Genesis of gold and antimony deposits in the Youjiang metallogenic province, SW China: Evidence from in situ oxygen isotopic and trace element compositions of quartz

Abstract

Abundant Carlin-type gold deposits and vein-type antimony deposits were discovered in the Youjiang basin of SW China, constituting the Youjiang Metallogenic Province (YMP). Although they had been widely studied by geologists, the genesis of these deposits remains debatable, while both intrusion-linked and non-intrusion linked models have been proposed. In this paper, new data of in situ trace elements (LA-ICP MS) and oxygen isotope (SIMS) analysis of hydrothermal quartz from the Yata Carlin-type gold deposit and the Qinglong vein-type antimony deposit in the province were provided to better understand the origin of ore-forming fluids as well as the genetic mechanism of Au and Sb mineralization. Four quartz generations were identified from the Yata (YTi to YTiv) and the Qinglong (QLi to QLiv) deposits. In the Yata deposit, the fluid inclusions in quartz have varied homogenization temperatures from 140–260 ℃ and salinities of 2.4–7.4 wt％ NaCleq, while in the Qinglong deposit, the temperatures and salinities ranged from 140–200 ℃ and 0.2–7.2 wt％ NaCleq., respectively. Both of the temperatures and salinities tend to decrease from early to late generations in the two deposits. δ18O values of initial fluids in the Yata (YTi: 7.70–10.56‰) and the Qinglong (QLi: 4.66–8.75‰) deposits are similar and suggest that they were mainly from magmatic or metamorphic fluids. The covariability of oxygen isotope and Al concentrations indicate that interaction between fluids and wall rocks is a significant factor in determining the compositions of fluids in Au mineralization, and the meteoric water is a key proxy in Sb mineralization, respectively. From these observations, we proposed that the Carlin-type Au deposit and vein-type Sb deposit in YMP were sourced from an analogous ore fluid. Different lithologies of wall rocks and the dilution of meteoric water controlled the compositional evolution of fluids, which might be the main reason for the diversity of Au and Sb mineralization.