Academic literature on the topic 'Bulk rock Sm-Nd'
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Journal articles on the topic "Bulk rock Sm-Nd"
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ALI, K., A. ANDRESEN, W. I. MANTON, R. J. STERN, S. A. OMAR, and A. E. MAURICE. "U–Pb zircon dating and Sr–Nd–Hf isotopic evidence to support a juvenile origin of the ~ 634 Ma El Shalul granitic gneiss dome, Arabian–Nubian Shield." Geological Magazine 149, no. 5 (December 16, 2011): 783–97. http://dx.doi.org/10.1017/s0016756811000975.
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AbstractThe calc-alkaline, gneissic El Shalul granite is the westernmost gneiss dome or core complex within the Arabian–Nubian Shield. Previous studies have indicated that it represents either a window into the underlying pre-Neoproterozoic Sahara metacraton or a melt derived from the metacraton. U–Pb LA-ICP-MS dating of magmatic zircons from two samples of the variably foliated El Shalul pluton gives ages of 637 ± 5 Ma and 630 ± 6 Ma, excluding it from representing exhumed cratonic rocks. The ages are, however, indistinguishable from the age of the Um Ba'anib pluton, constituting the core of the Meatiq Gneiss Dome, as well as several other plutons in the Eastern Desert, indicating an important magmatic pulse in the Arabian–Nubian Shield in Late Cryogenian time. Major and trace element data indicate a within-plate setting. Bulk rock Nd-isotope and Hf-isotope data on zircons from the El Shalul pluton indicate derivation of the primary melt from a relatively juvenile source, either the lower crust of a mid-Neoproterozoic volcanic arc or as a result of fractionation of a mantle-derived mafic melt. Sm–Nd bulk rock isotopic data indicate a model age of c. 720 Ma for the protolith from which the melt was derived. Time-corrected Hf-isotope data obtained on the magmatic zircons indicate that the bulk of the source rock was extracted from the mantle around 810 Ma.
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Stevenson, Ross K., P. J. Patchett, and R. F. Martin. "Sm–Nd isochron from a granodiorite–granite complex in the Portman Lake region, Northwest Territories." Canadian Journal of Earth Sciences 26, no. 12 (December 1, 1989): 2724–29. http://dx.doi.org/10.1139/e89-232.
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Whole-rock samples for a granodiorite–granite intrusion in the Portman Lake area of the Northwest Territories yield an Sm–Nd isochron with an age of 2577 ± 36 Ma. The addition of a garnet analysis results in an age of 2562 ± 21 Ma. An Sm–Nd isochron is rare for granitic samples because of small ranges in 147Sm/144Nd values and variability in the initial Nd isotopic ratios. A wide range in 147Sm/144Nd values among samples in this study is considered a result of garnet fractionation and (or) variable concentrations of titanite in the samples. The εNd values for the initial Nd isotopic ratios of the isochrons are essentially zero or bulk Earth values. The evolution of the intrusion at 2.56 Ga reflects either the remelting of (2.7–2.8 Ga) preexisting continental crust or the mixing of depleted mantle material and crust older than 2.8 Ga. In either case, the data argue for a crustal history of at least 200 Ma prior to the intrusion of the complex in this section of the Churchill Province.
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Demonterova, Elena I., Alexei V. Ivanov, Ekaterina M. Mikheeva, Anastasia V. Arzhannikova, Andrei O. Frolov, Sergei G. Arzannikov, Nikolai V. Bryanskiy, and Lyudmila A. Pavlova. "Early to Middle Jurassic history of the southern Siberian continent (Transbaikalia) recorded in sediments of the Siberian Craton: Sm-Nd and U-Pb provenance study." Bulletin de la Société géologique de France 188, no. 1-2 (2017): 8. http://dx.doi.org/10.1051/bsgf/2017009.
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The deposition of Jurassic continental sedimentary rocks in the southern part of the Siberian continent (Transbaikalia) reflects the intensification of tectonomagmatic processes in this region. The most likely cause of this intensification was associated with the formation and development of the Mongol-Okhotsk orogenic belt. The latter was controlled in its turn by the closure of the Mongol-Okhotsk Ocean, for which the timing of its closure, as well as the formation of a collisional orogeny and its subsequent collapse are still under debate. We address this question by studying sediments of the Irkutsk Basin, which were deposited in a short time span in the Middle Jurassic, most likely during the Aalenian. The Sm-Nd data for bulk-rock sandstones demonstrate that the youngest samples of the Irkutsk Basin are characterized by a prominent contribution from a source within the juvenile crust of the Mongol-Okhotsk orogenic belt. U-Pb detrital zircon ages concur with the Sm-Nd data and show that the amount of material derived from local cratonic sources decreased in time whereas material from the remote Transbaikalian sources increased. Our data provide evidence that mountain growth in Transbaikalia intensified rapidly close to the Early and Middle Jurassic boundary.
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Maneiro, Kathryn A., Ethan F. Baxter, Scott D. Samson, Horst R. Marschall, and Jack Hietpas. "Detrital garnet geochronology: Application in tributaries of the French Broad River, Southern Appalachian Mountains, USA." Geology 47, no. 12 (October 15, 2019): 1189–92. http://dx.doi.org/10.1130/g46840.1.
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Abstract Nineteen single-grain detrital garnet ages from a tributary to the French Broad River (North Carolina, USA) establish a novel approach to Sm-Nd detrital garnet geochronology wherein the equilibrium bulk-rock composition lost during weathering and transport is replaced with the composition of inclusions leached from within each garnet grain. Detrital garnet ages were compared to published detrital zircon and monazite ages from the same river tributary system. Results show that 87% of the zircons have inherited Proterozoic ages; only zircon rims give Paleozoic ages. Monazites are exclusively Ordovician (weighted average: 460.9 ± 3.0 Ma). Our new detrital garnet ages (and the detrital zircon rims) record younger ages spanning the Late Ordovician to Early Devonian, likely reflecting prolonged metamorphic heating. The weighted average age of the detrital garnet population is Silurian (430.1 ± 7.2 Ma). Statistical tests confirm that the garnet population is younger than the monazite. The new detrital garnet ages illuminate a previously uninterpreted Silurian tectonometamorphic signal in this region.
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Mikhalsky, E. V., A. A. Laiba, B. V. Beliatsky, and K. Stüwe. "Geology, age and origin of the Mount Willing area (Prince Charles Mountains, East Antarctica)." Antarctic Science 11, no. 3 (September 1999): 338–52. http://dx.doi.org/10.1017/s0954102099000437.
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Mount Willing in the Prince Charles Mountains (East Antarctica) is part of the Fisher Volcano–plutonic complex which formed as part of the global-scale Grenvillian mobile belt system. Mount Willing is composed of four rock complexes: 1) a metamorphic sequence, 2) gabbro intrusions, 3) deformed felsic intrusives, and 4) abundant post-metamorphic dykes and veins. Three rock types constitute the metamorphic sequence: amphibole–biotite felsic plagiogneiss, mafic to intermediate biotite–amphibole schist, and biotite paragneiss. The bulk composition of the mafic schists classifies them as tholeiitic basalts, and rarely as basaltic andesites or andesites. Index mg ranges widely from 47 to 71. Concentrations of TiO2, P2O5, and high-field strength elements are high in some rocks. These rocks are thought to have been derived from enriched (subcontinental) mantle sources. Sm–Nd and U–Pb isotopic data indicate a series of Mesoproterozoic thermal events between 1100 and 1300 Ma. In particular, these events occurred at 1289 ± 10 Ma (volcanic activity), at 1177 ± 16 Ma (tonalite intrusion), at 1112.7 ± 2.4 and at 1009 ± 54 Ma (amphibolite facies metamorphic events). Rb–Sr systematics also indicates a thermal overprint at 636 ± 13 Ma. Mafic schists show low initial 877Sr/86Sr ratios between 0.7024 and 0.7030. Felsic rocks show higher Sri values between 0.7037 and 0.7061. Basaltic andesite metavolcanic and plutonic rocks form a calc-alkaline evolutionary trend, and probably originated from subduction-modified mantle sources in a convergent plate margin environment. An oceanic basin may have existed in central Prince Charles Mountains about 1300 Ma ago and was closed as a result of continental collision around 1000 to 800 Ma.
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Windom, Kenneth E., W. Randall Van Schmus, Karl E. Seifert, E. Timothy Wallin, and Raymond R. Anderson. "Archean and Proterozoic tectono-magmatic activity along the southern margin of the Superior Province in northwestern Iowa, United States." Canadian Journal of Earth Sciences 30, no. 6 (June 1, 1993): 1275–85. http://dx.doi.org/10.1139/e93-109.
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A Precambrian igneous body of ultramafic and mafic rocks, named the Otter Creek layered igneous complex, occurs within the basement of northwestern Iowa, United States. It is marked by a circular magnetic anomaly, one of several that lie north and west of an inferred suture between the Archean Superior Province and Early Proterozoic juvenile crust. Sm–Nd whole-rock analyses for several rock types from the Otter Creek complex yield an isochron age of 2890 ± 90 Ma, with an εNd(t) of −0.9 ± 2.4. A block of older banded iron formation, itself intruded by lamprophyre dikes, is contained within the layered sequence. The iron formation – lamprophyre block has undergone high-temperature metamorphism followed by a retrograde event. A quartz monzodiorite gneiss, with a U–Pb age of 2523 ± 5 Ma, occurs near the layered complex, but the contact relations are not known. The layered series is overlain by Proterozoic keratophyre with a U–Pb age of 1782 ± 10 Ma. These felsic pyroclastic rocks are extremely depleted in K, Rb, Ba, and Cs. Our data are consistent with Archean greenstone-belt formation, including chemical sedimentation followed by mafic–ultramafic magmatism at approximately 2.9 Ga, followed by two later episodes of magmatism, one at approximately 2.5 Ga and the other at approximately 1.78 Ga. The Otter Creek complex is the first Archean greenstone reported south of the Great Lakes Tectonic Zone (GLTZ); its 2.9 Ga age is older than those reported for the granite–greenstone rocks north of the GLTZ. The southern portion of the Superior Province thus appears to have formed later, and in a different tectonic environment, than the high-grade gneisses of the Minnesota River Valley, but before the bulk of the granite–greenstone rocks exposed in northern Minnesota, Ontario, and eastern Manitoba.
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Mitchell, Roger H. "Igneous Rock Associations 26. Lamproites, Exotic Potassic Alkaline Rocks: A Review of their Nomenclature, Characterization and Origins." Geoscience Canada 47, no. 3 (September 28, 2020): 119–42. http://dx.doi.org/10.12789/geocanj.2020.47.162.
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Lamproite is a rare ultrapotassic alkaline rock of petrological importance as it is considered to be derived from metasomatized lithospheric mantle, and of economic significance, being the host of major diamond deposits. A review of the nomenclature of lamproite results in the recommendation that members of the lamproite petrological clan be named using mineralogical-genetic classifications to distinguish them from other genetically unrelated potassic alkaline rocks, kimberlite, and diverse lamprophyres. The names “Group 2 kimberlite” and “orangeite” must be abandoned as these rock types are varieties of bona fide lamproite restricted to the Kaapvaal Craton. Lamproites exhibit extreme diversity in their mineralogy which ranges from olivine phlogopite lamproite, through phlogopite leucite lamproite and potassic titanian richterite-diopside lamproite, to leucite sanidine lamproite. Diamondiferous olivine lamproites are hybrid rocks extensively contaminated by mantle-derived xenocrystic olivine. Currently, lamproites are divided into cratonic (e.g. Leucite Hills, USA; Baifen, China) and orogenic (Mediterranean) varieties (e.g. Murcia-Almeria, Spain; Afyon, Turkey; Xungba, Tibet). Each cratonic and orogenic lamproite province differs significantly in tectonic setting and Sr–Nd–Pb–Hf isotopic compositions. Isotopic compositions indicate derivation from enriched mantle sources, having long-term low Sm/Nd and high Rb/Sr ratios, relative to bulk earth and depleted asthenospheric mantle. All lamproites are considered, on the basis of their geochemistry, to be derived from ancient mineralogically complex K–Ti–Ba–REE-rich veins, or metasomes, in the lithospheric mantle with, or without, subsequent contributions from recent asthenospheric or subducted components at the time of genesis. Lamproite primary magmas are considered to be relatively silica-rich (~50–60 wt.% SiO2), MgO-poor (3–12 wt.%), and ultrapotassic (~8–12 wt.% K2O) as exemplified by hyalo-phlogopite lamproites from the Leucite Hills (Wyoming) or Smoky Butte (Montana). Brief descriptions are given of the most important phreatomagmatic diamondiferous lamproite vents. The tectonic processes which lead to partial melting of metasomes, and/or initiation of magmatism, are described for examples of cratonic and orogenic lamproites. As each lamproite province differs with respect to its mineralogy, geochemical evolution, and tectonic setting there is no simple or common petrogenetic model for their genesis. Each province must be considered as the unique expression of the times and vagaries of ancient mantle metasomatism, coupled with diverse and complex partial melting processes, together with mixing of younger asthenospheric and lithospheric material, and, in the case of many orogenic lamproites, with Paleogene to Recent subducted material.
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Sushchevskaya, N. M., T. A. Shishkina, M. V. Portnyagin, V. G. Batanova, and B. V. Belyatsky. "Long-lasting influence of the Discovery plume on tholeiitic magmatism in the South Atlantic: data on basalts recovered by hole 513a, dsdp leg 71." Геохимия 64, no. 2 (March 15, 2019): 107–27. http://dx.doi.org/10.31857/s0016-7525642107-127.
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The paper presents the very first data on concentrations of major and trace elements; Sr, Nd, and Pb isotopic ratios of rocks; and the composition of olivine phenocrysts of 38-Ma basalts recovered by Hole 513a (DSDP Leg 71) in the South Atlantic. The bulk-rock samples and the chilled glasses are mildly magnesian (7–8 wt % MgO) and bear elevated FeO and low Na2O concentrations, as is typical of MORB of the TOR-1 type. Olivine phenocrysts (Fo84.5–88) in these rocks contain concentrations of trace elements (Ni, Mn, Cr, and Zn) that are typical of classic MORB, which are produced by partial melting mantle peridotite. The rocks are strongly depleted in incompatible elements [(La/Sm)n ~ 0.6] but have elevated Ba/Nb, K/Nb, and Pb/Ce ratios and Cu, Ag, and Au concentrations that are 1.5–4 times higher than in typical depleted MORB (N-MORB) and in most rift basalts in the South Atlantic. Isotope compositions of the basalts (average ratios 206Pb/204Pb ~ 18.0; 207Pb/204Pb ~ 15.6, 208Pb/204Pb ~ 38.0, 143Nd/144 Nd ~ 0.5130, and 87Sr/86Sr ~ 0.7040) are close to those in modern tholeiites from the southern MAR segment (SMAR) north of the Agulhas Fracture Zone. The data indicate that the magmas were derived from a strongly depleted mantle source that contained a minor (~3%) admixture of an enriched component, which is discernible in the magmas of the Discovery hotspot. The composition of the source, which is more depleted than DM, and the high degrees of melting of this source explain why the basalts from DSDP Hole 513a are enriched in chalcophile elements. It is believed that spreading magmatism at 45°–48° S in SMAR as far back as 40 Ma was already affected by the Discovery hotspot. This hotspot might be related to the Tristan plume system, and its origin and long-lasting influence on spreading magmatism in the South Atlantic are regarded as evidence of the extensive effect of the Tristan plume.
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Saleeby, Jason B. "Age and tectonic setting of the Duke Island ultramafic intrusion, southeast Alaska." Canadian Journal of Earth Sciences 29, no. 3 (March 1, 1992): 506–22. http://dx.doi.org/10.1139/e92-044.
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Concordant U–Pb zircon ages on hornblende–plagioclase pegmatites and a related granophyre from marginal and roof zones of the Duke Island ultramafic intrusion, and from leucoquartz diorite internal to hornblende–clinopyroxenite of nearby Mary Island cluster between 108 and 111 Ma. Sm–Nd mineral and bulk-rock data from pegmatite and granophyre zircon samples and from wehrlites and clinopyroxenites of the main Duke Island cumulate sequence are consistent with the consanguinity of the ultramafic cumulates and the zircon-bearing feldspathic rocks, and with an Early Cretaceous igneous age for the intrusion. Wall rocks for the intrusion consist of Ordovician–Silurian amphibolite- and greenschist-grade metamorphosed plutonic, volcanic, and minor sedimentary rocks and crosscutting Late Triassic gabbro–diorite of the Alexander terrane.The Duke Island ultramafic intrusion formed as a northwest-trending elongate funnel-shaped stratiform body commensurate with extensional brittle–ductile faulting in its roof and adjacent wall rocks. Intrusion occurred in a basinal setting within the Gravina volcanic arc along the Cordilleran continental margin. During the latter phases of intrusive activity the Gravina basin began to close by regional thrust faulting, which in the Duke Island region was west-northwest directed. The intrusion may have still had local intercumulate liquid upon initiation of thrust faulting. It responded first by open folding with incipient crystal plasticity. Once completely solidified, the intrusion behaved like a large "augen" with ductile deformation concentrated along its margins and within quartzo-feldspathic and micaceous members of its wall-rock complex. Much of the intrusion's northern margin behaved as a ductile shear zone serving as a tear fault between thrust plates to the northeast and an oblique thrust complex that roots beneath the southwest margin of the intrusion. The intrusion may thus be tectonically transported relative to its original underpinnings. North-trending high-angle faults and parallel fracture cleavage also cut the intrusion in response to axial loading as a result of its initial elongate shape and orientation relative to the thrust kinematics.
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Shaw, D. M., A. P. Dickin, H. Li, R. H. McNutt, H. P. Schwarcz, and M. G. Truscott. "Crustal geochemistry in the Wawa–Foleyet region, Ontario." Canadian Journal of Earth Sciences 31, no. 7 (July 1, 1994): 1104–21. http://dx.doi.org/10.1139/e94-099.
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Fifty-three rock samples from the Kapuskasing structural zone (KSZ) and 56 from the Wawa domal gneiss terrane (WGT), Ontario, have been analysed for major elements, 32 trace elements, and δ18O; δD was measured in a few samples.Average chemical compositions for the KSZ and WGT regions have been calculated from map unit averages weighted by regional abundance. Compared with estimates of the composition of the upper continental crust (UCC), the KSZ is enriched in Al, Fe, Mg, Ca, P, transition elements, Sc, and Sr; depleted in Si, B, most rare earth elements, Zr, Hf, Nb, Ta, Li, Na, K, U, Th, Ba, and Rb; but similar in composition to estimates of the lower continental crust. The WGT is closer in composition to the UCC. These data support the interpretation, on geophysical and petrological grounds, that the crust here is layered and has been uplifted, the WGT and KSZ regions representing progressively deeper levels.Igneous rock and orthogneiss δ18O values in the KSZ and WGT show good correlation with the weight percentages of SiO2. Paragneisses and clastic sediments and metavolcanics in the Michipicoten greenstone belt have higher ratios, as in other greenstone belts. Low δ18O and high δD values in most of the higher grade mafic gneisses show that they have never undergone low-temperature marine alteration. However, a few mafic gneisses with relict pillows show δ18O and δD values indicating low-temperature aqueous alteration. The δ18O and δD evidence throughout the two regions supports the view that no regional fluid homogenization took place.Errorchron ages of 2725 ± 130 Ma (Rb/Sr) and 2755 ± 110 Ma (Sm/Nd) were obtained for tonalite–granodiorite gneiss and agree within error with results from other workers. The intrusive Floranna Lake complex is 2580 ± 120 Ma (Rb/Sr), not significantly different from the age of the tonalite. Scatter in the data is to be attributed to localized late-stage alteration under low water–rock ratios by Sr-rich–Rb-poor brines. Model Nd ages suggest that there is no old crust [Formula: see text] in the region and that the 2700 Ma mantle was depleted relative to the bulk earth.
Dissertations / Theses on the topic "Bulk rock Sm-Nd"
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Chaumba, Jefferson B. "The Russell Lake Allochthon, southern Appalachians structure, petrography, bulk-rock and mineral chemistry, O, H, and Sm-Nd isotope geochemistry /." 2009. http://purl.galileo.usg.edu/uga%5Fetd/chaumba%5Fjefferson%5Fb%5F200908%5Fphd.
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Thesis (Ph. D.)--University of Georgia, 2009.Directed by Michael Roden. For abstract see https://getd.libs.uga.edu/pdfs/chaumba%5Fjefferson%5Fb%5F200908%5Fphd.pdf. Includes bibliographical references (leaves 246-279).
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Job, A. L. "Evolution of the basal Adelaidean in the northern Flinders Ranges: deposition, provenance and deformation of the Callanna and lower Burra Groups." Thesis, 2011. http://hdl.handle.net/2440/96175.
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This item is only available electronically.The rift and deformational evolution of the Adelaide Fold Belt’s northern-most extent, the northern Flinders Ranges, has received comparatively little attention than that of the southern Adelaide Fold Belt. The Arkaroola area, located in the mid-north northern Flinders Ranges, exposes the lowermost Adelaidean stratigraphy of this rift complex, the Callanna and lower Burra Groups, in a near complete sedimentary sequence. The rift history of this stratigraphy is complex, with deposition being largely controlled by the northeast-southwest orientated Paralana Fault and similarly orientated local growth faults. Locally, the Paralana Fault deviates from its regional orientation and forms a north-south striking segment, which under a considered sinistral strike-slip regime during extension would potentially create localised transtension in a ‘releasing bend’ environment. Rifting in the Arkaroola area is therefore considered to be analogous to the formation of a pull-apart basin. U-Pb dating of detrital zircons from the Paralana Quartzite, Humanity Seat Formation and Blue Mine Conglomerate from the Callanna and lower Burra groups yields ages that are comparable to local source regions the Gawler Craton, Mount Painter Basement Complex and the Curnamona Province, and suggest proximal derivation during early rift phases. Sm-Nd bulk rock analysis on the finer grained Woodnamoka Formation implies derivation from the Mount Painter Basement Complex or the upper Willyama Supergroup of the Curnamona Province, the latter of which potentially suggests a more distal provenance region outside of the Australian continent. Deformation in the northern Flinders Ranges has previously been largely ascribed to the ca. 500 Ma Delamerian Orogeny. However, the Arkaroola area exhibits complex deformation not observed in the directly overlying gently folded stratigraphy. Reactivation of pull-apart rift structures during transpression is considered a possible mechanism for producing and localising such deformation. The possibility of an early Neoproterozoic deformational event occurring prior to deposition of the lesser-deformed overlying stratigraphy is also considered, but in lieu of an unequivocal orogenic unconformity, cannot be confidently ascribed. Temporal constraints defined by this study are too broad to accurately define the timing of deformation, and therefore its timing and potential relationship to the Delamerian Orogeny remains largely enigmatic.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011