An Early Permian epithermal gold system in the Tulasu Basin in North Xinjiang, NW China: Constraints from in situ oxygen-sulfur isotopes and geochronology. (March 2018)

• Record Type: Journal Article
• Authors: Dong, Leilei; Wan, Bo; Deng, Chen; Cai, Keda; Xiao, Wenjiao
• Is Part Of: Journal of Asian earth sciences. Volume 153(2018)
• Page Start: 412
• Page End: 424
• Publication Date: 2018-03
• Subjects: Epithermal Au deposits -- Axi -- Jingxi-Yelmand -- In situ analysis -- O-S isotopes -- Ti-in-quartz thermometer; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2017.07.044
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: Ore forming fluids in the Axi and Jingxi-Yelmand deposits were associated with magmatic fluids. Both of these deposits formed in the Early Permian. The Axi deposit is an intermediate sulfidation epithermal deposit. The Axi and Jingxi-Yelmand gold deposits belong to the same magmatic-hydrothermal system in the Early Permian. Abstract: The Axi and Jingxi-Yelmand gold deposits, being the largest gold deposits in the Chinese North Tianshan, NW China, are located ca. l0 km apart in the Tulasu Basin, and are hosted by the Late Devonian - Early Carboniferous Dahalajunshan Formation. In situ LA-ICP-MS titanium analyses on quartz from the Axi and Jingxi-Yelmand deposits are broadly identical. Accordingly, the calculated ore-forming temperatures by Ti-in-quartz thermometer give average temperatures of 279 °C and 294 °C, respectively. Results of in situ SIMS analyses of oxygen and sulfur isotopes on quartz and pyrite from these two deposits are similar. Temperature-corrected fluids of the Axi deposit have δ 18 O values of 2.6–8.1‰ and δ 34 S values of 0.8–2.4‰, whereas the fluids of the Jingxi-Yelmand deposit have δ 18 O of 6.4–8.9‰ and δ 34 S of −0.4 to 4.0‰. The oxygen and sulfur isotopes from the two deposits indicate a magmatic origin. LA-ICP-MS zircon U-Pb ages of Aqialehe Formation sandstone provided a lower limit for the mineralization timing of the Axi deposit (288 Ma). In situ SIMS U-Pb analyses on entrapped zircon (297 Ma) and newly recognized 284.5 Ma columnar rhyolite implies that the Jingxi-Yelmand deposit formed in the Early Permian. Based on the magmatic affinity of the ore fluids, similar age and ore-formation temperatures, we propose that the Axi and Jingxi-Yelmand deposits comprise an epithermal gold system, which was driven by the same Permian magma in the Tulasu Basin. The ore geological features together with our new results indicate that the Axi and Jingxi-Yelmand deposits are intermediate and high sulfidation type epithermal deposits, respectively.