| 东秦岭地区钼矿床的铼-锇同位素年龄及其意义 |
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| 引用本文：.1994.Re-Os isotope ages of molybdenum deposits in east Qinling and their significance[J].Mineral Deposits,13(3):221~230 |
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| 基金项目:国家人事部非教育系统留学回国人员科技活动A类经费 |
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| 中文摘要:金属矿床的成矿年龄多年来一直是矿床地质工作者关注的问题之一。中国地质科学院岩矿测试技术研究所建立的铼-锻同位素定年实验室，为研究钼矿床的形成时代提供了新的手段。因辉钼矿是最主要的含铼矿物之一，且基本上不含普通锇，其中所含187Os是由187Re衰变而来，故放射成因187Os的积累是矿物年龄及铼含量的函数。本文采用同位素稀释一等离子体质谱法，测定了东秦岭钼矿带中几个不同类型的大型钼矿床的Re-Os年龄：黄龙铺碳酸岩脉型钼(铅)矿床的Re-Os年龄为印支期，其余的斑岩型钼矿床和斑岩-矽卡岩型钼（钨）矿床的Re-Os年龄均为燕山期。 |
| 中文关键词:钼矿床 187Re和187Os同位素 Re-Os年龄 东秦岭地区 |
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| Re-Os isotope ages of molybdenum deposits in east Qinling and their significance |
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| Abstract:The East Qinling molybdenum ore belt lies on the southern margin of the North China platform and is one of tile areas in China where important molybdenum deposits are concentrated. The belt includes porphyry type molybdenum deposits (Jinduicheng and Shijiawan in Shaanxi Province) and perphyry-skarn molybdenum-tungsten deposit (Nannihu-Sandaozhuag in Henan Province) related to Mesozoic granites, as well as carbonatite vein-type moly-Bdenum-(1ead)-uranium deposits(Huanglongpu and Huayangchuan in Shaanxi Province) not related to Mesozoic granites. The ages of these ore deposits are generally represented by ages of related rock bodies determined by Rb-Sr isochron or K-Ar method. However, these ore-bearing rock bodies were commonly subjected to different degress of hydrothermal alteration and hence the Rb-Sr and K-Ar Systems are not as satisfactory as closed ones, rendering the rock-forming ages determined by the above methods unreliable. It is well known that molybdenite contains essentially no common, osmium and 187Re is radioactive and yields stable 187Os through βdecay. Therefore, accumulation of radiogenetic 187Os is a function of age and Re content of molybdenite. In this paper 187Re and 187Os contents of molybdenite from these molybdenum deposits are determined by Inductively Coupled Plasma Mass Spectrometry(ICP-MS), with the Re-Os ages calculated. The analytical errors of Re and Os are around±3％(2σ)，and the errors of Re-Os ages are between 3％and 4％(2σ)．The results show that the apparent Re-Os ages of the Jinduicheng and Shijiawan deposits are 129×106?139×106a and 138×106a.respectively, The apparent age of the Nannihu-Sandao-Zhuang molybdenum-tungsten deposit is 146×106?156×106 a with an isochron age of 147×106 a(n=5)，and the Huanglongpu Mo (Pb) deposit is 222×106?230×106 a with an isochron age of 221×106a(n=5)．The Re-Os dating method not only provides directly reliable ore-forming ages for these deposits, but also demonstrates that there exist two metallogenic epochs of molybdenum deposits in the East Qinling Mountains, i.e. Indosinian and Yanshanian periods. The result is of importance in outlining the temporal and special distribution of molybdenum deposits and the evolution of molybdenum mineralization in this region． |
| keywords:molybdenum deposit,187Re and 187Os isotopes, Re-Os age, east Qinling area |
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