Leucogranite, typically as an important signature of continent-continent collision, records valuable information on evolution of continental crust and provides an insight into the geodynamic processes during continental collision. Here, we present zircon U-Pb and muscovite Ar-Ar dating, major and trace elements, and Sr-Nd isotope data for the Yuanbaoshan leucogranites in southeast Inner Mongolia, with the aim of discussing its petrogenesis and tectonic implications. Zircon U-Pb dating reveals that the leucogranite formed at 239 ± 3 Ma, similar to the plateau age of 230.9 ± 2.2 Ma given by muscovite ⁴⁰Ar/³⁹Ar dating, indicating that the leucogranite formed during the period of latest Middle Triassic to earliest Late Triassic, not the early Permian as previously believed. The Yuanbaoshan leucogranites are characterized by containing aluminum-rich minerals of muscovite and garnet, high silica and alkali contents, belonging to weakly peraluminous and high-K calc-alkaline series. Their closed correlation in major elements and high similarity in Nd isotopic compositions (ε_Nd(t) values ranging from −5.08 to −4.59) with the coeval Shuangjingzi granites in the adjacent area, together with the relatively lower TiO₂, TFe₂O₃, MgO, CaO and P₂O₅ contents and more strongly negative Eu anomalies (Eu/Eu* = 0.27–0.88), indicate a more evolved cogenetic magma probably originated by partial melting of juvenile crustal materials with some old components. Furthermore, the Yuanbaoshan leucogranites show the extreme depletion in total REE contents, serious deviation in Zr/Hf and Nb/Ta ratios from the common range of magmatic rocks, and a tetrad effect of the REE distribution, all of whose specific trace element behaviors typically occur in highly evolved magmatic systems. Taken together, these leucogranites seem to be highly similar in petrological and geochemical characteristics to those of Himalayan leucogranites undergone an intensive crystal fractionation in the later of orogenic period. Combined with regional geological data, we conclude, therefore, that the Yuanbaoshan leucogranites were most probably formed in the post-orogenic tectonic setting, in response to the initial collapse of the thickened lithosphere related to the collision between the Sino-Korean and Siberian paleo-plates, and that a destructive collision, probably similar to Himalayan orogeny, might have occurred after final closure of the Paleo-Asian Ocean between the Sino-Korean and Siberian paleo-plates in the Late Permian, and lasted at least until the middle Triassic.

白云石通常作为大陆-大陆碰撞的重要标志，它记录了有关大陆壳演化的宝贵信息，并提供了对大陆碰撞过程中地球动力学过程的见解。在这里，我们介绍了内蒙古东南部元宝山无色花岗岩的锆石U-Pb和白云母Ar-Ar年代，主要和微量元素以及Sr-Nd同位素数据，目的是讨论其成因和构造意义。锆石U-Pb测年表明，白云石形成于239±3 Ma，与白云母⁴⁰ Ar / ³⁹给出的高原年龄230.9±2.2 Ma相似Ar定年，表明该花岗石在最近的中三叠纪至最早的三叠纪形成，而不是先前认为的早二叠纪。元宝山白云石的特征是含白云母和石榴石的富铝矿物，高二氧化硅和碱含量，属于弱高铝质和高钾钙碱性。其主要元素和高相似性在Nd同位素组成闭合相关（ε_钕（t）值范围从-5.08到-4.59）与双井同时代花岗岩在邻接区域与，一起相对降低的TiO ₂，中TFe ₂ ö ₃，MgO，CaO和P ₂ O ₅含量和更强的负Eu异常（Eu / Eu * = 0.27–0.88），表明更多的共生岩浆可能是由具有某些旧成分的幼年地壳材料部分熔融引起的。此外，元宝山的花岗花岗岩显示出稀土元素总含量的极度减少，Zr / Hf和Nb / Ta比值与普通岩浆岩的范围存在严重偏差，以及REE分布的四重效应，所有这些元素的典型微量元素行为通常发生在高度演化的岩浆系统中。综上所述，这些隐花岗石的岩石学和地球化学特征似乎与在造山期后期经历了密集的晶体分级分离的喜马拉雅隐花岗石的高度相似。因此，结合区域地质数据，我们得出结论：