Source of the Chaoyangzhai Gold Deposit, Southeast Guizhou: Constraints from LA-ICP-MS Zircon U–Pb Dating, Whole-rock Geochemistry and <i>In Situ</i> Sulfur Isotopes

• Main Authors: Hinyuen Tsang, Jingya Cao, Xiaoyong Yang
• Format: Article
• Language: English
• Published: MDPI AG 2019-04-01
• Series: Minerals
• Subjects: zircon U–Pb age; in situ sulfur isotopes; gold source; ore genesis; Chaoyangzhai gold deposit; Southeast Guizhou
• Online Access: https://www.mdpi.com/2075-163X/9/4/235

The Chaoyangzhai gold deposit is one of the newly discovered medium to large scale turbidite-hosted gold deposits in Southeast Guizhou, South China. In this study, laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) zircon U&#8211;Pb dating on the tuffaceous- and sandy-slates of Qingshuijiang Formation, Xiajiang Group, and gold-bearing quartz vein yielded similar age distributions, indicating that zircon grains in gold-bearing quartz vein originated from the surrounding tuffaceous- and sandy-slates. In addition, the youngest weighted mean ages of the zircon grains from the tuffaceous- and sandy-slates were 775 &#177; 13 Ma and 777 &#177; 16 Ma, respectively, displaying that the tuffaceous- and sandy-slates of the Qingshuijiang Formation were likely deposited in Neoproterozoic. Based on their major and trace element compositions, the tuffaceous- and sandy-slates were sourced from a felsic igneous provenance. The sandy slates have higher contents of Au (mostly ranging from 0.019 to 0.252 ppm), than those of the tuffaceous slates (mostly lower than 0.005 ppm). The &#948;³⁴S_V-CDT values of pyrite and arsenopyrite of the gold-bearing samples range from +8.12&#8240; to +9.99&#8240; and from +9.78 to +10.78&#8240;, respectively, indicating that the sulfur source was from the metamorphic rocks. Together with the evidence of similar geochemical patterns between the tuffaceous- and sandy-slates and gold-bearing quartz, it is proposed that the gold might be mainly sourced from sandy slates. The metamorphic devolatilization, which was caused by the Caledonian orogeny (Xuefeng Orogenic Event), resulted in the formation of the ore-forming fluid. Gold was likely deposited in the fractures due to changes of the physico-chemical conditions, leading to the formation of the Chaoyangzhai gold deposit, and the large-scale gold mineralization in Southeast Guizhou.