Geochemistry of pyrite from stratabound massive sulfide deposits, Tongling region, China: Implication for their genesis

摘要

Stratabound massive sulfide deposits are widely distributed along Middle-Lower Yangtze River metallogenic belt, in eastern China. There has much debate as to whether these deposits were associated with Late Mesozoic igneous or Carboniferous sedimentary exhalative (SEDEX). Three-type pyrites, i.e., colloform (Py1), fine-grained (Py2) and medium- to coarse-grained (Py3), from Xinqiao and Taoyuan stratabound massive sulfide deposits in Tongling region were investigated using electron probe microanalysis (EPMA), in-situ laser-ablation inductivelycoupled plasma-mass spectrometry (LA-ICP-MS) and sulfur isotopic analysis. The analytic data indicate that the three-type pyrites have high S and As, and relatively consistent Au contents. The Au, Ag, Bi, Sb and Pb elements are mainly of lattice bound appearance in the Xinqiao and Taoyuan pyrites. Low Au (mainly < 5 ppm) and Ni (commonly < 10 ppm) contents, high Co/Ni (mainly > 1), Se/Tl (mainly > 1) and delta S-34(CDT) (4.0 parts per thousand to 5.9 parts per thousand) values of the studied Xinqiao and Taoyuan pyrites imply a magmatic-hydrothermal origin. High Bi (> 1 ppm) and Mo contents, and low Co/Ni ratios (< 0.1) of the studied Xinqiao and Taoyuan pyrites reflect a sedimentary contribution to the magmatic-hydrothermal system. Combined with previous results, the Xinqiao stratabound mineralization is most likely to be genetically with the magmatic-hydrothermal fluids by the addition of a sedimentary component.