Contrast Study On Iron Deposits Between Kawa Region And Jingtieshan In The Western North Qilian

The North Qilian orogenic belt,one of the important polymetallic metallogenic belts,is payed close attention by researchers in the world.After the Jingtieshan large iron deposit was discovered in the early 1950's,the Kawa ore enrichment region,in the 60 km southeastern Jingtieshan,had been discovered by No.4 Geology and Exploration Team,Gansu provincial Bureau of Geology and Mineral Exploration Development in 2011.It is of great significance for economic development in northwest China.This paper,through contrastive geological characteristics and geochemical characteristics study between the iron ore enrichment regions of Kawa,Taligangou,Shuanglong and Jingtieshan in the same metallogenic belt,exploring the Proterozoic iron mineralization in the Western North Qilian,provided new thoughts for prospecting work on iron deposit in the Western North Qilian orogen.The main understandings as following:(1)Through field geological survey,the Kawa area,dissociating into relatively independent small blocks derived by Qilian unified geodynamic(mantle plume)in the late neoproterozoic-early Paleozoic and aggregated in the late early Paleozoic,emerged the present regional tectonic framework.(2)Comparing with iron deposit geological characteristics,the iron deposits of the Kawa region and Jingtieshan in the same structural belt,are belong to sedimentary metamorphic type.They have similar tectonic deformation in late metallogenic epoch and dominating mineral factors.But the causes of different ore body scale are the different mineral sources,different sedimentary environment and other factors.Based on the analysis of geochemical characteristics,average value w(Si O₂)/w(Al₂O₃)of the iron deposit in Kawa region is 8.64(Taligangou and Shuanglong are both more than 10),the average value(Sr/Ba)is 0.34,the Y/Ho ratio is 23.83 on average,R²_Fe-Mn=0.0033,R²_Al-Ti=0.6573.The data indicate that the iron ore metallogenic substances of the iron deposit of Kawa region are derived from Marine chemistry and a large number of terrigenous clastic deposits,and had certain relations with volcanism.And previous research results showed Jingtieshan metallogenic materials mainly came from the seabed hydrothermal.(3)By the comparative study on the geological background and formation,The quartzite and mottled phyllite,belonging to the iron deposits of the Jingtieshan and Taligangou,are homologous the same stratums respectively,and the mottled phyllite of the Taligangou iron deposit is the Jixian System product.Through chronological study,the Kawa area iron deposits metallogenic epoch is the Changcheng System(later than 1529 Ma),the Jingtieshan iron deposit metallogenic epoch is the Jixian System(1309-1309 Ma).Since the Jingtieshan group of the Jixian System is above the Huashugou formation of the Changcheng System,the iron deposits between the Kawa region and Jingtieshan are not the same time geological products.If in the region of western Jingtieshan and Jingtieshan,the Huashugou formation can be found in underlying stratums of Jingtieshan Group,implying it still has iron ore-prospecting potential.(4)Through comparative study on the two large iron deposit enrichment regions and analyses of the mesoproterozoic iron deposits mineralization in the western North Qilian,we establishes the ore-prospecting marks of the period of iron deposit preliminarily about formation,tectonic,and geochemical setting.