Geochronology, geochemistry, and tectonic significance of Permian intrusive rocks from the Shaolanghe region, northern margin of the North China Craton

In situ zircon U-Pb ages and Hf isotopic data, whole-rock major and trace element contents, and Sr-Nd isotopic compositions are reported for Permian intrusive rocks at Shaolanghe in Eastern Inner Mongolia in order to explore the magmatic origin and tectonic significance of these rocks for the evolution of the northern margin of the North China Craton. Three intrusive rocks, quartz diorite, Xishuiquan granite, and Xinglong granite, yield zircon U-Pb ages of 285.9 +/- 3.1, 274.2 +/- 2.9, and 260.0 +/- 8.4 Ma, respectively. The quartz diorite and Xishuiquan granite belong to the high-K calc-alkaline series, enriched in large ion lithophile elements (e.g., Rb) and depleted in high field strength elements (e.g., Nb and Ti). They are defined as I-type granites. The quartz diorite has initial Sr-87/Sr-86 ratios of 0.7049-0.7051, epsilon(Nd)(t) values of -10.0 to -11.4, and epsilon(Hf)(t) values of -15.2 to -9.9. The epsilon(Hf)(t) values of the Xishuiquan granite (-4.8 to 4.0) vary in discrete segments, whereas the epsilon(Nd)(t) values (-12.9 to -13.3) are consistent with those of the quartz diorites (-10.0 to -11.4). A magma mixing model is proposed for the formation of the quartz diorites of the Shaolanghe region, and the Xishuiquan granite was likely derived from partial melting of the Paleoproterozoic crust with involvement of mantle components. Geochemical analyses show that the tectonic setting of the northern margin of the North China Craton during the late Palaeozoic was an Andes-type active continental margin associated with subduction of the Paleo-Asian Ocean plate.