Paleoproterozoic continental crust accretion on the northern margin of the North China Craton: Evidence from the Shangyi Complex at the eastern segment of the Khondalite Belt

Abstract

The North China Craton (NCC) is considered a part of the Columbia Supercontinent, and geological records related to the convergence and breakup events of the Columbia Supercontinent have been preserved to varying degrees. The Shangyi Complex, located at the tectonic conjunction of the Khondalite Belt and the Trans-North China Orogen (TNCO) on the northern margin of the NCC, recorded the tectonic magmatic activities related to the collision orogeny of the Ordos Block and the Yinshan Block at ∼1950 Ma and the Western and Eastern Blocks at ∼1850 Ma respectively. The Shangyi Complex mainly comprises leucogranite, garnet granite, and gabbro. In this paper, LA-ICP-MS zircon U-Pb dating, whole rock geochemistry, and Lu-Hf isotope studies on leucogranite and garnet granite are conducted, and the ages of the zircons are 1961 ± 20 Ma and 1873 ± 20 Ma respectively. Geochemical characteristics show that they are all S-type granites. The results of the zircon Lu-Hf isotope show that the ε_Hf(t) values of the leucogranite zircons range from −5.86 to + 5.88, with an average value of +1.11, and the two-stage model ages (T_DM2) range from 2943 Ma to 2222 Ma, which is formed by the partial melting of ancient crusts during the collision of the Yinshan Block and the Ordos Block. The ε_Hf(t) values of the garnet granite zircon range from +0.86 to +2.53, with an average value of +1.50, and the two-stage model ages (T_DM2) range from 2464 Ma to 2361 Ma, which is formed by the partial melting of Paleoproterozoic crusts during the collision of the Western Block and the Eastern Block. The gabbro geochemical characteristics show that it possess alkaline rock property, which was formed by the underplating of mantle-derived magma in the post-collision extension stage after the collision of the Western and Eastern Blocks.