Geochemistry of The Dangchuan Granitic Batholith in West Qinling

Located in the area of the Qilian and west Qinling orogenic belts,the Dangchuan granitic batholith is composed of 9 granitic intrusives. Geochemically,the batholith in general is poor in Ga,Rb, Zr and rich in Th,Ta,Hf and HREE. The Devonian and post-Devonian plutons are obviously rich in Th and Hf,but poor in Rb and Co. The FREE,LREE/HREE and δEu of these plutons are similar to the adamellitoids in the northern Qinling. The lithogeochemstry characteristics between all these plutons show an evident similarity in their sources,tectonic environments,and origin,and also continuity and inheritance in evolution. While the Silurian intrusives are obviously rich in Cr,Co,Nb and rich in Y,but poor in Ga,Rb,Zr,FREE, LREE/HREE and BEu. These Silurian intrusives are not only different from the Devonian ones but also different from the contemporaneous dioritoids in the Qinlin-Bashan areas. It has been agued that the Silurian intrusives are island arc dioritoids which were formed during subduction orogenesis,while the Devonian and post-Devonian plutons were derived from crustal sources related to that has relations to crustal uplift or continent rifting during post-orogenic period.