Geochemistry And Geochronology Research Of The Ore-forming Intrusive Body In The Chagandeersi Molybdenum Deposit, Inner Mongolia

Chagandeersi molybdenum deposit located in Wulatehouqi, Inner Mongolia, is a large scale deposit which discovered in recent years. The molybdenum deposit tectonic position is located in the northwestern margin of the North China Continental, the middle of the Bao Yin figure uplift and south wing of the Sujiyinhua anticline, and it’s mineralization is closely related to the composite rock mass combined by plagiogranite, monzogranite, moyite and fine grained granite. It is generally believed that the deposit posses the characteristics of porphyry type deposit. This paper focuses on the research of Geochemistry and geochronology of the composite rock mass.Zircon U-Pb dating shows that the composite rock age 225.9±4.4Ma ~256.6±3.4Ma, which belongs to the Indosinian. From the plagiogranite, monzogranite, moyite to fine grain granite, age gradually become smaller, plagiogranit 252.1±3.4 Ma~256.6±3.4Ma; monzogranite 247.5±4.4 Ma; moyite 236.8±4.5Ma~244.3± 4.2Ma; fine grain granite 225.9±4.4Ma. Therefore, we can see that different lithologies represent different stages of evolution of magma. Molybdenite rhenium osmium isotopic age was 239.2±5.8Ma. The mineralization age is close to composite rock age, consequently, the mineralization could be express to the Indosinian granite intrusion metallogenic, mineralization age is between the diagenetic stage of moyite. But neighboring(Chaganhua molybdenum deposi) comparison shows that Chagandeersi molybdenum deposit may share the same characteristic that there is time time difference between diagenesis and mineralization, and taking into account that mineralized quartz veins are visible in fine grain granite so its mineralization may also continue to fine grain granite stock were formed. Overall, in Chagandeersi Mining, The different stages and different lithology of granites may be both related to mineralization.Petrological and geochemical characteristics show that the composite granite body’ major elements with characteristics of high silicon, Metaluminous peraluminous, alkali rich and high K calc-alkaline series; characteristics of trace elements and rare earth elements also indicate that the composite rock mass are genetically continental crust melt granites. on the other hand, composite granite mass composition changes gradually, and there are differences between magma evolution components, but the differences are weak and Is not obvious. This is because each magmatic intrusive phase intervals shorter, magma could not fully focused differentiation, and this effect might contribute to the active chemical properties ore-forming elements gathering in advanced magmatite rapidly. Granite rock background research indicates that Composite rock may be partial melting of Proterozoic Baoyintu group metamorphic rocks, in Late Permian, post-collision environment.