Growth of early Paleozoic continental crust linked to the Proto-Tethys subduction and continental collision in the East Kunlun Orogen, northern Tibetan Plateau
Growth of early Paleozoic continental crust linked to the Proto-Tethys subduction and continental collision in the East Kunlun Orogen, northern Tibetan Plateau
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青藏高原北部东昆仑造山带的早古生代大陆地壳的生长与原特提斯俯冲和大陆碰撞有关
DOI：
10.1130/b36292.1
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发表时间：
2022-11
期刊：
影响因子：
--
通讯作者：
Zhang Weikang
中科院分区：
文献类型：
--
作者：
Fu Lebing;Bagas Leon;Wei Junhao;Chen Yao;Chen Jiajie;Zhao Xu;Zhao Zhixin;Li Aobing;Zhang Weikang
青藏高原北部东昆仑造山带记录了早古生代和早中生代两次大陆碰撞造山事件和岩浆作用。然而，在早古生代碰撞造山作用的不同构造阶段，EKO陆壳生长过程中可能存在的岩浆补充作用被忽略了。本文报道了鄂尔多斯东部香日德-库海地区早古生代三期深成岩体的详细研究结果。最古老的岩浆套(1期)包括织宇侵入杂岩中约471 Ma的魁龙二长闪长岩和约454 Ma的花岗闪长岩。二长闪长岩具有类闪长岩成分，具有较高的二氧化钛和Y含量，解释为来自交代地幔楔二辉橄榄岩的部分熔融。花岗闪长岩具有高SiO_2含量、高Sr/Y比和亏损Hf同位素的特征，解释为俯冲的原特提斯洋壳熔融产生的埃达克岩类熔体。岩浆作用可能与原特提斯洋在520-450 Ma之间向北俯冲有关。第二阶段的岩浆作用表现为大约450−431Ma侵位的深成岩套，具有I型花岗岩成分。其中，约447 Ma由过铝花岗岩组成的富含NdHf同位素的侵入体指示了造山带中元古代的火成岩来源。瓦列加和织宇侵入杂岩中约450−434 Ma的二长花岗岩和花岗闪长岩具有不同的元素和同位素组成。它们可能是来自旧地壳的长英质熔体与来自交代岩石圈地幔的镁铁质岩浆混合而成的，镁铁质熔体比例为30%。瓦列加侵入杂岩中约431 Ma的石英闪长岩是由交代岩石圈地幔衍生的镁铁质岩浆经地壳同化和分离结晶形成的，镁铁质熔体比例为60%。在450−426 Ma期间，原特提斯洋支闭合和随后的大陆碰撞期间，第二阶段套侵位。在大陆岩石圈折返过程中，岩浆作用在约426-410 Ma之间减弱，这表明EKO中存在逆行榴辉岩。第三阶段岩浆套包括约408 Ma朗穆里侵入体和约403 Ma碾塘正长花岗岩。这些深成岩类埃达克岩或具有A型花岗岩成分，富含Nd-Hf同位素。它们可能来源于410−390 Ma期间碰撞后伸展环境中古老的和年轻的陆壳的重熔。来自俯冲的原特提斯洋壳和阶段2的交代岩石圈地幔的部分熔体的鉴定表明，地壳下物质已显著转移到上覆大陆地壳。因此，大洋俯冲(第一阶段)和大陆碰撞中的岩浆作用
The East Kunlun Orogen (EKO) in the northern Tibetan Plateau records two continental collisional orogenic events and magmatism in early Paleozoic and early Mesozoic. However, possible magmatic additions to the continental crust growth of the EKO in different tectonic stages of early Paleozoic collisional orogeny have been overlooked. Three phases of early Paleozoic plutons from the Xiangride-Kuhai area in the east of the EKO have been chosen for detailed investigation and the results are reported here. The oldest magmatic suite (Stage 1) includes the ca. 471 Ma Qurelong Monzodiorite and ca. 454 Ma granodiorite in the Zhiyu Intrusive Complex. The monzodiorite has a sanukitoid-like composition with high TiO2 and Y contents and is interpreted as being derived from partial melting of metasomatized mantle wedge lherzolite. The granodiorite is typified by its high SiO2 content, high Sr/Y ratio, and depleted Hf isotope, and is interpreted as an adakite-like melt derived from the melting of a subducted Proto-Tethys oceanic crust. The magmatism can be linked to northward subduction of the Proto-Tethys Ocean between 520 and 450 Ma. Stage 2 magmatism is represented by a plutonic suite emplaced during ca. 450−431 Ma with an I-type granitic composition. Of these, the ca. 447 Ma Kengdenongshe Intrusion composed of peraluminous granite with enriched Nd-Hf isotopes is indicative of a Mesoproterozoic igneous source in the orogen. The ca. 450−434 Ma monzogranite and granodiorite in the Walega and Zhiyu intrusive complexes exhibit variable element and isotope compositions. They would have been generated by magma mixing of felsic melts from the old crust and mafic magmas derived from the metasomatized lithospheric mantle, with a mafic melt proportion of 30%. The ca. 431 Ma quartz diorite in the Walega Intrusive Complex is formed through crustal assimilation and fractional crystallization of mafic magmas derived from the metasomatized lithospheric mantle, with a mafic melt proportion 60%. Stage 2 suite was emplaced during the closure of Proto-Tethys oceanic branches and subsequent continental collision during 450−426 Ma. Magmatism diminished between ca. 426 and 410 Ma during exhumation of the continental lithosphere as indicated by the presence of retrograde eclogites in the EKO. Stage 3 magmatic suite includes the ca. 408 Ma Langmuri Intrusion and ca. 403 Ma Niantang Syenogranite. These plutons are adakite-like or have an A-type granitic composition and are enriched in Nd-Hf isotopes. They might have been derived from the remelting of old and juvenile continental crust in a post-collisional extensional setting during 410−390 Ma. Identification of partial melts, derived from the subducted Proto-Tethys oceanic crust and metasomatized lithospheric mantle in stage 1 and 2 plutons, show that the subcrustal materials have been significantly transferred to the overlying continental crust. Hence the magmatism in oceanic subduction (Stage 1) and continental collision