Geological Characteristics And Mineralization Of The Mogutu Fe-Sn Deposit In Inner Mongolia

The Mogutu Fe-Sn deposit,located in the southwest Huanggangliang to Ganzhuermiao Tin-polymetal metallogenic belt in Southern Da Hinggan Mountains,characterized by Fe-Sn ore body,which is rare in tin-polymetallic deposits.Based on detailed field geological survey,mineralogical,geochronology and geochemical study,the features of deposit,metallogenetic intrusion were discussed,the ore-controlling factors were analysed,and metallogenic model was established.Main research achievements are as follows:1.Zircon LA-ICP-MS dating of the biotite syenogranite yields a concordant age of 148.8¹52.7Ma,which means that the Mogutu granite pluton intruded at the Late Jurassic.The Mogutu granites is characterized with high content of SiO₂?K₂O,but depletion in P?Ti?Ba?Sr,strong negative Eu anomalies,higher zircon saturation temperatures?795⁹11??,and belong to highly fractionated A2 post-orogenic granite,which are the production of partial melting of upper crust and formed during the crustal extension-thinning.2.There are two types of fluid inclusions,for gas-liquid and polyphase type.The gas-liquid inclusions were mainly composed of H₂O,and the minor compositions contained less H₂ and CH₄,which belongs to the H₂O-NaCl ore fluid system.The study of fluid inclusions shows that the temperature of ore-forming fluid is decreasing from earlier to later phase,but salinity is increaseing.The fluid inclusions in Mogutu show the features of the assemblage of saturated and oversaturated saline vapor boiling fluid inclusions,which means boiling played an important role on the deposition of cassiterite,sulfides and magnetite.3.The S-Pb isotope component in the ores of Mogutu Fe-Sn Deposit is homogenous,and the characteristics of the Pb isotope is similar to the feldspar lead of the granite.The results show that the sulfur and lead are derived from deep magma,and ore material mainly from the deep magmatic hydrothermal solution.4.Mogutu Fe-Sn deposit was formed in the Mongolia-Okhostk tectonic regime.In crustal extensional environment,underplating of mantle-source magma leaded to the partial melting of crust.By crystallization differentiation,the parental magma gradually became to granite magma rich in Fe and Sn.By contact metasomatism with carbonate formation,the metallogenic material were gradually enriched,leading to the formation of Mogutu Fe-Sn deposit eventually.