Origin of the Late Jurassic Juyuan tungsten deposit in Central Jiangxi, South China: Constraints from in-situ U-Pb dating of wolframite, trace elements of tungsten minerals and Sr isotope of scheelite

Abstract

The Juyuan tungsten deposit is one of the few large quartz vein-type scheelite deposits in South China, but its ore-forming age and fluid evolution history remain unclear. In this study, we conducted U-Pb dating and trace element analysis of wolframite, as well as trace element and Sr isotope analysis of scheelite using in-situ LA-ICP-MS and LA-MC-ICP-MS, respectively. The ore-forming age of the Juyuan tungsten deposit is 155.8 ± 4.6 Ma (MSWD = 1.9), which is consistent with the magmatic age of the Juyuan granite porphyry. Wolframite exhibits a low δEu value and is enriched in Nb and Ta. The formation of Juyuan scheelite occurred in three stages: Sch-I scheelite has a high total REE content, a ‘hump-shaped’ chondrite-normalized REE distribution curve, and the lowest δEu value; Sch-II scheelite also has a high REE content, but the MREE gradually depletes, the chondrite-normalized REE distribution curve flattens, and the δEu value increases; Sch-III scheelite shows significant MREE depletion, a concave distribution curve, and a strong positive Eu anomaly. The ore-forming environment was reduced in the early stage of Juyuan tungsten mineralization, but the introduction of atmospheric precipitation increased oxygen fugacity and decreased salinity. Sr isotope analysis of scheelite confirms that the Juyuan tungsten deposit is genetically related to the granite porphyry, and due to water–rock interactions, the initial ⁸⁷Sr/⁸⁶Sr ratio increased.