摘要:拉浪麦钨多金属矿位于青海东昆仑东段察汗乌苏河地区，是近年新发现的矽卡岩型矿床。本文对矿区与成矿关系密切的英云闪长岩进行了详细的岩相学、年代学和地球化学研究，为东昆仑原特提斯岩浆构造演化提供新的约束。笔者利用LA-ICP-MS锆石U-Pb定年，获得拉浪麦英云闪长岩加权平均年龄为421.5±5.0 Ma （n = 21，MSWD = 0.34），厘定其形成时代为顶志留世。岩石地球化学研究表明，英云闪长岩为弱过铝质低钾拉斑—钙碱性系列岩石，成因为Ⅰ型花岗岩类型。岩石明显富集大离子亲石元素（Rb、Sr、K）、活泼的不相容元素（如U、Th）和Pb，相对亏损高场强元素（如Nb、Ta、P、Ti）。Rb/Sr、Nb/Ta特征反映出岩石具壳幔混合岩浆的特点。结合东昆仑地区已有年代学资料和区域地质构造演化特征，认为拉浪麦英云闪长岩形成于原特提斯构造旋回的后碰撞阶段。综合分析认为加里东晚期也是东昆仑地区一个重要的多金属成矿期，在今后的找矿工作中应引起足够的重视。
关键词: 地球化学/
LA-ICP-MS锆石U-Pb定年/
英云闪长岩/
拉浪麦/
东昆仑
Abstract:Lalangmai tungsten-polymetallic ore district, which is located in the eastern section of East Kunlun in Qinghai Province, is a newfound skarn-type ore deposit in recent years in Chahanwusuhe area. Detailed researches on petrography, geochronology and geochemistry of the Lalangmai tonalite, which is closely related with mineralization, can provide new constraints for the Proto-Tethys tectono-magmatic evolution in East Kunlun. LA- ICP-MS zircon U-Pb dating shows that the weighted mean age of tonalite is 421.5±5.0 Ma （n = 21, MSWD = 0.34）, in the Top Silurian. Detailed lithogeochemical studies show that the tonalite belongs to weakly peraluminous low potassium （tholeiitic） to calc-alkaline series, and the genetic type of the tonalite is Ⅰ-type granite. This suite of rocks are enriched in LILE （such as Rb, Sr, K）, more mobile incompatible elements （such as U, Th） and Pb, relatively depleting in HFSE （such as Nb, Ta, P, Ti）. Rb/Sr and Nb/Ta reflect the characteristics of crust-mantle mixing magma origin. Based on a combined study of geochronology and evolutionary characteristics of regional structures, the authors consider that the tonalite emplaced in the post-collisional stage of the tectonic cycle of Proto-Tethys. Late Caledonian is an important polymetallic metallogenic epoch in East Kunlun, and we should pay sufficient attention to Late Caledonian plutons in further ore-prospecting work.
Key words:Geochemistry/
Zircon LA-ICP-MS U-Pb dating/
Tonalite/
Lalangmai/
East Kunlun
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