Geochemistry, zircon U-Pb geochronology and Hf-O isotopes of the Late Mesozoic granitoids from the Xiong'ershan area, East Qinling Orogen, China: Implications for petrogenesis and molybdenum metallogeny.

• These granitoids were emplaced between 132 Ma and 127 Ma. • These granitoids derived from mixing of Taihua Group, Xiong'er Group and mantle. • The ore-bearing granite porphyry possesses higher fO 2 than the ore-barren plutons. The petrogenesis and genetic relationship of molybdenum mineralization in the Late Mesozoic granitoids from the Xiong'ershan area remains controversial. This study presents integrated whole-rock geochemistry, zircon U-Pb geochronology and Hf-O isotopes for Late Mesozoic ore-bearing granite porphyry stock (Leimengou granite porphyry) and ore-barren plutons (Haoping and Jinshanmiao plutons) in the Xiong'ershan area of the East Qinling Orogen Belt (EQOB). The ore-barren granitoids are high-K subalkaline, metaluminous, and show negative correlations between Al 2 O 3 , MgO, TiO 2 , MnO, CaO, FeOT and P 2 O 5 with SiO 2. However, the Leimengou granite porphyry lacks distinctive linear correlation between major oxides with SiO 2 except Al 2 O 3 , K 2 O and Na 2 O. These granitoids are enriched in LREE over HREE with slightly negative europium anomalies. Most samples show enrichment of Rb, Ba, Th, U, K and Pb, and depletion of Nb, Ta, P and Ti, mostly overlapping the ranges of the Taihua Group. Zircon U-Pb ages from the Haoping pluton, Jinshanmiao pluton and Leimengou granite porphyry are 130.9 ± 0.4 Ma, 127.7 ± 0.7 Ma and 131.5 ± 0.9 Ma, respectively. The Hf-O isotopic features of zircon from the Leimengou granite porphyry (δ18O zircon = 5.03‰ − 5.86‰, εHf (t) = −24.3 to −14.4) are markedly similar with the Haoping pluton (δ18O zircon = 5.17‰ − 5.61‰ and εHf (t) = −26.6 to −21.4). Zircon grains from the Jinshanmiao pluton have unique δ18O zircon ranging from 6.01‰ to 8.90‰ and εHf (t) from −15.6 to −12.2. The co-variations of whole-rock geochemistry and Hf-O isotopic features in the samples suggest that Haoping pluton and Leimengou granite porphyry originated from mixture of partial melts of the Taihua Group with mantle-derived material, whereas the Jinshanmiao pluton originated from mixture of Xiong'er Group and mantle-derived material, with minor input of Taihua Group. The zircon grains from the Leimengou granite porphyry have significant higher Ce4+/Ce3+ (mean 547) and δEu (mean 0.65) ratios than those in the ore-barren Haoping pluton (mean 207 and 0.54, Ce4+/Ce3+ and δEu, respectively) and the Jinshanmiao pluton (mean 235 and 0.62, respectively). The main controlling factors for porphyry-type Mo mineralization are likely the oxygen fugacity (fO 2) of the magma and input of mantle-derived material in the Xiong'ershan area. The geochemical and isotopic data show that the emplacement of these intrusions in the EQOB occurred in the post-collision settings during 132–127 Ma. [ABSTRACT FROM AUTHOR]