Characteristics of rare earth and trace elements of the Sawayaerdun gold deposit, Southwest Tianshan: Implications for ore genesis

The Sawayaerdun gold deposit in Wuqia, Xinjiang was discovered in the early 1990’s and is considered the first Muruntau-type gold deposit in the Chinese Tianshan. Gold mineralization occurred in Triassic and associated with quartz veins, showing similarities to the Muruntau gold deposit. Three major hydrothermal events can be identified at Sawayaerdun: An early barren quartz vein stage, middle stage quartz veins with pyrite and mineralization and late carbonate (-quartz) veins. The contents of rare earth elements (REE) and trace elements in early barren quartz veins are lower than those of mineralized quartz. REE distribution patterns of the fluids trapped in mineralized quartz are generally consistent with LREE enrichment and Eu positive anomaly, which probably indicates high Ca in fluids or a relatively reduced environment. High Pb in ore-forming fluids and leaching of Ca and Pb from the host rock may suggest the reaction between fluids and host rock. The precipitation of metals may be associated with fluid mixing, which is not identified in early barren quartz due to the low contents of REE and trace elements. Fluids in mineralized quartz from the largest IV ore zone have higher REE and trace elements than those of other ore zones, probably indicating a stronger fluid mixing. The II ore zone shows more similarities to zone IV than others. Characteristics of REE and trace elements of the Sawayaerdun gold deposit indicate that host rock is an important source for ore-forming fluids and fluid mixing played a critical role during mineralization, which is consistent with previous fluid inclusion and isotope studies and comparable with the general characteristics of orogenic gold deposits.