| QiXiashan Pn-Zn deposit at the weatern end of Nanjing-Zhenjiang mountain range is situated in the fractured depression of the middle-lower reaches of the Yangtze river, and mineralization has great vision. Genesis type of the QiXiashan Pn-Zn deposit in the area is uncertain. Research work for the genesis of the Pb-Zn deposit is very important, which can provide a theoretical basis for the regional metallogenic regularity and exploratory forecast. Based on the field investigation of QiXiashan Pb-Zn deposits, the data colledtion and analyzed, microscope identification of slices, stable isotope analysis and study on fluid inclusion, the major results and understandings are obtained as following:1. The geological frame of the QiXiashan deposit is composed of two structural beds with an unconformable contact between them. No significant magmatic intrusion and its alteration have been obverved on the surface or intersected by drilling. The lead-zinc-silver orebodies of the deposit are mainly localized in the bottom horizon of the middle Carboniferous carbonate formation, fractured unconformable plane, paleo-karst in limestone and some transverse faults. The main ore bodies of QiXiashan Pb-Zn deposits are layed, stratiform or lentic ular.2. Sulfide in the hand specimen and slices are fine-grained, reflecting the characteristics of rapid deposition. Mineral composition is simple. There are sphalerite+galena+Pyrite+chalcopyrite+gypsum+calcite+barite+quartz.3. We also make r a detailed study of the ore deposit on QiXiashan Pn-Zn deposit:a wide range of δ34S%o values, and Sulphur isotopes have the characteristic of light S, shows that sulfur was mainly from deep source, but clearly influenced by the biological effects; The isotopic compositions of lead argues that the lead of ore sulfide originated from the basements rocks; This study made a systematic research works on fluid inclusions in sphalerite. The type of fluid inclusions is very sample, mainly the liquid (H2O)-rich inclusions. The fluid inclusion studies show that there are two types: Ha, the primary liquid-rich fluid inclusions, the homogenization temperatures and primary salinities of fluid inclusion are230-260℃and1.0-8.0wt%NaCleqv, respectively; Ⅱb, the secondary Liquid-rich fluid inclusions, the homogenization temperatures and primary salinities of fluid inclusion are140-180℃and5-7wt%NaCleqv, respectively. And that the main component of fluid is H2O, without other vapors, determined by Raman microspectroscopy; the data shows that the main ore-forming fluid is sea water.4. We integrated compared QiXiashan Pn-Zn deposit with MVT and SEDEX characteristics of ore deposits, conclude that QiXiashan Pn-Zn deposit is Sedimentary Exhalative Deposit. |
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