GAO Ren 1,2, ZHANG Ming-hua 2, WANG Guo-hua 2, WEN Run-tao 2, CHEN Tian-di 2

(1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;
2. No.2 Geological Team, Jiangxi Bureau of Geology, Jiujiang 332000, China)

Abstract: The Xianglushan deposit in the northern part of Jiangxi Province, is one of giant tungsten deposits in the northwestern margin of the world-class Jiangnan tungsten metallogenic belt. It contains three adjacent subordinate oreblocks, named the Xianglushan-Xingping, Dayanxia and Zhangtianluo oreblocks. The Xianglushan-Xinping oreblock comprises mainly lenticular and stratiform-like skarn-type W orebodies in the contact between argillaceous limestone of the Cambrian Yangliugang Formation and a biotite granite pluton. The Dayanxia and Zhangtianluo oreblocks comprise hornfels-type W orebodies distributed mainly along the bedding of carbonaceous shales of the Sinian Doushantuo Formation and carbonaceous argillaceous siliceous rocks of the Sinian Dengying Formation. The H-O isotopic results of quartzs from tungsten ore samples in the Dayanxia oreblock show that the δ18OH2O and δDV-SMOW values for fluids in quartzs of the early quartz-oxide stage range from -3.3‰ to 0.7‰ and from -67.9‰ to -78.0‰, respectively, while those of the late quartz-sulfide stage range from -7.5‰ to -0.3‰, and from -64.6‰ to -66.4‰, respectively. These H-O isotopic signatures suggest that magmatic fluid and meteoric water were mixed to have formed the ore-forming fluids of both quartz-oxide and quartz-sulfide stages, with up to about 40% of meteoric water in the ore-forming fluid of quartz-sulfide stage. Sulfides from various subordinate oreblocks of the Xianglushan deposit have very similar δ34 S values varying generally from 1.2‰ to 5.4‰ which are consistent with the characteristics of magmatic sulfur. Integrated with the regional geological background, previously published data, and our results, it is suggested that the initial ore-forming fluid was formed by the mxing of magmatic hydrothermal fluid, which was derived from the uplifting W-rich fertile magma formed by the partial melting of the Upper Proterozoic material under the regional extension background in the Early Cretaceous, and meteoric water near the earth surface. The evolved ore-forming fluid, which was then formed with the continuous mixing of meteoric water near earth surface, resulted in the metasomatism and alteration of calcium-bearing wallrocks of multiple strata and the final formation of the Xianglushan scheelite deposit.

Keywords: hydron-oxygen-sulfur isotopes; skarn deposit; Xianglushan tungsten deposit; Jiangnan tungsten metallogenic belt

ACTA MINERALOGICA SINICA Vol. 43, No. 4, 2023, Page 501