Age and Geochemistry of Rutile as an Indicator of Tungsten Source in the Wangu Au-W-Sb Deposit, Northeastern Hunan, China

The Jiangnan Orogenic Belt is a world-renowned metallogenic region for Au-W-Sb mineralization, with the Wangu deposit being a representative one. Previous research has demonstrated that tungsten in this Au-W-Sb deposit is sourced from the hosting metasedimentary rocks, but the specific mineral that provides tungsten is still unclear. This study evaluates the tungsten source by conducting petrographic observations and geochemical and geochronological analyses on the rutile from the host slate the Wangu deposit. The results show that rutile from wall rocks of the Wangu deposit yields an age of 955 ± 13 Ma, which is older than both the ore-forming age of the deposit and the age of the host strata. Electron microprobe analyses (EMPA) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) elemental analyses show that detrital rutile is enriched in elements such as Fe, Cr, V, and W, as well as high-field-strength elements (HFSE) including Nb, Ta, Zr, and Hf. The total rare earth element (ΣREE) ranges from 3.37 ppm to 156.85 ppm. The samples are generally enriched in light rare earth elements (LREEs) and exhibit distinct negative Eu anomalies. These geochemical features and a geochronological age of 955 ± 13 Ma suggest that the rutile is of detrital origin and they are possibly derived from the Grenvillian rocks. It is concluded that the detrital rutile in the metasediments could be an important source for hydrothermal tungsten enrichment.