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云南腾冲地块老象坑铁多金属矿床位于三江成矿带中南段,成矿条件和成矿潜力优越。通过野外实地勘查,结合主量、微量、稀土元素与Pb同位素分析,探讨其矿床地质特征与成矿物质来源。结果表明:矿体多呈透镜状,似层状等;矿石以致密块状、角砾状为主;镜下可见磁铁矿,磁黄铁矿,黄铜矿等多种金属矿物。磁铁矿矿石和磁铁矿单矿物微量元素变化趋势基本一致,可明显看出呈强不相容元素相对富集的右倾锯齿状;明显富集K,U,P,Ti,Nb,Sr等大离子亲石元素和重稀土元素Lu;而相对亏损Th,Ce,Nd,Zr,Sm,Y等元素;稀土元素分布总体上呈左倾模式,LREE相对亏损,HREE明显富集,LREE分布模式平坦,HREE分布变化大。磁铁矿矿石δEu为0.245~0.866,δCe为0.524~0.969,磁铁矿单矿物δEu为0.330~1.165、δCe为0.445~1.020,均具有明显的Eu负异常和较弱的Ce负异常。磁铁矿的Pb同位素组成(~(208)Pb/~(204)Pb为38.606~39.173,~(207)Pb/~(204)Pb为15.649~15.727,~(206)Pb/~(204)Pb为18.357~19.284)与腾冲地区基性-超基性岩相似,且磁铁矿与基性-超基性岩形成了很好的线性排列,表明其具有同源关系。腾冲老象坑磁铁矿的铅同位素组成主要源于造山过程;结合实际地质特征及矿区内最新的钻孔资料,认为老象坑铁多金属矿矿床类型应为超基性岩浆热液-断裂填充型铁矿床。
The old elephant pit iron polymetallic deposit in the Tengchong block in Yunnan Province is located in the middle and southern part of the Sanjiang metallogenic belt with favorable metallogenic conditions and potential for metallogenesis. Through the field investigation, combined with the main, trace, rare earth elements and Pb isotopic analysis, to explore the geological characteristics of the deposit and source of metallogenic material. The results show that the ore body is mostly lenticular and lamellar. The ore is mainly composed of dense massive and brecciated. Magnetite, pyrrhotite, chalcopyrite and other metal minerals can be seen under the microscope. Magnetite ore and magnetite single mineral trace elements are basically the same trend, it is clear that the strong incompatible elements are relatively enriched right serrated; obviously enriched in K, U, P, Ti, Nb, Sr, etc. LREE, LREE, LREE, LREE, LREE, LREE, LREE, LREE, LREE, LREE, LREE, and LREE; , HREE distribution changes. The δEu of magnetite ore is 0.245-0.866 and δCe is 0.524-0.969. The δEu of magnetite single mineral is 0.330-1.165 and the δCe is 0.445-1.020, both of which have obvious Eu anomaly and weak Ce anomaly. The Pb isotopic composition of magnetite is about 38.606-39.173 for 208 Pb / 204 Pb and 15.649-15.727 for 206 Pb / 204 Pb, Pb is 18.357 ~ 19.284) is similar to the basic-ultrabasic rocks in the Tengchong area, and the magnetite and the basic-ultrabasic rocks form a good linear arrangement, indicating that they have homology. The lead isotopic compositions of the Tengchong old elephant magnetite mainly originated from the orogenic process. According to the actual geologic characteristics and the latest drilling data in the ore district, it is considered that the Laoxiangkui iron polymetallic deposit should be ultrabasic magmatic hydrothermal-fractured Filled iron ore bed.