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Full-Text Articles in Social and Behavioral Sciences
U-Pb Zircon Geochronology And Nd Isotopic Signatures Of The Pre-Mesozoic Metamorphic Basement Of The Eastern Peruvian Andes: Growth And Provenance Of A Late Neoproterozoic To Carboniferous Accretionary Orogen On The Northwest Margin Of Gondwana, A Cardona, U G. Cordani, J Ruiz, V A. Valencia, R Armstrong, D Chew, A Nutman, A W. Sanchez
U-Pb Zircon Geochronology And Nd Isotopic Signatures Of The Pre-Mesozoic Metamorphic Basement Of The Eastern Peruvian Andes: Growth And Provenance Of A Late Neoproterozoic To Carboniferous Accretionary Orogen On The Northwest Margin Of Gondwana, A Cardona, U G. Cordani, J Ruiz, V A. Valencia, R Armstrong, D Chew, A Nutman, A W. Sanchez
Faculty of Science - Papers (Archive)
This study integrates U-Pb zircon geochronology (from LAM-ICP-MS, SHRIMP, and TIMS) with Nd isotopic data from orthogneisses and metasedimentary rocks of the pre-Mesozoic basement of the eastern Peruvian Andes to provide new information on the tectonic evolution and Neoproterozoic-Paleozoic paleogeography of this segment of the proto-Andean margin. A high-grade orthogneiss unit yields U-Pb zircon protolith crystallization ages of ~613 Ma. It was metamorphosed and intruded by an Early Ordovician granitoid. Subsequently, two different volcano-sedimentary sequences were laid down and metamorphosed, probably as a consequence of terrane accretion. The older sequence was deposited and metamorphosed between 450 and 420 Ma, and …
In Situ U-Pb, O And Hf Isotopic Compositions Of Zircon And Olivine From Eoarchaean Rocks, West Greenland: New Insights To Making Old Crust, Joe Hiess, Vickie C. Bennett, Allen P. Nutman, Ian S. Williams
In Situ U-Pb, O And Hf Isotopic Compositions Of Zircon And Olivine From Eoarchaean Rocks, West Greenland: New Insights To Making Old Crust, Joe Hiess, Vickie C. Bennett, Allen P. Nutman, Ian S. Williams
Faculty of Science - Papers (Archive)
The sources and petrogenetic processes that generated some of the Earth's oldest continental crust have been more tightly constrained via an integrated, in situ (U-Pb, O and Hf) isotopic approach. The minerals analysed were representative zircon from four Eoarchaean TTG tonalites and two felsic volcanic rocks, and olivine from one harzburgite/dunite of the Itsaq Gneiss Complex (IGC), southern West Greenland. The samples were carefully chosen from localities with least migmatisation, metasomatism and strain. Zircon was thoroughly characterized prior to analysis using cathodoluminescence, scanning electron, reflected and transmitted light imaging. The zircon from all but one sample showed only minor post-magmatic …
High Resolution Analysis Of Uranium And Thorium Concentration As Well As U-Series Isotope Distributions In A Neanderthal Tooth From Payre (Ardeche, France) Using Laser Ablation Icp-Ms, R. Grun, Maxime Aubert, Renaud C. Joannes-Boyau, M-H Moncel
High Resolution Analysis Of Uranium And Thorium Concentration As Well As U-Series Isotope Distributions In A Neanderthal Tooth From Payre (Ardeche, France) Using Laser Ablation Icp-Ms, R. Grun, Maxime Aubert, Renaud C. Joannes-Boyau, M-H Moncel
Faculty of Science - Papers (Archive)
We have mapped U (238U) and Th (232Th) elemental concentrations as well as U-series isotope distributions in a Neanderthal tooth from the Middle Palaeolithic site of Payre using laser ablation ICP-MS. The U-concentrations in an enamel section varied between 1 and 1500 ppb. The U-concentration maps show that U-migration through the external enamel surface is minute, the bulk of the uranium having migrated internally via the dentine into the enamel. The uranium migration and uptake is critically dependent on the mineralogical structure of the enamel. Increased U-concentrations are observed along lineaments, some of which are associated with cracks, and others …
New U-Pb Shrimp Zircon Ages For Pre-Variscan Orthogneisses From Portugal And Their Bearing On The Evolution Of The Ossa-Morena Tectonic Zone, Umberto G. Cordani, Allen Phillip Nutman, Antonio S. Andrade, Jose F. Santos, Maria Do Rosario Azevedo, Maria Helena Mendes, Manuel S. Pinto
New U-Pb Shrimp Zircon Ages For Pre-Variscan Orthogneisses From Portugal And Their Bearing On The Evolution Of The Ossa-Morena Tectonic Zone, Umberto G. Cordani, Allen Phillip Nutman, Antonio S. Andrade, Jose F. Santos, Maria Do Rosario Azevedo, Maria Helena Mendes, Manuel S. Pinto
Faculty of Science - Papers (Archive)
New SHRIMP U-Pb zircon ages for the Portalegre and Alcáçovas orthogneisses document a complex pre-Variscan history for the Iberian basement in Portugal. The available geochemical and geochronological data for the Alcáçovas orthogneiss (ca. 540 Ma) tend to favor its involvement in a Cadomian orogenic event. This is consistent with the development of an active continental margin setting at the end of the Proterozoic and supports a Gondwanan provenance for the Iberian crust. On the other hand, the Ordovician emplacement age obtained for the magmatic precursors of the Portalegre orthogneisses (497 ± 10 Ma) provides additional evidence for the occurrence of …
Models For Genesis Of Kamchatka Are Magmas: New Insights From U-Series, Anthony Dosseto, Bernard Bourdon
Models For Genesis Of Kamchatka Are Magmas: New Insights From U-Series, Anthony Dosseto, Bernard Bourdon
Faculty of Science - Papers (Archive)
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