Banca de QUALIFICAÇÃO: GENILSON RIBEIRO DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : GENILSON RIBEIRO DA SILVA
DATE: 01/12/2020
TIME: 14:00
LOCAL: Videoconferencia - https://cutt.ly/6fcqwHK
TITLE:

Petrology and Geochronology of Volcanic Rocks of the Morro Redondo Complex, Graciosa
Province (PR-SC), South Brazil

KEY WORDS:

A-type volcanism; post-collisional; Morro Redondo Complex

PAGES: 60
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The S-SE region of Brazil, between the states of São Paulo and Santa Catarina, has as an important characteristic the occurrence of an intense post-collisional Neoproterozoic magmatism with a chemical signature similar to the A-type granites and rhyolites. This magmatism was responsible for the generation at 580-583 Ma of a number of plutons that form the Graciosa A-type Province of granites and syenites. Additionally, volcanic rocks with A-type affinities occur in several volcano-sedimentary basins formed during the post-collisional stages of the Brasiliano Orogeny in this region. The Morro Redondo Complex is one of the main occurrences within the province, being composed of two granitic plutons with contrasting geochemical affinities (peralkaline and peraluminous), and adjacent acidic to basic contemporary volcanic and subvolcanic rocks. Although these plutons are relatively well characterized, volcanic and subvolcanic rocks still lack detailed studies that address their connections with their plutonic equivalents, as well as their relationship with volcanic and volcaniclastic sequences in contemporary post-collisional basins. This work presents a characterization of the volcanic rocks of the Morro Redondo Complex based on (1) petrographic, (2) magnetic susceptibility, (3) lithochemistry, (4) mineral chemistry and (5) geochronological data. Partial results show that acidic volcanic and subvolcanic are predominantly A-type rhyolites and granophyres with low magnetic susceptibilities and peralkaline (comendites), with sodic and calcic-sodic amphiboles and clinopyroxenes, and peraluminous affinities, with biotite and hornblende. Basic types are basalts and microgabbros/microdiorites with pigeonite/augite and andesine/labradorite and high magnetic susceptibility. Zircon U-Pb dating (LA-ICP-MS) points crystallization ages around 585 ± 5 Ma (peraluminous rhyolites) which are slightly older than those obtained for the Morro Redondo granites (578-580 Ma). The textural, mineralogical, chemical and geochronological similarities between: (a) the Morro Redondo rhyolites and granophyres and granites; and (b) the Morro Redondo volcanic rocks with those filling post-collisional volcano-sedimentary basins in S-SE Brazil, suggest a volcano-plutonic connection among these rocks and possible common petrogenetic mechanisms and processes.

BANKING MEMBERS:
Presidente - 2042352 - FREDERICO CASTRO JOBIM VILALVA
Externa à Instituição - CARLA JOANA SANTOS BARRETO - UFPE
Externo à Instituição - SILVIO ROBERTO FARIAS VLACH - USP