Banca de QUALIFICAÇÃO: MATCHELLON JAIME BARBOSA PINHEIRO
Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.DISCENTE : MATCHELLON JAIME BARBOSA PINHEIRO
DATA : 13/07/2018
HORA: 08:30
LOCAL: Sala 1 - PPGG
TÍTULO:
CHARACTERIZATION OF SHOSHONITIC MAGMATISM AND ITS RELATIONSHIP WITH THE TECTONO-MAGMATIC EVOLUTION IN THE EXTREME NE OF THE BORBOREMA PROVINCE
PALAVRAS-CHAVES:
Borborema Province; Shoshonitic Suite; Granitoids.
PÁGINAS: 28
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:
Ediacaran to Cambrian plutonism in the extreme northeast of Borborema Province (PB) is one of the most important geological features, represented in all its extension by batholiths, stocks and dykes. The granitoids of shoshonitic nature, over the last few years have been studied in an individualized way and it has a scarcity of studies in the regional scope, with respect to the comparative analysis of these plutons, in the same magmatic suite as to those in which they occur associated. In this context, eleven plutons were selected and grouped according to their occurrence in the field: Group I, represented by the isolated bodies Casserengue, Poço Verde and Riachão; Group II, characterized by enclaves or basic to intermediate facies in the plutons of the porphyritic high K calc-alkaline suite, represented by Acari, Monte das Gameleiras, Prado, Serrinha and Totoró plutons; Group III, characterized by enclaves or basic to intermediate facies in the plutons of the equigranular high K calc-alkaline, represented by rocks of the Serra do Caramuru and Tapuio; and Group IV, characterized by enclaves or basic to intermediate facies in the Japi pluton, associated with alkaline suite. Petrographically, these bodies can be regrouped based on their mafic paragenesis into facies 1 (F1), which is composed of ± forsterite ± ortopyroxene + clinopyroxene + amphibole + biotite, plagioclase richer in anortita (An22-63%), and melanocratic rocks such as norites, gabbronorites and diorites; (F2), characterized by orthopyroxene + clinopyroxene + amphibole + biotite, plagioclase with anortitic contents (An21-50%), usually in the andesine field, quartz is present with more relevant contents, and melanocytic to leucocratic rocks, with predominance of mesocratic terms, such as diorites, monzogabbros, granodiorites, monzonites and qz-monzonites; and facies 3 (F3), constituted of biotite + amphibole, with plagioclase ranging between oligoclase and andesine (An22-45%) and rocks with predominance of leucocratic terms, such as qz-diorite, qz-monzodiorite, granodiorite, qz-monzonite and monzonite. The geochemical aspects indicate the basic to intermediate character of these rocks (SiO2 = 47.53-64.56%), with moderate to high values of Al2O3 (13,57-19,78%), Fe2O3t (4,86-14,48 %), MgO (1.62-8.17%) and CaO (3.08-9.93%). Considering the less evolved nature of these rocks, the alkalis content is relatively high where K2O + Na2O are generally greater than 6%, ranging between 3.94 and 9.79%, except for the Riachão pluton which presents very low values (1.54-6.84%). Accordingly to the alumina saturation index the rocks are in their majority metaluminous. Discriminant diagrams of magmatic series show that the Riachão pluton tends to be calc-alkaline, while the other plutons confirm its shoshonitic nature. Preliminary mineral chemistry data for some bodies are presented, with analyzes for pyroxenes, amphiboles, biotite and plagioclase. Clinopyroxenes are mainly diopside (Wo36-49En35-45Fs7-25) and orthopyroxenes occur as enstatite (Wo1-6En50-73Fs26-49) and ferrosilite (Wo1-5En26-29Fs67-72). The amphiboles are calcic, varying mainly due to their alkali contents (Na + K) at site A. The biotite are shown as phlogopite - only for Pluton Riachão -, Mg-biotite and Fe-biotite. Plagioclase vary from oligoclase to labradorite (An21-61Ab39-79Or0-4), with predominance of the term andesine.
MEMBROS DA BANCA:
Presidente - 1513243 - MARCOS ANTONIO LEITE DO NASCIMENTO
Interno - 080.368.454-15 - ANTONIO CARLOS GALINDO - UFRN
Interno - 2042352 - FREDERICO CASTRO JOBIM VILALVA