SHRIMP zircon U-Pb dating of the Xiaohongshan vanadium-titanium magnetite deposit, Ejin Banner, Beishan, Inner Mongolia, and its geological implications

The Xiaohongshan vanadium titanium magnetite deposit is a medium-sized deposit discovered in recent years in Beishan area of Inner Mongolia. It is located on the northern margin of the Beishan rift zone, which is on the northern margin of the Dunhuang- Alxa massif on the southern side of the Hongtoushan-Ertuoshan fault. The ore-bearing gabbro body was emplaced in Pingtoushan Formation of Jixianian System. The rock mass is characterized by whole rock mineralization, but the economic orebodies mainly occur in the medium-coarse grained gabbro. The authors used the SHRIMP zircon U-Pb dating method for geochronologic investigation of Xiaohongshan medium-coarse grained gabbro body and obtained zircon micro-area in situ SHRIMP U-Pb age of 424±6Ma (95% confidence interval, MSWD=0.31), which shows that the Xiaohongshan vanadium titanium magnetite mineralization occurred in the Middle Silurian. The discovery of the vanadium titanium magnetite deposit reveals that the Beishan area was in a continental margin rift environment in the early Paleozoic. The results achieved by the authors have a great significance for the restudying and understanding of the geological structure evolution and the prospecting for magmatic ore deposits in Beishan area.