Evolution of the paired metamorphic belt in the coastal cordillera of Central Chile: metamorphism and tectonics of the proto-andean margin in South American Continent

• Grant number: 12/01191-1
• Support type: Regular Research Grants
• Duration: May 01, 2012 - October 31, 2014
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Caetano Juliani
• Grantee: Caetano Juliani
• Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Assoc. researchers: Lena Virginia Soares Monteiro

Abstract

The metamorphic series of the Chilean geological basement crop out within the Coastal Cordillera in Central Chile (34p-36pS). These series define a late paleozoic paired metamorphic belt and comprise the Western and Eastern Series. The former was generated in high pressure-low temperature regime and the later was formed under low pressure-high temperature conditions. The HP-LT series include metapsamopelites, greenschists, amphibolites, blueschists and garnet amphibolites relics, plus metacherts, graphitic schists, banded iron formations, serpentinites and marbles. The Eastern Series comprise metapelites and metagraywackes, which were affected by a high temperature-low temperature metamorphism (LP-HT) associated to the intrusion of a late paleozoic calc-alkaline batholith. Detailed geothermobarometric and geochemical studies, based on systematic sampling and petrographic studies, are insufficient in this metamorphic belt. In part, the tectono-metamorphic evolution of this region has been achieved by the extrapolation of local geothermobarometric and geochemical data to the entire belt. In fact, this kind of simplification seems inadequate considering the existence of petrological and structural complexities identified by previous works. Therefore, differences between the involved processes on the formation of protholits and during the metamorphism along the Chilean orogenic margin should be considered. Thus, this project aims to quantify the P-T conditions of both metamorphic series, based on geothermobarometry, the blastese relationships with deformation structures. Additionally, the determination of metamorphic ages will be used to the construction of P-T-t-d paths to this segment of the paired metamorphic belt. The geochemical study of metabasites from the HP-LT series will contribute to the understanding of crucial aspects on the tectono-metamorphic history of this part of the Chilean Coastal Cordillera, providing the definition of: a) the paleo-environment features of the subducted oceanic crust segment; b) the geochemical characteristics of the protholits submitted to high pressure and low temperature conditions; and c) the identification of hydrothermal alterations occurred during oceanic metamorphism and retrograde metamorphism, which are essential to the understanding of the blueschist belt generation. (AU)

Scientific publications

(6)

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

ANGIBOUST, SAMUEL; CAMBESES, AITOR; HYPPOLITO, THAIS; GLODNY, JOHANNES; MONIE, PATRICK; CALDERON, MAURICIO; JULIANI, CAETANO. A 100-m.y.-long window onto mass-flow processes in the Patagonian Mesozoic subduction zone (Diego de Almagro Island, Chile). GEOLOGICAL SOCIETY OF AMERICA BULLETIN, v. 130, n. 9-10, p. 1439-1456, SEP 2018. Web of Science Citations: 5.

ANGIBOUST, SAMUEL; HYPPOLITO, THAIS; GLODNY, JOHANNES; CAMBESES, AITOR; GARCIA-CASCO, ANTONIO; CALDERON, MAURICIO; JULIANI, CAETANO. Hot subduction in the middle Jurassic and partial melting of oceanic crust in Chilean Patagonia. GONDWANA RESEARCH, v. 42, p. 104-125, FEB 2017. Web of Science Citations: 7.

HYPPOLITO, THAIS; ANGIBOUST, SAMUEL; JULIANI, CAETANO; GLODNY, JOHANNES; GARCIA-CASCO, ANTONIO; CALDERON, MAURICIO; CHOPIN, CHRISTIAN. Eclogite-, amphibolite- and blueschist-facies rocks from Diego de Almagro Island (Patagonia): Episodic accretion and thermal evolution of the Chilean subduction interface during the Cretaceous. LITHOS, v. 264, p. 422-440, NOV 1 2016. Web of Science Citations: 12.

HYPPOLITO, T.; JULIANI, C.; GARCIA-CASCO, A.; MEIRA, V.; BUSTAMANTE, A.; HALL, C. LP/HT metamorphism as a temporal marker of change ofdeformation style within the Late Palaeozoic accretionary wedge of central Chile. JOURNAL OF METAMORPHIC GEOLOGY, v. 33, n. 9, p. 1003-1024, DEC 2015. Web of Science Citations: 3.

HYPPOLITO, T.; GARCIA-CASCO, A.; JULIANI, C.; MEIRA, V. T.; HALL, C. Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P-T paths and timing of metamorphism of deep-seated garnet-mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34 degrees S). LITHOS, v. 206, p. 409-434, OCT 2014. Web of Science Citations: 14.

HYPPOLITO, THAIS; JULIANI, CAETANO; GARCIA-CASCO, ANTONIO; MEIRA, VINICIUS TIEPPO; BUSTAMANTE, ANDRES; HERVE, FRANCISCO. The nature of the Palaeozoic oceanic basin at the southwestern margin of Gondwana and implications for the origin of the Chilenia terrane (Pichilemu region, central Chile). INTERNATIONAL GEOLOGY REVIEW, v. 56, n. 9, p. 1097-1121, 2014. Web of Science Citations: 12.