Stable isotope characteristics and origin of ore-forming fluids in copper-gold-polymetallic deposits within strike-slip pull-apart basin of Weishan-Yongping continental collision orogenic belt, Yunnan Province, China

Abstract

More than 140 middle-small sized deposits or minerals are present in the Weishan Yongping ore concentration area which is located in the southern part of a typical Lanping strike-slip and pull-apart basin. It has plenty of mineral resources derived from the collision between the Indian and Asian plates. The ore-forming fluid system in the Weishan Yongping ore concentration area can be divided into two subsystems, namely, the Zijinshan subsystem and Gonglang arc subsystem. The ore-forming fluids of Cu, Co deposits in the Gonglang arc fluid subsystem have &deltaD values between –83.8‰ and –69‰, &delta¹⁸O values between 4.17‰ and 10.45‰, and&delta¹³C values between –13.6‰ and 3.7‰, suggesting that the ore-forming fluids of Cu, Co deposits were derived mainly from magmatic water and partly from formation water. The ore-forming fluids of Au, Pb, Zn, Fe deposits in the Zijinshan subsystem have &deltaD values between –117.4‰ and –76‰, &delta¹⁸O values between 5.32‰ and 9.56‰, and &deltaC values between –10.07‰ and –1.5‰. The ore-forming fluids of Sb deposits have &deltaD values between –95‰ and –78‰, &delta¹⁸O values between 4.5‰ and 32.3‰, and &delta¹³C values between –26.4‰ and –1.9‰. Hence, the ore-forming fluids of the Zijinshan subsystem must have been derived mainly from formation water and partly from magmatic water. Affected by the collision between the Indian and Asian plates, ore-forming fluids in Weishan–Yongping basin migrated considerably from southwest to northeast. At first, the Gonglang arc subsystem with high temperature and high salinity was formed. With the development of the ore-forming fluids, the Zijinshan subsystem with lower temperature and lower salinity was subsequently formed.