广东省长坑金银矿床硅质岩石成因分析
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P581 P588.24

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中国地质调查局国土资源大调查资助项目 ( 2 0 0 3 10 2 0 0 0 72 )


The genesis of siliceous rocks in the Changkeng gold-silver deposit, Guangdong Province
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    摘要:

    通过对长坑金银矿床中硅质岩石的岩相学、地球化学特征的分析发现,岩石主要由次生石英(50%~90%)和黄铁矿组成,含少量重晶石、雄黄、雌黄、伊利石、迪开石等;岩石具热液交代和交代残余结构,发育典型构造岩的角砾、碎裂、碎斑、微裂隙及孔洞构造,无沉积岩结构构造;硅质岩石(矿石)由成矿过程中蚀变硅化作用形成,是标准的似碧玉岩。蚀变硅化在金矿化阶段可分为3期,银矿化阶段为1期;似碧玉岩∑REE低,尤其是含银似碧玉岩,含金似碧玉岩轻稀土元素较重稀土元素富集,含银似碧玉岩中稀土元素富集;似碧玉岩与典型热水沉积硅质岩40个北美页岩组合样标准化稀土元素分布型式的显著Ce负异常和Eu正异常存在较大差异。认为该矿床内硅质岩石非海水与沉积物界面之间的热水沉积成因或海水沉积作用形成的硅质岩,而是低温热液交代硅化形成的似碧玉岩。

    Abstract:

    Composed mainly of secondary quartz (50%~90%) and pyrite and minor realgar, orpiment, barite, illite as well as dickite, siliceous rocks are often characterized by typical hydrothermal metasomatic texture and metasomatic relict texture, and typical tectonite structures such as bracciated structure,cataclastic structure, porphyroclastic structure and small fissure and pore structures, with no sedimentary structures and textures. Gold-bearing or silver-bearing siliceous rocks are produced by silicification during mineralization. Undermicroscope, the silicification consists of 3 stages in the gold-forming period and 1 stage in the silver-forming period. REE compositions of the rocks show that ΣREE is especially low in silver-bearing rocks, LREE is richer than HREE in gold_bearing rocks, and MREE is rich in silver-bearing rocks. Therefore, the NASC normalized distribution curves dip towards right in gold-bearing rocks and upwards in silver-bearing rocks. In addition, the curves show slight negative ceriumanomaly and apparnt negative europium anomaly or indistinct positive europium anomaly, which differ from the curves of typical hydrothermal sedimentary chertsor sedimentary exhalation cherts with obvious negative cerium anomaly and positive europium anomaly. So the rocks should be typical jasperoid, which, instead of being formed by hydrothermal sedimentation or sedimentary exhalation between seawater and the surface of sediments, is a product of hydrothermal metasomatism. 

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毛晓冬 刘云华,2004,广东省长坑金银矿床硅质岩石成因分析[J].岩石矿物学杂志,23(2):158~166. MAO Xiao-dong~,LIU Yun-hua~,2004,The genesis of siliceous rocks in the Changkeng gold-silver deposit, Guangdong Province[J]. Acta Petrologica et Mineralogica,23(2):158~166.

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