湖南常宁新盟山英安玢岩岩石成因及其与矿化关系研究

通过对湖南省常宁市新盟山英安玢岩进行岩石地球化学、锆石U-Pb定年以及绿泥石矿物化学等综合研究,结合前人研究成果,探讨其岩石地球化学性质、形成时代、物质来源及其与成矿作用的关系.LA-ICP-MS锆石U-Pb定年结果显示,新盟山英安玢岩的n(206Pb)/n(238U)加权平均年龄为152.9±1.2 Ma,属于晚侏罗...

Petrogenesis of Xinmengshan Dacite Porthyry in Changning,Hunan Province: Implications for Relationship of Magmatism and Mineralization

Based on detailed geological investigation, this paper investigated the whole-rock element geochemistry, zircon U-Pb dating and chlorite mineral chemistry of Xinmegnshan dacite porphyry in Changning City, Hunan Province. With reference to previous research, we discussed petrochemical characteristics, magmatic age, magma sources, as well as relationship with mineralization in Shuikoushan orefield. LA-ICP-MS zircon U-Pb isotopic analyses showed that Xinmegnshan dacite porphyry erupted during the Late Jurassic, with a weighted mean 206Pb/238U age of 152.9±1.2 Ma (MSWD=0.27, 2σ, N=17). Xinmegnshan dacite porphyry was rich in Light Rare Earth Elements (LREEs) and Rb, Th, U, La, Pb, Nd, Zr, Hf, while depleted in Heavy Rare Earth Elements (HREEs) and Nb, Ta, Ba, Sr, P, showing crust-derived affinities, and might be contaminated by mantle material. Chlorite was mainly clinochlore with alteration temperature of 280℃ , which was similar to that of the Cu-Mo mineralization in this orefield. During Late Jurassic, the tectonic extension and thinning of the continental lithosphere in the study area induced partial melting of the crust, and produced granitic magma, which might mix with a small amount of mantle material. The magma then invaded along deep faults and formed Xinmegnshan dacite porphyry. At the late stage of magma crystallization, as Cu-Mo precipitation, the hydrothermal fluid replaced the dacite porphyry continuously and resulted in widespread chloritization.