Writers : Ashrafpour, E.; Ansdell, K. M.;Alirezaei, S.
Refference : Scientific Quaterly Journal Geosciences, Vol.18, No. 70, 2009
Publishing Year : 1387

Abstract :

Arghash gold district includes five gold-bearing vein systems, (Au-I to Au-V) and one antimony-rich vein hosted by intermediate to silicic volcanic rocks, tuffs, granite, and diorite. Pyrite is the main sulfide mineral consisting of four generations (Py-I to Py-IV). Py-I to III are intimately associated with gold; however, Py-IV is barren. The 534S values of pyrites in conventional bulk analyses fall into two groups, one highly enriched in 34S (S34S=+9.3 to +21.8%o), and the other less enriched to slightly depleted in 34S (534S= +5.1 to -4.3%o). In-situ laser probe experiments were carried out to characterize various generations of pyrite. The results indicate a relatively narrow range for Py-I to Py-III (834S= -5.8 to +0.1%o) consistent with a magmatic source for sulfur. Py-IV is highly enriched (S34S=+8.9 to +23.7%o), implying contributions of sulfur from sources enriched in 34S, like evaporites. The high 834S values in the enriched group can be attributed to a significant occurrence of Py-IV in this group.
The 834S values of two stibnites from Sb ore (-18.8 and -14.4%o) suggest a different sulfur, and possibly metal source, and/or radical changes in the physicochemical conditions of the fluid during deposition of stibnite. Metasedimentary basement rocks could contribute sulfur and metal to the circulating fluids. δ13CPDB values of vein calcites are near 1 per mil suggesting a sedimentary source for carbon. Carbonate units and interlayers in the area are a suitable source for CO2 in the ore fluids. The stable isotope data suggest that hydrothermal fluids experienced a complex history of water/rock interaction and that ore components, were derived, at least partly, from country rocks.

Subject List : gold, Isotopic study