Geology and Geochemistry of the Buerkesidai and Kuoerzhenkuola Gold Deposits in the Sawuershan Region, Xinjiang Uigur Autonomous Region, Northwest China

Abstract

The Sawuershan region, one of the important gold metallogenic belts of Xinjiang, is located in the western part of the Kalatongke island arc zone of north Xinjiang, NW China. There are two gold deposits in mining, namely the Kuoerzhenkuola and the Buerkesidai deposits. Gold ores at the Kuoerzhenkuola deposit occur within Carboniferous andesite and volcanic breccias in the form of gold-bearing quartz -pyrite veins and veinlet groups containing native gold, electrum, pyrite, pyrrhotite and chalcopyrite. Gold ores at the Buerkesidai deposit occur within Carboniferous tuffaceous siltstones in the form of gold-bearing quartz veinlet groups and altered rocks, with electrum, pyrite and arsenopyrite as major metallic minerals. Both gold deposits are hosted by structurally controlled faults associated with intense hydrothermal alteration. The typical alteration assemblage is sericite + chlorite + calcite + quartz, with an inner pyrite -sericite zone and an outer chloritecalcite -epidote zone between orebodies and wall rocks. 72 -18.56, 15.34 -15.61, and 37.21 -38.28, respectively. These sulfur and lead isotope compositions imply that ore-forming materials might originate from multiple, mainly deep sources. He and Ar isotope study on fl uid inclusions of pyrites from ores of Kuoerzhenkuola and Buerkesidai gold deposits produces 40 Ar/ 36 Ar and 3 He/ 4 He ratios in the range of 282 -525 and 0.6 -9.4 R/Ra, respectively, indicating a mixed source of deep-seated magmatic water (mantle fl uid) and shallower meteoric water. In terms of tectonic setting, the gold deposits in the Sawuershan region can be interpreted as epithermal. These formations resulted from a combination of protracted volcanic activity, hydrothermal fl uid mixing, and a structural setting favoring gold deposition. Fluid mixing was possibly the key factor resulting in Au deposition in the gold deposits in Sawuershan region.

A review of mineral systems and associated tectonic settings of northern Xinjiang, NW China

“…These authors also inferred that gold was transported as AueS complex and precipitated under reducing condition. Zeng et al (2007) reported, d 34 S values ranging from 1.5& to 3.5&, and averaging 1.9&, suggesting that the ore-forming sulphur were sourced from magmas that fed subvolcanic intrusions and surface volcanism. The estimated d 18 O water values vary from 1.8& to 3.2&, with corresponding dD values of from À84& to À89&, which are indicative that the ore-forming fluidsystem is a mixture of magmatic and meteoric waters.…”

“…Hydrothermal alteration includes kaolinitization, silicification, sericitization, chloritization, epidotization, alunitization and fluoritization. Because of the strong kaolinitization and alunitization the deposit is considered a high sulphidation-style epithermal system (Shen et al, , 2008Zeng et al, 2007). All the gold orebodies are contained within these alteration zones.…”

Epithermal deposits in North Xinjiang, NW China

“…These authors also inferred that gold was transported as Au-S complex and precipitated under reducing condition. Zeng et al (2007) reported, d 34 S values ranging from 1.5 to 3.5%, and averaging 1.9%, suggesting that the oreforming sulfur were sourced from magmas that fed subvolcanic intrusions and surface volcanism. ore-forming fluid system is a mixture of magmatic and meteoric waters.…”

“…The alteration includes kaolinitization, silicification, sericitization, chloritization, epidotization, alunitization and flouritization. Because of the strong kaolinite and alunite alteration the deposit was considered to be a HS-style epithermal system Zhang 1998;Shen et al 2004Shen et al , 2007Shen et al , 2008aZeng et al 2005Zeng et al , 2007.…”

The Sources of Ore‐forming Fluids from the Jinchang Gold Deposit, Heilongjiang Province, NE China: Constraints from the He–Ar Isotopic Evidence

“…The source of ore‐forming fluid is one of the key issues to the ore genesis. In the past 30 years, noble gas isotopes, particularly He and Ar, have been widely used to discriminate the origin and evolution history of the ore‐forming fluids, and considerable progress has been made (Simmons et al, ; Stuart et al, ; Hu et al, ; Shen et al, , ; Zeng et al, , ). Since the rare gas is chemically inert, therefore remaining unchanged during the geological evolution, and ore‐forming fluids from various sources have different isotopic composition characteristics, these can reflect the original information of the origin and evolution of the ore‐forming fluids.…”