内蒙古白乃庙铜金矿床侵入岩年代学及其地质意义

内蒙古白乃庙铜金矿床位于华北板块北缘中段陆缘增生带,区内侵入岩发育,主要岩性有花岗闪长岩、白云母花岗岩、石英闪长岩,对其中5件样品采用LA-MC-ICP-MS锆石U-Pb方法测年,获得花岗闪长岩加权平均年龄(443.2±1.7)Ma、(447.6±1.8)Ma,白云母花岗岩加权平均年龄(429.1±2.7)Ma、(43...

Geochronology and Geological Significance of Intrusive Rocks in the Bainaimiao Cu-Au Deposit,Inner Mongolia

The Bainaimiao Cu-Au deposit in Inner Mongolia is located in the continental marginal accretionary zone in the northern margin (middle section) of the North China Craton. Intrusive rocks are developed at Bainaimiao, with major lithologies including granodiorite, muscovite granite, and quartz diorite. LA-MC-ICP-MS zircon U-Pb dating indicate that the granodiorite was emplaced at (443.2±1.7) Ma and (447.6±1.8)Ma, the muscovite granite was formed at (429.1±2.7) Ma and (431.6±4.2) Ma, and the quartz diorite was formed at (424.5±2.0) Ma. Combined with the ore deposit geological characteristics, we considered that the Bainaimiao Cu mineralization occurred in the Late Ordovician-Early Silurian (432-447 Ma), related to the granodiorite emplacement. The Bainaimiao gold deposit was formed at about 430 Ma, which is related to the hydrothermal fluid enrichment brought by the muscovite granite emplacement. Under the Early Paleozoic subduction tectonics of the Paleo-Asian Ocean beneath the North China Craton, the porphyry Cu mineralization was dominated by the compression tectonics, whilst the epithermal Au mineralization occurred in a relatively extensional setting. Under the volcanic rock-magma process of the Bainaimiao island arc, the Bainaimiao Cu and Au mineralization constitutes an integral porphyry-epithermal mineral system.