Late Neoarchean to Paleoproterozoic arc magmatism in the Shandong Peninsula, North China Craton and its tectonic implications

Abstract

The transition in tectonic regime of our planet during the late Archean with the initiation broadly modern style subduction system is one of the major topics of interest in earth science. The North China Craton (NCC), one of the oldest cratonic nuclei in the world, preserves important records of Archean and Paleoproterozoic crustal evolution, cratonization and related geodynamic history that are important in understanding the continental growth of the early Earth. Here we investigate a suite of Archean to Paleoproterozoic rocks including hornblendite, amphibolite, gabbro, diorite, basalt, plagiogranite, granite porphyry and greenschist from Shandong Peninsula within the southwestern Jiaoliao block of the eastern NCC using zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock geochemistry. We aim to understand the timing and petrogenesis of the rock suite and its implications on the geodynamic history of the NCC. Zircon U-Pb data show 207Pb/206Pb ages in the range of 2.68–1.83 Ga, and is divided into three groups of 2.68–2.43, 2.38–1.96 and 1.95–1.83 Ga. Among these, the 2.68–2.43 Ga group confirms with the major magmatic phase during Neoarchean-Paleoproterozoic transition in the eastern NCC, whilst the other groups of 2.38–1.96 and 1.95–1.83 Ga ages might represent the Paleoproterozoic orogenic events in the NCC. Zircon Lu-Hf isotopic data display εHf(t) values ranging from −0.4 to 10.0 and TDMC of 3074–2080 Ma, which are subdivided into one group with U-Pb ages of 2672–2445 Ma characterized by εHf(t) values from −0.4 to 7.0 and TDMC of 3074–2588 Ma and another group (2134–2009 Ma) with εHf(t) values in the range of 2.8–10.0 and TDMC ranging from 2458 to 2080 Ma. These results indicate that the magmas (2672–2445 Ma group) were sourced mainly from Late Mesoarchean to Neoarchean juvenile components with minor input of reworked Mesoarchean crustal components, whereas the 2134–2009 Ma group was derived from Paleoproterozoic juvenile components. Whole-rock geochemical data of the granite porphyry and plagiogranites show typical subduction-related arc signature with the enrichment of LREEs and LILEs and depletion of HREEs and HFSEs (e.g. Nb, Ta, Ti), and mainly belong to I-type granites generated at arc-related setting. The ultramafic–mafic magmatic suite corresponds with tholeiitic to calc-alkaline series which were formed by partial melting of enriched mantle within an island arc setting in an active continental margin. In conjunction with the results from previous studies in the NCC, we correlate the 2.68–2.43 Ga ages with Late Neoarchean amalgamation of microblocks and cratonization of the NCC driven by late Neoarchean oceanic plate subduction, and the 2.38–1.83 Ga ages represent Paleoproterozoic orogenic events including the assembly of major crustal blocks in the NCC within the Paleoproterozoic supercontinent Columbia, and the final collision of these crustal blocks and cratonization.