Banca de DEFESA: ROBSON RAFAEL DE OLIVEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : ROBSON RAFAEL DE OLIVEIRA
DATE: 31/01/2020
TIME: 14:00
LOCAL: Auditório do CCET
TITLE:

The Catolé do Rocha Batholith (RN-PB): An A-type granitic magmatism within the Rio Piranhas-Seridó Domain, Borborema Province, NE Brazil 

KEY WORDS:

Catolé do Rocha Batholith, A-type granites, Geochemistry, Borborema Province

PAGES: 110
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The Catolé do Rocha Batholith (CRB) is within the geological context of the central-north portion of the Borborema Province, west of the Rio Piranhas-Seridó Domain, and represents an important example of the tectono-magmatic event affecting this region during the Brasiliano Cycle (ca. 580 Ma). The CRB is composed of metaluminous to slightly peraluminous syenogranites to syenites (granitic facies), basic to intermediate rocks, and subordinate microgranitic dykes and pockets. These rocks are intrusive into the Paleoproterozoic rocks of the Caicó Complex and Poço da Cruz Suite. The CRB has been classified in the literature as an I-type granite of the high-K calc-alkaline suite in the northeasternmost part of the Borborema Province. However, many of the CRB chemical characteristics are akin to the A-type granites. This work presents a review of the geology, petrography, mineralogy and chemistry (bulk-rock and mineral chemistry) of the CRB aiming to better define its chemical and typological classification (I-type vs. A-type). The CRB shows álcali-calcic to alcaline signatures, given by relatively high contents of total alkalis relative to CaO. The CRB granites also have a ferroan character, with high values of the ratio Fe/Mg, as well as significant abundances of LILE and HFSE, and relative LREE enrichment over HREE. They have iron-enriched mafic minerals, typically annitic biotite and the calcic amphiboles ferro-edenite and hastingsite. These caracteristics put the CRB close to the group of the post-collisional A₂-type granites. Geothermobarometric estimates point to crystallization temperatures around 773 and 918ºC, under pressures of 4.6 – 6.3 kbar. Oxygen fugacity estimates, based on amphibole, biotite and zircon mineral chemistry indicate that the CRB formed under reduced conditions (log_ƒO2 entre -18 e -14). Therefore, the CRB is reclassified as a post-collisional reduced A₂-type granite. Based on these chemical signatures, along with the behavior of major and minor elements in Harker-type variation diagrams that suggest that the CRB granites and mafic-intermediate rocks are not cogenetic, it is arguably inferred the formation of the CRB magmas through partial melting of metasomatized lithospheric mantle and/or lower crust. These magmas evolved mainly by fractional crystallization processes associated to mingling in a minor scale.

BANKING MEMBERS:
Presidente - 2042352 - FREDERICO CASTRO JOBIM VILALVA
Externo à Instituição - LUANA MOREIRA FLORISBAL - UFSC
Interno - 350630 - ZORANO SERGIO DE SOUZA