Geochemical characteristics of pyrite in Duolanasayi gold deposit, Xinjiang

Abstract

The Duolanasayi gold deposit, 60 km NW of Habahe County, Xinjiang Uygur Autonomous Region, is a mid-large-scale gold deposit controlled by brittle-ductile shearing, and superimposed by albitite veins and late-stage magma hydrothermal solutions. There are four types of pyrite, which are contained in the light metamorphosed rocks (limestone, siltstone), altered-mineralized rocks (chlorite-schist, altered albite-granite, mineralized phyllite), quartz veins and carbonatite veinlets. The pyrite is the most common ore mineral. The Au-barren pyrite is present mainly in a simple form and gold-bearing pyrite is present mainly in a composite form. From the top downwards, the pyrite varies in crystal form from {100} and {210}+{100} to {210}+{100}+{111} to {100}+{111}. Geochemical studies indicate that the molecular contents of pyrite range from Fe_1.057S₂ to Fe_0.941S₂. Gold positively correlates with Mn, Sr, Zn, Te, Pb, Ba and Ag. There are four groups of trace elements: Fe-Cu-Sr-Ag, Au-Te-Co, As-Pb-Zn and Mn-V-Ti-Ba-Ni-Cr in pyrite. The REE characteristics show that the total amount of REE (ΣREE) ranges from 32.35×10⁻⁶ to 132.18×10⁻⁶; LREE/HREE, 4.466–9.142; (La/Yb)_N, 3.719–11.133; (Eu/Sm)_N, 0.553–1.656; (Sm/Nd)_N, 0.602–0.717; La/Yb, 6.26–18.75; δEu, 0.628–2.309; δCe, 0.308–0.816. Sulfur isotopic compositions (δ³⁴S=−2.46‰–−7.02‰) suggest that the sulfur associated with gold mineralization was derived from the upper mantle or lower crust.