Early Cretaceous adakitic granitoids from the Zhijiazhuang skarn iron deposit, North Taihang Mountain, China: Implications for petrogenesis and metallogenesis associated with craton destruction

摘要

The North Taihang Mountain region located within the Trans-North China Orogen is one of the major Mesozoic metallogenic belts in the North China Craton and carries varied polymetallic mineralization associated with multiple magmatic pulses. Here, we investigate the Zhijiazhuang skarn iron deposit from this region through petrological, geochemical, zircon U-Pb geochronological and Lu-Hf isotopic studies of the associated granitoids to constrain the ages, petrogenesis, and process of mineralization. Zircon U-Pb dating shows multiple pulses of magmatism with three major peaks at 134, 129, and 125 Ma as well as some scattered spot ages of 121, 118, and 112 Ma consistent with regional multistage magmatic events during the Early Cretaceous. Zircon Hf data display negative epsilon(Hf) (t) values from -21.7 to -7.8 and two-stage crustal model ages (T-DM (c)) in the range of 1,680-2,560 Ma, indicating magma derivation from reworking of late Neoarchean to early Paleoproterozoic crustal materials possibly with minor lithospheric mantle input. Geochemical data indicate I-type adakitic signature for the intrusion, suggesting the involvement of subduction-related components. The adakitic rocks identified in this study originated from a mixture of crustal and lithospheric mantle components followed by upper crustal fractional crystallization. Collectively, the data suggest that the granitoids were formed by interaction of crust-mantle materials through partial melting of a thickened or delaminated lower continental crust and lithospheric mantle corresponding to the peak event of lithospheric thinning and craton destruction of the North China Craton. The tectonics is correlated with the westward subduction of the Paleo-Pacific Plate. Combined with information from previous studies associated with porphyry-skarn-type deposits in the whole Taihang Mountain region, we correlate the multiple phases of magmatism and mineralization of the deposit to the peak event of lithospheric thinning and destruction of the North China Craton, and the Zhijiazhuang skarn iron deposit was likely generated by the interaction of magmas and fluids with the dolomitic wall rocks.