Granitoids, an important part of the continental crust, are the direct and indelible evidence of the accretion and reworking process of the continental crust in different tectonic settings. Therefore, these early geodynamic mechanisms can be roughly reconstructed by analysing the geochemical characteristics of granitoids. In this study, the Permian–Triassic Granitoids widely distributed in the East Kunlun Orogenic Belt (EKOB) are studied to determine their chronology and petrogenesis to restrict their source regions and establish the significance of their geodynamic and crustal growth. Zircon inductively coupled plasma mass spectrometry (ICP–MS) dating results show that the crystallization ages of these granitoids are between 252–240 Ma, during the early and middle Triassic. These granitoids have high SiO₂ and medium Na₂O + K₂O contents, plotting into the granite region, and calc-alkaline to high-K calc-alkaline series on the SiO₂–Na₂O + K₂O and SiO₂–K₂O diagrams, respectively. All the samples have aluminium saturation index (A/CNK) values from 1.00 to 1.25 showing peraluminous characteristics. In terms of trace and rare earth elements, the samples are depleted in high field strength elements (HFSEs) such as Nb, Ta, P, and Ti and are enriched in large ion lithophile elements (LILEs) such as Rb, K, Ba, and U. Moreover, all granitoids show right-inclined rare earth element (REE) distribution patterns with weak to moderate Eu anomalies (δEu = 0.50–0.93). In addition, the samples have low P₂O₅ contents, 10,000*Ga/Al ratios (1.65–2.39), and Zr + Nb + Ce + Y (212–262 ppm) displaying affinities to I-type granite. Combined with their ε_Hf (t) values of −2.31 to 4.44, with 1.0–1.4 Ga two stage model ages (T_DM2), they are considered to be the products of the reworking of the Mesoproterozoic lower crust; therefore, they are not related to the continental net growth in the EKOB. On the tectonic discrimination diagrams of granitoids, all the samples fall into the area of volcanic arc granite (VAG) and continental margin arc; this suggests that the Paleo-Tethys Ocean slab was still in the subduction stage during 252–240 Ma, and the continental collision had not yet started. Based on the plenty of magmatic rock dating results published previously, it appears there are two magmatic peak periods (260–240 Ma and 230–210 Ma) and one magmatic intermittence period (240–230 Ma) during the late Permian to Triassic of the EKOB, corresponding to three geodynamic evolution stages of subduction, post-collision extension, and syn-collision, respectively.

胶-辽-吉造山带北段辽河群和集安群中的古元古代镁铁质侵入体成因及其指示的地球动力学背景一直存在较大争议。原因之一在于研究资料多集中于辽河群中出露的镁铁质侵入体,而对集安群中的镁铁质侵入体报道较少,制约了对胶-辽-吉造山带地球动力学演化的整体性认识。因此,本文对集安群中镁铁质侵入体进行详细的野外实地调查、地球化学、年代学和同位素研究,讨论这些岩石成因,揭示地幔源区性质并制约地球动力学背景。锆石LA-ICP-MS U-Pb定年结果显示这些变质辉长岩侵入体变质时代介于1866~1871Ma,为古元古代晚期的产物;一粒锆石核部²⁰⁷Pb/²⁰⁶Pb年龄为2139±14Ma,可能代表了原岩的结晶时代。样品属于亚碱性系列,并具有向富铁成分演化的拉斑系列特征。岩石富集大离子亲石元素(如Ba、Rb、Sr和K),亏损高场强元素(如Nb、Ta和Ti);这些特征与典型岛弧玄武岩相似,指示了它们来自俯冲流体交代的地幔源区。结合样品2.07~2.45Ga的一阶段Hf同位素模式年龄,认为交代作用发生在古元古代早期。本次研究的集安群中变质辉长岩侵入体与前人研究的辽河群中镁铁质岩石在结晶变质时代和地球化学特点方面具有很多相似性:(1)同属于亚碱性系列并具有向富铁成分演化的趋势;(2)相似的微量和稀土元素配分曲线;(3)具有高场强元素亏损和大离子亲石元素富集这一"俯冲流体交代信号"; (4)轻度富集的Sr-Nd-Hf同位素和古元古代早期的一阶段Hf同位素模式年龄;(5)一致的结晶年龄(2139~2099Ma)与变质时代(1879~1852Ma)。这些相似性指示了集安群和辽河群在古元古代早期可能经历了相同的岩浆-构造-变质事件。镁铁质岩石应来源于古元古代早期经历了俯冲流体交代的地幔源区。在构造环境判别图解上,集安群和辽河群中镁铁质岩石大部分样品都落入弧后盆地环境中。结合同期火成岩组合和演化特点,认为胶-辽-吉造山带东北段在古元古代早期处于弧后盆地背景中,古元古代晚期则处于造山后伸展的地球动力学背景下。