Meso-Cenozoic multiple exhumation in the Shandong Peninsula, eastern North China Craton: Implications for lithospheric destruction

Abstract

The Shandong Peninsula in the eastern North China Craton (NCC) forms part of the region that witnessed extensive tectonic reactivation with concomitant craton destruction and lithospheric thinning during the Meso-Cenozoic. Previous studies concentrated mainly on the timing, mechanism and tectonic setting of the Meso-Cenozoic magmatism, with inadequate evidence from low temperature thermochronology to constrain the thermo-tectonic exhumation history of this region. In this study, we present new apatite U-Pb (AUPb) and fission track (AFT) data with corresponding thermal history models for igneous rocks from the two flanks of the Tan-Lu Fault Zone (TLFZ) that bisects the Shandong Peninsula, with a view to gain insights into the Meso-Cenozoic exhumation history of this region and to evaluate its implications on the lithospheric destruction of the NCC. The newly obtained AUPb ages of 2.5-1.5 Ga for the Precambrian intrusive rocks and of 162-112 Ma for the Mesozoic igneous suite are mainly used to constrain their thermal history models. In addition, the Mesozoic AUPb ages of 162-112 Ma highly overlap with their corresponding zircon U-Pb ages (161-115 Ma), suggesting shallow granitoid emplacement and associated rapid post-magmatic cooling in response to the westward subduction of the Paleo-Pacific Plate. The AFT dating results yield two groups of AFT central ages at 122-113 Ma and 98-59 Ma, and corresponding thermal history models also reveal two rapid cooling stages during the Early Cretaceous (130-105 Ma) and Late Cretaceous to Paleogene (85-55 Ma). By integrating previous low temperature therrmx:hronological studies with this study, we interpret that the Early Cretaceous rapid exhumation corresponds to the peak timing of craton destruction, resulting from the Paleo-Pacific slab rollback within a back-arc extensional setting. The Late Cretaceous rapid exhumation is interpreted as a response to continuing craton destruction, derived by the NNW-directed Pacific Plate subduction.The Paleogene cooling might represent the termination of craton destruction of Shandong Peninsula associated with a dextral motion along the TLFZ, triggered by the change in direction of the Pacific Plate from NNW to WNW and/or far-field effect of the India-Eurasia collision. (C) 2020 Elsevier B.V. All lights reserved.