江南古陆北缘青阳钨钼矿集区成岩成矿作用研究

青阳钨钼矿集区处于江南古陆北缘钨-多金属成矿带的北部,区内钨钼矿床均分布于青阳-九华山复式岩体周边、以钨钼矿化为主。本文在综合分析青阳钨钼矿集区内钨钼-多金属矿床的地质特征、成岩成矿年代、岩石地球化学特征得到如下认识:1)青阳钨钼矿集区成岩成矿年代可以分为早(146~135Ma)、晚(134~128Ma)两期,早期成矿作用较强烈,矿点广泛分布在青阳岩体周边;晚期成矿作用主要分布于九华山岩体边部及外围,呈北东东向展布。2)青阳钨钼矿集区成矿斑岩体主要为高钾钙碱性、准铝质-弱过铝质岩石,成矿斑岩体以壳源岩浆岩为主、从早到晚具有源区深度变浅的趋势,演化程度具有由花岗闪长(斑)岩(早期)→花岗(斑)岩(晚期)的增高、向富钼岩浆岩演化特点。3)青阳钨钼矿集区内钨钼矿床赋存在震旦系-奥陶系地层中,主要包括震旦系蓝田组、奥陶系仑山组及寒武纪碳酸盐地层,赋矿有利层位为成矿元素丰度值高、镁质含量较高的碳酸盐地层。青阳钨钼矿集区中成矿斑岩体与复式岩基的源区及演化过程均存在差异,他们可能是燕山期太平洋板块俯冲的同一时空背景下,不同源区组分发生部分熔融的岩浆经历不同演化过程的产物。

Study on the magmatism and mineralization in the Qingyang W-Mo orefield, northern Jiangnan terrane

The Qingyang W-Mo orefield is located at the northern part of the northern Jiangnan terrane. There mineral deposits are characterized by consistently distributing around Qingyang-Jiuhuashan complex pluton, with mainly W-Mo mineralization. After systematically considering the geology, geochronology and geochemistry of those W-Mo deposits in Qingyang orefield, several metallogenic understandings can be summarized as following:(1) the granitoid intrusion and mineralization epoch can be subdivided as early stage (146~135Ma) and late stage (134~128Ma). The early stage W-Mo mineralization is more intensive than the late ones, which widely distribute around the Qingyang granodiorite pluton, while the late stage ones are NNE distributing around the Jiuhuashan granite pluton or its periphery. (2) The fertile granitoid porphyries in Qingyang W-Mo orefield are generally high K calc-alkaline, and metaluminous to weak peraluminous rocks in lithology, which are dominantly derived from crustal materials, the W-Mo fertile melt are characterized by shallowing magmatic sources, increasing fractional crystallization degrees, and rising Mo/W ratios through timing evolution. (3) The mineralization hosted strata in Qingyang W-Mo orefield are from Sinian to Ordovician, mainly including the Sinian Lantian Formation, the Ordovician Lunshan Formation and Cambrian carbonate strata. Those mineralization occurring strata were characterized by higher W and Mo concentrations, and higher Mg content than other strata, which are favorable indicators to the ore formation. Although the W-Mo fertile granitoid porphyries in Qingyang W-Mo orefield and the Qingyang-Jiuhuashan complex pluton are formed in the same subduction background of The Pacific Ocean plate in Yanshannian, their melts were probably derived from different magmatic source and experienced different evolutions separately.