A porphyry-skarn metallogenic system in the Lesser Xing'an Range, NE China: Implications from U-Pb and Re-Os geochronology and Sr-Nd-Hf isotopes of the Luming Mo and Xulaojiugou Pb-Zn deposits

The monzogranites from the Luming and Xulaojiugou deposits are enriched in and Rb, Th, U, Pb and light rare earth elements (LREEs), and are depleted in Ba, Nb, Ta, P, Ti and Eu. They have positive εHf(t) values of 1.0-4.0 with two-stage Hf model ages (TDM2) of 868-1033 Ma. Whole-rock Sr and Nd isotopes show restricted ranges of initial compositions, with (87Sr/86Sr)i between 0.706346 and 0.707384 and εNd(t) between −3.5 and −1.8. These data indicate that their primary magmas originated from the partial melting of a depleted lithospheric mantle which had been metasomatized by subducted slab-derived fluids/melts. The early Jurassic magmatic-metallogenic events in the Lesser Xing'an Range are interpreted as a response to the subduction of the Paleo-Pacific Plate.