METALLOGENIC CHARACTERISTICS AND ISOTOPIC COMPOSITION OF SAWAYARDUN GOLD DEPOSIT,XINJIANG

The Sawayardun gold deposit,located in the west of Xinjiang,is one of the most important gold deposits found in China in the recent years.The deposit occurs in the Middle-Upper Carboniferous turbidite sequence,and the mimeralization is restricted to the fracture zones developed in the sequence.With layered or lensoid morphology,the orebodies extend in NE trend,consistent with the extension of the fracture zones.The ore is composed of gold-bearing quartz and quartz-siderite stringer stockwork with disseminated metal sulfides.The gold in the ore is characterized by microtexture and low fineness and associated with pyrite,arsenopyrite,and chalcopyrite.The lead compositions obtained from the ore are as follows:²⁰⁶Pb/²⁰⁴Pb ranging from 18.645 to 18.382;²⁰⁷Pb/²⁰⁴Pb from 15.470 to 15.659;²⁰⁸Pb/²⁰⁴Pb from 38.752 to 38.062.The δ³⁴S values of the metal sulfides analyzed range between +2.61‰ and -1.02‰. The δD values from quartz and siderite vary from -42.5‰ to -72.2‰; the δ¹⁸O,from +2.94‰ to -11.57‰;and the δ13C_co2,from -2.35‰ to -10.50‰.The mineralization dates between 167±18 and 98±9 Ma by K Ar method.Based on the characteristics of the isotopic composition,it is suggested that the Sawayardun deposit was developed during the late Yanshan movement,and the host and underlying strata supplied the source for the mineralization.It could formulate a model of circulating meteoric water becoming a heated hydrothermal fluid in the depth,dissolving gold and other metals from the country rocks through which it traversed,and carrying them up to the pressure reduced environment-the fracture zones,where they were precipitated because of the boiling derived from the pressure reduction.