Genesis And Metallogenic Potential Analysis Of The Bijigou Fe-Ti-V Oxide Deposits In The Northern Margin Of The Yangtze Block

The Bijigou large-scale vanadium titanium magnetite ore deposit is located in the most northern part of the Hannan-Micangshan tectonic belt of the northern margin of the Yangtze block, the location of contact of the northern margin of Yangtze block and south Qinling tectonic zone from the view of the tectonic position, which is in favour of the richment of the metallogenic element. The tectonic belt is NE-SW direction, in which there is a magmatic belt with a width of about 60 km and length of 130 km, and the part distributed in southern Hanzhong was called Han complex. Although the typical rock body of Han complex was studied by the former, there are still differences in the structural setting of neoproterozoic era in the northern margin of the Yangtze block.In this paper, the outcrop characteric and scale of Bijigou rock body, lithofacies assemblage and zoning features, typical rock mineral and metallic mineral features, whole rock main trace and REE geochemistry, zircon U-Pb chronology and Hf isotopic characteristics are studied, finding out the characteristics of magmatic source and evolution, mineralization epoch and genesis of ore deposit. The study on tectonic setting of magmatism and mineralization provide a constraint for neoproterozoic’s tectonic evolution of the northern margin of the Yangtze block, and metallogenic potential analysis is made in this magmatic rock zone by looking for the same with the Bijigou vanadium titano-magnetite. The main achivemtnes are as follows:(1)The Bijigou rock body is constituted by the lower plagioclase peridotites facies zone, lower-middle gabbro facies zone, upper-middle different Strip gabbro facies zone and upper dorite facies zone. The main rock types are Peridotite, plagioclase peridotites, troctolite, olivine gabbro, gabbro, gabbro-diorite and diorite. The Rock-forming minerals are olivine, orthopyroxene, clinopyroxene, plagioclase and hornblende. Main ore minerals are magnetite and ilmenite, rich ore is mainly distributed in the rich orerich orerich orerich oreupper-middle different Strip gabbro facies zone.(2)The geochemical studies show that the Bijigou gabbro has the characteristics of tholeiite series, poor Si, rich Al and Ca, medium Fe and Mg, low Na and K. The chondrite normalized REE curve shows a "smooth form right", Eu positive anomaly, light REE lightly enrichment and heavy REE relative loss. Enrichment of LILE, loss of HFSE,Th and U negative anomalies,Sr positive anomaly.Those indicated the distinct crystallization differentiation during the evolution of magma, and show geochemical characteristics of island arc origin.(3) The zircon U-Pb dating is conducted for main rock type including the gabbro and wall rock granite, the gabbro with 766.9±4.5Ma, wall rock granite with 784.2±3.6Ma and 788.6±4.3Ma, and granite vein within the rock of Liangxinhe titanium magnetite-bearing mafic rock.Thereby three phases magmatic events in the neoproterozoic are determined in the area, studies on zircon Hf isotopic from Bijigou mafic rocks suggest that the magma source is from depleted mantle and experiencing contamination form crustal material.