Banca de DEFESA: GRACIANO CARLOS DE FREITAS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GRACIANO CARLOS DE FREITAS
DATE: 30/10/2024
TIME: 09:00
LOCAL: PPGMEG
TITLE:

Petrological Studies of the Subvolcanic Bodies of the Passa Quatro Alkaline Complex in the Pico dos Três Estados Region and Adjacencies, in the States of MG, RJ and SP.

KEY WORDS:

Fractional crystallization, partial melting, magma mixing, subvolcanic rocks.

PAGES: 68
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SPECIALTY: Petrologia
SUMMARY:

This dissertation presents a geological study of the subvolcanic bodies present in and around Pico dos Três Estados (SP, RJ and MG) in the Passa Quatro Alkaline Complex. In this study, we used data collected in the field, petrological data and geochemical analysis. The petrological data showed that the region studied has characteristics similar to those found in most of the alkaline bodies found on the southeastern coast of Brazil, especially in terms of alkali feldspar content, types of feldspathoid minerals and the volume of mafic minerals. After more detailed fieldwork, we found that the region, which seemed to have only two lithologies in previous work, had a facies complex with at least six distinct facies, especially the phonolitic body that forms the Pico dos Três Estados (2,665 meters high). ). Still in relation to the fieldwork, we found that there is evidence of magma mixing processes in the area. The modeling indicates that 10% of the fractional crystallization was able to derive the phonolitic rocks from a trachytic liquid based on the following elements: Y, Nb, Yb, Ce, Sm, Eu, La, Nd, Hf and Pr. The batch modal partial melting shows the possible mantle sources for the magmatism in this area. These data point to the involvement of a mantle source enriched in the La/Yb ratio by at least 16 times more than an OIB-type mantle.

COMMITTEE MEMBERS:
Presidente - 1648928 - ARTUR CORVAL VIEIRA
Externo à Instituição - Mauro Cesar Geraldes - UERJ
Interna - ***.607.040-** - RENATA DA SILVA SCHMITT - UFRJ