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Petrology of the volcanism from the west portion of the Rio Grande Rise, South Atlantic Ocean

Grant number: 20/01356-7
Support type:Scholarships in Brazil - Master
Effective date (Start): June 01, 2020
Effective date (End): January 31, 2022
Field of knowledge:Physical Sciences and Mathematics - Geosciences - Geology
Principal researcher:Valdecir de Assis Janasi
Grantee:Júlia Taciro Mandacarú Guerra
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The Rio Grande Rise (RGR) is an extensive plateau located approximately 1000 km away from the Brazilian coast. It is considered a basaltic Large Igneous Province, but its origin and geology are not well known yet due to its remote location and access limitations. Recent studies by the Institute of Oceanography from the University of São Paulo (IO-USP) focusing on the genesis and economic potential of its ferromanganese crusts, dredged volcanic rock fragments from its west portion, including basic rocks with alkaline affinity and trachytes. In partnership with IO-USP, we hereby propose a petrologic study a representative set of ~20 samples of these volcanic rocks, thus far not described in literature, to determine its main petrographic and geochemical characteristics, as a contribution to improve the knowledge of the RGR geology. These rocks will be characterized by petrography, scanning electron microscopy, whole-rock geochemistry analysis for major elements (X-ray fluorescence) and trace and rare-earth elements (ICP-MS), as well as geochemistry of the main and accessory minerals by electron probe microanalyser (major elements) and LA-ICPMS (trace elements). Additionally, Sr-Nd-Pb isotopic signatures of representative samples will be investigated by analysis of whole-rock and (for the Pb-Pb system) alkali feldspar concentrates. The combination of elemental and isotope geochemistry will allow the identification of contributions from different mantle reservoirs (and potentially also continental lithosphere) in the genesis of these magmas. (AU)

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