矿床地球化学国家重点实验室知识库

The Jintonghu porphyry Cu (Mo) deposit locates in the northeastern Zijinshan ore field. Whole-rock major, rare and trace elements, Nd isotopic composition and zircon LA-ICP-MS U-Pb age of quartz-syenite porphyry from Jintonghu deposit are analyzed in this paper. The major elements results show that the contents of SiO2 and alkali range from 57.59% to 71. 19% and 7. 73% to 10. 01%, respectively. The Rittmann Index and Aluminum Saturation Index are from 2. 21 to 6. 05 and 1. 24 to 1.53 respectively, indicating that the rock belong to peraluminous and high-K calc-alkaline series. The quartz-syenite porphyry have Sigma REE range from 152 x 10(-6) to 212 x 10(-6), and negative Eu anomalies (E/Eu* = 0. 71 -0. 97), with (La/Yb)(N) values from 16.62 to 33.49, exhibiting relative LREE enrichment and HREE depletion. Compared to primitive mantle values, all the rocks are enriched in LILEs and depleted in HFSEs (Nb, Ta, P, Ti). The geochemical results show characteristic of arc volcanic rock. The low ENd t) values and low Nd isotopic model ages, which range from -6. 60 to -4. 37 and from 1. 25Ga to 1. 43Ga respectively, indicate the characteristic of crust-mantle interaction. In situ zircon U-Pb LA-ICP-MS dating on the two quartz-syenite porphyry samples yielded ages of 95. 3 +/- 0. 9Ma and 96. 7 +/- 0. 9Ma. Combined with former researches, we conclude that the quartz-syenite porphyry formed in an extensional tectonic setting, and was a product of mixing of lithospheric mantle material (modified or influenced by subduction components) and granitic magma (derived from partial melting of middle and lower crust).