Thermobarometric evolution (P-T) of the volcano sedimentary rocks of the eastern edge of the Magmatic Arc of Santa Quitéria, Ceará

Abstract

The Borborema Province (PB) is a complex geotectonic unit with polycyclic evolution. Its structure is associated to the neoproterozoic amalgamation of the Amazonian Craton, West African-Sao Luis Craton and Sao Francisco Craton in the so-called Brasilian/Pan-African orogeny. In the northwest of this province is inserted the Central Ceara Domain (DCC), region in which is located the Continental Magmatic Arc of Santa Quiteria (AMCSQ) and the ultra high pressure zone of Forquilha, given by retroeclogites with coesite, in the west of the arc. High-pressure lithotypes were identified in the eastern portion of the arc but they lack petrogenetic detail and contextualization in the tectonic scenario of DCC. DCC arcs and eclogites imply geotectonic environment with subduction of oceanic plate, continental collision and exhumation of lithospheric mantle. The direction to which this subduction points remains controversial. While some studies point to E-SE, others advocate a W- NW orientation. Some go even further with a dual subduction in opposite directions. Therefore, this work aims to study metabasic and metasedimentary rocks located at the eastern border of the AMCSQ by establishing their metamorphic trajectory of pressure (P) and temperature (T) during the Neoproterozoic. This study shall focus on the detailed field survey, petrographic analysis with optical and electron microscopy, and Raman spectroscopy, for they are essential in the characterization of different stages of metamorphism (progressive, peak metamorphic and retrograde). In addition, conventional geothermometers and geobarometers combined with thermobarometric modeling (pseudosection) will provide data to establish the P and T conditions to which these bodies were subjected, seeking a better understanding of the tectono-metamorphic evolution of that portion of PB in the context of the reconstruction of Western Gondwana. (AU)