Banca de QUALIFICAÇÃO: CHRISTIAN CAMPOS BATISTA ROCHA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : CHRISTIAN CAMPOS BATISTA ROCHA
DATE: 29/08/2024
TIME: 14:30
LOCAL: DEPARTAMENTO DE GEOLOGIA - SALA 27
TITLE:

Petrology and gravimetry of the Serra do Dorna Granite – Northern Acari Batholith, Seridó Belt

KEY WORDS:

Acari Batholith, Serra do Dorna Granite, gravimetric modeling, petrography and lithochemistry.

PAGES: 84
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geofísica
SUMMARY:

The Acari Batholith is prominent in the geological and metallogenetic evolution of the Seridó Belt due to its size, facies diversity, and association with W-skarn deposits. Its northern segment, known as the Serra do Dorna Granite (GSD), is historically linked to the scheelite mineralizations of the Brejuí-Boca de Laje District. However, conflicting geochronological data and the absence of granites in the mines raise questions about the intrusion's role in these mineralizations. Surface observations and the lack of detailed geological mapping, as well as geochemical and petrological studies, limit understanding of the spatial distribution of the granites. This study aims to address these gaps through two primary approaches. The first involves 2.5D direct gravimetric modeling of the central-northern portion of the Acari Batholith to investigate the geometry, depth, and location of the roots of the body, and to discuss its relationship with the geological context of the Seridó Belt. Ten E-W oriented profiles with 2 km spacing were modeled using the GM-SYS extensions in Seequent Oasis Montaj®. The second approach examines the petrographic and lithochemical aspects of the Dona Inês-type granites of the GSD. A geological mapping of the GSD at a scale of 1:50,000 was conducted to identify magmatic facies, field relations, and structures. The GSD is mainly composed of equigranular to microporphyritic monzogranites to syenogranites, distinguished from the typical porphyritic granites of the Acari Batholith by the considerably smaller size of K-feldspar crystals. Late dikes of coarse to pegmatitic hololeucocratic granites complete the sequence. The granites exhibit a predominantly NE-SW magmatic fabric, aligned with the orientation of the host rocks and the transcurrent shear zones delineating the batholith. Solid-state deformation is reflected in the microtextures of the granites, which transform into muscovite mylonitic gneisses along the Totoró Shear Zone. Gravimetric modeling reveals two roots in the eastern segment of the Acari Batholith, aligned NE-SW. The northern root lies between the mineralizations of the Brejuí Mine and the Acauã Stock, while the southern root is beneath the outcropping area of the batholith, west of the Gargalheiras Reservoir. Lithochemical analyses show that the GSD granites are peraluminous and ferroan, with alkali-calcic to calc-alkaline signatures and they scatter between the high-K calc-alkaline and shoshonitic series on the K2O vs. SiO2 diagram. Discussions regarding the genesis and evolution of the GSD will be further explored with trace element and rare earth element analyses, integrated with the results of petrography and gravimetric modeling.

COMMITTEE MEMBERS:
Presidente - 2042352 - FREDERICO CASTRO JOBIM VILALVA
Interno - 349684 - WALTER EUGENIO DE MEDEIROS
Interno - 350630 - ZORANO SERGIO DE SOUZA