Determination of the Early Cretaceous metamorphic core complex in Zhangbaling Uplift: Constraints on the Tan-Lu fault and its relationship with metallogenesis

The gently dipping ductile shear zone widely distributed in the Zhan baling uplift is obviously different from the steeply dipping ductile shear zone formed by the translation of the Tanlu fault. Based on the geometry and kinematics analysis of gently dipping ductile shear zone, combined with the characteristics of the Early Cretaceous basins and the isotopic dating of extensional detachment faults and syntectonic magmatic rocks of the metamorphic core complexes in eastern China, the Early Cretaceous metamorphic core complex of Zhangbaling uplift is defined. Its upper plate is composed of the Nanhua-Ordovician sedimentary strata and the Early Cretaceous sediments, the lower plate is composed of Neoproterozoic metamorphic clastic sedimentary rocks, metamarine volcanic rocks (basement) and early Cretaceous intrusive rocks. The upper and lower plates are separated by a main extensional detachment fault. The long axis of the metamorphic core complex is NE-SW, with indicative structure reflecting shear slipping to SE of the upper plate, which is completely consistent with the extension direction of the metamorphic core complex in eastern China. Through the determination of the metamorphic core complex, combined with field geological facts, it is believed that the Guandian-Machang fault is a secondary fault of Tanlu fault, which is a response to the third left-lateral translation of Tanlu fault zone at the end of Early Cretaceous. On the basis of comprehensive research, a regional tectonic-magmatic-metallogenic relationship model is established, which revealing that the Zhangbaling uplift has undergone three tectonic stages during early Cretaceous: Early extension(metamorphic core complex stage)-compression strike-slip (Guandian-Machang fault formation stage)-late extension (dioritic dike emplacement stage). The superimposition of multi-stage structuring and magmatism results in the formation of gold polymetallic minerals deposits in this area.