Investigation on Mineral Characteristic of Diamond and Geochemical Characteristic of Its Host in Langan Area,Anhui Province
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摘要: 安徽栏杆金刚石矿位于郯庐断裂带西侧，主要产生在碱性基性岩中，大多为黄色－褐黄色，透明，金刚光泽，立方体与曲面菱形十二面体聚形为主，另有立方体与八面体聚形、八面体与菱形十二面体聚形，粒径大小0.50～0.60mm。激光拉曼光谱的测试结果显示，在1 332cm－1具有典型金刚石峰，且谱形谱峰一致。本区的含金刚石母岩的微量元素特征显示其富集大离子亲石元素（K、Rb、Sr、Th和Ba），高场强元素（Nb、Ta、Zr和Hf）无明显亏损，暗示其形成于大陆板内环境，为地幔低度部分熔融的产物；稀土元素特征表现为轻稀土强烈富集，重稀土相对亏损，暗示了源区富集特征，Eu的负异常则显示岩浆经历了明显的斜长石结晶分异。结合中国东部碱性基性岩的金刚石成因条件及地球化学特征分析认为，本区碱性基性岩具有金刚石成矿地质背景。Abstract: The diamond ore occurring in the alkali-basic rocks in Langan area，Anhui Province，which is located in the west side of Tanlu（Tancheng-Lujiang）fault zone.Special care is taken to prevent cross contamination of synthetic diamonds used in the normal drill bits by using a special alloy drill bit.Diamonds are yellow-brownish or yellow colour，transparent，with adamantine luster.These diamonds mainly showed combined growth habit of cube and dodecahedron，a few of cube and octahedron，and a few of octahedron and dodecahedron.The size distribution is 0.5-0.6mm.Laser Raman spectroscopy showed the typical diamond peak at 1 332cm-1.The host rocks（dolerite）of these diamonds were formed in a tectonic setting of intraplate，with the characteristics of enrichment in LILE（K，Rb，Sr，Th and Ba），and depletion in HFSE（Nb，Ta，Zr and Hf）.The REE features demonstrated the rocks coming from the deep mantle，and undergoing low-degree partial melting of peridotite before emplacement.The obvious Eu negative anomaly indicated the magma was clearly fractionated by crystallization of plagioclases.Based on these geochemical observations，we believe that these alkali-basic rocks in the Langan area may have the possibility of the diamond ore formation.
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Keywords:
- diamond /
- mineral characteristic /
- geochemical characteristic /
- alkali-basic rock /
- Langan area
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