GEOCHEMICAL CHARACTERISTICS AND FORMING ENVIRONMENT OF THE CARBONIFEROUS GABBRO IN YADUWULA MOUNTAIN AREA, MIDDLE DAXINGANLING

Large area of gabbro occurs in the Mt Yaduwula region in the middle section of Daxinganling Mountains. The gabbro is lithochemically with the characteristics of sub-alkaline and tholeiitic rock series. To compare with oceanic type of ultrabasic rocks, the gabbro in Mt Yaduwula area is characterized by low Mg content, with notable positive Rb and Th anomalies and relative deficiency of high field strength elements. The rock is rich in Cr, Ni, Co, V and Ti, suggesting a mantle source. The gabbro is in a zircon U-Pb age of 532 Ma, formed in Late Carboniferous, showing an extensional tectonic environment in the Mt Yaduwula area of Middle Daxinganling Mountains. The magma of gabbro is derived from the mantle (deep source), formed in a transitional environment of submarine rift and epicontinental island arc.