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    武夷山成矿带龙岩地区晚石炭世热水成因硅质岩的发现及其地质意义

    The discovery of Late Carboniferous hydrothermal cherts in the Longyan area of the Wuyishan metallogenic belt and its geological implications

    • 摘要: 武夷山成矿带发育多期海相火山成矿建造,是近些年矿产勘查的重要对象。基于该成矿带龙岩地区晚石炭世经畲组铅锌矿化角砾岩层的宏观地质特征,对其中硅质岩进行了岩相学和岩石地球化学研究,探讨铅锌来源与富集机制等问题。研究发现,硅质岩SiO2和Al2O3呈负相关,Fe2O3/FeO大多数<1,并具有Eu正异常特征,说明硅质岩为热水沉积成因。硅质岩Al2O3/(Al2O3+TFe2O3)值为0.73~0.80(平均值为0.77)、Al2O3/(Al2O3+TFe2O3+MnO)值为0.60~0.65(平均值为0.62),LaN/CeN为0.86~2.49(平均值为1.52),表明硅质岩形成时受到了陆源物质影响。龙岩地区晚石炭世经畲组铅锌矿化角砾岩层是海底热水喷口塌陷作用的产物,对指导该区铅锌矿找矿工作具有重要意义。

       

      Abstract: Multiple submarine volcanic mineralization formations developed in the Wuyishan metallogenic belt have received much concern in recent years’ mineral exploration. Based on the geological characteristics of the lead-zinc mineralized breccia layer of Late Carboniferous Jingshe Formation in the Longyan area, petrographical and lithogeochemical studies of cherts from the breccia layer have been carried out in order to understand element(Zn and Pb)sources and enrichment mechanism. The research suggests that cherts have negative correlation between SiO2 and Al2O3, with most Fe2O3/FeO ratios less than 1 and positive Eu anomaly, which indicates a hydrothermal sedimentary genesis for cherts. The cherts have Al2O3/(Al2O3+TFe2O3)values of 0.73~0.80(averaging 0.77), Al2O3/(Al2O3+TFe2O3+MnO)of 0.60~0.65(averaging 0.62), and LaN/CeN of 0.86~2.49(averaging 1.52), which show that the cherts were influenced by continential materials. Finally, it can be concluded that the lead-zinc mineralized breccia layer of Late Carboniferous Jingshe Formation was the product of hydrothermal vent collapse on the seafloor. This study has significant implications for guiding mineral exploration in the Wuyishan metallogenic belt.

       

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