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首页> 外文期刊>Journal of Asian earth sciences >Generation of Triassic post-collisional granitoids in the Linxi region (Inner Mongolia, NE China) and crustal growth in the eastern Central Asian Orogenic Belt through melting of relict oceanic crust
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Generation of Triassic post-collisional granitoids in the Linxi region (Inner Mongolia, NE China) and crustal growth in the eastern Central Asian Orogenic Belt through melting of relict oceanic crust

机译：林西地区（内蒙古，中国东北）三叠纪碰撞后花岗岩的生成和中亚造山带东部地壳的生长是通过遗留的洋壳融化而实现的。

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The Linxi area is located in the eastern segment of the Central Asian Orogenic Belt (CAOB), which is the largest accretionary orogen on Earth. However, it remains highly debatable about the mechanism for crustal growth through the tectonic evolution history, in particular after the closure of the paleo-Asian Ocean. Early Triassic post-collisional granitoids (241-249 Ma) from the Linxi area in Inner Mongolia, NE China are distributed along the Xar Moron fault and comprise mainly granodiorite and monzogranite. These felsic rocks show peraluminous (aluminum index, A/CNK = 1.10-1.18, A/CNK = Al2O3 /(CaO + Na2O + K2O) in molar ratio) and magnesian affinities, and are characterized by enrichment in large ion lithophile elements (LILEs) and light rare earth element (LREEs) but depletion in Nb-Ta. They also have radiogenic Nd (whole-rock epsilon(Nd)(t) = + 1.7- + 3.3) and Hf (zircon epsilon(Hf)(t) = + 8.9- + 15.2) and mantle-like O isotopic compositions (zircon delta O-18 = 5.4-6.8 parts per thousand). Compared with their Paleozoic and Cretaceous counterparts, the early Triassic granitoids have higher values of whole-rock epsilon(Nd)(t) and zircon epsilon(Hf)(t), which requires a significant contribution of juvenile crustal components during their genesis. The combined results indicate that the early Triassic granitoids originated from melting of a mixed source consisting predominantly of mafic crust with minor pelagic sediment. These crustal components represent a lithologic assemblage typically observed in relict oceanic crust. The compositional similarities between the early Triassic igneous rocks and bulk continental crust, together with their spatial distribution along the Solonker-Xar Moron-Changchun suture, suggest that melting of relict oceanic crust may have been an important mechanism for Mesozoic crustal growth after continental collision.
机译：林西地区位于中亚造山带（CAOB）的东部，这是地球上最大的增生造山带。但是，在整个构造演化史中，特别是在古亚洲洋封闭之后，关于地壳生长的机制仍存在高度争议。来自中国东北内蒙古临西地区的早三叠世碰撞后花岗岩（241-249 Ma）沿Xar Moron断层分布，主要由花岗闪长岩和辉长花岗岩组成。这些长英质岩石表现出高铝质（铝摩尔比，A / CNK = 1.10-1.18，A / CNK = Al2O3 /（CaO + Na2O + K2O）的摩尔比）和镁的亲和力，其特征是富含大型离子亲石元素（LILEs） ）和轻稀土元素（LREEs），但Nb-Ta耗尽。它们还具有放射成因的Nd（整个岩石epsilon（Nd）（t）= + 1.7- + 3.3）和Hf（锆石epsilon（Hf）（t）= + 8.9- + 15.2）和类似地幔的O同位素组成（zircon O-18增量=千分之5.4-6.8）。与古生代和白垩纪相比，早期三叠纪花岗岩类的全岩石ε（t）和锆石ε（Hf）（t）值更高，这需要在它们的成因中对幼年地壳成分做出重大贡献。综合结果表明，早期的三叠纪花岗岩是由混合源融化而形成的，混合源主要由镁铁矿壳和少量上层沉积物组成。这些地壳成分代表了典型的在遗迹大洋地壳中观察到的岩性组合。早三叠世火成岩和块状大陆壳之间的成分相似性，以及它们沿Solonker-Xar Moron-Changchun缝合线的空间分布，表明遗留性洋壳融化可能是大陆碰撞后中生代地壳生长的重要机制。

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