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

<p>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 173 Ma, 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 (<sup>87</sup>Sr/<sup>86</sup>Sr)<i><sub>i</sub></i> values of 0.704105–0.704706, <i>ε</i><sub>Nd</sub>(<i>t</i>) values of −0.67 to −0.07, and <i>ε</i><sub>Hf</sub>(<i>t</i>) values of −0.4 to 2.8, yielding Hf two-stage model ages (<i>T</i><sub>DM2</sub>) 1250–1067 Ma, and Nd model ages of 1.04–0.96 Ga, indicating that the pre-mineralization magmas were generated by the remelting of Neoproterozoic juvenile crustal material. The monzogranitic porphyry has (<sup>87</sup>Sr/<sup>86</sup>Sr)<i><sub>i</sub></i> values of 0.704707–0.706134, <i>ε</i><sub>Nd</sub>(<i>t</i>) values of 0.29–1.33, and <i>ε</i><sub>Hf</sub>(<i>t</i>) values of 1.0–2.9, yielding <i>T</i><sub>DM2</sub> model ages of 1173–1047 Ma. The rhyolitic porphyry has (<sup>87</sup>Sr/<sup>86</sup>Sr)<i><sub>i</sub></i> ratio of 0.702129, <i>ε</i><sub>Nd</sub>(<i>t</i>) value of −0.21, and <i>ε</i><sub>Hf</sub>(<i>t</i>) values of −0.5 to 7.1, <i>T</i><sub>DM2</sub> model ages from 1269 to 782 Ma. 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 (<sup>87</sup>Sr/<sup>86</sup>Sr)<i><sub>i</sub></i> ratio of 0.705284, <i>ε</i><sub>Nd</sub>(<i>t</i>) value of 0.82, and <i>ε</i><sub>Hf</sub>(<i>t</i>) 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 (240–230 Ma), Early Jurassic (200–180 Ma), and Later Jurassic (160–150 Ma) 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.</p>