Geochemical Characteristics of Hydrothermal Cherts of Erlangping Group in East Qinling and Their Geologic Significance
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摘要: 二郎坪群硅质岩成因研究对二郎坪群的构造背景和铜多金属矿床成因的确定具有重要意义。通过对二郎坪群中三种硅质岩的地质特征和岩石地球化学分析，认为二郎坪群硅质岩是典型的热水沉积硅质岩。常量元素地球化学特征值（N(Al)/N（Al+Fe+Mn））指示该硅质岩的沉积环境存在东西差异，南阳盆地以东弧后盆地的规模较大（N(Al)/N（Al+Fe+Mn）=0.30~0.45），沉积环境类似远洋盆地，硅质岩的热液成分比例大，受陆缘物质影响小；而南阳盆地以西弧后盆地的规模较小（N(Al)/N（Al+Fe＋Mn）=0.59），沉积环境为近大陆的边缘海，硅质岩Al含量相对较高，受到陆缘物质影响相对大。地质特征和稀土元素特征（负Eu异常、弱负Ce异常）揭示了二郎坪群硅质岩是弧后盆地型低温热液流体和海水混合形成，这为二郎坪群形成于弧后盆地构造环境的认识提供了新的重要证据。热水沉积硅质岩与铜多金属矿床的共生关系证明研究区铜金属矿床的成因是海底热液喷流沉积作用。
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关键词:
- 东秦岭二郎坪群硅质岩热水沉积
Abstract: The genetic study of the cherts in Erlangping Group is the key to reveal copper polymetallic deposits genesis and tectonic setting of Erlangping Group.By studying the geological and geochemical characters of the three types of cherts in Erlangping Group in the east Qinling orogenic belt, it is believed that the cherts in Erlangping Group are hydrothermal sedimentogenic rocks. The major elements characteristic value (N(Al)/N（Al+Fe+Mn）) indicates that the cherts were formed in different marine environments .The cherts formed at the west of Nanyang basin were deposited in continental margin basin environment, but those formed at the east of Nanyang basin were deposited in pelagic environment and had a little of material from the continental margin. Comprehensive analysis of rare earth elements geochemistry(negative Eu ,Ce anomaly) and geologycharacteristics of the cherts show sthat the cherts of Erlangping Group are formed by the mixing of backarc basin type hydrothermal solutions of low temperature and seawater, so a new evidence is provided to determine the backarc basin tectonic setting of Erlangpin Group.The paragenetic relationship of hydrothermal sedimentogenic cherts and copper polymetallic deposits manifest that the copper polymetallic deposits are formed by the submarine hydrothermal exhalative lithogenesis and mineralization.-
Key words:
- East Qinling Mountain
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