No abstract

Late Mesozoic extensional mechanisms in the Great Xing'an Range (GXR) and relevant crust-mantle interactions are complicated, which result in widespread magmatisms with diverse parental origins and petrogenesises. In this paper, we present the lithology, whole-rock geochemistry, and zircon U-Pb-Lu-Hf isotopes for granodiorite-monzogranite rocks (GM) and their enclaves of quartz monzodiorites in the Zhalantun area, east of central GXR. Zircon U-Pb dating results reveal that both GM rocks and their enclaves of quartz monzodiorites yield a nearly identical crystallization age of $125 Ma. The GM rocks exhibit weak peraluminous and high-K calcalkaline compositions with high SiO 2 , Na 2 O + K 2 O, and Al 2 O 3 contents, and low MgO, Mg # , Fe 2 O 3T , and TiO 2 contents, which are characterized by fractionated REE patterns, relatively strong negative Eu anomalies, enrichments of LILEs (e.g., Rb, Ba, and K), and depletions of Nb, Ta, P, and Ti. The parental origins for GM samples were juvenile crustal materials, with positive zircon ε Hf (t) values of +2.5 to +12.9. The whole-rock and zircon geochemical simulations limit slightly lower GM magma crystallization temperatures (T Ti-Zrn ) of 683-824 C and relatively more oxidizing conditions (log(fO 2 ) = FMQ+7.6-FMQ-6.8), and further confine that they were probably formed by $10-35% degrees of fluid-present partial melting of lower to middle crustal materials, with fractional crystallization and/or residual mineral phases of plagioclase, amphibole, clinopyroxene, and garnet. By contrast, the enclaves of quartz monzodiorites possess lower SiO 2 and Na 2 O + K 2 O compositions, but higher MgO, Mg # , Fe 2 O 3T , and TiO 2 values, which are consistent with metaluminous-weak peraluminous and high-K calc-alkaline series. All quartz monzodiorites exhibit subparallel right-declined REE patterns, negligible to none Eu anomalies, enrichments of LILEs, and depletions of Nb, Ta, and Ti. Combined with mineral morphology and disequilibrium structures, the whole-rock geochemical and Hf isotopic simulations imply that parental magmas for quartz monzodiorites were hybrid mixtures between $50% host GM acid magmas and $50% ancient crust compositions, with a wide range of zircon ε Hf (t) of +14.0 to À7.7, slightly higher T Ti-Zrn of 710-835 C, and lower log(fO 2 ) of FMQ+8.2-FMQ-10.5. Taken together, felsic plutons in the Zhalantun area