| The Fule dispersed element-polymetallic deposit is located in the southwestern margin of the Yangtze block, at the southeastern part of the Sichuan-Yunnan-Guizhou Zn-Pb polymetallic district. The deposit is a medium-scale Zn-Pb associated with large-scale Cd, Ge, Se and small-scale Ga deposit. The deposit is poorly studied.The deposit occurs in dolomite and limestone of the Lower Permian Maokou Formation. The ore bodies are typically layer- or lens-like. The ore consists of sphalerite, galena, dolomite and calcite typically shows massive or brecciated structures and coarse-grained texture. Based on systematic studies on geochemistry of major elements, trace elements, rare earth elements and stable isotopes as well as characteristics of ore-forming fluids, the following achievements have been obtained:1. The distribution characteristics of dispersed elements. Cd, Ge, Se, and Ga exist principally in sphalerite, with average contents of 16183 ppm Cd, 163 ppm Se, 135 ppm Ge and 86 ppm Ga. Cd, Ge, and Se occur in crystal lattice of sphalerite, where Cd and Ge occupy the position of Zn and Se occupies the position of S. Ga partially exists in crystal lattice of sphalerite and partially is adsorbed in lattice defect as micro-adsorption form. Cd enriches in dark color sphalerite, Ge in light color sphalerite, and Ga in yellow-brown sphalerite, while the content of Se in sphalerite does not change with color. In sphalerite Zn is negatively correlated with Cd, positively correlated with Ge, but insignificantly correlated with Se.2. The color genesis of sphalerite. The color of sphalerite is uneven internally, varying from purple, red, yellow to blank. The color seen by naked eyes is a synthetic effect of inside crystal and caused by Ni, Cu, T1, Ga, Hg, Fe, Cr, etc., of which the most important elements are Ni, Cu, Ga. Ni induces purple, Cu red and Ga yellow. Cd enriches in dark color sphalerite because itspositive correlation with Ni and Cu.3. Ore deposit geochemistry. The ores have a low total content of rare earth elements (￡REE=2.66—10.19 ppm), relatively enriched light rare earths and a negative Eu anomaly. The hydrogen, carbon and oxygen isotopic compositions of ore fluids are 5 D=-76~-60%o, 6 18O= 10.8—14.7%o and 8l3C=-19.1—-2.6%. Carbon and oxygen isotopic compositions of dolomite and calcite are 518O= 16.64-19.91% and 513C=1.12-3.02%. 6 34S values vary from 12.97 to 14.91 %o for sphalerite and from 7.91 to 11.14% for galena. The lead isotopic compositions of sulfides are 206Pb/204Pb= 18.470-18.586, 2O7Pb /204Pb = 15.542-15.707, and 208Pb/204Pb = 38.283—38.643. It was mainly derived from evolved formation water with slight amounts of oil-field brines. Sulfate reduction in the strata was the main source of sulfur for sulfide precipitation. CO2 came mainly from carbonates dissolution and partly from oxidatin of CH4.4. Discussion on ore genesis. The Mile—Shizong fracture zone may serve as an ore conductive fault, while the interlayer faults at the core of the Tuoniu-Duza anticline are favorable ore-hosting structures. The deposit contains abundant fluid inclusions. The ore-forming fluid has a medium-low temperature (160-240 °C)i a low salinity (4.5~10 wt%NaCl), and a low pressure (52.9~60.1 MPa). The ore-forming elements may have been derived from several sources, among which the sedimentary rock cover was the main source, especially the Permian Maokou Formation and the Carboniferous Baizuo Formation. The ore precipitated in a slightly alkalic and reducing environment with medium sulfur fugacity. The driving force for ore fluids was tectonic stress. This deposit belongs to the Mississippi Valley-type lead-zinc deposit and its metallogenic epoch is Yanshanian. Favorable source beds and oil-field brines were important for the deposit to enrich in dispersed elements.
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