Calcic Skarn Ore Deposits of the North-East Russia
Abstract In this paper, we summarize characteristics of calcic skarn ore deposits in Northeast Asia. The study area includes a wide variety of terranes, which experienced both subduction and collisional granite magmatism, and contains a skarn deposits of various types, mostly of sub-economic. This provides an opportunity to examine the relationships among skarn metal types, host rocks, and plutons, within various tectonic settings. The paper is based on the authors’ observations (at 17 deposits and prospects) as well as on a review of published data on these and other skarn deposits. Major skarn mineralization in Northeast Asia was formed in the Late Mesozoic accretionary and post-accretionary periods. Skarn deposits of Fe, W, Mo, Pb-Zn, and Au (Co) show the same type of skarn mineralogy. The type of host rocks, more rarely granitoid, and the type of mineralization control the composition of garnet and pyroxene, formed in the skarn deposits. Garnet and vesuvianite, associated with tin skarn deposits, have high Sn concentrations. The garnet, associated with skarn deposits in terrigenous terranes, has higher TiO2 concentrations than those in the garnet in skarn deposits from carbonate platform terranes. During skarn deposit formation, the Fe content of the main skarn minerals (garnet and pyroxene) increases. Ore mineralization, which accompanied skarns, exposes isotopic compositions of crustal Pb. Island arc granitoids have primitive 87Sr/86Sr values, while collision granitoids show more elevated crustal 87Sr/86Sr signatures.