向璐, 郑建平, 黄远成, 李永刚. 贵州镇远马坪金伯利岩及其捕虏晶对金刚石成矿条件的指示意义[J]. 地质通报, 2019, 38(1): 177-188.
    引用本文: 向璐, 郑建平, 黄远成, 李永刚. 贵州镇远马坪金伯利岩及其捕虏晶对金刚石成矿条件的指示意义[J]. 地质通报, 2019, 38(1): 177-188.
    XIANG Lu, ZHENG Jianping, HUANG Yuancheng, LI Yonggang. The Maping kimberlites and its xenocrysts as indicators of diamond minerogenetic condition in Zhenyuan area, Guizhou Province[J]. Geological Bulletin of China, 2019, 38(1): 177-188.
    Citation: XIANG Lu, ZHENG Jianping, HUANG Yuancheng, LI Yonggang. The Maping kimberlites and its xenocrysts as indicators of diamond minerogenetic condition in Zhenyuan area, Guizhou Province[J]. Geological Bulletin of China, 2019, 38(1): 177-188.

    贵州镇远马坪金伯利岩及其捕虏晶对金刚石成矿条件的指示意义

    The Maping kimberlites and its xenocrysts as indicators of diamond minerogenetic condition in Zhenyuan area, Guizhou Province

    • 摘要: 贵州镇远是中国金刚石原生矿找矿的重点区域之一。镇远地区马坪D1号岩体是1965年中国首次发现的含原生金刚石金伯利岩。该岩体岩石具典型的金伯利岩结构和组成特征,其中的锆石捕虏晶U–Pb年代学和Hf同位素分析结果表明,该地区存在未暴露的太古宙基底物质残余。基于壳幔耦合性规律,可能对应有古老的岩石圈地幔,这种古老的克拉通属性是金刚石形成的有利因素。但另一方面,马坪金伯利岩普遍含有伴生矿物含铬镁铝榴石,其CaO含量较高,多数属于G9(二辉橄榄岩)类型,不是全球富含金刚石的方辉橄榄岩原岩类型(G10),暗示当时的岩石圈发生了部分改造而可能不利于高品质金刚石的形成。需要注意的是,在金刚石找矿过程中,应该以详细的野外工作与岩石学对比研究为基础,同时依赖于金伯利岩及其相关的岩浆活动所携带的捕虏体/捕虏晶的研究,配合以岩浆成分来反演地幔源区特征,才能较全面地揭示古老大陆岩石圈的形成年龄与演化历史、物质组成与精细结构,以及大陆岩石圈根的厚度、热状态、氧逸度、流体作用等,进而为寻找金刚石提供重要的依据。

       

      Abstract: Zhenyuan area of Guizhou Province is one of the key areas for diamond primary ore prospecting in China. In the Maping D1 rock mass of Zhenyuan area, the kimberlite occurrence with containing primary diamonds was discovered for the first time in 1965. The rocks have structural and componential characteristics of typical kimberlites, the U-Pb geochronology and Hf isotope analyses of zircon xenocrysts entrained in the Maping D1 diamondiferous kimberlites indicate the existence of unexposed Archean basement remnants beneath the study area. Based on the regularity of crust-mantle coupling, with corresponding to the old lithospheric mantle, this nature of ancient craton is a favorable factor for diamond formation. On the other hand, the Maping kimberlites commonly contain associated minerals of Cr-pyrope with high CaO content, most of which belong to the G9 (lherzolite) type rather than the global diamond-rich harzburgite protolith type (G10), suggesting that the state of lithosphere had been partly modified at that time and may not be conducive to the formation of high-quality diamonds. Note that in the processes of diamond prospecting, it should be based on the detailed field work and comparative petrological study, and rely on the investigation of diverse xenoliths/xenocrysts carried by kimberlites and the other associated magma activities, in combination with inversing the characteristics of mantle source by the composition of magmas. Therefore, it is possible to comprehensively reveal the ancient subcontinental lithosphere about the formation age and evolution history, material composition and fine structure, as well as the thickness, thermal state, oxygen fugacity, fluid activity and some other aspects of the subcontinental lithospheric root, thus providing important evidence for diamond prospecting.

       

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