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U-Pb geochronologicevidence for theevolution of theGondwanan margin ofthe north-centralAndes David ChewUrs SchalteggerJan Košler2007 год

U-Pb geochronologic evidence for the evolution of the Gondwanan margin of the north-central Andes
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Аннотация: We investigated the Neoproterozoic–early Paleozoic evolution of the Gondwanan margin of the north-central Andes by employing U-Pb zircon geochronology in the Eastern Cordilleras of Peru and Ecuador using a combination of laser-ablation–inductively coupled plasma–mass spectrometry detrital zircon analysis and dating of syn- and post-tectonic intrusive rocks by thermal ionization mass spectrometry and ion microprobe. The majority of detrital zircon samples exhibits prominent peaks in the ranges 0.45–0.65 Ga and 0.9–1.3 Ga, with minimal older detritus from the Amazonian craton. These data imply that the Famatinian-Pampean and Grenville (= Sunsas) orogenies were available to supply detritus to the Paleozoic sequences of the north-central Andes, and these orogenic belts are interpreted to be either buried underneath the present-day Andean chain or adjacent foreland sediments. There is evidence of a subduction-related magmatic belt (474–442 Ma) in the Eastern Cordillera of Peru and regional orogenic events that pre- and postdate this phase of magmatism. These are confirmed by ion-microprobe dating of zircon overgrowths from amphibolite-facies schists, which reveals metamorphic events at ca. 478 and ca. 312 Ma and refutes the previously assumed Neoproterozoic age for orogeny in the Peruvian Eastern Cordillera. The presence of an Ordovician magmatic and metamorphic belt in the north-central Andes demonstrates that Famatinian metamorphism and subduction-related magmatism were continuous from Patagonia through northern Argentina to Venezuela. The evolution of this extremely long Ordovician active margin on western Gondwana is very similar to the Taconic orogenic cycle of the eastern margin of Laurentia, and our findings support models that show these two active margins facing each other during the Ordovician.
Год издания: 2007
Авторы: David Chew, Urs Schaltegger, Jan Košler, Martin J. Whitehouse, Marcus Gutjahr, Richard Spikings, Aleksandar Mišković
Издательство: Geological Society of America
Источник: Geological Society of America Bulletin
Ключевые слова: Geological and Geochemical Analysis, Geochemistry and Geologic Mapping, earthquake and tectonic studies