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宋生琼,潘力川,魏文凤. 2019. 赣南淘锡坑钨矿床He-Ar同位素地球化学研究. 岩石学报, 35(1): 243-251
赣南淘锡坑钨矿床He-Ar同位素地球化学研究
作者单位
宋生琼 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081
贵州省国土资源勘测规划研究院, 贵阳 550005 
潘力川 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081 
魏文凤 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081
成都理工大学地球科学学院, 成都 610059 
基金项目:本文受中科院战略性先导科技专项(XDB18000000)和国家"973"项目(2007CB411400)联合资助.
摘要:
      华南石英脉型黑钨矿的形成一直被认为是与地壳沉积物质重熔形成的S型花岗岩有关。然而,近年来对南岭中生代成岩成矿机制的研究发现,地幔组分可能参与了钨、锡成矿作用。本文对淘锡坑石英脉型钨多金属矿床与黑钨矿共生的黄铁矿和毒砂中流体包裹体的He、Ar同位素进行了研究。结果显示,上述矿物中流体包裹体的3He/4He值为0.37~2.11Ra(Ra为空气的3He/4He值,1Ra=1.39×10-6),介于地幔与地壳的3He/4He值之间;40Ar/36Ar值为309.5~383.6,平均335.4,略高于大气的40Ar/36Ar比值(295.5)。研究表明,成矿流体具有壳-幔两端元混合的特征。其中,地壳端元的流体为经过地下循环的低温饱和大气水,地幔端元的流体为矿区隐伏花岗岩体成岩过程中分异出的岩浆流体。结合前人研究成果,认为该矿床的形成与华南中生代燕山期发生的软流圈上涌、岩石圈减薄、地壳伸展等地球动力学作用有密切联系。这种动力学过程为地幔组分带来的热引起地壳沉积物质重熔形成钨多金属成矿花岗岩浆提供了条件。
英文摘要:
      China accounts for about 60% tungsten reserves of the world. More than 90% of the Chinese tungsten resources occur in the Nanling region as tungsten polymetallic deposits. The Nanling region locates at the central west Cathaysia Block in South China where abundant Jurassic granitic intrusions are distributed. Previous studies have significantly advanced our understanding of the tungsten ore formation in the Nanling region. These deposits are usually of the quartz-wolframite vein type. They have ages of about 150~160Ma, and are spatially and temporally related to the Jurassic granites, believed to be produced by crustal anatexis. The formation of quartz-vein type tungsten deposits in South China has always been considered to be related to S-type granite derived from remelting of crustal materials. However, in recent years, studies on the metallogenic mechanism of Mesozoic W-Sn deposits in Nanling region have demonstrated that mantle material and mantle fluid may be involved in tungsten and tin mineralization. The Taoxikeng deposit is a large-sized W deposit located at Jiangxi. Here, we conducted studies He and Ar isotope of pyrite- and arsenopyrite-trapped fluid inclusions on Taoxikeng quartz-vein type wolframite deposit. The analytical results of He and Ar isotope of pyrite- and arsenopyrite-trapped fluid inclusions show that, 3He/4He ratio of arsenopyrite between 1.38 and 2.11Ra (Ra is 3He/4He in air, 1Ra=1.39×10-6). The 3He/4He of pyrite between 0.67 and 0.37Ra. The concentration of 4He is between 1.98×10-7 and 49.1×10-7cm3 STP/g. The concentration of 40Ar is 4.19×10-7~51.4×10-7cm3 STP/g, 3He/4He is 0.37~2.11Ra. 40Ar/36Ar is 309.5~383.6, slightly higher than the ratio of atmosphere 40Ar/36Ar (295.5), the ratio of 38Ar/36Ar is 0.19~0.23, with the average of 0.183, which is close to the atmospheric value (0.188). These indicate that the ore-forming fluid has the characteristics of mixing both ends of the crust and mantle. The crustal fluid is composed of low temperature atmospheric water interacted with crustal rocks, and the fluid containing mantle-derived components is exsolved from granite. Combined with previous studies, it is believed that the deposit is closely related to Mesozoic large-scale asthenosphere upwelling, lithospheric thinning and crustal extension in South China, which provided favorable condition to lead the mantle-derived He/heat upward and then to melt the crustal materials and to form the ore-forming granitic magmas.
关键词:淘锡坑钨矿床  流体包裹体  He和Ar同位素  S型花岗岩  地幔组分
投稿时间:2018-08-02  修订日期:2018-11-16
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