Banca de DEFESA: Gabriel da Silva Seidler

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Gabriel da Silva Seidler
DATE: 27/03/2024
TIME: 08:00
LOCAL: Sala de Videoconferência do IGD
TITLE:

CONTROLS ON THE GOLD MINERALIZATION AND ARCHITECTURE OF THE MINERALIZING SYSTEM AT THE JACOBINA MINING DISTRICT

KEY WORDS:

Mineral Systems; Gold high grade ore shoots; 3D Modelling; X-Ray Computed Microtomography; Jacobina Mine.

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

In the Jacobina Mining District, a significant gold deposit associated with metaconglomerates, whose mineral inventory approaches 10 million ounces (as of 2023), economically viable mineralization is associated to the metaconglomerates of the Serra do Córrego Formation, occurring predominantly in tabular bodies N-S oriented. However, the majority of studies conducted in the region throughout its extensive production history have been primarily focused on the genesis of mineralization. This work presents an alternative perspective, utilizing concepts from mineral systems, in the pursuit of understanding the controlling factors of high-grade gold ore shoots generation at a deposit scale. To achieve this, surface mappings and surveys of underground mine galleries were conducted to identify active tectonic events contributing to the system's development and the resulting structures. Geological and structural modelling methods, maximum intensity projections, Radial Basis Function (RBF) interpolations, and interpolations of gold concentration versus thickness, using diamond drill hole and channel sampling data, were employed to recognize architectural and geometrical patterns of the mineralized system at a mine scale. Descriptions of drilling cores, petrographic analyses, and the application of modern Micro-Computed Tomography (Micro-CT) techniques were utilized for a detailed examination of textural and mineralogical characteristics of high-grade zones. Four significant deformational events were identified: (i) Rift basin distensive event; (ii) Frontal compressive event verging to the west; (iii) Transpressive event with left-lateral regional kinematics; (iv) Distensive event associated with orogen collapse, responsible for the construction of the structural framework and the architectural and geometrical conformation of the Jacobina Mineral System. Analysis of structural patterns in district mines led to their classification into three structural domains: North Domain comprising Canavieiras Sul, Canavieiras Central, and Canavieiras Norte mines, Central Domain including Morro do Vento and Morro do Cuscuz mines, and South Domain represented by the João Belo Norte mine. Integration of field observations with three-dimensional modelling and Micro CT-derived products facilitated the understanding of controls governing fluid pathways that remobilized gold and, notably, elucidated factors controlling its accumulation and high-grade gold concentration as follows: First-order structures, predominantly N-S oriented, acted as conduits for mineralized fluids, facilitating their circulation through host rocks across the Jacobina Mining District. Second-order structures, oriented E-W, functioned as permeability barriers or low-pressure zones, leading to the accumulation of mineralized fluids at intersections with first-order structures, ultimately forming regions of high gold concentration across all structural domains studied. In the North Domain, antiformal structures served as significant fluid accumulation zones, resulting in higher gold grades compared to other structural domains studied. In conclusion, the deposit-scale study of critical factors in the Jacobina Mining District, combining classical geological mapping and petrography with modern methodologies such as three-dimensional modelling and Micro-Computed Tomography, not only provided a robust understanding of the system's architecture and geometry but also defined parameters involved in high-grade or shoots generation, proving to be an efficient approach in comprehending the prolific and unique Jacobina Mineral System.

COMMITTEE MEMBERS:
Presidente - 1555904 - CATARINA LABOURE BEMFICA TOLEDO
Interno - 418965 - CLAUDINEI GOUVEIA DE OLIVEIRA
Externo à Instituição - FERNANDO CESAR ALVES DA SILVA - UFRN
Interno - 2370895 - LUIS GUSTAVO FERREIRA VIEGAS