U-Pb isotopic age for detrital zircons from the Williams Point Beds, Livingston Island PDF Download
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Author: W.P. LOSKE
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Languages : en
Pages :
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Author: W.P. LOSKE
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Category :
Languages : en
Pages :
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Category : Antarctica
Languages : en
Pages : 414
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Category : Geology
Languages : en
Pages : 1676
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Author: Yan Luo
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ISBN: 9781361438718
Category :
Languages : en
Pages :
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This dissertation, "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" by Yan, Luo, 羅彥, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled 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 Submitted by Luo Yan for the degree of Doctor of Philosophy at The University of Hong Kong in December 2005 The North China Craton (NCC) is the largest and oldest known continental block in China. The Jiao-Liao-Ji mobile belt along the eastern margin of the NCC is one of the rarely preserved Paleoproterozoic integrities in the world. As an important Paleoproterozoic sedimentary sequence of this belt, the Liaohe Group consists of an assemblage that includes a lower arkose- and volcanic-rich sequence (Langzishan, Li'eryu /Gaojiayu Formations), through a middle carbonate-rich sequence (Dashiqiao Formation) to an upper argillaceous sequence (Gaixian Formation). Traditionally, this group was subdivided into the North and South Liaohe Groups. Associated with the Liaohe Group are large volumes of granitoid rocks (Liaoji Granite), whose emplacement age has been dated at 2.1-2.2 Ga. Regionally, the Liaohe Group and the associated Liaoji Granite extend along a NEE-trending belt that is flanked by 2.45-2.55 Ga basement gneisses. Because of the lack of knowledge about the timing of deposition and metamorphism, nature of the sedimentary provenance and the basement, controversy exists on several issues including the depositional environment and tectonic significance of these rocks. The present work aims to constrain key issues by studying U-Pb, Hf isotopic and trace elemental compositions of detrital zircons from the Liaohe Group. Modern analytical technology such as cathodoluminescence (CL) imaging, laser ablation inductively coupled plasma mass spectrometry and laser ablation multiple collector inductively coupled plasma mass spectrometry were employed. CL images reveal that most detrital zircon grains from the Liaohe Group are characterized by concentric oscillatory zoning, suggesting magmatic origin. However, a small number of zircon grains have structureless recrystallization rims, indicating metamorphic origin. Results of this study show that the zoned zircon grains of the Langzishan Formation, the lowest sequence of the Liaohe Group, have concordant U-Pb ages ranging from 2.24-2.05 Ga, suggesting that the minimum depositional time of the Liaohe Group is at 0.2815 and 0.2813), similar Hf model ages (T, peaks at 2.66 Ga 2.75 DM Ga, and 2.8 3.0 Ga) and similar εHf values ( -5 +9 and -7 +5). Data of this study suggest that the metasedimentary rocks of the Liaohe Group were deposited between 2.05 and 1.93 Ga, a short time after emplacement of the Liaoji Granite. The provenance of the Langzishan, Li'eryu and Gaixian Formations, is particularly dominated by the Liaoji Granite. Furthermore, the protoliths of the North and South groups may have formed simultaneously and could have developed on a single late Archean basement rather than two different blocks. This
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Category : Antarctica
Languages : en
Pages : 764
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Author: Thomas R. Lovell
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 178
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Detrital zircon U-Pb geochronology and thin-section petrology of core samples taken from onshore Alabama and offshore federal lease blocks, including Destin Dome, Pensacola, and Mobile, constrain sediment provenance for the Upper Jurassic Norphlet Formation in the eastern Gulf of Mexico. Previous research of the Norphlet Fm. in onshore Alabama suggests that sediments near onshore areas of Alabama originated from metamorphic rocks of the Talladega slate belt and Piedmont. This study provides evidence that the Gondwanan Suwannee terrane is another potential source for the Norphlet Fm. in the EGOM. This study determined U-Pb ages for 1111 detrital zircons from 13 Norphlet Fm. core and cutting samples were determined using LA-ICPMS. The Norphlet Fm. yields four major U-Pb age ranges: 197.9 - 350 Ma, 350 - 770 Ma, 800 - 1650 Ma, and 1650 - 3390 Ma. These ages correspond with known U-Pb ages of source terranes common to Laurentia, including the Grenville (950 - 1300 Ma), (Granite-Rhyolite (1350 - 1550 Ma), Yavapai-Matzatzal (1650 - 1750 Ma), Penokean (1800 - 1900 Ma), and Superior Provinces (>2500 Ma). U-Pb ages also reveal sourcing from the Gondwanan Suwannee Terrane (540 - 580 Ma and 2000 - 2200 Ma). This study establishes four geochronologic source terranes: the ancient Appalachian Mountains, the Appalachian foreland basin, Mesozoic rift basins, and the Suwannee Terrane. Ten samples from onshore Alabama yield detrital zircon U-Pb ages characteristic of Laurentian sources (Appalachian mountains and Appalachian foreland basin), whereas two offshore samples yield characteristic Gondwanan (Suwannee Terrane) ages. Four samples located adjacent to the Mesozoic rift basin reveal ages characteristic of both Laurentia and Gondwana - indicating an area of sediment mixing during the late Jurassic. Twelve thin-sections taken from 9 cores in the onshore and state waters areas were point counted for 400 grains each for compositional analysis. Petrolographic analyses reveal plagioclase and potassium feldspars, polycrystalline quartz, metamorphic and volcanic lithic fragments as dominant grain types. Petrologic data corroborate that onshore Alabama samples were sourced by recycled orogenic and cratonic rocks of Laurentia and southern samples were sourced by less mature sources characteristic of a rift basin (Mesozoic rift basins). A paleogeographic reconstruction illustrates sediment being distributed from Laurentian and Gondwanan sources via alluvial, fluvial, eolian, and marine depositional environments.
Author: Geological Survey (U.S.)
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ISBN:
Category :
Languages : en
Pages : 35
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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: Dassanayake Mudalige G. S. Dassanayake
Publisher:
ISBN: 9781361027486
Category :
Languages : en
Pages :
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This dissertation, "U-Pb Detrital Zircon Geochronology for Tabbowa Beds in Sri Lanka" by Dassanayake Mudalige G S, Dassanayake, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Detrital zircon geochronology has proven to be a useful tool for correlating sedimentary sequences with their source rocks. The objective of this study was to get provenance details of Tabbowa Beds utilizing U-Pb detrital zircon geochronology. Two rock samples were collected from Tabbowa Beds. The analysis to get U-Pb isotopic ratios has been performed using LA-ICP-MS system for 200 zircon grains separated from the samples. Zircon populations showed complex internal texture variations. Three main regions were identified from the histograms and concordia diagrams plotted for the isotopic data which showed a clear relationship to the crust formation age and the post geological events happened in the Wanni Complex of Sri Lanka. Most of the detrital cores showed comparatively older U-Pb ages which indicated the crust formation age of the Wanni Complex. Magmatic zircons identified from the samples showed 850 - 700 Ma and 1000 - 880 Ma age ranges giving evidences for the Pre Pan African magmatic events happened in the Wanni Complex. Overgrowth of detrital cores and newly grown metamorphic zircons identified from the samples had 650 - 430 Ma age range which signified the metamorphic age of the Wanni complex. U-Pb detrital zircon ages and their morphology gave evidences for three different source rocks that supplied sediments to the Tabbowa Basin. Therefore, it was concluded that the identified source rocks of Tabbowa Beds existed in the Wanni Complex and the age data represented the post magmatic events and metamorphism happened in the Wanni Complex. DOI: 10.5353/th_b5677163 Subjects: Geology - Sri lanka
Author: Yan Luo (Geologist.)
Publisher:
ISBN:
Category : Cratons
Languages : en
Pages : 398
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