安徽沿江地区燕山期含铜岩体稀土、微量地球化学特征

GEOCHEMICAL CHARACTERISTICS OF YANSHANIAN COPPER-BEARING ROCKS ALONG THE YANGTZE RIVER IN ANHUI PROVINCE

安徽沿江地区位于长江中下游岩浆成矿带中段，其中众多矿床的形成与燕山期岩浆密切相关。对安徽沿江地区（铜陵、安庆和庐纵）燕山期中酸性含铜岩体地球化学研究表明：含铜岩体稀土特征总体表现为右倾型，LREE富集，HREE亏损但表现为平缓的曲线，无明显的Eu异常，∑REE含量变化范围在85．84×10^-6～446．26×10^-6，（La／Yb）N值为7．87至63．8，具有高Th，Sr；低Cr，Ni；La／Nb（平均值为3．4），Nb／U（平均值为5．24）和Nb／Pb（平均值为1．47）等特征，结合同位素特征，为壳幔混熔的物源区。研究还表明，本区燕山期含铜岩体可能来自于底侵的慢源碱性玄武岩浆同化混染古老地壳物质同时结晶分异的产物。其中岩体中的铜能否参与成矿关键取决于是否发生热液蚀变交代作用。

Anhui Province is located at the middle section of the Yangtze magmatic metallogenesis belt, where the formation of ore deposits had a close genetic relation with Mesozoic intrusions. The trace elements and REE characteristics of copper-bearing rocks in the area （Anqing, Tongling and Luzong） were studied. It revealed the characteristics of LREE enrichment and HREE depletion without obvious Eu anomalies, with ∑REE = 85.84 ×10^-6-446.26×10^-6, （La/Yb）N =7.87-19.96, presence of Th and St, low Cr and Ni, indistinct negative Eu anomalies. The ratios of La/Nb （mean 3.4）, Nb/U （mean 5.24） and Nb/Pb （mean 1.47） indicated that the materials resulted from the crust-mantle mixture melting provenance. The research results also demonstrated that the Yanshanian Cu-bearing rocks were possibly the crystallization products of the underplated alkaline basaltic magma associated with assimilation of old crustal materials, and the enrichment of copper was controlled by erosion and metasomatism of thermal liquid.