The Duobagou Permian–Triassic granites of the Dunhuang orogenic belt are of great importance in understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt. LA-ICP-MS U–Pb zircon ages indicate that Permian–Triassic granitic intrusions from the Duobagou area formed at 276–274 Ma and 246 ± 1 Ma. These granites have high SiO2, Na2O and K2O, but low Al2O3, CaO and MgO contents and belong mainly to the high-K calc-alkaline I-type granite series. Based on whole-rock geochemistry and Sr–Nd and zircon Hf isotopes, the Duobagou Permian–Triassic granites were dominantly derived from the partial melting of lower continental crust formed during late Palaeoproterozoic to Mesoproterozoic times in a post-collisional extensional setting. Permian granites with zircon ϵHf(t) values of −5.4 to +3.1 and Hf model ages of TDM2 = 1.14–1.70 Ga indicate the involvement of a mantle component in their petrogenesis. Triassic granites with higher zircon ϵHf(t) values (+0.5 to +3.8) and TDM2 = 1.08–1.31 Ga suggest more juvenile sources caused by a greater contribution of mantle-derived melts, indicating a significant crustal growth. Regional extension from lithospheric delamination and heating from asthenospheric upwelling were proposed to have triggered the partial melting of lower crust, resulting in the generation of the Permian–Triassic magmatism. This may have been the mechanism for the significant crustal growth during Permian and Triassic times in the southernmost Central Asian Orogenic Belt.

中文翻译：

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敦煌造山带多巴沟二叠系-三叠系花岗岩：对中亚造山带最南端构造演化的启示

敦煌造山带多巴沟二叠系—三叠系花岗岩对了解中亚造山带最南端的构造演化具有重要意义。LA-ICP-MS U-Pb 锆石年龄表明多巴沟地区二叠系-三叠系花岗岩侵入体形成于 276～274 Ma 和 246±1 Ma。这些花岗岩具有高 SiO2, 钠2O 和 K2O，但低铝2○3、CaO、MgO含量，主要属于高钾钙碱性I型花岗岩系列。基于全岩地球化学和 Sr-Nd 和锆石 Hf 同位素，多巴沟二叠系-三叠系花岗岩主要来源于晚古元古代至中元古代形成的下陆壳在碰撞后伸展环境中的部分熔融。二叠纪花岗岩含锆石 ϵ氢氟酸(t) -5.4 到 +3.1 的值和 T 的 Hf 模型年龄DM2= 1.14-1.70 Ga 表明地幔成分参与了它们的岩石成因。三叠系花岗岩具有较高的锆石 ϵ氢氟酸(t) 值 (+0.5 至 +3.8) 和 TDM2= 1.08-1.31 Ga 表明地幔衍生熔体的贡献更大，导致更多的少年来源，表明地壳生长显着。岩石圈剥离的区域伸展和软流圈上升流的加热被认为引发了下地壳的部分熔融，导致了二叠纪-三叠纪岩浆作用的产生。这可能是中亚造山带最南端二叠纪和三叠纪时期地壳显着增长的机制。