Potential of combined U-Pb geochronology and Hf isotope geochemical studies on zircon to aid sedimentary provenance within Antarctica PDF Download
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Author: M.J. Flowerdew
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Category :
Languages : en
Pages :
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Author: M.J. Flowerdew
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: M.J. Flowerdew
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Category :
Languages : en
Pages :
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Author: John M. Hanchar
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 1501509322
Category : Science
Languages : en
Pages : 520
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Volume 53 of Reviews in Mineralogy and Geochemistry covers the most important aspects of zircon-related research over the past twenty-years and highlight possible future research avenues. The chapters review the structure of zircon and other mineral (and synthetic) phases with the zircon structure; the minor and trace element compositions of igneous, metamorphic and hydrothermal zircons; the study of melt inclusions in zircon; experimental and natural studies of zircon saturation and the use of zircon saturation thermometry for natural rocks; cation diffusion and oxygen diffusion in zircon; the historical development of zircon geochronology from the mid-1950s to the present; ID-TIMS, SIMS and ICP-MS; the application of zircon chronology in constraining sediment provenance and the calibration ofthe geologic time-scale; other isotopic systematics; the spectroscopy of zircon, both crystalline and metamict and an atlas of internal textures of zircon.
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Category : Antarctica
Languages : en
Pages : 312
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Author:
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Category :
Languages : en
Pages : 0
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Provenance study is a fundamental element of basin analysis, where understanding of sedimentation patterns and their driving mechanisms often requires information about the source of basin sediments. Many recent studies have turned to the geochronology (particularly single detrital zircon ages) and isotope geochemistry in sedimentary rocks to derive detailed information about sediment sources. This dissertation applies geochronology and isotope geochemistry to provenance questions in different settings, utilizing zircon U/Pb ages, feldspar common Pb isotope ratios, and carbonate 87Sr/86Sr ratios to gain new insights into provenance in three well-studied sedimentary systems. The first chapter, set in the Gualala Basin of northern California, provides an example of how conventional provenance indicators, detailed study of conglomerate clasts, U/Pb zircon ages, and common Pb isotope ratios of feldspar from the sand-sized fraction can all provide useful information. Combined, these different data types can produce a more complete picture of sedimentary source areas than any of them would be able to alone. In a continued investigation of applications for detrital zircon ages in provenance study, the second chapter develops a new "Confidence Envelope" method for comparing age distributions. The method developed here is based on characterizing the expected range of variability in samples drawn from the age distribution of a proposed sediment source area, and testing whether a sample of unknown provenance falls within that range. Using the uniquely well-constrained setting of the Green River Formation in Wyoming, the last two chapters investigate paleo-water provenance using an unprecedented dataset of 87Sr/86Sr ratios and Sr concentrations, compiled from both new data and data collected from previous studies. These data demonstrate that isotopic ratios in the Green River Formation lacustrine system changed rapidly, therefore lacustrine sediments were an extremely high-resolution recorder of lacustrine Sr evolution
Author: Gwen Margaret Linde
Publisher:
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Category : Electronic books
Languages : en
Pages : 360
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This dissertation investigated Neoproterozoic–Devonian units of the western Laurentian passive margin and Roberts Mountains allochthon (RMA) and determined U-Pb detrital ages and Hf isotope zircon analyses that provide new insights into the early Paleozoic tectonics of western Laurentia. The three chapters investigate several difficult questions and contradictions in the understanding of early Paleozoic tectonism in western Laurentia through analysis of sedimentary units. The provenance, depositional histories, and tectonic evolution of the lower Paleozoic sedimentary strata of north-central Nevada have long been subjects of speculation and debate. Detrital zircon U-Pb geochronology and Hf-isotope analyses indicate the provenance, sedimentary distribution patterns, and tectonic evolution of Upper Neoproterozoic–Cambrian passive margin strata and Ordovician–Devonian strata of the RMA, with a special emphasis on the enigmatic Harmony Formation. The study reported in Chapter 1 uses detrital zircon U-Pb geochronology to determine whether or not the Upper Neoproterozoic–Lower Cambrian Osgood Mountain Quartzite and the Upper Cambrian–Lower Ordovician Preble Formation in the Osgood Mountains of northern Nevada were units of the western Laurentian passive margin. Within the Osgood Mountain Quartzite, U-Pb age populations of the detrital zircons shift with stratal age. This shift indicates that the zircons were shed in different proportions from the source terranes, which suggests a change in provenance within the Osgood Mountain Quartzite. These changes are consistent across a Great Basin transect of coeval passive margin strata. The change in provenance is due to a shift in sedimentary transport patterns, which was caused by the Late Neoproterozoic-Early Cambrian uplift of the Transcontinental Arch. This study provided independent corroboration of the existence of the Transcontinental Arch and better precision for the timing at which the Arch uplifted. The study also recorded the impact of the uplifted Arch on continent-wide sediment dispersal patterns—the change in predominant source terranes—and confirmed the Arch as a sediment source for passive-margin strata. Regional coeval changes in detrital zircon U-Pb age patterns provide a correlative tool in unfossiliferous sediments and could be useful in future studies. Chapter 2 describes how detrital zircon U-Pb geochronology and Hf-isotope analyses were used to determine the provenance, sedimentary transport, and tectonic evolution of RMA strata. Workers have speculated for decades, with little agreement, on the origin, depositional basin(s), and subsequent tectonic transport of the RMA. Zircon grains from six Ordovician to Devonian arenite samples were analyzed for U-Pb ages; approximately one-quarter of these grains were further analyzed for Hf isotope ratios. Five of the studied units have similar U-Pb age populations and Hf-isotope ratios, while the U-Pb ages and Hf-ratios of the Ordovician lower Vinini Formation are significantly different. Comparison of these data with known analyses of igneous basement rocks and other sedimentary units of Laurentia reveals that the lower Vinini Formation originated in the north-central Laurentian craton. The other five units, as well as Ordovician passive margin sandstones of the western Laurentian margin, had a common source in the Peace River Arch region of western Canada. All of the RMA strata were deposited near the Peace River Arch region and subsequently tectonically transported south along the Laurentian margin, from where they were emplaced onto the craton during the Antler orogeny. This study determined the origin, location of the depositional basin, and proposed a subsequent tectonic evolution that accounts for origin, deposition, and current location of the RMA strata. Chapter 3 describes the origin, age, and tectonic development of the Harmony Formation. The Harmony Formation has always been difficult to explain—it is mostly an immature feldspathic arenite, which would argue for minimal transport from origin to deposition. However, its general position as the top thrust plate in the RMA stack argues for deposition oceanward of other more texturally mature RMA strata. The age of the Harmony Formation is equally contentious—published age determinations range from Cambrian to Mississippian. Zircon grains from ten arenite samples were analyzed for U-Pb ages; grains from eight of these samples were further analyzed for Hf-isotope ratios. Seven of the arenite units have similar U-Pb age peaks and Hf isotope ratios, whereas three differ significantly. The data confirmed the subdivision of the Harmony Formation into two petrofacies, quartzose (Harmony A) and feldspathic (Harmony B). Harmony A originated in the central Laurentian craton. Harmony B had a common source in eastern Alberta–western Saskatchewan, north of the source of the Harmony A. All of the Harmony Formation strata were deposited near eastern Alberta in Late Neoproterozoic through Cambrian time and subsequently tectonically interleaved with the Roberts Mountains allochthon strata. The entire package was tectonically transported south along the Laurentian margin. Subsequently, it was emplaced eastward onto the craton during the Late Devonian to Early Mississippian Antler orogeny. This study proposed a reasonable solution to one of the longest enduring and most puzzling conundrums of the western Cordillera—the origin, age, and transport of the Harmony Formation. These three studies demonstrated the utility of detrital zircon U-Pb geochronology and Hf-isotope analyses in better understanding difficult sedimentary and tectonic problems. The studies also provided new insights into the Early Paleozoic tectonic evolution of western Laurentian.
Author: Charles Ryan Jeffcoat
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 96
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Author: Matthew J. Kohn
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110561891
Category : Science
Languages : en
Pages : 596
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Book Description
Petrochronology is a rapidly emerging branch of Earth science that links time (ages or rates) with specific rock-forming processes and their physical conditions. It is founded in petrology and geochemistry, which define a petrogenetic context or delimit a specific process, to which chronometric data are then linked. This combination informs Earth’s petrogenetic processes better than petrology or geochronology alone. This volume and the accompanying short courses address three broad categories of inquiry. Conceptual approaches chapters include petrologic modeling of multi-component chemical and mineralogic systems, and development of methods that include diffusive alteration of mineral chemistry. Methods chapters address four main analytical techniques, specifically EPMA, LA-ICP-MS, SIMS and TIMS. Mineral-specific chapters explore applications to a wide range of minerals, including zircon (metamorphic, igneous, and detrital/Hadean), baddeleyite, REE minerals (monazite, allanite, xenotime and apatite), titanite, rutile, garnet, and major igneous minerals (olivine, plagioclase and pyroxenes). These applications mainly focus on metamorphic, igneous, or tectonic processes, but additionally elucidate fundamental transdisciplinary progress in addressing mechanisms of crystal growth, the chemical consequences of mineral growth kinetics, and how chemical transport and deformation affect chemically complex mineral composites. Most chapters further recommend areas of future research.
Author: J.L. Smellie
Publisher: Geological Society of London
ISBN: 178620536X
Category : Science
Languages : en
Pages : 802
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This memoir is the first to review all of Antarctica’s volcanism between 200 million years ago and the Present. The region is still volcanically active. The volume is an amalgamation of in-depth syntheses, which are presented within distinctly different tectonic settings. Each is described in terms of (1) the volcanology and eruptive palaeoenvironments; (2) petrology and origin of magma; and (3) active volcanism, including tephrochronology. Important volcanic episodes include: astonishingly voluminous mafic and felsic volcanic deposits associated with the Jurassic break-up of Gondwana; the construction and progressive demise of a major Jurassic to Present continental arc, including back-arc alkaline basalts and volcanism in a young ensialic marginal basin; Miocene to Pleistocene mafic volcanism associated with post-subduction slab-window formation; numerous Neogene alkaline volcanoes, including the massive Erebus volcano and its persistent phonolitic lava lake, that are widely distributed within and adjacent to one of the world’s major zones of lithospheric extension (the West Antarctic Rift System); and very young ultrapotassic volcanism erupted subglacially and forming a world-wide type example (Gaussberg).
Author: M. Satish-Kumar
Publisher: Geological Society of London
ISBN: 9781862392687
Category : Science
Languages : en
Pages : 472
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Book Description
Geological correlations of East Antarctica with adjoining continents have been puzzling geologists ever since the concept of a Gondwana supercontinent surfaced. Despite the paucity of outcrops because of ice cover, difficulty of access and extreme weather, the past 50 years of Japanese Antarctic Research Expeditions (JARE) has successfully revealed vital elements of the geology of East Antarctica. This volume presents reviews and new research from localities across East Antarctica, especially from Dronning Maud Land to Enderby Land, where the geological record preserves a history that spans the Archaean and Proterozoic. The reviews include extensive bibliographies of results obtained by geologists who participated in the JARE. Comprehensive geological, petrological and geochemical studies, form a platform for future research on the formation and dispersion of Rodinia in the Mesoproterozoic and subsequent assembly of Gondwana in the Neoproterozoic to Early Palaeozoic.
