Paleozoic tectonism and magmatism of Kekesu-Qiongkushitai section in southwestern Chinese Tianshan and their constraints on the age of the orogeny
Paleozoic tectonism and magmatism of Kekesu-Qiongkushitai section in southwestern Chinese Tianshan and their constraints on the age of the orogeny
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发表时间：
2007
影响因子：
1.8
通讯作者：
Shu Liang;C. Urm
中科院分区：
文献类型：
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作者：
Shu Liang;C. Urm
天山是一条多期碰撞增生造山带，其造山时代一直是人们争论的焦点。西南天山的可克苏—琼库什台段经历了以顶北向逆冲为主和北东向南西延伸的韧性走滑断裂为主的复杂变形，该段可细分为伊犁岩浆弧、伊犁元古代基底和高压变质杂岩三个岩石构造单元。野外，伊犁岛弧花岗闪长岩侵入绿片岩相变质岩中，切削绿片岩叶理。可克苏河钾花岗岩锆石 U-Pb LA-ICPMS 测年结果分别为 341±6 Ma 和 338±8Ma，琼库石台含黑云母花岗闪长岩测年结果为 313±4Ma。花岗闪长岩中黑云母测年结果为~(40)Ar/~(39)Ar高原年龄为263.4±0.6Ma，揭示了二叠系重要的热叠印。花岗闪长岩地球化学表明其属于钙碱性系列，Nb、Ta含量显着偏低，Rb、Ba、Th富集。这些特征与弧型岩浆岩的地球化学成分一致。结合前人高压变质岩的研究结果结合西天山地区的岩浆岩和俯冲碰撞事件,提出西南天山俯冲碰撞事件发生在晚石炭世之前,碰撞后的韧性走滑断裂证实了西南天山碰撞造山过程结束于二叠纪。
The Tianshan is a polyphase collision-accretion orogenic belt,its ages of orogeny is an issue in hot debate.The Kekesu- Qiongkushitai section of southwestern Chinese Tianshan experienced complicated deformations including mainly top-to-the-north thrust and NE-SW extending ductile strike-slip faulting.This section can be subdivided into three lithotectonic units,namely Yili magmatic arc,Yili Proterozoic basement and HP metamorphic complex.In the field,granodiorite of Yili arc intrudes in greenschist facies metamorphic rocks cutting foliations of greenschists.Zircon U-Pb LA-ICPMS dating yields 341±6 Ma and 338±8Ma for K-granite from Kekesu River,and 313±4Ma for biotite-bearing granodiorite from Qiongkushitai,respectively.Biotite from granodiorite yields a ~(40)Ar/~(39)Ar plateau age at 263.4±0.6Ma,revealing an important thermal overprint in Permian.Geochemistry of granodiorite indicates that it belongs to calc-alkaline series,with significant low compositions in Nb and Ta,and enrichment in Rb,Ba and Th.These features are consitent with the geochemical components of arc-type magmatic rocks.Taking into account the previous results on HP metamorphic and magmatic rocks in west Tianshan areas,this paper proposes that the subduction-collision events in southwestern Chinese Tianshan occurred before Late Carboniferous,post-collisional ductile strike-slip faulting confirms that the collisional orogenic processes ended in Permian for the southwestern Chinese Tianshan belts.