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    湖南黄沙坪钨钼多金属矿床矽卡岩地球化学特征及其地质意义

    Skarn geochemistry of the Huangshaping W-Mo polymetallic deposit in Hunan and its geological significance

    • 摘要: 提要:湖南黄沙坪钨钼多金属矿床位于中国南岭成矿带中段,是一个以矽卡岩型为主的多金属矿床。对矿床内矽卡岩、围岩(灰岩、大理岩)和与矽卡岩形成相关的花岗斑岩岩体进行地球化学分析表明:在主量元素方面,Fe、Al、Mg、Si等元素在花岗斑岩与矽卡岩中发生了迁入迁出,矽卡岩SiO2含量与MgO、MnO、CaO、Fe2O3+FeO含量呈线性递减的关系;在稀土元素方面,矽卡岩具有明显的LREE富集,HREE亏损,发育有明显的Eu负异常。花岗斑岩具有与矽卡岩相同的REE配分模式,其成岩年龄也与矽卡岩型辉钼矿的Re-Os同位素年龄 (158.4±1.3 Ma)相一致,说明两者在成因上具有一定联系。同时根据矿床内矽卡岩几乎不发育Ce异常,说明形成矽卡岩的流体中没有海水的混合。结合矿床内不同岩石的地球化学特征,强烈的轻、重稀土分异,明显的Eu负异常,推测黄沙坪地区矽卡岩是由岩浆热液流体的接触交代作用形成的。

       

      Abstract: Abstract:The Hangshaping large-size W-Mo polymetallic ore deposit lies in the Nanling metallogenic belt. The authros chose the skarn as well as wall rocks(limestone and marble)and ?granite porphyry related to the skarn to conduct component analysis. The result shows that the major elements (Fe, Al, Mg and Si) migrated between the granite porphyry and the skarn, and the content of SiO2 shows linear descending relationship with the content of MgO, MnO, CaO and Fe2O3+FeO in the skarn. The skarn is enriched in LREE and depleted in HREE, with obvious Eu negative anomalies. The granite porphyry has the same REE distribution patterns as the skarn. The precise Re-Os dating of the molybdenite from skarn-type ore yielded an ore-forming age of 158.4±1.3 Ma. which is the same as the age of the granite porphyry, suggesting their relationship in petrogenesis. The poorly-developed Ce anomalies in skarn rocks imply that the fluids for the formation of skarn were mainly derived from the magma and mixed with meteoric water. Combined with the geochemical characteristics of different rocks, intense differentiation of LREE and HREE and Eu negative anomalies, the authors infer that the skarn in the Huangshaping ore deposit was formed by fluid metasomatism.

       

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