Evolution of the Qianlishan Granite Stock and its Relation to the Shizhuyuan Polymetallic Tungsten Deposit

The Qianlishan granite stock consists of three peraluminous granites; in order of intrusion they are pseudoporphyritic biotite granite, equigranular biotite granite, and dikes of granite porphyry. There is no obvious evolutionary relationship in petrochemistry between the first two granitoids and the granite porphyry. From pseudoporphyritic biotite granite to equigranular biotite granite, the differentiation degree increases so that the basic elements and the Zr/Hf and La/Yb ratios decrease, Eu depletion is stronger, and acid-incompatible elements, volatile components, ore-forming elements, and Rb/Sr and U/Th ratios increase. The first two phases of granitic intrusions are associated with polymetallic tungsten mineralization. The differentiation degree of the granite porphyry is lower than that of the two early granitic rocks, and so are its Rb/Sr and U/Th ratios; Zr/Hf and La/Yb ratios, however, are higher, and Eu depletion becomes weaker. The granite porphyry is associated with lead, zinc, and silver mineralizations. The granitoids in the Qianlishan granite stock are highly enriched in F, Li, Br, Be and Ga, and are characteristic Be, Li, and F (BELIF) ore-forming rocks. Furthermore, because of the enrichment in radioactive elements such as uranium and thorium, these granitoids are considered to be typical high-heat-production (HHP) granites. The pseudoporphyritic biotite granite, equigranular biotite granite, and granite porphyry, as measured by the whole-rock Rb-Sr isochron method, have ages of 152 Ma, 136 Ma to 137 Ma, and 131 Ma. Sr-Nd-isotopic data indicate that protoliths of the granite suite were the crust, and whereas the first two intrusive phases were derived from melting of Lower Proterozoic strata, the granite porphyry was derived by melting of Middle Proterozoic strata.