内蒙古边家大院铅锌银矿区侵入岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义

摘要

内蒙古边家大院铅锌银矿床位于大兴安岭成矿带南段,是一个典型的热液脉型多金属矿床。为了精确厘定该矿床的成岩时代,对区内与成矿关系密切的辉长岩体及闪长岩岩脉中的锆石进行了 LA-ICP-MS U-Pb 定年,获得辉长岩与闪长岩样品的形成年龄分别为133±0.86 Ma和130±0.75 Ma,表明岩体为早白垩世岩浆活动的产物。岩石化学研究表明,辉长岩与闪长岩具有低钛高钾、稀土元素分配模式为轻稀土富集型、大离子亲石元素(LILE)富集明显、高场强元素(HFSE)相对亏损的特征,推断岩浆来源于岩石圈地幔,形成于张性环境。结合矿床地质特征及前人在区域上的研究成果,认为燕山期是大兴安岭南段成矿和成岩高峰期之一,矿区侵入岩可能形成于由全面挤压向伸展过渡阶段的构造背景。%Located in the southern section of the Daxing’anling metallogenic belt, the Bianjiadayuan Pb-Zn-Ag deposit is a typical hydrothermal vein-type polymetallic deposit. In order to determine the diagenetic age of the deposit, LA-ICP-MS U-Pb age study was conducted on the zircons in the gabbro and diorite associated with the mineralization. The results suggest that the gabbro and diorite were crystallized in 133.19 Ma and 130.48 Ma, respectively. The gabbro and diorite are enriched in LILE, LREE and depleted in HFSE, which indicate that the magma were derived from lithospheric mantle and formed in extensional tectonic setting. Combined with the geological characteristics and the previous research in this region, the Yanshanian is considered to be a peak period of mineralization and magmatism of the southern Daxing’anling. The tectonic setting of the intrusive rocks was in the transition period from lithosphere compression to extension.