Trace element distribution in sulfides from the Chalukou porphyry Mo-vein-type Zn-Pb system, northern Great Xing' an Range, China: Implications for metal source and ore exploration

Located in the northern Great Xing' an Range, the giant Chalukou Mo deposit has been the largest porphyry Mo deposit so far in China, with the direct superimposed vein-type Zn-Pb ore body on the porphyry Mo mineralization. Major and trace elements compositions in pyrite, sphalerite and galena from different stages at Chalukou deposit are analyzed by EMPA and ICP-MS. Mo is enriched in all sulfides, and other elements in sulfides from different stages do not show regularity, except for the enrichment of Zn, Pb, Mn, Cd, Ga, Ag, Bi in the pyrite of Zn-Pb stage. Mo, Co content of sphalerite and Bi, Cd and Ag content of galena decrease from transitional stage to Zn-Pb stage. They are the consequence of fluid cooing and mixing with meteoric water. The REE patterns of pyrite are characterized by LREE enrichment, HREE depletion, and obvious Eu negative anomalies. These features are similar to those of ore-forming intrusions and wall-rocks. Furthermore, most of the Y/Ho values in pyrite (25.0 similar to 39.0) strap the wide range of oreforming intrusions (27.4 similar to 38.7). It is suggested that ore-forming material is sciurced predominantly from ore-forming intrusions with some contribution from wall-rocks. And the exceptional enrichment of Mo in sulfides is attributed to the deep giant porphyry Mo magmatic-hydrothermal system. Compared to the distal hydrothermal vein-type Zn-Pb deposit in east Qinling-Dabie W-Mo-Pb-Zn district, trace elements compositions of pyrite from proximal vein-type Zn-Pb ore body at Chalukou deposit show higher Mo/Ag-Bi/Sb ratio and Mo/Pb-Sn/Sb ratio. That means high Mo content in shallow sulfides and elevated ratios of some elements of pyrite may provide new clues for prospecting the underlying porphyry Mo mineralization beneath the vein-type Zn-Pb ore body. Compared to other vein-type and porphyry deposits, enrichment of moderate-high temperature elements in sulfides at Chalukou deposit is obvious. In addition, the enrichment of trace element in sulfides from different types of deposits show different features, according to the collected data (porphyry, epithermal, vein-type, skarn, VMS, MVT deposits), and this attempt could indicate a new perspective of distinguishing the ore genetic type.