Metamorphism of metapelites and metamarls of the Lajeado group in the contact aureole of the Apiaí Gabro, Southern Ribeira belt

• Grant number: 15/26756-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): April 01, 2016
• Effective date (End): December 31, 2016
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Frederico Meira Faleiros
• Grantee: Lucas Agostinho Milani
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

This work aims the mapping of metamorphic zones developed in metasedimentary rocks from the Lajeado Group (1200-880 Ma) along the Apiaí Gabbro (877 Ma) contact aureole, as well as the identification of mineral phases and assemblages developed during this process and its relationships with structural and microstructural elements. The microtectonic analysis will play a key role on the reconstruction of the temporal relationship between the regional and thermal (contact) metamorphic events, besides to allow the identification of occurrence of partial melting of the metasedimentary rocks due to the intrusion heat. It will be studied the influence of mineral chemistry on the metamorphic assemblages, and geothermobarometric calculations to quantify metamorphic conditions. The Lajeado Group (Stenian to Tonian) comprises a distal shelf sedimentary rock succession deposited on a passive margin of the Paranapanema cratonic block. It is composed of rocks with terrigenous (metaconglomerate, metasandstone and metapelite) and pure to impure carbonatic (marble and metamarls) composition. During the collage of the supercontinent Western Gondwana, these rocks undergone a greenschist facies regional metamorphism. The superior portion of the Lajeado Group undergone a pre-orogenic contact metamorphism related to the intrusion of the Apiaí Gabbro. Nevertheless, this metamorphic record was never subjected to detailed study, as has been proposed in this project.