Trace elements in sphalerite in Laochang Pb-Zn polymetallic deposit, Lancang, Yunnan Province
云南澜沧老厂铅锌多金属矿床闪锌矿微量元素组成

As one of the most important Pb-Zn polymetallic deposit, Laochang, Lancang, Yunnan Province is located on the southern end of Sanjiang metallogenic belt. Researching on trace elements for sphalerite by LA-ICPMS and ICP-MS in the deposit, it show that the sphalerite belongs to marmatite, formed on medium temperature and be characterized by riching in Fe, Mn, Cd, In etc., which are present isomorphously in sphalerite. There are wide variation ranges for Pb, Cu, Sn, Bi and other trace elements, which present as micro-inclusion (e.g. galena, chalcopyrite etc.) in sphalerite. The character of rich in Fe and Mn is similar to that of VMS deposit in sphalerite, but the anomalous enrichment of In and Cd may imply that there is a particular metallogenic mechanism in the deposit. Our research show that the trace elements composition of sphalerite is same as that of some Chinese volcanogenic massive sulfide Pb-Zn deposits which were overprinted by Himalayan-Yanshanian granite (e.g. Bainiuchang, Yunnan Province and Dabaoshan, Guangdong Province) and quite different with that of skarn Pb-Zn deposits (e.g. Hetaoping and Luziyuan, Baoshan, Yunnan Province), MVT Pb-Zn deposit (e.g. Niujiaotang, Huize and Mengxing) and Jinding Pb-Zn deposit. Based on the geological feature of the deposit, it is suggested that, with the multi-stages opening and closing of Paleo Tethys Ocean, it formed a obvious multi-stages overprint metallization at same place in the deposit. The trace elements composition is characterized by that of volcanogenic massive sulfide Pb-Zn deposits, and there are no any genetic relationship between Pb-Zn mineralization and concealed Himalayan granite-porphyry, but the sulfide assemblage and their trace elements composition were changed to some extent with the intrusion of the rock mass (e.g. enrichment of Sn and Sb partly). Furthermore, the contrast of two different analysis method for trace elements in sphalerite show that LA-ICPMS could provide more accurate results, it not only show the exist of different trace elements real-timely, but also avoid the error resulted in by impure sample in ICP-MS analysis.