Study On The Geological Characteristics And Genesis Of Yejili Ti-Fe Oxide Ore Deposit,Southern Margin Of Alashan Block

Yejili Ti-Fe ore deposit is located in the Beidashan upwelling area which belongs to the southern margin of Alashan block.It is in the tectonic setting position where lie in the top of mainland arc of Late Paleozoic Era,between Beidashan and Bayanwulashan.magmatic activities are very strong in the Beidashan upwelling area.The main rock tapy in the regionare is granitoid rocks and the following is the basic-ultrabasic rocks.There are three phrases of magmatic activities,i.e.from the late Carboniferous epoch to the early Permian,from the early to the late Permian and the late Permian.exists different cognitive of magmatic activity backgrounds : the rift valley、Paleo-Asian Ocean subduct 、post-tectonic stretch and so on.This paper take the Yejili Ti-Fe ore deposit as the research subject,the Yejili Ti-Fe ore deposit occuers in the basic-ultrabasic rock which can represent the basic rock characteristics of magmatic activity in Beidashan.The paper relies on two of the Natural Science Foundation of China,The jobs that have been done to Yejili Ti-Fe ore deposit include the geological mapping the geology of rock mass,the distribution of ore body,geochemistry and isotope chronology of the ore deposit.We also discussed the diagenesis and mineralization process,ore-forming geological background in Yejili Ti-Fe ore deposit,which may direct the future prospecting in this region.The main achievements is followed:(1)The rock types consists of gabbro,olive gabbro,bojite of the Yejili Ti-Feore deposit.And the metallic minerals include magnetite,ilmenite metal minerals and a little of pyrite,chalcopyrite metal sulfides and so on.The main ore bearing rock is olive gabbro.(2)According to the characteristic of petrography,geochemical of mineral and deposit,isotope,we propose that the parental magma is generated by different evolution of the Fe-Ti enriched basaltic magma,which also suffers crustal contamination of 5% degree.(3)The zircon U-Pb dating for gabbro of Yejili basic rock body is310.1±2.7Ma.The moyite is 317.3±1.5Ma,and the later granite is 292±2Ma.Combining with chronology and geological background of regional magmatic activity,I consider that the Yejili Fe-Ti ore deposit is relevant to the southward subducting of Paleo-Asian Ocean of the Late Paleozoic Era.The ore deposit is formed from the intrusion of Fe-Ti riched basaltic magma derived from the partial-melting of lithosphere.