Geochemical characteristics and metallogenic significance of Huangshan Nb-Ta deposit in northeast Jiangxi Province

The main and trace elements of biotite monzogranite, granite pegmatite and fine-grained biotite granite in Huangshan Nb-Ta mining area were analyzed and compared with the typical A-type granites in the metallogenic belt. It shows that they belong to highly differentiated granite, characterized with rich silicon, high alkali, poor calcium and low magnesium, and A/CNK value>1, belonging to quasi aluminous-peraluminous rock. The rocks are enriched with high field strength elements Nb, Th, Ta, Zr, U, Hf and large ion lithophile element Rb, and depleted with large ion lithophile elements Ba, Sr, P and high field strength element Ti. The distribution form of rare earth elements belongs to "Seagull type", with strong Eu negative anomaly. 1 000×Ga/Al values are higher than 2.60, and the total amount of Zr+Nb+Ce+Y is much higher than 350×10^-6. The genetic type of the rock is A1 subclass of intraplate granite. It is inferred that the rock mass is underplated due to the upwelling of mantle material under extensional tectonic setting, which promotes the partial melting of the lower crust to form the initial magma, and there is the contamination of crustal material in the upwelling process. The crystallization differentiation of magma in the process of emplacement separates niobium tantalum and other metallogenic elements from magmatic melt. The joint action of highly differentiated evolution melt and volatile rich (mainly F, Cl) fluid is the main factor for the enrichment of niobium tantalum.