Two epochs of magmatism and metallogeny in the Cuihongshan Fe-polymetallic deposit, Heilongjiang Province, NE China: Constrains from U-Pb and Re-Os geochronology and Lu-Hf isotopes

The large-sized Cuihongshan Fe-polymetallic deposit is located in the north segment of the Lesser Xing'an range, NE China. The Fe orebodies are dominantly hosted in the contact zone between the alkali-feldspar granite and the dolomitic crystalline limestones or skarns, whereas the Pb-Zn (Cu) and W-Mo orebodies are mostly hosted in the contact zone between the syenogranite and skarns, as well as within the syenogranite. The alkali-feldspar granite and syenogranite yield zircon U-Pb ages of 491.1 +/- 2.4 Ma and 199.8 +/- 1.8 Ma, with epsilon(Hf)(t) values of -3.7 to 13 and 2.5 to 3.9, respectively. Both of them are characterized by high SiO2 and Na2O + K2O content, enrichment in Rb, Th, U and Pb, and depletion in Ba, Sr, Nb, Ta, P, Ti and Eu, indicating an A-type affinity. The Re-Os model ages of the molybdenite range from 198.0 to 202.1 Ma. These data suggest that the Fe-related alkali-feldspar granite was formed by partial melting of the Mesoproterozoic crust in an extensional setting after the final collision between the Xing'an and Songnen Blocks, while the Pb-Zn (Cu) and W-Mo-related syenogranite was probably generated by crystal fractionation from depleted-mantle-derived magmas, which are products of lithospheric delamination. (C) 2014 Elsevier B.V. All rights reserved.