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首页> 外文期刊>Geological Magazine >Geochronology, geochemistry, and geological implications of late Carboniferous - early Permian mafic and felsic intrusive rocks from Urad Zhongqi, western Inner Mongolia
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Geochronology, geochemistry, and geological implications of late Carboniferous - early Permian mafic and felsic intrusive rocks from Urad Zhongqi, western Inner Mongolia

机译：内蒙古西部乌拉特中旗晚石炭世-早二叠世镁铁质和长英质侵入岩的地球年代学，地球化学及其地质意义

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The mafic and felsic Haertaolegai intrusions crop out in Urad Zhongqi, western Inner Mongolia and are dominated by monzogranite, porphyritic granite, and gabbroic diorite intrusions. We investigate the tectonic setting, geochronology, and anorogenic characteristics of the western Inner Mongolia through field investigation, microscopic and geochemical analyses of samples from the Haertaolegai bimodal intrusions and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) zircon U-Pb dating of gabbroic diorite and adakitic granites. Petrographic and geochemical studies of the bimodal intrusions indicate that the gabbroic diorites formed from a primary magma generated by the partial melting of lithospheric mantle material that had previously been modified by subduction-related fluids. The felsic rocks are high-K calc-alkaline and metaluminous, have characteristics of adakitic rocks and were generated during the partial melting of juvenile crustal material. Zircon U-Pb dating indicates that the felsic portion of this pluton was emplaced during late Carboniferous - early Permian time, with the mafic portion of the pluton emplaced during early Permian time. The zircons of adamellites have epsilon Hf(t) values and T-DM2 ages of + 1.0 to + 2.7 and 1032-1128 Ma, respectively, suggesting that they formed from magmas generated by partial melting of juvenile Mesoproterozoic lower crust. These data, combined with the geology of the region, indicate that the late Carboniferous - early Permian bimodal intrusive rocks in western Inner Mongolia record a transitional period from collisional compression to post-collisional extension. These results indicate that the Paleo-Asian Ocean in western Inner Mongolia closed before 300 Ma.
机译：内蒙古西部乌拉特中旗出现了基性和长质性的哈尔陶勒盖侵入岩，其中以辉长花岗岩，斑状花岗岩和辉长岩闪长岩侵入为主。我们通过现场调查，哈陶陶莱双峰侵入岩样品的显微和地球化学分析以及激光烧蚀多收集器电感耦合等离子体质谱法（LA-MC-ICP-MS），对内蒙古西部的构造环境，年代学和造山作用特征进行了研究。 ）辉长岩闪长岩和adakitic花岗岩的锆石U-Pb年代。对双峰侵入岩的岩石学和地球化学研究表明，辉长岩闪长岩是由岩浆层地幔物质部分熔融而产生的原生岩浆形成的，该岩浆先前已被俯冲相关流体修饰。长英质岩石是高钾钙碱性和金属质的，具有埃达克质岩石的特征，是在幼年地壳物质部分熔融过程中产生的。锆石U-Pb测年表明，该岩体的前质部分是在石炭纪晚期-二叠纪早期，而岩体的镁铁质部分是在二叠纪早期。钙钛矿的锆石的εHf（t）值和T-DM2年龄分别为+ 1.0至+ 2.7和1032-1128 Ma，这表明它们是由青少年中元古代下地壳部分熔融产生的岩浆形成的。这些数据与该地区的地质情况相结合，表明内蒙古西部的石炭纪晚期－二叠纪早期双峰侵入岩记录了从碰撞压缩到碰撞后伸展的过渡时期。这些结果表明，内蒙古西部的古亚洲洋在300 Ma之前就关闭了。

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