Characteristics of fine grain granitic rock and its metallogenic significance for Zhujiding copper deposit in western Sichuan, China.

Zhujiding copper deposit is a typical copper deposit of the "Three Parallel Rivers" polymetallic metallogenic belt. The ore body is formed within the fine grain granitic rock. So far, three large-scale copper-bearing fine-grained granitic rocks have been delineated. The highest copper grade reaches around 11.42%. The results show that the fine grain granitic rock belongs to LREE enrichment and negative Eu anomalies with relative enrichment of Rb, Th and U and distinct negative anomalies of Ba, Nb, Sr, P and Ti. According to the similarity of the REE and trace element patterns, we deduce maybe the magma originated from the mid-lower crust and formed from the lagging-type volcanic arc environment. Wall-rock alteration and vertical zoning of secondary oxidation show the characteristics of porphyry-type copper deposit. Cu-Mo anomalies are significantly weaker and Pb-Zn anomalies are relatively stronger. So we infer that Zhujiding copper deposit belongs to hydrothermal-porphyry copper deposit. The surface is at the top of ore-bearing porphyry and the main ore body may be buried at some depth. in addition to Cu , there is maybe also Zn, Bi, Co and As concentrated.