Petrogenesis and tectonic implications of 1.86–1.80 Ga A-type granites in the Daqingshan Complex, Khondalite Belt, North China Craton

Abstract

The Khondalite Belt is regarded as a Paleoproterozoic continent–continent collisional belt along which the Yinshan Block and the Ordos Block amalgamated to form the Western Block in the North China Craton. Associated with the collision of the Yinshan and Ordos Blocks was granitic magmatism represented by quartz monzogranites in the Khondalite Belt, whose petrology, geochemistry and petrogenesis will provide important insights into understanding of the crustal evolution of the Khondalite Belt in the late Paleoproterozoic. In this paper, we carried out a detailed study on the petrography, geochronology, whole-rock geochemistry, and zircon Lu-Hf isotope of quartz monzogranites exposed in the Daqingshan Complex of the Khondalite Belt. Zircon LA-ICP-MS U-Pb dating results show that the Daqingshan quartz monzogranites were formed at 1.86–1.80 Ga, at some time posterior to the ∼ 1.95 Ga collision of the Yinshan and Ordos Blocks. Geochemically, the Daqingshan quartz monzogranites belong to ferroan, metaluminous to peraluminous, calc-alkalic to alkalic-calc series, exhibiting high SiO2, Na2O, K2O and FeOT / (FeOT + MgO), low Al2O3, MgO and CaO, and high Zr, Nb, Ce and Y, low Cr and Ni contents, with an affinity of A-type granites. In terms of REE and trace elements, the Daqingshan quartz monzogranites have right dipping patterns and negative Eu anomalies, enriched large ion lithophile elements (LILEs) (e.g. Rb, Zr and Hf), and depleted high field strength elements (HFSEs) (e.g. Ta, P and Ti). Zircon Lu-Hf isotopic characteristics (εHf(t) = -9.63 – −4.31, TDMC = 2744–3050 Ma) indicate that the Daqingshan quartz monzogranites were most likely originated from the partial melting of a Neoarchean ancient crust. Combining new results presented in this paper with previous data, we propose that the quartz monzogranites in the Daqingshan Complex were derived from the partial melting of Neoarchean TTG rocks under high temperatures caused by the upwelling of mantle magmas under a post-collision extensional setting. Meanwhile, it indicates that the Khondalite Belt completed collision at 1.86–1.80 Ga to form the Western Block.