Robust Timing Constraints for Granitic Magmatism and Hydrothermal Mineralization in the Tieshanlong W-Sn Ore Field, Eastern Nanling Range, South China

Abstract

The Tieshanlong ore field is an important part of the Nanling Range, which is famous worldwide for its W-Sn mineralization. Notably, the mineralization age of the Tieshanlong ore field is not well constrained, and our field investigation reveals that granitic emplacement occurred at different stages. However, previous studies have not distinguished these multiple stages of magmatism. The Tieshanlong granite complex is closely related to the Huangsha quartz vein-type W-Sn deposit and Tongling skarn-type Cu-W-Sn deposit in this field. Through field investigations and isotopic age analyses, this work studies the relationship between multistage magmatic activity and mineralization in the Tieshanlong ore field. LA-ICP-MS zircon U-Pb isotope analyses revealed that the first- and second-staged granites formed at 154.2 ± 0.6 Ma (MSDW = 1.4) and 151.2 ± 0.4 Ma (MSDW = 1.5), with zircon ε_Hf(t) values ranging from -13.1 to -10.5 and from -14.7 to -11.1, respectively. These data suggest that the Tieshanlong granite complex was derived from the partial melting of ancient crustal material. LA-ICP-MS U-Pb dating of wolframite and cassiterite reveals that W-Sn mineralization occurred at 160–150 Ma, which agrees well with the U-Pb dating results of the second-staged granite within analytical errors. The magmatic activity in this ore field can be divided into three stages: 175–154 Ma, 154–150 Ma and 150–145 Ma. The quartz vein- and skarn-type W-Sn mineralization is closely related to second-staged fine-grained two-mica granite, and formed earlier than skarn-type Cu- mineralization. This study establishes a metallogenic model for the Tieshanlong ore field, and this model has important practical significance for identifying concealed W-Sn(-Cu) deposits around other granitic complexes in the Nanling Range.