Thèses : « Pb zircon age »

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TADESSE, Tarekegn, Kazuhiro SUZUKI et Mitsuo HOSHINO. « Chemical Th-U-total Pb isochron age of zircon from the Mereb Granite in northern Ethiopia ». Dept. of Earth and Planetary Sciences, Nagoya University, 1997. http://hdl.handle.net/2237/2833.

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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. Hepburn
Thesis 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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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 Hepburn
The 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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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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Gärtner, Andreas. « Geologic evolution of the Adrar Souttouf Massif (Moroccan Sahara) and its significance for continental-scaled plate reconstructions since the Mid Neoproterozoic ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-234103.

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Located in the south of the Moroccan Sahara, the Adrar Souttouf Massif is the northern continuation of the Mauritanides at the western margin of the West African Craton. The massif itself exhibits a complex polyphase geologic history and contains four geologically different, SSW-NNE trending main units named from west to east: Oued Togba, Sebkha Gezmayet, Dayet Lawda, Sebkha Matallah. They are thrusted over each other in thin-skinned nappes with local windows of the discordantly overlain Archaean Reguibat basement. The eastern margin of the massif is bordered by the Tiris and Tasiast-Tijirit areas of the Reguibat Shield as well as its (par-) autochthonous Palaeozoic cover sequence, termed Dhloat Ensour unit. More than 5.500 U-Th-Pb age determinations and over 1.000 Hf isotopic measurements on single zircon grains from igneous, metamorphic, and sedimentary rocks of all the massifs units and its vicinity have yet been obtained. Most of the zircons were studied with respect to their morphological features. This method improves the accuracy of provenance studies by detecting varying zircon morphologies in space and time. These data are accompanied by U-Th-Pb age determinations on apatite as well as rutile. Together, they allow proposing a model of the geologic evolution of this poorly mapped area for the last 635 Ma. A combination of the obtained data with extensive zircon age databases of the surrounding cratons and terranes facilitates continental-scaled palaeogeographic reconstructions. Regarding the geologic evolution of the Adrar Souttouf Massif, the assembly of the first units began prior to 635 Ma. Although containing all the major zircon age and Hf-isotope populations of the West African Craton as well as some Mesoproterozoic grains, the Sebkha Gezmayet unit lies to the west of the Dayet Lawda unit of oceanic island arc composition. Hence, the Sebkha Gezmayet unit must have been rifted away from the craton prior to the formation of the oceanic unit within the West African Neoproterozoic Ocean at about 635 Ma. Recently published Hf and zircon age data of this unit suggest that the island arc was derived from a juvenile mantle source. Subsequently, the accretion of precursors of the Oued Togba and Sebkha Gezmayet units as well as a partial obduction of the oceanic Dayet Lawda unit and the Neoproterozoic sediments of a foreland basin (Sebkha Matallah unit) onto the Reguibat Shield took place. Peak metamorphism in the obducted oceanic rocks was reached at about 605 Ma. Magmatism in the western units between 610 and 570 Ma suggests on-going tectonic activity. The Early and Middle Cambrian is characterised by the erosion of the Ediacaran orogen and deposition of thick sedimentary sequences at the Sebkha Matallah unit, which acted as foreland basin. These sediments show a mostly West African zircon record with only some Mesoproterozoic grains provided by the westernmost parts of the massif. Initial rifting of the Oued Togba and Sebkha Gezmayet units from the remaining areas presumably occurred during the Late Cambrian. Coeval granitoid intrusions occurred on both sides of the rift. The two rifted units were likely involved to the polyphased Appalachian orogenies, which is emphasised by Devonian magmatism. Thus, and with respect to the isotopic data, the Oued Togba unit is interpreted to be of Avalonia affinity, while the Sebkha Gezmayet unit can likely be linked to Meguma. The units which remained at the West African Craton underwent intense sediment recycling during the entire Ordovician to Devonian times. Final accretion of all units and formation of the current massif was achieved during the Variscan-Alleghanian orogeny. This was accompanied by magmatism in the Sebkha Gezmayet unit and intense metamorphism of the Reguibat basement, whose zircons often show lower discordia intercepts of Carboniferous or Permian age. The post-Variscan period is characterised by erosion of the orogen and subjacent alternating cycles of sedimentation and deflation. The Adrar Souttouf Massifs importance for palaeogeographic reconstructions is given by the striking differences in the zircon age and Hf-isotope record of its westernmost Oued Togba unit and the remaining area. The results obtained from the Oued Togba unit resemble the published data of the Avalonia type terranes including prominent Mesoproterozoic, Ediacaran-Early Cambrian, as well as Early Devonian age populations. Many Mesoproterozoic zircons, which are exotic for the West African Craton prior to 635 Ma, form a ca. 1.20 to 1.25 Ga age peak that is an excellent tracer for detrital provenance studies and source craton identification of the sedimentary rocks. This is also valid for some sedimentary samples that do not show ages younger than 700 Ma, but large quantities of Mesoproterozoic zircon. These rocks can be correlated to similar sediments in Mauritania and W-Avalonia and are thought to be of pre-pan-African", i.e. pre-Ediacaran or even pre-Cryogenian age. They may give direct insights to the source area in Early to Mid Neoproterozoic times. Accordingly, comparison with published data of Amazonia and Baltica, allows setting up new hypotheses for the pre-Ediacaran history of the Avalonian type terranes. Lacking of magmatism in Amazonia between ca. 1200 and ca. 1300 Ma favours Baltica as source craton for the Avalonian terranes and requires a new point of view for the Neoproterozoic palaeogeography.

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Luo, Yan, et 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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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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Zeng, Wen. « The evolution of the metamorphic series in the NW Fujian Province, the NE Cathaysia Block, and the significance in the reconstruction of Precambrian Supercontinents ». Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1091.

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This thesis focuses on the Paleoproterozoic to Late Paleozoic basement evolution of the metamorphic rocks scattered in the NW Fujian Province, the NE Cathaysia Block the southeastern area of South China. Field observation, systematic sampling and petrographic investigation combined with of whole rock geochemistry, zircon U-Pb, Lu-Hf isotopes, trace elements, amphibole and biotite 40Ar/39Ar analyses and mineral chemistry study were applied in this project to determine the nature, ages and relations of the leucosomes, felsic paragneiss and mafic metamorphic rocks in study area and their implications to the reconstruction of the Precambrian Rodina Supercontinent.Following conclusions are made: 1. Based on this study, according to their metamorphism and deformation characteristics, the metamorphic rock series in the study area can be divided into two types, moderately to strongly metamorphosed rock series that experienced ductile deformation and moderately metamorphosed rock series that have experienced ductile deformations. New La-ICPMS U-Pb zircon ages presented here and in previous study suggest that the original lithostratigraphy should be abandoned and the terminology “Complex” should be used instead of “Group” and “Formation” for the high grade metamorphic rock series in northwestern Fujian, where the protoliths were strongly reworked by Early Paleozoic tectono-thermal events.2. Obvious zircon U-Pb age peaks of ~1800 Ma suggest that the protoliths ofthe Cathaysia Block be comparable to the basements of North America ratherthan those of Eastern India and East Antarctica. Although the peaks of ~1800Ma are also present in Western Australia, their 176Hf/177Hf ratios (0.280706 -0.281510) are apparently lower than those of zircons from SW Cathaysia (0.281515 - 0.282098) and from this study (0.281232 - 0.282213, NECathaysia). Besides, detrital zircons in Cathaysia and NW Yangtze indicatesignificant juvenile input during Paleo- to Mesoproterozoic according to thezircon Hf isotopes, which are distinctly different from Western Australia.These evidences suggest that the basement of the Cathaysia share similaritieswith that of North America, lending support for the Rodinia configurationproposed by Li et al. (2008), in which Cathaysia was next to western Laurentia before and during the late Mesoproterozoic assembly of Rodinia.2. Obvious zircon U-Pb age peaks of ~1800 Ma suggest that the protoliths of the Cathaysia Block be comparable to the basements of North America rather than those of Eastern India and East Antarctica. Although the peaks of ~1800 Ma are also present in Western Australia, their 176Hf/177Hf ratios (0.280706 - 0.281510) are apparently lower than those of zircons from SW Cathaysia (0.281515 - 0.282098) and from this study (0.281232 - 0.282213, NE Cathaysia). Besides, detrital zircons in Cathaysia and NW Yangtze indicate significant juvenile input during Paleo- to Mesoproterozoic according to the zircon Hf isotopes, which are distinctly different from Western Australia. These evidences suggest that the basement of the Cathaysia share similarities with that of North America, lending support for the Rodinia configuration proposed by Li et al. (2008), in which Cathaysia was next to western Laurentia before and during the late Mesoproterozoic assembly of Rodinia.3. The protoliths of the felsic paragneiss in the NW Fujian area are immaturesediments, consisting of greywacke, arkose and lithic arenite compositions.The significant input of the paragneiss protolith was dominantly formed byseveral magmatic events during Neoproterozoic (820 ± 6 Ma, 780 ± 6 Ma, 776± 6 Ma, 758 ± 3 Ma, 740 ± 8 Ma and 722 ± 9 Ma), probably deposited notearly than middle Neoproterozoic (~680 Ma). Many metamorphic rockscontain 0.99 - 0.72 Ga detrital magmatic zircons, which are interpreted asreflecting the tectono-thermal events related to the assembly and break-up of the Rodinia supercontinent during the Neoproterozoic.4. In this study, new La-ICPMS U-Pb anatectic zircon data from the NWFujian area suggest that the strong and widespread tectono-thermal eventswere related to the orogeny probably having started during the MiddleCambrian and lasted until the Middle Devonian, consisting of at least threemain episodes (~473 Ma, ~445 Ma, ~423 Ma), with major orogeny events(including syn- to post-orogenic melting) constrained between ~473 Ma and~407 Ma in the NE Cathaysia, and between ~468 Ma and ~415 Ma in the SWCathaysia. The age peaks in the Cathaysia Block (ca. 488, 471, 455, 440 and415 Ma) are within the age range of the Qinling-Tongbai-Dabie orogen during 512 - 406 Ma. This suggests a possible linkage or interaction of the two orogens.5. The duration of the “Caledonian” orogeny in the NW Fujian area was noshorter than ~50 Myr, starting at ~473 Ma (~Early Ordovician) or earlier, andterminating at ~423 Ma (~Middle Silurian) or later. The “Caledonian”orogenic event in the Cathaysia Block was likely due to an intracontinentalcollision rather than the subduction of oceanic crust or arc-continentalcollision. Considering the inhomogeneous cooling paths for the Tianjingping,the Jiaoxi and Mayuan complexes, and different time restraint of thewidespread anatectic and magmatic events occurred in different places, the“Caledonian” tectono-thermal events in the Cathaysia Block might vary between different segments of the orogen.

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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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D'ADDA, PAOLO. « Eo-alpine evolution of the central southern alps. Insights from structural analysis and new geochronological constraints ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/19018.

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The timing of the Alpine deformation in the Central Southern Alps (CSA or Orobic Alps) has always been a debated topic, since the scarcity of reliable absolute age constraints has prevented an accurate chronological reconstruction of the evolution of this sector of the European Alps. In this work, detailed structural analyses performed in different areas of the CSA allowed us to distinguish different compressive features within both the crystalline basement and the sedimentary cover. The integration of these field data with new isotopic data provides time constraints for the reconstruction of the evolution of the CSA during the Alpine orogeny. In the northern sector of the belt a Variscan polymetamorphic basement is stacked southward on the Permian to Mesozoic cover along two main regional faults (Orobic and Porcile thrusts). Fault zones, slightly postdating a first folding event of Alpine age (D3), experienced a complex evolution through the ductile and brittle deformation regime, showing greenschists facies mylonites overprinted by a penetrative cataclastic deformation (D4). Generation of fault-related pseudotachylytes marks the onset of brittle conditions, lasting up to the youngest episodes of fault activity. Thrusting along this structures also produced thrusting within the Permian-Triassic cover with the formation of different south-verging thrust stacks. This first thrusting event was followed by the activation of new deeper thrust surfaces leading to the emplacement of three regional anticlines (Orobic Anticlines) which tilted to the south the previously stacked units. During this long compressive stage (Orobic-Porcile thrusts and Orobic Anticlines) the sedimentary cover of the CSA was also involved in thrusting and different stacks of Mesozoic units were emplaced to the south. 40Ar/39Ar dating of the pseudotachylyte matrix of 9 samples from both the Orobic and Porcile thrusts give two separated age clusters: Late Cretaceous (80-68 Ma) and Early to Middle Eocene (55-43 Ma). These new data provide evidence that the pre-Adamello evolution of the CSA was characterized by the superposition of different tectonic events accompanying the exhumation of the deepest part of the belt through the brittle-ductile transition. The oldest pseudotachylyte ages demonstrate that south-verging regional thrusting in the CSA was already active during the Late Cretaceous, concurrently with both the HP metamorphism that affected the Austroalpine units of the eastern Alps, and the development of a syn-orogenic foredeep basin where the Upper Cretaceous Lombardian Flysch was deposited. In the Early to Middle Eocene a minor reactivation of the Orobic and Porcile thrusts occurred, as testified by the youngest pseudotachylyte ages obtained by 40Ar/39Ar dating. This event was probably related with the closure of the Ligurian-Piedmont and the ongoing of the Europe-Adria collision. South of the Orobic Anticlines system the Triassic sedimentary succession is stacked into several units bounded by south-verging low-angle thrust faults, which are related to different steps of crustal shortening. Different thrust stacks occur within the Triassic cover between the Como Lake to the west and the Adamello batholith to the east. They usually have an antiformal arrangement and are separated by each other by different N-S trending transverse zones, such as the poorly known Grem-Vedra Transverse Zone (GVTZ), formed during complex deformational phenomena in a transpressional regime coeval with thrust emplacement. The GVTZ formed during the southward imbrication of the older thrust sheets of the Menna-Arera group, strongly interacting with syn-thrust ductile structures, and was reactivated during the growth of the Orobic Anticlines belt. The GVTZ and other transverse zones of the CSA probably reflect the occurrence of pre-existing fault systems that characterize the Norian to Jurassic rifting history of the Lombardian basin, and were reactivated as strike-slip features during Alpine tectonics. In the Gandino and Presolana areas thrust surfaces are cut by high-angle extensional and strike-slip faults, which controlled the emplacement of hypabissal magmatic intrusions that post-date thrusts motions. Intrusion ages based on SHRIMP U-Th-Pb zircon dating span between 42±1 and 39±1 Ma, suggesting close time relationships with the earliest Adamello intrusion stages and, more in general, with the widespread calc-alkaline magmatism described in the Southern Alps. Fission track ages of magmatic apatites are indistinguishable from U-Pb crystallization ages of zircons, suggesting that the intrusion occurred in country rocks already exhumed above the partial annealing zone of apatite (depth < 2-4 km). These data indicate that the northern and central sectors of the CSA were already structured and largely exhumed in the Middle Eocene and no major internal deformations has occurred in these areas after the Bartonian. Neogene deformations were instead concentrated further south, along the frontal part of the belt (Milano Belt). These new data provide a direct evidence that thrusting and nappe stacking were active during Late Cretaceous times not only in the Eastern Alps, but also in the CSA, significantly extending southward the sector of the Alpine belt affected by the Cretaceous orogenic event. In this view, the Late Cretaceous Southern Alps can be interpreted as the south-verging retrobelt of a pre-collisional orogenic wedge, which formed during the subduction of the Alpine Tethys beneath the attenuated northern Adria margin.

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Guerin, Gwénaël. « Contraintes cinématiques et thermiques de l'évolution des "metamorphic core complexes" du SE Arizona (Santa Catalina-Rincon) ». Rennes 1, 1988. http://www.theses.fr/1988REN10130.

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Ces domes metamorphiques de la province bassin and range sont significatifs de la deformation de la croute ductile pendant l'extension tertiaire et de nombreux modeles d'extension intracontinentale furent proposes. Il est demontre la presence d'un epaississement important ante-extension lie a l'orogenese sevier laramienne, il apparait donc que les modalites d'extension risquent d'etre controlees par l'evenement compressif. Cette etude structurale a permis de differencier 3 deformations ductiles, et des datations u-pb sur zircon ont permis de reconstituer la chronologie des evenements. Une compilation des donnees geochronologiques retrace l'evolution temperature-temps

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Gruber, Leonardo. « Geocronologia U-Pb em Zircão Detrítico aplicada ao estudo de proveniência de metassedimentos do Complexo Metamórfico Porongos – Região de Santana da Boa Vista, RS ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/56342.

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Estudos de proveniência em zircões detríticos através do método U-Th-Pb (LA-ICP-MS) dos metassedimentos do Complexo Metamórfico Porongos determinaram a existência de duas áreas-fontes principais de onde derivaram idades paleoproterozóicas e mesoproterozóicas para os xistos Arroio Areião, Cerro Cambará e quartzo milonitos associados. Foram obtidas idades entre 967 ± 15 Ma e 2454 ±26 Ma para a seqüência Arroio Areião, entre 894 ± 30 Ma e 2783 ± 18 Ma para a seqüência Cerro Cambará, e idades entre 1621 ± 16 Ma e 3185 ± 117 Ma para os quartzo milonitos associados. A área fonte com idades paleoproterozóicas pode ser correlacionada ás rochas do Complexo Encantadas, que faz parte do embasamento das unidades supracrustrais. As áreas-fontes para os zircões mesoproterozóicos (entre 967 e 1621 Ma) não foram ainda reconhecidas no Cinturão Dom Feliciano. Estes zircões podem ser derivados de associações de rocha pertencentes aos cinturões mesoproterozóicos (orogêneses Elzeverian e Greenville), associados ao sistema geodinâmico que incluí os crátons Amazonas, Kalahari, Congo – São Francisco e Laurencia e cinturões associados. O ambiente geotectônico de formação da paleobacia Porongos é compatível com a margem passiva, onde se estabeleceu um arco magmático. Este trabalho demonstra que do ponto de vista isotópico e estratigráfico, não existem diferenças significativas de idades detríticas entre as seqüências metassedimentares que afloram nos flancos da Antiforme de Santana da Boa Vista.
Provenance studies based upon detritic zircon grain U-Th-Pb methodology (LA-ICP-MS) from metasediments of Porongos Metamorphic Complex have determined the existence of two principal source-areas with paleoproterozoic and mesoproterozoic ages to the schists of Arroio Areião, Cerro Cambará and associated quartz mylonites. Where obtained ages between 967 ± 15 Ma and 2454 ±26 Ma to the Arroio Areião sequence, between 894 ± 30 Ma and 2783 ± 18 Ma to Cerro Cambará sequence, and 1621 ± 16 Ma e 3185 ± 117 Ma to the associated quartz mylonites. The source-area with paleoproterozoic ages can be related to the Encantadas Complex rocks, which is basement of the supracrustal sequences. The source-areas to the mesoproterozoic zircons (between 967 and 1621 Ma) are not recognized in the Dom Feliciano Belt. These zircons can be related to mesoproterozoic petrotectonic associations (Greenville and Elzeverian orogens) associated to the geodynamic system that includes the Amazon, Kalahari, Congo – São Francisco and Laurentia cratons, and associated belts. The tectonic environment of Porongos paleobasin it’s compatible with a passive margin, after where established a magmatic arc environment. This work shows that from isotopic and stratigraphyc point of view there is no significantly differences between the metasedimentary sequences cropping out in both Santana da Boa Vista antiform flanks.

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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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Wilson, John Robert. « U/Pb Zircon Ages of Plutons from the Central Appalachians and GIS-Based Assessment of Plutons with Comments on Their Regional Tectonic Significance ». Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35248.

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The rocks of the Appalachian orogen are world-class examples of collisional and extensional tectonics, where multiple episodes of mountain building and rifting from the pre-Cambrian to the present are preserved in the geologic record. These orogenic events produced plutonic rocks, which can be used as probes of the thermal state of the source region. SIMS (secondary ion mass spectrometry) U/Pb ages of zircons were obtained for ten plutons (Leatherwood, Rich Acres, Melrose, Buckingham, Diana Mills, Columbia, Poore Creek, Green Springs, Lahore and Ellisville) within Virginia. These plutons are distinct chemically, isotopically, and show an age distribution where felsic rocks are approximately 440 Ma, and Mafic rocks are approximately 430 Ma. Initial strontium isotopic ratios and bulk geochemical analyses were also performed. These analyses show the bimodal nature of magmatism within this region. In order to facilitate management of geologic data, including radiometric ages, strontium isotope initial ratios and major element geochemistry, a GIS based approach has been developed. Geospatially references sample locations, and associated attribute data allow for analysis of the data, and an assessment of the accuracy of field locations of plutons at both regional and local scales. The GIS based assessment of plutons also allows for the incorporation of other multidisciplinary databases to enhance analysis of regional and local geologic processes. Extending such coverage to the central Appalachians (distribution of lithotectonic belts, plutons, and their ages and compositions) will enable a rapid assessment of tectonic models.
Master of Science

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Yihunie, Tadesse. « Chemical Th-U-total Pb isochron ages of zircon and monazite from granitic rocks of the Negele area, southern Ethiopia ». Dept. of Earth and Planetary Sciences, Nagoya University, 2003. http://hdl.handle.net/2237/7624.

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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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Liu, Chaohui, et 刘超辉. « Paleoproterozoic basins in the Trans-North China Orogen : stratigraphic sequences, U-PB ages and HF isotopes of detritalzircons and tectonic implications ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47163902.

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The Trans-North China Orogen (TNCO) has been recognized as a continent-continent collisional belt along which the Eastern and Western Blocks amalgamated to form the North China Craton. However, controversy has surrounded the timing and tectonic processes involved in the collision between the two blocks, ranging from the westward-directed subduction with final collision at ~2.5 Ga, through the west-dipping subduction with two collisional events at ~2.1 Ga and ~1.85 Ga, to the eastward-directed subduction with final collision at ~1.85 Ga. This project aims to present detailed lithostratigraphic, geochronological and isotopic data for the low-grade supracrustal successions in the TNCO to examine current models and to establish a reasonable scenario for the tectonic evolution of the TNCO in the Paleoproterozoic. The low-grade supracrustal successions include the Hutuo and Yejishan Groups in the middle sector of the TNCO and the Songjiashan, Lower Zhongtiao, Upper Zhongtiao, Danshanshi and Songshan Groups in the southern sector. Lithostratigraphic data indicate that the Songjiashan, Lower Zhongtiao Groups and lower parts of the Hutuo and Yejishan Groups are composed of metaclastic rocks, carbonates and metavolcanic rocks, interpreted as back-arc basin deposits, whereas the Upper Zhongtiao, Danshanshi, Songshan Groups and the upper parts of the Hutuo and Yejishan Groups consist only of metaconglomerates and metasandstones, interpreted as foreland basin deposits. To constrain the provenance and maximum depositional ages for these low-grade supracrustal successions, the LA-MC-ICP-MS technique was applied to analyze U-Pb and Hf isotopic compositions for detrital zircons from them. For the Hutuo and Yejishan Groups, we found major age peaks at ~2.5 and ~2.2 Ga and minor amounts of 2.8-2.6 Ga detrital zircons, which are consistent with ages of the lithological units in the middle sector of the TNCO. On the other hand, for the Songjiashan, Lower Zhongtiao, Upper Zhongtiao, Danshanshi and Songshan Groups, detrital zircons from them have the major age population of 2.85-1.95 Ma and the minor age population of 3.6-3.1 Ga, of which the former is comparable with ages of the lithological units in the southern sector of the TNCO and the latter was derived from the Paleoarchean and Mesoarchean crust of the Eastern Block. The maximum depositional ages of the low-grade supracrustal successions have also been well constrained in this study. For the back-arc basin deposits, their maximum depositional ages were constrained between ~2.15 and ~2.10 Ga. For the foreland basin deposits, the presence of ~1.85 Ga detrital zircons indicates that they were deposited after this time. Taken together, we present a brief scenario for the evolution of the sedimentary basins in the TNCO. At 2.15-2.10 Ga, a series of back-arc basins developed behind an “Andean-type” arc that were subsequently incorporated into the TNCO during the collision of the Eastern and Western Blocks. At ~1.85 Ga, the two blocks collided along the TNCO, resulting in the crustal thickening followed by rapid exhumation/uplift, which shifted the back-arc basins to foreland basins. Such a shift in the late Paleoproterozoic supports the model that the collision between the Eastern and Western Blocks occurred at ~1.85 Ga.
published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy

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LIMONCELLI, MARTA. « Short-term erosion pattern in the Alps-Apennines belt constrained by downstream changes of zircons morphology and U-PB ages from the Po drainage modern sands ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/29393.

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Downstream changes of the geochronological signature in the Po drainage allow to assess the relative sediment contributions shed from the orogenic source areas, in order to constrain the short-term (102-104 y) erosion pattern in the Alps-Apennines orogenic couple. In this perspective, we collected modern sands in selected tributaries draining the major tectonic units exposed in the orogen, as well as along the Po River trunk and in different sites of the Po Delta. Zircon concentrates were separated according to specific quantitative procedures coupled with grain-size and grain-density analyses, which provide an evaluation of zircon content in source rocks, of hydraulic sorting effects, and related intersample/intrasample zircon variability. Our methodological approach allows to perform sediment budgets and evaluate mineral content in diverse sediment sources (mineral fertility). Budget calculations were performed by investigating geochronological signals upstream and downstream of major confluences. We employed, LA-ICPMS U-Pb geochronology on detrital zircons, because this technique allows a full control of zircon populations during separation procedures and data analysis; we found, instead, that fission track dating on detrital zircon is affected and biased by selective grain loss. Results of U-Pb analysis performed on single grains show that all samples from the Po Delta yield similar grain-age distributions, and include grain-age populations that are rather constant both in age and size. Major peaks are found at ca. 30 Ma, ca. 280 Ma, and 400-500 Ma. Peaks in these distributions can be traced upstream up to their sources. The bulk of the geochronological signature of the Po Delta sands is displayed already upstream of the confluence of the Northern Apennines rivers, suggesting that short-term erosion rates were much lower in the Northern Apennine than in the Western and Central Alps. Age peaks typical of the eastern Lepontine dome also characterize the Apenninic tributaries, reflecting Oligo-Miocene sedimentary transfer from the Central Alps to the Adriatic foredeep, and next tectonic accretion of turbidite wedges to the Apennine belt. U-Pb analyses were complemented by zircon typology of the whole dataset, integrated by SEM observations on selected samples. Major typological groups can be traced from entry points in the Po Plain down to the Po Delta. Euhedral zircons are largely shed from the External Massifs (Mont Blanc and Argentera) and the Periadriatic plutons. Zircon grains showing signs of chemical abrasion, possibly acquired under high-grade metamorphic conditions, were detected in tributaries draining the Lepontine area.

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Melleton, Jérémie. « Modalités du recyclage de la croûte continentale dans l'orogène varisque par traçage in situ des zircons hérités (mesures U -Pb/LA-MC-ICPMS) ». Phd thesis, Université d'Orléans, 2008. http://tel.archives-ouvertes.fr/tel-00388706.

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Ce travail de thèse est essentiellement consacré à l'investigation des populations de zircons et de l'âge des protolithes des formations varisques grâce à une datation U-Pb in situ systématique par le couplage Laser/MC-ICPMS, dans des formations orthodérivées, métasédimentaires et magmatiques tardi-orogéniques du Massif Central français et du domaine Sud armoricain. Cette étude a montré que les populations de zircons sont largement héritées, s'étalant de l'Archéen au Paléozoïque inférieur. L'ensemble des pics d'âges obtenus, ainsi que l'absence d'âge mésoprotérozoïque (1.7-1.1 Ga) accréditent l'affinité gondwanienne de ces formations. Des âges maximum de dépôt sont proposés pour les métasédiments des principales unités définies dans le Massif Central. Ces âges maximum de dépôt sont décroissants suivant l'empilement lithotectonique reconnu. En marge de ce travail, nous avons pu déterminer que les âges de mise en place des granitoïdes du Sillon Houiller (Massif Central) et du golfe du Morbihan se situent aux alentours de 300 Ma. Des âges plus anciens, principalement obtenus sur monazite lors d'études antérieures, ont été réinterprétés comme des âges hérités. L'abondance de zircons hérités d'âge ordovicien et néoprotérozoïque met en évidence la large contribution des métagranites et métasédiments fertiles de ces périodes dans la source des granites tardi-orogéniques varisques. Le granite de Sarzeau expose de plus les traces d'un protolithe silurien. Le recyclage de la croûte continentale est caractérisé par une évolution polycyclique au cours de l'orogénèse varisque, avec tout d'abord l'érosion de formations du craton africain, majoritairement d'âge néoprotérozoïque, puis la superposition des événements magmatiques cambro-ordoviciens et syn-orogéniques varisques.

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Toteu, Sadrack-Félix. « Chronologie des grands ensembles structuraux de la région de Poli : Accretion crustale dans la chaîne panafricaine du Nord Cameroun ». Nancy 1, 1987. http://www.theses.fr/1987NAN10057.

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Les nouvelles données structurales, géochimiques et géochronologiques indiquent un important volume de matériel d'âge protérozoïque supérieur dans le "complexe de base" et dans la "série de Poli". L'évolution tectonique et métamorphique est comparable pour les deux ensembles. Les caractéristiques géochimiques et isotopiques de l'essentiel des formations plutoniques et volcaniques de l'essentiel des formations plutoniques et volcaniques montrent qu'il s'agit de matériel juvénile nouvellement mis en place en bordure d'une croûte plus ancienne. Une chronologie des évènements panafricains est établie. Les nouveaux résultats permettent d'interprêter l'orogénèse panafricaine du Nord Cameroun en terme de tectonique des plaques

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Demouy, Sophie. « La naissance des Andes au Crétacé supérieur : origine et construction du Batholite côtier sud-péruvien (région d'Arequipa) ». Toulouse 3, 2012. http://thesesups.ups-tlse.fr/2201/.

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Durant le Crétacé supérieur-Paléocène, une intense activité magmatique localisée le long de l'arc Toquepala a entraîné la création d'un relief important le long de la marge sud-péruvienne. La croissance de cet arc coïncide avec le seul soulèvement connu le long de la marge, ce qui permet de proposer qu'il en est un moteur principal. Notre étude se concentre sur une section du Batholite Côtier péruvien qui s'étend sur 80x60 km pour une épaisseur supérieure à 7 km. Les données structurales décrivent un objet complexe, constitué d'unités plutoniques dont certaines ont subi des épisodes de déformation extensive syn à post mise en place. De grandes failles normales structurent le batholite en réponse à des contraintes tectoniques et à la croissance exagérée de l'arc. L'étude géochronologique souligne la construction discontinue du batholite, au Jurassique (200-175 Ma) et au Crétacé-Paléocène (90-60 Ma). L'exploitation des données géochimiques et isotopiques (Hf, Sr, Nd) permet d'identifier un premier stade dans l'activité de l'arc, caractérisé par une prédominance des processus de mélange et de cristallisation fractionnée, et un second stade durant lequel les magmas homogénéisés évoluent seulement par cristallisation fractionnée pour se mettre en place au niveau du batholite sous la forme d'unités très volumineuses. La maturité du système s'exprime par un phénomène de flare-up entre 70-60 Ma durant lequel plus de 70% du batholite est mis en place. Ce phénomène de haut flux magmatique est caractérisé par des signatures juvéniles des magmas et constitue un apport non négligeable à la croûte continentale
During the Late Cretaceous and Paleocene, intense magmatic arc activity resulted in the building of a continuous relief along the Peruvian margin. This arc growth coincided with the only known significant uplift along the coastal southern Peru. Our study has focused in the Arequipa area, on a batholith segment extending 80x60 km for a thickness bigger than 7 km. The structural study describes an object that is complex and consists of different plutonic units, that for some underwent extensive deformation syn to post emplacement. Major faults affect the batholith as a consequence of tectonic strains and exaggerate growth of the arc. The geochronological study indicates a discontinuous construction of the batholith, during the Jurassic (200-175 Ma) and the Late Cretaceous-Paleocene (90-60 Ma). Exploitation of the geochemistry and isotopic data (Hf, Sr, Nd) allows to identify an initiation stage of the arc during which fractional crystallization and mixing are predominant, and a thermal maturation stage during which magmas are homogenized in the deep crust, and evolve by fractional crystallization until the batholith level. This period leads to the construction of more than 70 % of the batholith and can thus be considered as a flare-up event. This event is characterized by juvenile signatures and also contributes significantly to the growth of the continental crust

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Roberts, Richard James. « The Seiland Igneous Province, Northern Norway : age, provenance, and tectonic significance ». Thesis, 2008. http://hdl.handle.net/10539/4993.

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The Seiland Igneous Province, of which 5400 km2 is exposed, is hosted within a discrete terrane within the northernmost part of the Caledonian orogenic belt. The Province consists of numerous mafic and ultramafic plutons emplaced into a sedimentary succession indicative of a continental setting. Accompanying this mafic magmatism is a significant volume of intermediate monzonitic and dioritic rock (10% of the total exposed igneous rock), as well as numerous nepheline syenite and carbonatitic intrusions. This study reports ID-TIMS U-Pb analyses on magmatic zircons from a range of intrusions, which indicate that the bulk of the Seiland magmatism took place between 560 Ma and 570 Ma, whereas previous studies had produced a range of ages between 420 Ma and 830 Ma. The data indicate that only one magmatic episode is represented in the rocks of the Seiland Igneous Province, invalidating previous models involving multiple rifting events over a period of 300 m.y. Detailed geochemical investigation of several plutons from an evolved high alkali suite of gabbroic intrusions in the Seiland Igneous Province has shown that these plutons are generally enriched in trace elements compared to layered intrusions from other areas across the globe, but that geochemically the gabbros are relatively homogenous. The rocks yield εHf and εNd values for the gabbroic rocks ranging from +8 to -6 and from +4 to -4, respectively, indicative of the contamination of mantlederived material with crustal material. The most primitive isotopic values are similar to those obtained from the carbonatites and nepheline syenites, indicating the same mantle source gave rise to the magmas that were subsequently emplaced as the Seiland Igneous Province. The homogeneous trace element content of the different mafic rocks most likely indicates a relatively homogeneous mantle source for the original magmas of the province, which has subsequently been affected by processes of assimilation and crustal contamination. The monzonitic and dioritic bodies in the Seiland Igneous Province are not derived from melted silicic crustal material and may have been formed by the melting of pre-existing mafic material. The new geochronology invalidates the metamorphic framework previously proposed for the Seiland Igneous Province, which postulated several orogenic events between the emplacement of the magmas and the Caledonian Orogeny. There is no evidence for metamorphic activity in the period between 570 Ma and 420 Ma, and there are monazites in gneissic rocks hosted within mafic rocks of Seiland age that preserve an age of 640 Ma. This leads to the conclusion that only one metamorphic event, the 420 Ma Caledonian Orogeny caused by the collision of Baltica and Laurentia, affected the Seiland terrane after the emplacement of the Seiland magmas. The new data obtained lead to a model for the evolution of the Seiland Province in which a number of heavily modified and contaminated mantle-derived mafic magmas derived from the mantle were emplaced into the continental crust of the Seiland nappe between 560 and 570 Ma. This magmatism was accompanied by the injection of alkaline magmas into the same area of the crust, and the melting of mafic rock emplaced earlier. This magmatic event is considered to have occurred in an extensional stress regime, possibly during intracontinental rifting or back-arc spreading. This event took place well before the 420 Ma Caledonian Orogeny, and thus the Seiland Igneous Province can be considered a remnant of an older geological terrane that was emplaced onto the margin of Baltica during the Caledonian Orogeny.

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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.

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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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Zul, Zugeerbai, et 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.

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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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Tsai, Meng-Hao, et 蔡孟澔. « Detrital Zircon U-Pb Age Study of the Pre-Miocene Formation in Offshore Southern Taiwan ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/49655642898735185807.

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碩士
國立臺灣師範大學
地球科學系
104
Zircon occurs in almost all sedimentary deposits and may provide a link in understanding the source provenance and the depositional age. Detrital zircon U-Pb dating from 14 samples coming from 13 wells (C-9, C-10, C-16, S-1, T-1, P-21, F-35, W-1, W-4, E-1, C-6, K-1 and J-1) offshore southwestern Taiwan were performed by using LA-ICP-MS method. The youngest Detrital zircon U-Pb ages are: Samples from F-35 well (1300 m) is 88 Ma; Samples from Taixinan basin (3279、3315、3358、3671、3869 m) are 66, 45, 133, 42, 41 Ma; Samples from Penghu basin (2584、2399 m) are 45, 43 Ma; Samples from Penghu rifting (2029、2026 m) are 79, 83 Ma; Samples from Beigang high (805、3876 m) are 86, 74 Ma. These youngest age from detrital zircon U-Pb dating represent the deposit age or the oldest possible deposit age. The samples from F-35 well were dominantly coming from local sedimentary source. The sedimentary provenance for C-9, C-10, C-16, C-6, S-1 wells were mainly derived from the neighboring regions or partially from the nearby Jiulong river region. The provenance of T-1 and P-21 regions were from probably ancient Yangtze river tributary in the early stage. After the uplift of the Wuyishan, the source region changed to the Jiulong river drainage area. The sedimentary provenance for W-1 and W-4 well were from Min river drainage area. The provenance for peak 118 Ma from K-1 and E-1 well was probably from the local source. And the provenance for the peak about 170 Ma from K-1 and J-1 was the local source.

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Liu, Cheng-Hao, et 劉丞浩. « Detrital zircon U-Pb age study of the Tailuko belt in the Tananao Schist, eastern Taiwan ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/95632935175248364658.

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碩士
國立臺灣大學
地質科學研究所
101
The oldest rocks exposed in Taiwan are the Tananao Schist that exposed along the eastern slope of the Central Range. It mainly consists of schist, marble, and metamorphosed granites. The protolith for marble is supposed to be late Permian, and the protolith for schist is middle Mesozoic. Because of lacking fossils and radiometric dating, the depositional age of schist was difficult to define. U-Pb ages of detrital zircons represent crystallization age of sediment sources (terranes), and the youngest age may be close to or older than the depositional age. Therefore, we use the detrital zircon U-Pb dating, by using LA-Q-ICPMS, to discuss the maximum depositional age of the Schist Belt. Samples collected from Paiyang schist and Kuyuan schist along the Central Cross-Island highway between Tianxiang and Taroko, Mugua river, and Heping river are quartz-mica schist (n=10), metachert (n=13), green schist (n=5), Metabasite (n=4), and Chloritoid (n=2). Results of this study show that (1) the youngest graphical age peak of samples is 109.5±2.5Ma, and the youngest single grain age of samples is 80±2Ma, which suggest the maximum depositional age of the schist should be not order than Cretaceous; (2) the deposition of marble took place in the Permo-Triassic, but deposition of schist took place in the Cretaceous, indicating that there is a hiatus between schist and marble; (3) I-type granites in Taiwan yield ages of 105-86Ma. Granitic plutons and depositional of the schist is at the same time, which suggest Taiwan-Fujian region is in a subduction environment of paleo-Pacific plate underneath the Eurasian plate during Mesozoic.

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Cappello, Mariko. « New radiometric age constraints on the Ordovician-Silurian boundary from Anticosti Island (eastern Canada) and the Siljan district (Sweden) ». Thesis, 2019. http://hdl.handle.net/1828/11089.

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The transition from the end of the Ordovician to the beginning of the Silurian Period is characterized by the glaciation of the Gondwana paleocontinent, eustatic sea level change, a perturbation to the global carbon cycle and one of the ve major mass extinctions of the Phanerozoic Eon. Due to signi cant sea level fall, the Ordovician-Silurian (O-S) boundary is often marked by hiatus and exposure in the shallow marine geologic record (e.g., Copper et al. [2013]). Two locations that host stratigraphic succession close to the boudary are Anticosti Basin of Quebec (Canada, e.g., Desrochers et al. [2010]), and the carbonate mounds of the Siljan ring district (Dalarna County, Sweden, e.g., Ebbestad et al. [2015]). The exact timing and dynamics of the glaciation and mass extinction are yet to be understood. Similarly, the interplay between those events and the carbon cycle perturbation are still unclear. As a result, there is a serious need for radiometric age constraints in this crucial part of the Paleozoic Era. The acquisition of more radiometric dates, achieved in this study, aims to address the present dearth of absolute dates close to the boundary. The dates produced in this study represent the first modern geochronologic constraints on the O-S boundary, leveraging the development of the EARTHTIME initiative and the latest U-Pb dating techniques that have improved accuracy and allowed for dating of single zircon crystals at <=0.1% precision level. Here I present two new U-Pb zircon ages obtained via bentonite dating. The first bentonite, 443.61+-0.52 Ma (2, including analytical, tracer calibration and decay constant uncertainties) was collected from the base of the Lousy Cove Member, Ellis Bay Formation (Anticosti Island, Quebec, Canada). The second one, 443.28+-0.50 Ma (including analytical, tracer calibration and decay constant uncertainties) comes from a karstic void within the Boda Core Facies of the Boda Formation (Dalarna County, Sweden). U-Pb geochronology (chemical abrasion, isotope dilution, thermal ionization mass spectrometry: CA-ID-TIMS) on single zircons was used to obtain these ages. These results are the closest radiometric ages to the current O-S boundary (compared to any time constraints in the 2012 Geologic Time Scale) and allow to signifcantly reduce the uncertainty of the current age boundary (443.8+-1.5, Cohen et al. [2018]). Furthermore these absolute ages have been used to make models that explore drivers of Earth system change, such as an end-Ordovician global carbon cycle perturbation.
Graduate
2021-07-07

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Huang, Yi-Chang, et 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.

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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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Chiu, Han-Yi, et 邱瀚毅. « The Neotethyan subduction and Zagros orogeny:constraints from zircon U-Pb age and Hf isotopic study ofmagmatic rocks from Iran ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/76570780192304152961.

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博士
國立臺灣大學
地質科學研究所
101
This study reports the first combined LA-ICPMS analyses of zircon U-Pb and Hf isotope compositions for magmatic rocks from several major domains of Iran, including the Urumieh-Dokhtar magmatic arc (UDMA), Sanandaj-Sirjan structural zone (SSZ), Alborz Range, Central Iran and Sistan suture zone. These results, together with the literature data and some unpublished ages of our team, better delineate the magmatic evolution related to the Neotethyan subduction and subsequent Zagros orogeny that resulted from the Arabia-Eurasia collision. Moreover, this study also identifies two major magmatic events that formed during the late Neoproterozoic to Cambrian and the Late Triassic before the occurrence of broad magmatic activities which are related to the Neotethyan subduction. The first magmatic event represents a depleted mantle-derived magmatic feature and it has associated with the magmatism that produced the peri-Gondwanan terranes and Arabian-Nubian Shield. The second magmatic event is attributed to the Paleotethys evolution and shows an obvious magmatic signature of crustal contamination. The Neotethyan subduction-related magmatism was active during the Jurassic time, as evidenced by the presence of widespread I-type granitoids from the Middle to Late Jurassic (176-144 Ma) in the SSZ. These intrusive rocks, also exposed in the central part of the UDMA and the northern Lut block, show a heterogeneous isotopic affinity with variable zircon εHf(T) values between +12 and -5. After a protracted magmatic quiescence in the Early Cretaceous, the igneous activity renewed inland in the UDMA from which the Late Cretaceous granitoids (81-72 Ma) are found in the southeastern segment of the UDMA. These rocks from the Jiroft and Bazman areas have very different zircon εHf(T) values clustering from +15 to +11 and from +5 to -9, respectively, implying that the Bazman magmas were significantly mixed with the old crustal components. Then, the UDMA volcanism was most active and widespread during the Eocene and Oligocene (55-25 Ma), much longer lasting than the previously thought as just an Eocene pulse. Such a prolonged igneous “flare-up” event in the UDMA can be correlated to Armenia where the coeval calc-alkaline rocks are common. Similar ages are also obtained from the magmatic rocks in the northwestern SSZ and west Alborz. This magmatism, with mostly positive zircon εHf(T) values between +17 and -1, can further signify the formation of extensive juvenile crust in the regions owing to the Neotethyan subduction. The magmas with a primitive signature were also exposed in the southern Sistan suture zone and the Makran region during the Oligocene to Quaternary (32-1 Ma). By contrast, the ancient continental crust material was observed from the Central Iran, in Saghand area by the Eocene granitoids that yielded less radiogenic zircon Hf isotopes of εHf(T) values ranging from +6 to -7. The UDMA magmatism ceased progressively from the northwest to the southeast, with the magmatic activities ending in the Early Miocene (ca. 22 Ma) in Meghri, in the Middle Miocene (ca. 16 Ma) in Kashan and in the Late Miocene (ca. 10-6 Ma) in Anar. The southeastward magmatic cessation is consistent with the notion of the oblique and diachronous continental collision between Arabia and Eurasia. The post-collisional volcanism started at ca. 11 Ma in Saray, east off the Urumieh Lake, which, along with the later eruptions in Sahand (6.5-4.2 Ma) and Sabalan (≤0.4 Ma) volcanoes, forms a compositionally unique component of the vast volcanic field covering much of the Lesser Caucasus, NW Iran and eastern Anatolia regions.

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Feng, Han-Ting, et 馮瀚亭. « Zircon U-Pb Dating Constraint on the Formation Age of Metamorphic Rocks in the Suao-Nanao Area, Northern Taiwan ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/50666057639137521839.

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碩士
國立臺灣大學
地質科學研究所
99
The Tananao Schist, located in the northern Central Range, is considered as the oldest formation in Taiwan. It is mainly composed of schist, marble, amphibolite, and granitic gneiss. Because of the complicated tectonic and metamorphic history, and the lack of fossils and radiometric dating, it’s hard to confirm the relationship between formation age and occurrence. U-Pb ages of detrital zircon represent the age of sediment source, and the youngest age may be close to or older than the formation age. Therefore, we try to use zircon U-Pb dating to discuss the formation age.We collected samples from the Suao Formation, the Nansuao Formation, the Tungao Schist, the Nanaoling Schist, the Wuta Schist, and the Fangpouchienshan Gneiss along the Suhua highway which include metasandstone, quartz-mica schist, green schist, metamorphic pyroclastics, gneiss and amphibolite. The youngest age of detrital zircon from each formation shows in below: metasandstone the Suao Formation—28.3±1 Ma, the Nansuao Formation—26.4±1 Ma, the Tungao Schist—89±4 Ma (green schist) and 74±2 Ma (quartz-mica schist), the Nanaoling Schist—143±3 Ma (green schist) and 87±2 Ma (quartz-mica schist), the Wuta Schist—113±2 Ma (green schist) and 166±4 Ma (metamorphic pyroclastics), the Fangpouchienshan Gneiss—92±2 Ma. From result extrapolation, the Suao Formation and the Nansuao Formation may be close to or younger than the late Oligocene; the Tungao Schist and the Fangpouchienshan Gneiss may be close to or younger than late Cretaceous; the Wuta Schist may be close to middle Jurassic to early Cretaceous. And we classified the Nanaoling Schist to the Tungao Schist and the Wuta Schist.

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Chen, Jia-Huei, et 陳嘉蕙. « Zircon U-Pb age and geochemical constraints on the petrogenesis of Cretaceous to Eocene magmatic rocks in Eastern Pontides, Turkey ». Thesis, 2017. http://ndltd.ncl.edu.tw/handle/x99a6b.

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碩士
國立臺灣大學
地質科學研究所
105
The Neo-Tethyan orogenic evolution of eastern Turkey in the Arabia-Eurasia collision zone involves two tectonic units, i.e., the Pontides in north and the Anatolide-Tauride in south, separated by at least two ophiolite belts representing relicts of the oceanic crust from the northern and southern branches of Neo-Tethys, respectively. To better understand the complex geologic history of Eastern Pontides, particular during the Cretaceous and Eocene when the northern branch of Neo-Tethys may have closed, a combined geochronological and geochemical analysis of main magmatic outcrops was conducted. The result, including specifically zircon U-Pb age and geochemical data of 26 samples, allows us to divide the magmatism into three stages: (1) Early Cretaceous (ca. 144-128 Ma) calc-alkaline rocks, composed of gabbro to granodiorite lithologies; (2) Late Cretaceous (87-77 Ma) tholeiitic to high-K calc-alkaline rocks, composed of diversified lithologies from diorite to granite and from basalt to rhyolite; (3) Early Eocene (55-54 Ma) adakitic rocks, exclusively of felsic composition such as granodiorite and rhyolite; and Late Eocene (43-40 Ma) high-K clac-alkaline rocks, also of diversified lithologies. The Early Cretaceous magmatism, which can be correlated to broadly coeval granitoids emplaced in Armenia, is attributed to the subduction following opening of the northern branch of Neo-Tethys. The second stage of magmatism that exhibits significant lithological and geochemical variations is interpreted as the products of ending subduction and subsequent closure of the northern branch of Neo-Tethys and the opening eastern Black Sea Basin. Under this framework, the two suites of Eocene magmatism are post-collisional activities that resulted from partial melting of the lower part of a collision-thickened juvenile crust and the subduction-metasomatized continental lithospheric mantle, respectively.

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Hung, Chia-Chia, et 洪嘉佳. « Geochemical and zircon U-Pb dating analysis of metamagmatic rocks constraint on the age and tectonic implication of Tananao Schist, Taiwan ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/31695448530247551583.

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碩士
國立臺灣大學
地質科學研究所
104
The oldest rock of the Tananao Schist is exposed at the Backbone Range which consists of marble, schist, gneiss, and subordinate metabasites. According to the lithologic characteristics, the Tananao Schist can be divided into Tailuko belt and Yuli belt. The Tailuko belt consists of marble, gneiss, and subordinate scattered metabasite; the Yuli belt is composed of greenschist, serpentinite, meta-tuff, meta-gabbro, metabasite, and glaucophane-schist blocks which enclosed by spotted schist of the host rocks. The metamorphic belts were inferred as a Mesozoic mélange. It’s still controversial due to the difficulty of analyzing metamorphic rocks. In this study, we focus on the zircon U-Pb dating, geochemistry, and petrographic analysis of spotted schist, metabasite, meta-gabbro, and meta-tuff in order to constrain the formation and crystallization ages and interpret its tectonic setting. In Tailuko belt, we can divide metabasites to which intruded to marble, or which erupted to schist, and we use zircon U-Pb dating to figure out that metabasites intruded to marble occurred at 80-90 Ma. According to the geochemical characteristics, we figure out that the metabasites in Tailuko belt could be the same magma characteristic, for Th-Hf/3-Ta diagram and Zr/4-2Nb-Y diagram. It seems to interpret within-plate basalts. In Yuli belt, based on zircon U-Pb dating, the host rocks of spotted schist and the exotic blocks of meta-pyroclastic rock, meta-gabbro (16.5-14.5 Ma), and meta-basalt occurred at mid-Miocene. Geochemical characteristics for meta-basalt and meta-gabbro blocks show Ta-Nb-Ti depletion and LREE depletion in spider diagram occurring volcanic arc and N-MORB type affinities, respectively. Based on the results, Yuli belt have recorded magmatic rocks eruption and Yuli mélange process of Luzon arc. Early Miocene, the end of the South China Sea plate rifting, northwestern moving Luzon arc formed and erupted basalts incipiently, which captured Miocene sediments from the Cathaysia block, and deposited at forearc basin; the mid-Miocene, according to magmatic differentiation andesite erupted, and captured detrital zircon in sediments. Luzon arc continues to move northwest, while early igneous rocks of Luzon arc and Cenozoic sediments in the forearc basin thrusted together into the subduction zone; in mid-Miocene to Late Miocene , accretionary prism through rock metamorphism, and finally Luzon arc overthrusted the Eurasian continent, as part of the island of Taiwan, accretionary prism exposed to the surface during Penglai orogeny, formed Yuli metamorphic belt formed today.

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Gärtner, Andreas. « Geologic evolution of the Adrar Souttouf Massif (Moroccan Sahara) and its significance for continental-scaled plate reconstructions since the Mid Neoproterozoic ». Doctoral thesis, 2017. https://tud.qucosa.de/id/qucosa%3A30863.

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Located in the south of the Moroccan Sahara, the Adrar Souttouf Massif is the northern continuation of the Mauritanides at the western margin of the West African Craton. The massif itself exhibits a complex polyphase geologic history and contains four geologically different, SSW-NNE trending main units named from west to east: Oued Togba, Sebkha Gezmayet, Dayet Lawda, Sebkha Matallah. They are thrusted over each other in thin-skinned nappes with local windows of the discordantly overlain Archaean Reguibat basement. The eastern margin of the massif is bordered by the Tiris and Tasiast-Tijirit areas of the Reguibat Shield as well as its (par-) autochthonous Palaeozoic cover sequence, termed Dhloat Ensour unit. More than 5.500 U-Th-Pb age determinations and over 1.000 Hf isotopic measurements on single zircon grains from igneous, metamorphic, and sedimentary rocks of all the massifs units and its vicinity have yet been obtained. Most of the zircons were studied with respect to their morphological features. This method improves the accuracy of provenance studies by detecting varying zircon morphologies in space and time. These data are accompanied by U-Th-Pb age determinations on apatite as well as rutile. Together, they allow proposing a model of the geologic evolution of this poorly mapped area for the last 635 Ma. A combination of the obtained data with extensive zircon age databases of the surrounding cratons and terranes facilitates continental-scaled palaeogeographic reconstructions. Regarding the geologic evolution of the Adrar Souttouf Massif, the assembly of the first units began prior to 635 Ma. Although containing all the major zircon age and Hf-isotope populations of the West African Craton as well as some Mesoproterozoic grains, the Sebkha Gezmayet unit lies to the west of the Dayet Lawda unit of oceanic island arc composition. Hence, the Sebkha Gezmayet unit must have been rifted away from the craton prior to the formation of the oceanic unit within the West African Neoproterozoic Ocean at about 635 Ma. Recently published Hf and zircon age data of this unit suggest that the island arc was derived from a juvenile mantle source. Subsequently, the accretion of precursors of the Oued Togba and Sebkha Gezmayet units as well as a partial obduction of the oceanic Dayet Lawda unit and the Neoproterozoic sediments of a foreland basin (Sebkha Matallah unit) onto the Reguibat Shield took place. Peak metamorphism in the obducted oceanic rocks was reached at about 605 Ma. Magmatism in the western units between 610 and 570 Ma suggests on-going tectonic activity. The Early and Middle Cambrian is characterised by the erosion of the Ediacaran orogen and deposition of thick sedimentary sequences at the Sebkha Matallah unit, which acted as foreland basin. These sediments show a mostly West African zircon record with only some Mesoproterozoic grains provided by the westernmost parts of the massif. Initial rifting of the Oued Togba and Sebkha Gezmayet units from the remaining areas presumably occurred during the Late Cambrian. Coeval granitoid intrusions occurred on both sides of the rift. The two rifted units were likely involved to the polyphased Appalachian orogenies, which is emphasised by Devonian magmatism. Thus, and with respect to the isotopic data, the Oued Togba unit is interpreted to be of Avalonia affinity, while the Sebkha Gezmayet unit can likely be linked to Meguma. The units which remained at the West African Craton underwent intense sediment recycling during the entire Ordovician to Devonian times. Final accretion of all units and formation of the current massif was achieved during the Variscan-Alleghanian orogeny. This was accompanied by magmatism in the Sebkha Gezmayet unit and intense metamorphism of the Reguibat basement, whose zircons often show lower discordia intercepts of Carboniferous or Permian age. The post-Variscan period is characterised by erosion of the orogen and subjacent alternating cycles of sedimentation and deflation. The Adrar Souttouf Massifs importance for palaeogeographic reconstructions is given by the striking differences in the zircon age and Hf-isotope record of its westernmost Oued Togba unit and the remaining area. The results obtained from the Oued Togba unit resemble the published data of the Avalonia type terranes including prominent Mesoproterozoic, Ediacaran-Early Cambrian, as well as Early Devonian age populations. Many Mesoproterozoic zircons, which are exotic for the West African Craton prior to 635 Ma, form a ca. 1.20 to 1.25 Ga age peak that is an excellent tracer for detrital provenance studies and source craton identification of the sedimentary rocks. This is also valid for some sedimentary samples that do not show ages younger than 700 Ma, but large quantities of Mesoproterozoic zircon. These rocks can be correlated to similar sediments in Mauritania and W-Avalonia and are thought to be of pre-pan-African", i.e. pre-Ediacaran or even pre-Cryogenian age. They may give direct insights to the source area in Early to Mid Neoproterozoic times. Accordingly, comparison with published data of Amazonia and Baltica, allows setting up new hypotheses for the pre-Ediacaran history of the Avalonian type terranes. Lacking of magmatism in Amazonia between ca. 1200 and ca. 1300 Ma favours Baltica as source craton for the Avalonian terranes and requires a new point of view for the Neoproterozoic palaeogeography.

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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.

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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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Amarasinghe, Udeni Bandara. « A geochronological U-Pb zircon La-ICPMS age and provenance study of Wanni, Highland and Vijayan Complexes of Sri Lanka and Proterozoic Pranhita Godavari Purana Basin of India unveils origin of Sri Lanka ». Thesis, 2017. http://hdl.handle.net/2440/113324.

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The island of Sri Lanka is the focus of Neoproterozoic super continent Gondwana. But the geological origin and paleotectonic position of Sri Lanka are least understood without knowing age and provenance of the four main crustal units, the Wanni Complex (WC), Highland Complex (HC), Vijayan Complex (VC) and the Kadugannawa Complex (KC). The study of age and provenance of metaquartzites of the WC and HC, leucosomes and paleosomes of migmatites of the WC, and charnockites of the HC and VC of Sri Lanka and sedimentary rocks of neighboring Proterozoic rift basins like Pranhita-Godavari basin of central India is significant in research on origin of Sri Lanka and also continental evolution to unravel the paleotectonic position of Sri Lanka before Gondwana being amalgamated in the Neoproterozoic. This study examined age of detrital zircon cores and metamorphic rims of metaquartzite, migmatite and charnockite samples along two west to east transects across the island of Sri Lanka as well as sedimentary rock samples from the Pranhita-Godavari rift basin of India using the LA-ICPMS method. The U-Pb zircon isotopic data from metaquartzites of WC ( near WC-HC boundary) and HC demonstrate dominant Mesoarchaean to Paleoproterozoic (2.0-2.8 Ga) detrital input into the metasedimentary make up and near boundary WC and HC metaquartzites were deposited between 2000 Ma and ~550 Ma with a maximum age of deposition ~ 2000 Ma, however a sample from the western WC was deposited in early Neoproterozpoic and mixed with Paleoproterozoic to Neoarchaean detritus indicating WC and HC terranes existed adjacent to each other since early Neoproterozoic and current WC-HC boundary is inaccurate and to be shifted westwards. This study reveals that parent materials of leucosomes of WC migmatitic gneisses are metasedimentary and showing late Mesoproterozoic to Neoproterozoic provenance (0.70-1.15 Ga) with maximum age of deposition at ~700 Ma. But paleosomes of WC migmatites show metaigneous origin with older Mesoarchaean ages (2.85-3.0 Ga) and have been identified in this study as the Mesoarchaean reworked continental basement material of WC. The HC charnockites clearly show metaigneous origin and primary intrusion ages of ~1.82 to 1.85 Ga. whilst a sample from the VC shows metasedimentary origin. A weighted mean of all rim data of WC and HC yields an age of 545.1 ± 9.7 Ma, supporting the age of Ediacaran-Cambrian metamorphism. Metaquartzite rocks of the HC of Sri Lanka are correlated with the Trivandrum Block and Northern Madurai Block of South India and the Itremo Group of Madagascar whilst metaquartzites of the western WC of Sri Lanka are correlated with the Southern Madurai Block of South India and the Molo Group of Madagascar and Sri Lankan metaquartzites were most probably sourced from east African igneous protolith sources. These differences in sedimentary provenance and maximum age of deposition prove and confirm that WC was a different crustal domain from the HC terrane. All this strongly supports a double subduction and collisional geological origin for the island of Sri Lanka with ‘HC orogeny’ occurred when the Southern Madurai Block of India (SMB)-WC and VC Mesoarchaean continental blocks collided with the HC orogenic belt and the oceanic crust of deeper basin of HC had subducted underneath the SMB-WC and VC continental blocks when ancient south Mozambique ocean closed along WC-HC boundary and HC-VC boundary sutures. This study reveals that Sri Lanka’s paleotectonic position could be south east of south India connecting Trivandrum Block to the HC and WC to the Southern Madurai Block. The study also reveals that the Pranhita-Godavari Basin was sourced from Eastern Ghats and Antarctica unlike Sri Lankan terranes were sourced from East Africa indicating Southern Granulite Terrane of India and Sri Lanka were not parts of mainland cratonic India until Ediacaran-Cambrian times.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 2017.

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Hung, Chien-Hui, et 洪千惠. « Zircon U-Pb Ages and Geochemical Characteristics of the McKinley Sequence and Associated Plutons, Central Alaska Range ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/79624985693253158305.

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碩士
國立臺灣大學
地質科學研究所
96
Plutonic rocks in the Central Alaska Range were emplaced during important tectonic events including the end of Late Cretaceous-Paleocene arc magmatism, the terminal phase of terrane accretion, the Kula ridge subduction, regional strike-slip faulting, oroclinal rotation of western Alaska, and Eocene resumption of arc magmatism along the proto-Aleutian arc system. Here we report the first set of LA-ICPMS and SHRIMP zircon U-Pb ages for granitoids from (1) the McKinley Sequence, (2) the Composite Plutons and (3) the Foraker Pluton, central Alaska Range. Two peraluminous granites from the McKinley Sequence yielded 206Pb/238U ages of 62±1 and 60±1 Ma; an A-type granite from the same area gave age of 64±1 Ma. Two granodiorites from the Composite Plutons and a granite from the Foraker Pluton gave ages of 69±1, 67±1 and 37±1 Ma, respectively. The age results indicate that the Composite Plutons and the McKinley Sequence granites are older than previously reported and that the McKinley granites can be divided into two magma suites that consist of peraluminous and A-type compositions occurring at ca. 62-60 and 64 Ma, respectively. Nd and Sr isotope data suggest a temporal change in the magma’s isotopic compositions, with the Foraker granites showing higher and more heterogeneous εNd(T) values that range from about +6 to -2 and the Composite and McKinley Sequence granitoids showing lower and less heterogeneous εNd(T) values from +1 to -3. Besides, zircon Hf isotopic data of the dated samples show that a granite from the Foraker plutons has the highest zircon εHf(T) values from +15 to +10, in contrast to the Composite plutons that show apparently lower zircon εHf(T) values from +4 to -3. Peralumous and A-type granites from the McKinley Sequence have zircon εHf(T) values from +2 to -5 and +8 to +1, respectively. The Composite and McKinley Sequence plutonic rocks are interpreted as products of the ending phase of Late Cretaceous-Paleocene arc magmatism. The peraluminous granites from the McKinley sequence may have been sourced from the remnant mantle wedge, previously responsible for generating the Composite plutons and earlier arc magmas. Besides, generation of the A-type granites can be attributed to the v oroclinal rotation of western Alaska and ridge subduction that started around 64 Ma, a mechanism that may also have resulted in broadly coeval volcanism in the nearby Cantwell basin and northern Talkeetna Mountains. The Foraker pluton are interpreted as the product of renewed magmatism along the proto-Aleutian arc, in response to north or northwestward subduction of the Pacific plate during 45-30 Ma.

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Fields, C. E. « Liebig-aged (c. 1640 Ma) magmatism and metamorphism in c. 1760 Ma crust in the Warumpi and southern Aileron Province, central Australia : a case for revising the tectonic framework of Proterozoic Australia ». Thesis, 2012. http://hdl.handle.net/2440/92217.

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The southern margin of the North Australian Craton (NAC) has been suggested to represent a long-lived (c. 1860 to 1600 Ma) active margin that preserves a cryptic record of the growth and assembly of the Australian continent. The Warumpi Province is juxtaposed against the southern Aileron Province, and has been interpreted as exotic to the NAC, though the timing of collision between the Warumpi Province and the southern Aileron Province is contentious. U-Pb zircon and monazite LA-ICP-MS geochronology from granulite facies metapelites and granitic gneisses along the southern margin of the Aileron Province and northern margin of the Warumpi Province, has shown it is characterised by c. 1780-1740 Ma magmatic rocks and c. 1640-1615 Ma magmatic and metamorphic rocks. The evidence for these events is preserved in kilometre-scale migmatitic boudins and low-strain zones enveloped by pervasive E-W trending higher strain belts. The overprinting high strain fabrics are Grenvillian age and constrained to c. 1175-1070 Ma. Phase equilibria modelling on a garnet-sillimanite-cordierite metapelite dated at c.1616 Ma, from a low-strain domain within the southern Aileron Province, indicates that peak metamorphic conditions were ~7-8 kbar and between 740-900 °C, and were associated with a down-pressure or decompressional P-T history. A metamorphic monazite age of c.1620 Ma was also preserved in a granitic gneiss located in an older, low-strain domain. The presence of the c. 1760 Ma and c. 1640 Ma timelines in both the Warumpi and Aileron Provinces calls into question the proposed exotic nature of the Warumpi Province. A speculative interpretation is that the Liebig-aged metamorphism and magmatism, seemingly associated with relatively shallow orientated, low strain fabrics, represents a period of extension rather than collision.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2012

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McLeish, Duncan Forbes. « Structure, stratigraphy, and U-Pb zircon-titanite geochronology of the Aley carbonatite complex, northeast British Columbia : Evidence for Antler-aged orogenesis in the Foreland Belt of the Canadian Cordillera ». Thesis, 2013. http://hdl.handle.net/1828/4560.

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The tectonic significance and age of carbonatite intrusions in the western Foreland Belt of the Canadian Cordillera are poorly constrained. Recent 1:5,000 scale field mapping of one of these carbonatite intrusions, the Aley carbonatite (NTS 94 B/5), has demonstrated that it was emplaced as a syn-kinematic sill, coeval with a major nappe-forming tectonic event. Determining the age of the Aley carbonatite therefore provides a means of directly dating tectonism related to carbonatite magmatism. A U-Pb titanite age of 365.9 +/- 2.1 Ma was obtained from the Ospika pipe, an ultramafic diatreme spatially and genetically related to the carbonatite. We interpret the Late Devonian age of the Ospika pipe to be the minimum possible age of the carbonatite and syn-magmatic nappe-forming tectonic event. The maximum possible age of the carbonatite is constrained by the Early Devonian age of the Road River Group (ca. 410 Ma), the youngest strata intruded by carbonatite dykes and involved in the nappe forming event. Our dating results for the Aley carbonatite closely correlate with U-Pb zircon and perovskite ages obtained for the Ice River carbonatite complex in the western Foreland Belt of the southern Canadian Cordillera, and support the interpretation of carbonatite intrusions of the western Foreland Belt as genetically linked components of an alkaline-carbonatitic magmatic province. Structural, stratigraphic, and geochronological data from the Aley area indicate that deformation was similar in style to, and coeval with, structures attributable to the Antler Orogeny, and are consistent with the Antler orogen having extended the length of Cordilleran margin from the southern United States to Alaska. Deformed alkaline-carbonatite intrusions that characterize continental suture zones in Africa and Tibet may provide an analogue for the Aley carbonatite and correlative alkaline-carbonatite complexes in the western Foreland Belt.
Graduate
0372
mcleish@uvic.ca

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Castillo, Gonzalez Paula Alejandra. « Evolution of the patagonian-west antarctica margin of gondwana in the palaeozoic–early mesozoic : new models constrained by zircon u-pb ages, and o and hf isotopic compositions ». Phd thesis, 2016. http://hdl.handle.net/1885/130073.

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A number of conflicting tectonic models have been proposed to explain the geological relationships between southern South America (Patagonia) and West Antarctica within the palaeo-Pacific margin of Gondwana. Extensive fragmentation and isolation of the various tectonic blocks during Gondwana break-up have complicated interpretations and palaeogeographic reconstructions. In order to explore and test the different tectonic models, I combine zircon U-Pb, Lu-Hf and O isotopic data for samples from key locations throughout the north and south of Patagonia, the Antarctic Peninsula and the Ellsworth Mountains in West Antarctica. Zircon is a robust refractory mineral that occurs in igneous and metamorphic rocks and survives multiple sedimentary cycles with little change to its isotopic composition. It therefore preserves a perfect archive for testing tectonic correlations. Igneous rocks from the Ellsworth Mountains were dated at ca. 680 Ma, older than previously reported. These zircons indicate that rifting, which affected Mesoproterozoic crust, likely occurred in the Cryogenian and supports a connection between the Ellsworth-Whitmore Mountain block and East Antarctica before the amalgamation of Gondwana. This agrees with the break-up of Rodinia in the context of the southwest United States and East Antarctica configuration. U-Pb zircon dating and O-Hf isotopic compositions of detrital zircons from the Ellsworth Mountains also support this connection, indicating a likely East Antarctic provenance. A Cambrian magmatic event is recorded by zircon at ca. 520 Ma, also related to an extensional setting – but in this case with crustal recycling. I interpret this Cambrian magmatism as a result of a tectonic escape after a collision between the Australo-Antarctic and West Gondwana/Indo-Antarctic plates. In Tierra del Fuego, samples from drill cores indicate that Cambrian magmatism occurred between ca. 540 and 520 Ma with strong similarities to the Pampean Orogen of Argentina. Metamorphism occurred at ca. 265 Ma, when zircon crystallised from high temperature hydrous fluids that previously interacted with Grenvillian rocks. Importantly, igneous rocks from Tierra del Fuego record the first evidence of Permian magmatism at ca. 255 Ma, arising from melting of Cambrian rocks. This suggests prolongation of Permian magmatism from the North Patagonian Massif in northern Patagonia and also connections to the Eastern Domain of the Antarctic Peninsula. Granitic rocks in northern Patagonia record mantle-like O magmatic inputs at ca. 280 Ma and 255 Ma, but with reworking of upper crustal materials between these two events. In northwestern Patagonia, early Permian granites indicate continuity of the Permian magmatic belt along the western margin of South America farther north. Further, detrital Permian zircons in late Palaeozoic–early Mesozoic accretionary complexes suggest a continuation of a slightly older Permian subduction-related magmatic arc, partly located in Patagonia and extending to the Antarctic Peninsula. All this data, together with other geological considerations, are in line with an autochthonous or parautochthonous origin for northern Patagonia. It also confirms connections between southern Patagonia and the Antarctic Peninsula from late Palaeozoic to Jurassic times. I suggest that Patagonia rifted from the South African-Ellsworth sector of the paleao-Pacific margin of Gondwana to then collide with the same sector during the Guadalupian.

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