Age and tectonic setting of the Jingangku Besshi-type volcanogenic massive sulfide deposit from the Northern Shanxi, North China Craton

摘要

The Jingangku volcanogenic massive sulfide deposit is one of the largest Archean deposits in China. It is located in the Wutai greenstone belt in the northern part of the central orogenic belt in the North China Craton. The deformed deposit is hosted in a suite of Neoarchean metamorphosed volcano-sedimentary rocks (mica-quartz schist, plagioamphibolite, plagioclase schist and BIF). The orebodies are characterized by massive pyrite, and contain varied amounts of chalcopyrite, pyrrhotite and sphalerite. The country rock of the Jingangku VMS ores shows intense chloritization, silicification, sericitization and carbonation. The VMS-hosted pyrite and copper deposit is represented by the Jingangku deposit that yielded a LA-ICP-MS zircon age of 2500 +/- 15 Ma (MSWD = 0.87). The other two VMS-hosted pyrite and copper deposits are represented by the Houping and Haoditang deposits that formed between 2494 Ma and 2507 Ma. The late Neoarchean VMS deposits can be interpreted to have formed in a forearc setting, and subsequently tectonically transported in melange belts during continental collision, quite similar to the younger Besshi-type deposits in Japan. Sulfide orebodies are closely associated with the magnetite quartzite, and therefore, it is proposed that both the sulfide and magnetite quartzite were derived from the same material source and have the same formation age, and underwent the same history of deformation and metamorphism. Consequently, the Jingangku deposit most likely formed from submarine exhalative sedimentation, and later superimposed and transformed by metamorphic fluid.