Producción CyT

RELATORIO DO V SIMPOSIO BRASILEIRO DE METALOGENIA - A FIRST GLANCE INTO THE RAMAN ANALYSIS OF PYROBITUMEN ASSOCIATED WITH THE ZINC DEPOSITS HOSTED IN THE VAZANTE GROUP

Congreso

Autoría:

André L. S. Pestilho ; Lena V. S. Monteiro ; Caetano Juliani ; Francisco M. Neto ; MORS, RODOLFO AGUSTÍN ; Arruda J. A. A. C. ; Oliveira A. L. R. ; Rennan N. Pereira ; Daniel S. Dubois

Fecha:

2025

Editorial y Lugar de Edición:

Universidade Federal do Rio Grande do Sul

ISSN:

978-65-5973-279-1

Resumen *

Organic matter (OM) i s often reported as pyrobitumens (PB) in many sedimentary hosted ore deposits suchas the Carlin Au (e.g., Nanpanjiang Basin , China) and the Zn Pb deposits (e.g., Irish M id Carboniferous )).However , t he role of OM in the genesis of such ore deposits remains uncertain For instance, t he interactionbetween the OM and the hydrothermal fluids has been evoked as a relevant factor to several processes thatfavours ore precipitation: (i) acting as a s ource of metal and sulphur to the fluid; (i i) transport ing metal throughpolar organic compounds; (ii i ) promoting sulphate reduction reactions; (i v ) accelerating sulphide precipitationthrough organic catalysers; and (v) enhancing pore space development . Nevertheless, the timing and impactof each factor on a mineral system efficiency are not clear. In this study, we provide the preliminary resultsfrom the Raman analysis of the PB associated with hydrothermal alteration in the Vazante Group. Thisresearch aims to establish the link between both mineral and petroleum system s related to the abundant PBfrom ore deposits hosted in the Vazante Group Five samples bearing PB were collected from the BentoCarmelo Quarry BC; n=4) and the Bon sucesso Zn Pb deposit BS; n=1) 1). Confocal laser micro Ramanspectroscopy was used to characterize the signal from the OM within the r ange of 400 4000 cm 1 , using aHoriba XploRa Plus ™ . The analyses were performed with a n x 10 0 objective , a holographic grating of1200 groves/mm, 10 accumulations, hole slit set to 100 µ m , and lasers of 532 and 785 nm. A calibration thatuses the D 1 band change with temperature was employed to estimate the temperatures recorded by the PB .Additionally , we used a portable X Ray Fluorescence (pXRF) to qualitatively assess the metal content of thesample s . The BC area displays dolostone affected by large dissolution breccias infilled by coarse saddledolomite ± sphalerite. The PB in Bento Carmelo fill fracture porosity, vugs, the residual primary porosity, andsub horizontal stylolite s The Bento Carmelo PB comprise black blocky aggregates sharp edges against theeuhedral dolomite crystals. The BS dolomitic mudstone sample has c oarse PB infilling a large fracture withblocky shaped aggregates bearing conchoidal fracture pattern, vitreous lustre, and hardness > 7 Mohs.The Bonsucesso PB shares striking similarities with "glassy carbon." The pXRF data indicate the PB bearingsampl es are enriched in Zn BC: 220 1.100 ppm; BS: 30 290 ppm). The Raman data from both areas displaythe D, G S2, S3, and S4 spectral bands that indicate high temperature (> 200 °C). T he estimatedtemperatures for BC are of 228 306 °C (n=15), whilst the BS reported values of 279 315 °C (n=5). Thesepreliminary result s indicate temperatures comparable to the maximum homogenization temperatures of fluidinclusion s reported in adjacent deposit s (e.g., Morro Agudo, Fagund es, and Ambrósia) in the area . This mightsuggest that pyrobitumen was linked to the mineral system evolution . T herefore additional studies shouldindicate w hat role the organic matter played in the ore genesis of the Vazante GroupAcknowledgements: The authors would like to thank Petrobr a s and Nexa Resources for the support of this research. Información suministrada por el agente en SIGEVA

Palabras Clave

MVTPyrobitumenRamanHydrothermalism