| 东秦岭地区钼矿床铅同位索组成特征及成矿物质来源初探 |
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| 引用本文：.1984.Lead Isotope Compositions Of Molybdenum Deposits In East Qinling As Applied To The Problem Of Ore Sources[J].Mineral Deposits,3(4):20~28 |
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| Lead Isotope Compositions Of Molybdenum Deposits In East Qinling As Applied To The Problem Of Ore Sources |
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| Abstract:The east Shanxi to west HeⅡan section of the East Qinling region is one of the major molybdenum ore zones in China, where various types of molybdenum deposits, such as uranium-niobium-lead-rare earth mineralization of carbonatite vein type, molybdenum-lead deposits of carbonatite vein type, porphyry molybdenum deposits, and molybdenum-tungsten deposits of porphyry-skarn type, have long become known to the geologists. Studies show that lead isotope ratios of ores from these deposits vary considerably, showing a tendency of linear arrangement. Following are some data acquired from three typical deposits: the Hunglongpu molybdenum-lead deposits (averages of quite a few samples), Pb206/Pb204 = 17.378, Pb207/Pb204 = 15.383, Pb208/Pb204 = 37.418, μ= 8.7-9.2, Th/U=3.6-3.94; ore lead of the Jingduicheng molybdenum deposit (averages of two samples), Pb206/Pb204=17.410, Pb207/Pb204=15.428, Pb208/Pb204=37.702; ore lead of the Nannihu-Shandozhuang molybdenum-tungsten deposit, Pb206/Pb204 = 17.45, Pb207/Pb204 = 15.54, Pb208/Pb204 = 39 .01. Single-stage "model-lead" ages of these deposits range from 586 to 778 m.y., younger than the ages of Archeozoic and Proterozoic country rocks but older than the ages of mineralization. The disagreement of these ages with the definition of the normal lead implies that lead of these deposits belongs to abnormal one. It is inappropriate, therefore, to regard the single-stage model-lead ages as mineralization ages of these vein type and skarn type molybdenum deposits. The isotopic compositions of lead and the geological setting of these deposits suggest that ore-forming metals of the Hunglongpu deposit-molybdenum and lead-were derived chiefly from the upper mantle and partly from the country rocks whereas the ore-forming metal molybdenum of the Jinduicheng probably came from the anatectic magma . |
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