A ~2.5 Ga magmatic arc in NE China: New geochronological and geochemical evidence from the Xinghuadukou Complex

This study reports new LA-ICP-MS U-Pb zircon ages from the Xinghuadukou Complex from the Erguna Block, NE China. A suite of the Palaeoproterozoic orthogneiss and a suite of the Vendian to Cambrian paragneiss are recognized with the co-magmatic age of 2,464 +/- 26 Ma and the maximum depositional age of 561 +/- 10 Ma for their igneous and sedimentary protolith, respectively. The trace element geochemical analysis suggests a strong arc affinity for our orthogneiss, characterized by the enriched LREE and LILE, the elevated incompatible and fluid-mobile elements and the depleted yet negligible fractionated HREE and HFSE. By comparing our samples with a suite of Cenozoic mantle-derived granitoids from Hokkaido and a suite of Mesozoic active continental margin volcanics from NE China, it is suggested that the igneous protolith of our near Archaean orthogneiss formed in an arc environment and probably derived from the prior arc crust. The trace element features of the paragneiss highly resemble that of the orthogneiss, showing arc affinity, which suggests an arc basin environment for the sedimentary protolith of our Vendian to Cambrian paragneiss. Based on the synthesized evidence from the Xinghuadukou Complex, a new tectonic scenario is proposed that the basement of the Erguna Block might be forged by the accretion and collision of multi-episodic igneous arcs and their correlated arc basins, which was probably lasting through the Proterozoic and followed by the Pan-African period high-grade metamorphism. The consolidated Erguna Block was later involved into the CAOB tectonic domain, modified and disrupted with the assembly of NE China.