range started to expose and had 1-9% proportion among the source area. Subsequently, Oligocene strata widely exposed after 2.3 Ma (with 17-40% proportion among the source area). The drainage system have begun to carry the sediments from Eocene strata of Hsuehshan Range (1-9% proportion among the source area) since late Pleistocene (~1.46 Ma). After that, Eocene strata widely exposed (with 28% proportion of the source area) in the meantime as Linkou formation deposited. In central Taiwan, the Hsuehshan Range was also uplifted during late Miocene. Foreland basin also received the sediments from the Miocene strata of Hsuehshan Range since Pliocene. During early Pleistocene (2.1-1.0 Ma), Oligocene strata of Hsuehshan Range started to expose and had 5-15% proportion among the source area. Eocene strata of Hsuehshan Range started to widely expose since late Pleistocene (~1.0 Ma) with 46% proportion among the source area. During 1.0-0.7 Ma, the sum of proportion of Eocene and Oligocene strata gradually decreased (from 60% to 23%), in converse, proportion of Miocene strata gradually increased (from 40% to 77%), which suggested that the Miocene strata of Western Foothills were widely eroded. According to the statistical analysis of the upper Toukoshan deposit (~0.7-0.3 Ma), the proportion of the provenances were similar to the framework of mountain nowadays.
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Al-Kiyumi, M. "Constraining the age and provenance of the basal quartzites of the Centralian Superbasin." Thesis, 2018. http://hdl.handle.net/2440/130321.
Full textAbstract:
This item is only available electronically.The Heavitree Formation of the Amadeus Basin, central Australia, is thought to correlate with a number of similar formations in the Officer, Ngalia, Georgina and Murraba Basins that formed the Centralian Superbasin. The Jasper Gorge Formation of the Victoria Basin and Jamison Sandstone of the Beetaloo Sub-basin are also thought to be corollaries. These formations are all constrained to being younger than ca. 1.0 Ga by U-Pb detrital zircon studies. However, in all cases, this is suspected to considerably pre-date the timing of deposition. Here, we present new U-Pb and Hf data from seven samples of the Amadeus Basin Heavitree Formation to a) better constrain the age of the Heavitree Formation, b) investigate the spatial variation in provenance of the Heavitree Formation, and, c) compare it with other ‘Supersequence 1’ quartzites from the wider Centralian Superbasin.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018
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楊智宇. "Detrital Zircon U-Pb Age Study of the Guizhulin Formation in Miaoli." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/98271288484313183935.
Full textAbstract:
碩士國立臺灣師範大學
地球科學系
101
The sediments of the Kueichulin Formation were deposited during Late Miocene to Early Pliocene. This formation should be able to shed some lights on the records of the transition from passive margin to foreland basin sedimentary environment in western Taiwan. This study presents U–Pb dating results of detrital zircons by single collector Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer (LA-ICP-MS) to investigate the evolution of sedimentary source region during the deposition of the Kueichulin Formation near Chuhuangkeng Anticline in Miaoli. Samples were collected all the way from the Miocene Peiliao Sandstone to the Pliocene Chinshui Shale. The U-Pb dating of zircons from the Early Miocene Peiliao Sandstone to the Late Miocene Tongken Fomation display age spectra with similar major peaks at 95-165 Ma, 200-250 Ma, and 750-850 Ma. Then U-Pb dating of zircons from the terminal Miocene Shangfuchi Sandstone and Kuantaoshan Sandstone shows similar age spectra with peaks of 90-190 Ma and 200-250 Ma, which suggest that sediment supply should have changed since the terminal Miocene. According to the correlation with detrital zircon age spectra of possible sources, sediment supply of Miocene formations with abundant Proterozoic zircons should have come from the Cathaysia basement. On the contary, for that of the terminal Miocene formations, the sources would have dominantly derived from Yanshanian and granitic plutons in East Cathaysia. The results of this study suggest that the Shangfuchi Sandstone and Kuantaoshan Sandstone should have been deposited in the initial arc-continent collision between Luzon Arc and Eurasian passive continental margin. The arc-continental collision might have induced a sudden increase of the depositional slope which may have led of the noticeable change of sediment source in the terminal Miocene.
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Hsu, Chun-Chieh, and 許鈞傑. "Detrital Zircon U-Pb and Hf Isotopic Study in Northwestern Sumatra, Indonesia." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/25561429169923275462.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
104
In NW Sumatra, Tertiary sedimentary basins that occur in forearc and backarc settings with respect to the present-day subduction system were deposited in three major terranes, namely, the Woyla Nappe, the East Sumatra block, and the West Sumatra block. NW Sumatra represents the product of complex accretion/collision/subduction histories among these three terranes, which have originated from the eastern margin of Gondwanaland. To better understand the complex histories, we present a detrital zircon study in NW Sumatra that, together with our unpublished work on major magmatic rocks in the area, allow us to reach the following conclusions: (1) Detrital zircons from 14 samples (river sand or sandstone) in the forearc basin reveal seven age peaks at ~1050 Ma (n=74), ~550 Ma (n=65), ~214 Ma (n=138), ~131 Ma (n=14), ~100 Ma (n=65), ~52 Ma (n=238) and 17-0 Ma (n=303), respectively; (2) Detrital zircons from nine samples in the backarc basin show similar age populations; (3) The Late Triassic zircons, with εHf(T) values of -18 to 0, are sourced mainly from the Indosinian granitoids that are widespread in the East Sumatra block; (4) The less abundant Early Cretaceous zircons, with εHf(T) values of -5 to 0, are most likely from the West Sumatra block; (5) The Late Cretaceous zircons, with εHf(T) values of +11 to +16, are from the Woyla Nappe due probably to the Woyla accretion; (6) The Eocene and younger zircons, with εHf(T) values of +6 to +17, are from the initial stage and modern arc magmatic rocks related to the Indian Ocean plate subduction.
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Zul, Zugeerbai, and 李瑞清. "Detrital Zircon U-Pb Age Study of the Paleozoic－Mesozoic Sedimentary Rocks, Southwestern Fujian." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/16271485870090207846.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
99
Abstract The study is in located in the Southwest of Fujian Province, sandstone samples were collected from the Cambrian to Ordovician metamorphic rocks, and the Devonian to Jurassic sedimentary rocks. Detrital zircons of the Paleozoic-Mesozoic strata rocks were separated from10 samples by LA-ICP-MS measurements for U-Pb dating. The Southern China region undergo several plate collision, results in many phase tectonic activities, causing the variabilities of sequence stratigraphy, tectonic, and sedimentary environment. Result from the U-Pb dating, it indicates that the Jinning orogeny, Caledonian orogeny, Indosinian and Yanshanian magmatic detrital zircons re-accumulation of geological sigifcance. The comparison of these tectonic movements Caledonian, Indosinian and Yanshanian seems to slightly change of detrital zircon ages. The detrital zircon age assemblidge of Caledonian indicates that ＞2400 Ma (Wutai movement), 1700-1000 Ma, 1000-930 Ma (Sibao movement) higher proportion of about 95%. Some of igneous zircons deposite in the time without tectonic movement (1700-1000Ma). This study suggests that there remain sporadic igneous activity, such as the 750-450 Ma can be found in Fujian province during the sporadic distribution of igneous rocks. From the Caledonian movement and after, because nearly 40% from this period of igneous detrital zircons , with the result ＞750 Ma detrital zircons significantly reduced the proportion of the total, but this period is ＞2400 Ma and 850-750Ma for proportion of detrital zircon and more. The reason is Caledonian movement may cause the early Paleozoic, and Sinian strata exposed, resulting in 750-450 Ma and 850-750 Ma a higher proportion of the old in ＞2400 Ma detrital zircons more reasons, this study still can’t explain. Indosinian movement period, ＞750 Ma detrial zircon tended to decrease, probably a lot of volcanic rocks covering the surface gradually caused. But Indosinian movement 1900-1700 Ma (Luliang movement) the proportion of detrital zircons have a very high proportion of about 18%; Luliang movement is the main formation period the Catashyia, constitute the main base Catashyia, now exposed in Fujian northwest region, knows as Mayuan group. During the Indosinian movement, South China region the formation of large areas fault and folding result in a large basement area Cathaysia exposed surface, and become the main source.
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Lin, Hong-Chih, and 林虹志. "Detrital zircon U-Pb dating of the Tananao Schist in the Nanao region, eastern Taiwan." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/86627721517341739464.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
104
The Tananao Schist exposed from Dongao to Nanao region is located in the northern part of the eastern limb of Central Range. The lithological characters include quartz-mica schist, metachert, black schist, thin layer of marble, green schist, amphibolite, and gneiss. The Tananao Schist experienced the Nanao Orogeny and Penglai Orogenies. It is difficult to identify the relationships between various schists due to the above-mentioned two orogenies buy reginal metamorphism. In addition, previous studies provided insufficient information of fossil records and dating in the Tananao schist; therefore, it is very difficult to diseriminal the stratigraphic sequerence of these schists. Accordingly, zircon U-Pb dating was used to analyze the quartz-mic schist, green schist, metachert, and gnesiss in this study and determine the stratigraphic age. This study can help us to unravel the tectonic environment of the Tananao schist in Dongao and Nanao region. We analyzed 24 samples and obtain the results of the detrital zircons U-Pb youngest age. In assumption, we could discover the youngest age of detrital zircon of the sedimentary rock in oringal, as if we could find simultaneously igneous rocks that eroded and replaced in the same age. The schists from Dongao Schist, Nanaoling Schist, and Wuta Schist all have some common features such as the sedimentary rocks from the late Cretaceous as well as some other aged. The youngest depositional age is 75±2 Ma among various layer ages. The age may be presented a tectonic mélange in origen. During the late Mesozoic, the Paleo-Pacific Plate subducted beneth to the Cathaysia Bolck. The Paleo-Pacific oceanic plate has been squeezed and ruptured, withing the subduction zone, all different layers from different ages then have been mixed together such as amphibolite, marble, metamorphic rock, meta-volcaniclastic rock, quartz-mica schist, and green schist. Hence, it is suggested that the schists was situated in a tectonic mélange until 75 Ma at least.