Banca de DEFESA: Heriscarth Marcell Dantas Pinheiro

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Heriscarth Marcell Dantas Pinheiro
DATE: 14/09/2022
TIME: 14:00
LOCAL: Sala de videoconferência do IGD
TITLE:

Magnetite Enrichment Processes in Fe-Skarns Deposits of the Archean Nucleus of São José do Campestre, Rio Grande do Norte, Northeast of Brasil.

KEY WORDS:

Ground Geophysics; Magnetic Susceptibility; SATMAGAN; 3D inversion; Archean Nucleus of São José do Campestre

PAGES: 81
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The Archean Nucleus of São José do Campestre, located in the extreme northeast of Brazil, has a complex tectono-structural context, featuring geochronologically situated rocks ranging from paleo-arquean to cambrian. This environment favored the formation of magnetite-rich rocks with metallogenetic potential. Such rocks do not have well-defined genesis and are associated with the Serra Caiada Complex. In parallel, conventional techniques, especially those involving sampling and chemical analyses (whole rock and mineral chemistry), are expensive. In this sense, indirect techniques such as geophysics can prove to be good prospective guides when associated with other geological information. The present work aims to investigate magnetite enrichment in these rocks, through terrestrial geophysics. To better understand the relationships between mineralized bodies and country rocks, enhancement technics were applied and a geophysical model was generated (3D inversion). The enhancement techniques used, Analytical Signal Amplitude and First Vertical Derivative, provided an intensity map with 3 established domains, which increase in intensity from West to East; in addition to a map of magnetic structures with predominance of NE-SW directions and influence of shallow structures. The generated model accused two mineralized bodies in subsurface, Target 1 (dike-shaped) and Target 2 (pipe-shaped), with N-S and NE-SW directions, respectively. The geophysical results were associated with geological (petrographic analyses and field observations), petrophysical (Magnetic Susceptibility) and geochemical (SATMAGAN) Petrographic analyses helped to delimit and classify 4 zones or faciologies, according to the prograding mineral paragenesis: Pyroxene Skarn Anfibolium, Pyroxine Skarn, Piroxênio Skarn and Magnetite Skarn; in addition to correlating the country rocks with the regional geological context. SATMAGAN results showed values between 3.68 and 53.68% of magnetite, and measurements of portable magnetic susceptibility provided values between 91.25 and 2,867.25 x 10-3 SI for mineralized bodies. These numbers are compatible with the results obtained in 3D inversion, between 95 and 1,591.8 x 10-3 SI. Results are similar to literature parameters which classify such mineralization as Fe-Skarn type. Finally, the integration of the obtained results allows the interpretation of crustal rework of pre-existing rocks and remobilization of Iron from silicates, such as pyroxenes, and oxides and solubilized as magnetite in pockets and lenses, where the main conduit would be granite dikes.

BANKING MEMBERS:
Externo à Instituição - DAVID LOPES DE CASTRO - UFRN
Externo ao Programa - 2156153 - ELDER YOKOYAMA
Presidente - 1303786 - ELTON LUIZ DANTAS
Interna - 2697315 - MARIA EMILIA SCHUTESKY