Hot subduction in the middle Jurassic and partial melting of oceanic crust in Chilean Patagonia

Autor(es)

Angiboust, Samuel ; Hyppolito, Thais ; Glodny, Johannes ; Cambeses, Aitor ; Garcia-Casco, Antonio ; Calderon, Mauricio ; Juliani, Caetano

• Tipo de documento: Artigo Científico
• Fonte: GONDWANA RESEARCH; v. 42, p. 104-125, FEB 2017.
• Citações Web of Science: 7

Resumo

Rare remnants of a Mesozoic subduction high pressure (HP) accretionary complex are exposed on Diego de Almagro Island in Chilean Patagonia. We herein focus on the Lazaro unit, a coherent slice of oceanic crust exposed on this island that has been first affected by high temperature (HT) metamorphism followed by a lower temperature deformation event (LT). Its Pressure-Temperature-time (P-T-t) evolution is reconstructed using field and petrographic observations, phase relations, thermobarometry and geochronology. Remnants of a primary amphibolite to HP granulite-facies event in mafic rocks comprising garnet (with ilmenite exsolutions), diopside, trondhjemitic melt, pargasite, plagioclase +/- epidote are reported for the first time in neosomes, indicating peak P-T conditions of 1.1-1.3 GPa and c. 750 degrees C. This peak T paragenesis has been thoroughly overprinted by a phengite-chlorite-actinolite assemblage during isobaric cooling down to c. 450 degrees C. U-Pb dating of zircon metamorphic rims from a metasedimentary rock yielded a homogeneous age population of 162 +/- 2 Ma for the HT event. Sm-Nd dating of two peritectic garnet-bearing samples yield ages of 163 +/- 2 Ma and 163 +/- 18 Ma for the HT event. Multi-mineral Rb-Sr dating of a metasedimentary rock overprinted by LT deformation suggests retrograde shearing between 120 and 80 Ma. Our results show that the HT event in the Lazaro unit took place at around 160-165Ma, shortly before the onset of Patagonian Batholith emplacement. Partialmelting of subducted oceanic crust reported in the Lazaro unit is related to the early stages of hot subduction along the Gondwana western margin. The Lazaro unit remained at c. 40 km depth along the subduction interface for >80Ma, recording the deformation and long-term cooling of the subduction channel environment until the upper Cretaceous. (C) 2016 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 12/01191-1 - Evolução do cinturão metamórfico pareado na cordilheira da costa do Chile Central: metamorfismo e tectônica da protomargem Andina no Sul do Continente Sulamericano
• Beneficiário: Caetano Juliani
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/23422-0 - Decifrando a Dinâmica de Paleo Complexos de Subducção a partir do Estudo do Metamorfismo: O Caso do Complexo Acrescionário Cretácico de Alta Pressão de Diego de Almagro (Patagônia Chilena)
• Beneficiário: Thaís Nogueira Hyppolito
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 04/10203-7 - Petrogenese, metamorfismo e evolucao tectonica dos xistos azuis dos andes na colombia.
• Beneficiário: Caetano Juliani
• Modalidade de apoio: Auxílio à Pesquisa - Regular