U-Pb zircon, geochemical and Sr-Nd-Hf isotopic constraints on age and origin of the intrusions from Wunugetushan porphyry deposit, Northeast China: implication for Triassic-Jurassic Cu-Mo mineralization in Mongolia-Erguna metallogenic belt

摘要

The Wunugetushan porphyry Cu-Mo deposit is located in northeastern China. The deposit lies within the Mongolia-Erguna metallogenic belt, which is associated with the evolution of the Mongol-Okhotsk Ocean. The multiple episodes of magmatism in the ore district, occurred from 206 to 173Ma, can be divided into pre-mineralization stage (biotite granite), mineralization stage (monzogranitic porphyry and rhyolitic porphyry), and post-mineralization stage (andesitic porphyry). The biotite granite has (Sr-87/Sr-86)(i) values of 0.704105-0.704706, epsilon(Nd)(t) values of -0.67 to -0.07, and epsilon(Hf)(t) values of -0.4 to 2.8, yielding Hf two-stage model ages (T-DM2) 1250-1067Ma, and Nd model ages of 1.04-0.96Ga, indicating that the pre-mineralization magmas were generated by the remelting of Neoproterozoic juvenile crustal material. The monzogranitic porphyry has (Sr-87/Sr-86)(i) values of 0.704707-0.706134, epsilon(Nd)(t) values of 0.29-1.33, and epsilon(Hf)(t) values of 1.0-2.9, yielding T-DM2 model ages of 1173-1047Ma. The rhyolitic porphyry has (Sr-87/Sr-86)(i) ratio of 0.702129, epsilon(Nd)(t) value of -0.21, and epsilon(Hf)(t) values of -0.5 to 7.1, T-DM2 model ages from 1269 to 782Ma. These results show that the magmas of mineralization stage were generated by the partial melting of juvenile crust mixed with mantle-derived components. The andesitic porphyry has (Sr-87/Sr-86)(i) ratio of 0.705284, epsilon(Nd)(t) value of 0.82, and epsilon(Hf)(t) values from 4.1 to 7.4, indicating that the post-mineralization magma source contained more mantle-derived material. The Mesozoic Cu-Mo deposits which genetically related to Mongol-Okhotsk Ocean were temporally distributed in Middle to Late Triassic (240-230Ma), Early Jurassic (200-180Ma), and Later Jurassic (160-150Ma) period. The Middle Triassic to Early Jurassic Cu-Mo mineralization was dominated by Mongol-Okhotsk oceanic plate southeast-directed subducted beneath the Erguna massif. The Later Jurassic Cu-Mo mineralization was controlled by the continent-continent collision between Siberia plate and Erguna massif.