Composition and source of salinity of ore-bearing fluids in Cu-Au systems of the Carajás Mineral Province, Brazil

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Abstract

The composition and Cl/Br – NaCl ratios of highly saline aqueous inclusions from large tonnage (> 100 t) IOCG deposits (Sossego, Alvo 118, and Igarapé Bahia) and a Paleoproterozoic intrusion-related Cu-Au-(Mo-W-Bi-Sn) deposit (Breves; < 50 Mt)) in the Carajás Mineral Province have been analysed by LA-ICP-MS and ion chromatography. In both Cu-Au systems, brine inclusions are Ca-dominated (5 to 10 times more than in porphyry Cu-Au fluids), and contain percent level concentrations of Na and K. IOCG inclusion fluids, however, contain higher Sr, Ba, Pb, and Zn concentrations, but significantly less Bi, than the intrusion-related Breves inclusion fluids. Cu is consistently below detection limits in brine inclusions from the IOCG and intrusion-related systems and Fe was not detected in the latter. Cl/Br and Na/Cl ratios of the IOCG inclusion fluids range from entirely evaporative brines (bittern fluids; e.g. Igarapé Bahia and Alvo 118) to values that indicate mixing with magma-derived brines. Cl/Br and Na/Cl ratios of the Breves inclusion fluids strongly suggest the involvement of magmatic brines, but that possibly also incorporated bittern fluids. Collectively, these data demonstrate that residual evaporative and magmatic brines were important components of the fluid regime involved in the formation of Cu-Au systems in the Carajás Mineral Province.

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Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Composition and source of salinity of ore-bearing fluids in Cu-Au systems of the Carajás Mineral Province, Brazil
Year Published 2009
Language English
Publisher James Cook University School of Earth & Environmental Studies. Economic Geology Research Unit
Contributing office(s) Central Mineral and Environmental Resources Science Center
Larger Work Type Conference Paper
Larger Work Title Smart science for exploration and mining : proceedings of the 10th Biennial SGA Meeting, Townsville, Australia 17th-20th August 2009
Conference Title 10th Biennial SGA Meeting: Smart Science for Exploration and Mining
Conference Location Townsville, Australia
Conference Date August 17-20, 2009
Country Brazil
Other Geospatial Carajás Mineral Province
Online Only (Y/N) N
Additional Online Files (Y/N) N