Evolution Of The Continental Crust And Significance Of The Zircon Record A Case Study From The French Massif Central
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Evolution Of The Continental Crust And Significance Of The Zircon Record A Case Study From The French Massif Central
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Author : Simon Couzinié
language : en
Publisher:
Release Date : 2017
Evolution Of The Continental Crust And Significance Of The Zircon Record A Case Study From The French Massif Central written by Simon Couzinié and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
The formation of the continental crust is a major consequence of Earth differentiation. Understanding how the crust formed and evolved through time is paramount to locate the vast mineral deposits hosted therein and address its influence on the global climate, ultimately affecting the development of terrestrial life. Recent advances on the topic of continental crust evolution benefited from improvements of analytical techniques enabling in situ measurements of U-Pb- Hf-O isotope compositions in zircon, a widespread accessory mineral of continental igneous rocks. The time constrains derived from the U-Pb chronometer coupled with the petrogenetic information retrieved from Hf-O isotope signatures are currently used to unravel the diversity and succession of magmatic events affecting the continental crust at the regional and global scales. This study reconstructs the evolutionary path followed by the crust segment today exposed in the eastern part of the French Massif Central (FMC), a portion of the Variscan belt of Western Europe, with the aim to investigate the potential flaws of the zircon record of crust evolution. In this scope, the origin and geodynamic significance of the constituent FMC lithological units are tackled by combining conventional petrological observations with zircon U-Pb-Hf-O isotope data. The results obtained following this integrated approach are then confronted to the conclusions that would have been drawn solely from zircon isotopic signatures, taken out of their petrological context, as is commonly performed in studies investigating crust evolution. The oldest rocks of the FMC correspond to Ediacaran (590_550 Ma) meta-sediments deposited in back-arc basins along the northern Gondwana margin. Such basins were fed by a mixed detritus originating from the adjacent Cadomian magmatic arc and a distal Gondwana source, presumably the Sahara Metacraton. Partial melting of these meta-sediments at the Ediacaran/Cambrian boundary led to voluminous S-type granitic magmatism, pinpointing a first major crust reworking event in the FMC. The origin of anatexis likely stems from the transient thickening of the hot, back-arc crust caused by the flattening of the Cadomian subduction. Subordinate melting of the depleted backarc mantle at that time is also documented. During the Lower Paleozoic, rifting of the northern Gondwana provoked coeval crust and (limited) mantle melting. Mantle-derived igneous rocks show markedly diverse trace element and isotopic signatures, consistent with a very heterogeneous mantle source pervasively modi_ed by the Cadomian subduction. Finally, the Variscan collision resulted in crustal melting as evidenced by the emplacement of S-type granites and the formation of migmatite domes, the spatial distribution of which being partly controlled by the crustal architecture inherited from pre-orogenic events. Synchronous intrusion of mafic mantle-derived magmas and their differentiates testify for Variscan post-collisional new continental crust production in the FMC. Two major inconsistencies exist between these results and the zircon record. First, zircon Hf model ages would point to substantial Mesoproterozoic crust formation in the FMC whereas more than 60% of the crust is actually Neoproterozoic in age. Second, new additions to the continental crust volume during the Variscan orogeny are not recorded even though 5 to 10% of the exposed crust formed at that time. The origin of both discrepancies inherently lies in the mixed isotopic signature carried by many zircon grains. Such equivocal information can only be detected when additional petrological constrains on the zircon host rocks are available and provide guidance in interpreting the zircon record of crust evolution.
The Geology Of Central Europe Precambrian And Palaeozoic
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Author : Tom McCann
language : en
Publisher: Geological Society of London
Release Date : 2008
The Geology Of Central Europe Precambrian And Palaeozoic written by Tom McCann and has been published by Geological Society of London this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Science categories.
Publishers Weekly Top 10 Best of the Year In her new collection, Story Prize finalist Maureen F. McHugh delves into the dark heart of contemporary life and life five minutes from now and how easy it is to mix up one with the other. Her stories are post-bird flu, in the middle of medical trials, wondering if our computers are smarter than us, wondering when our jobs are going to be outsourced overseas, wondering if we are who we say we are, and not sure what we'd do to survive the coming zombie plague. Praise for Maureen F. McHugh: "Gorgeously crafted stories."—Nancy Pearl, NPR "Hauntingly beautiful."—Booklist "Unpredictable and poetic work."—The Plain Dealer Maureen F. McHugh has lived in New York; Shijiazhuang, China; Ohio; Austin, Texas; and now lives in Los Angeles, California. She is the author of a Story Prize finalist collection, Mothers & Other Monsters, and four novels, including Tiptree Award-winner China Mountain Zhang and New York Times editor's choice Nekropolis. McHugh has also worked on alternate reality games for Halo 2, The Watchmen, and Nine Inch Nails, among others. io9 Best SF&F Books of 2011 Tiptree Award Honor List Philip K. Dick Award finalist Story Prize Notable Book
Secular Evolution Of The Continental Crust Through Detrital Zircon
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Author :
language : en
Publisher:
Release Date : 2010
Secular Evolution Of The Continental Crust Through Detrital Zircon written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
4 D Framework Of Continental Crust
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Author : Robert D. Hatcher
language : en
Publisher: Geological Society of America
Release Date : 2007
4 D Framework Of Continental Crust written by Robert D. Hatcher and has been published by Geological Society of America this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Science categories.
"This book contains landmark papers on the processes of formation of continental crust from its beginnings in the Archean to modern processes, as well as discussions of several ancient and modern orogenic belts. The book is international in scope, with contributions from geoscientists dealing with crustal processes on five continents, and articles from more than 50 non-U.S. authors and co-authors."--Publisher's website.
The Generation And Evolution Of Silicic Magma And Juvenile Crust
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Author : Tamara Lou Carley
language : en
Publisher:
Release Date : 2014
The Generation And Evolution Of Silicic Magma And Juvenile Crust written by Tamara Lou Carley and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Electronic dissertations categories.
The Variscan Orogeny
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Author : K. Schulmann
language : en
Publisher: Geological Society of London
Release Date : 2014-07-28
The Variscan Orogeny written by K. Schulmann and has been published by Geological Society of London this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-07-28 with Science categories.
This volume summarizes the state of the art of Variscan geology from Iberia to the Bohemian Massif. The European Variscan belt consists of two orogens: the older, northern and the younger, southern. The northern Variscan realm was dominated by Late Devonian–Carboniferous rifting, subduction and collisional events as defined by sedimentary records, crustal growth, recycling of continental crust and large-scale deformations. In contrast, the southern European crust was reworked by major Late Carboniferous collision followed by Permian wrenching. The Late Carboniferous–Permian orogeny overprinted the previously accreted system in the north, but with much lower intensity, resulting in magmatic recycling and extensional tectonics. These two main orogenic cycles do not reflect episodic evolution of a single orogenic system but a complete change in orientation of stress field, thermal regime, degree of reworking and recycling of European crust, reflecting a major switch in plate configurations at the Early–Late Carboniferous boundary.
Exposed Cross Sections Of The Continental Crust
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Author : M.H. Salisbury
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Exposed Cross Sections Of The Continental Crust written by M.H. Salisbury and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
In the Fall of 1988, 64 geologists and geophysicists from 11 countries met in Killarney, Ontario, on the north shore of Lake Huron to examine evidence that suggests that the continental crust is exposed in cross-section at several key locations on the Earth's surface. The meeting, which was held under NATO auspices as an Advanced Study Institute, was a landmark event in that it was the first time that many of the lead scientists working on these complexes in relative isolation around the world had' ever gathered together to compare results. The present volume is a compendium of the invited lectures given on the principle sections, plus an array of supporting papers on these and other sections as well as on related topics such as crustal emplacement mechanisms, deformation and rheology. Nearly all of the best known sections are represented, including the Ivrea Zone, Calabria, the Kapuskasing Zone, Fiordland and many others. It is our hope that this Volume will serve as a reference for Earth scientists who are trying to understand levels of the crust not normally exposed to view, as well as a point of departure for new research and a teaching aid to new entrants in this relatively new field of study.
Archean Continental Crust Formation And The Rise Of Atmospheric Oxygen
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Author : Ann M. Bauer (Ph. D.)
language : en
Publisher:
Release Date : 2017
Archean Continental Crust Formation And The Rise Of Atmospheric Oxygen written by Ann M. Bauer (Ph. D.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
This thesis examines critical aspects of the terrestrial environment that have resulted in a habitable planetary surface: the establishment of the continental crust and the progressive rise of an oxygenated atmosphere. The volume of continental crust on the earliest Earth is a critical parameter for constraining the chemical evolution of major terrestrial reservoirs, and radiogenic isotope signatures document this varying geochemical character. Chapter 1 presents a Lu-Hf and U-Pb isotopic characterization of zircons from the 4.0-2.9 Ga Acasta Gneiss Complex (AGC) and documents the magmatic extraction history of this domain, including changes in source compositions. These results are compared with a complementary dataset obtained using solution methods in Chapter 2. The integration of these results demonstrates the utility of performing coupled solution- and laser-based analyses on the same zircon populations to parse out U-Pb and Lu-Hf systematics. Zircons from many of these orthogneisses exhibit isotopic complexity due to the combined effects of accumulated radiation damage and repeated metamorphic episodes. For this reason, it is best to subsample zircon grains to isolate domains of distinct age and isotopic composition. In order to obtain suitable precision for subsampled domains, it was necessary to develop analytical techniques (Chapter 3) suited to small-volume analysis of the U-Pb and Lu-Hf isotope systems in zircon (via both laser ablation and solution analysis). In contrast to the whole rock Nd isotopic record of the AGC, the zircon Hf isotopic record does not indicate that rocks within the AGC were derived from a strongly depleted mantle. In order to evaluate the polymetamorphic evolution of these rocks, in Chapter 4 1 present a combined U-Pb and Sm-Nd isotope and trace element study of MREE-rich accessory minerals. In Chapter 5, I investigate sedimentary pyrite formation pathways and the oxygenation history of the late Archean atmosphere using combined sulfur and iron isotope signals as recorded in distinct morphologies of pyrite. This work represents a critical step in deconstructing the pathways of S-MIF production, transfer and preservation in the sedimentary record. Collectively, these studies contribute to our understanding of the establishment and evolution of the early continental crust and an oxygenated atmosphere.
Ophiolites And Oceanic Crust
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Author : Yildirim Dilek
language : en
Publisher: Geological Society of America
Release Date : 2000-01-01
Ophiolites And Oceanic Crust written by Yildirim Dilek and has been published by Geological Society of America this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000-01-01 with Science categories.
The proceedings from the September 1998 conference in Marshall, California contain 39 papers on the following topics: ophiolites, ocean crust, and global tectonics; oceanic lower crust and upper mantle; structure and physical properties of upper oceanic crust; hydrothermal processes; Pacific Rim ophiolites; and, Ophiolites from Iapetus, Rheic-Pleionic, Neotethyan, and Indian Oceans. Contributors include scientists with backgrounds in structural geology, tectonics, geophysics, petrology, and geochemistry. Numerous black and white illustrations (and one in color) are included. Annotation copyrighted by Book News Inc., Portland, OR
Duration Rates And Patterns Of Crustal Growth At Slow Spreading Mid Ocean Ridges
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Author : Craig B. Grimes
language : en
Publisher: ProQuest
Release Date : 2008
Duration Rates And Patterns Of Crustal Growth At Slow Spreading Mid Ocean Ridges written by Craig B. Grimes and has been published by ProQuest this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Earth (Planet) categories.
This dissertation addresses temporal and spatial characteristics of magmatic and tectonic accretion processes occurring at mid-ocean ridges during formation of new ocean lithosphere. The accretion histories of plutonic crust recovered by deep drilling of footwalls to large-displacement normal faults at three locations on the MAR are emphasized. Pb/U zircon dating of evolved gabbros and oceanic plagiogranites show that magmatic accretion typically occurs over 100-200 kyr. Magmatic accretion occurs by emplacement of many short-lived intrusive pulses that are focused at different depths within the crust and mantle. During formation of the Atlantis Massif core complex (30° N, MAR), spreading may have been partitioned up to 100% on the North American plate for at least 200 kyr, implying crustal accretion was highly asymmetric. Cooling rates of 1000-2000° C/m.y. over 900-200° C are documented at Atlantis Massif and two locations from 14-16°N, MAR, consistent with rapid denudation of the footwall sections to the seafloor following emplacement. Spreading rates combined with the time interval over which cooling to