Abstract
LA-ICPMS analysis of pyrite in ten gold deposits is used to determine the precise siting of invisible gold within pyrite, and thus the timing of gold introduction relative to the growth of pyrite and related orogenic events. A spectrum of invisible gold relationships in pyrite has been observed which suggests that, relative to orogenic pyrite growth, gold introduction in some deposits is early at the start of pyrite growth; in other deposits, it is late toward the end of pyrite growth and in a third case, it may be introduced at the intermediate stage of orogenic pyrite growth. In addition, we report a distinct chemical association of invisible gold in pyrite in the deposits studied. For example, in the Gold Quarry (Carlin type), Mt Olympus, Macraes and Konkera, the invisible gold is principally related to the arsenic content of pyrite. In contrast, in Kumtor and Geita Hill, the invisible gold is principally related to the tellurium content of pyrite. Other deposits (Golden Mile, Bendigo, Spanish Mountain, Witwatersrand Carbon Leader Reef (CLR)) exhibit both the Au-As and Au-Te association in pyrite. Some deposits of the Au-As association have late orogenic Au-As-rich rims on pyrite, which substantially increase the value of the ore. In contrast, deposits of the Au-Te association are not known to have Au-rich rims on pyrite but contain nano- to micro-inclusions of Au-Ag-(Pb-Bi) tellurides.
Highlights
Understanding the mineralogical siting of gold in ore deposits is an important aspect of ore genesis studies and geometallurgical research to increase the recovery of gold [1]
Gold Quarry (Carlin type), million tonnes (Mt) Olympus, Macraes and Konkera, the invisible gold is principally related to the arsenic content of pyrite
Invisible gold-rich rims on arsenian pyrite are best developed in Carlin-type deposits, but we report them from the Witwatersrand Carbon Leader Reef (CLR) and Bendigo pyrite halo
Summary
Understanding the mineralogical siting of gold in ore deposits is an important aspect of ore genesis studies and geometallurgical research to increase the recovery of gold [1]. Both iron, entering distorted octahedral sites, whereas substitutes in the tetrahedral structure of pyrite is still not clear, it is assumed that ionic gold Au+ substitutes for iron, surface speciation, and distortion-expansion of the pyrite lattice by incorporation of As are considered entering distorted octahedral sites, whereas As substitutes for S in the tetrahedral sites [8] Both to be key processes in Au accumulation by arsenian pyrite [8,14]. In pyrite, using spotprevious analyses and laser mapping With respect Here, to the orogenic hydrothermal include LA-ICPMS pyrite in eleven sediment-hosted of pyrite in analytical each deposit,data and on other trace elements or orogenic pathfindersand associated with invisible gold gold deposits enrichment. Sample numbers for each deposit vary from six to over 50, and the number of LA-ICPMS pyrite analyses from 28 at Spanish Mountain to 958 for the Witwatersrand CLR (Table 1)
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