Abstract Cambrian mafic to felsic intrusive rocks intruding Precambrian rocks are recognized along the southern margin of the North Qilian suture zone. These intrusive rocks predate final closure of the North Qilian Ocean and consideration of these rocks is essential to any reconstruction of the tectonic framework of the Qilian Orogen. They include 517 Ma transitional I S type granite, 510 Ma I-type calc-alkaline diorite, 509–505 Ma calc-alkaline gabbro, and 498 Ma shoshonitic monzonite as well as highly fractionated syenogranite. Distinctive geochemical signatures and Sr-Nd-Hf isotopic compositions indicate derivation from multiple magma sources associated with subduction. Moreover, tectonostratigraphic correlation indicates that the Precambrian rocks along the southern margin of the North Qilian suture zone were associated with the Central Qilian microcontinent. These Cambrian mafic to felsic intrusive rocks are likely to be magmatic products of a continental arc built on the northern margin of the Central Qilian microcontinent during the processes of southward subduction of the North Qilian Ocean. Together, a Cambrian Andean-type arc, Cambrian-Ordovician Mariana-type intra-oceanic arc and multiple Early Paleozoic accretionary complexes within the North Qilian suture zone attest to various subduction-accretion processes that occurred within the Proto-Tethyan Ocean from Cambrian to Middle Ordovician time prior to terminal continental collision.

中文翻译：

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原特提斯洋多次俯冲过程：北祁连缝合带寒武纪侵入的意义

摘要 北祁连缝合带南缘发现了侵入前寒武系岩石的寒武系基性至长英质侵入岩。这些侵入岩早于北祁连洋最终闭合，考虑这些岩石对于重建祁连造山带的构造框架至关重要。它们包括 517 Ma 过渡 IS 型花岗岩、510 Ma I 型钙碱性闪长岩、509-505 Ma 钙碱性辉长岩和 498 Ma 钾长石二长岩以及高度分异的正长花岗岩。独特的地球化学特征和 Sr-Nd-Hf 同位素组成表明源自与俯冲相关的多个岩浆源。而且，构造地层对比表明，北祁连缝合带南缘的前寒武纪岩石与中祁连微大陆有关。这些寒武系基性至长英质侵入岩很可能是北祁连洋向南俯冲过程中在中祁连微大陆北缘形成的大陆弧的岩浆产物。北祁连缝合带内的寒武纪安第斯型弧、寒武纪-奥陶世马里亚纳型洋内弧和多个早古生代增生杂岩共同证明了原特提斯洋从寒武纪到中海发生的各种俯冲-增生过程大陆末期碰撞前的奥陶纪时间。这些寒武系基性至长英质侵入岩很可能是北祁连洋向南俯冲过程中在中祁连微大陆北缘形成的大陆弧的岩浆产物。北祁连缝合带内的寒武纪安第斯型弧、寒武纪-奥陶世马里亚纳型洋内弧和多个早古生代增生杂岩共同证明了原特提斯洋从寒武纪到中海发生的各种俯冲-增生过程大陆末期碰撞前的奥陶纪时间。这些寒武系基性至长英质侵入岩很可能是北祁连洋向南俯冲过程中在中祁连微大陆北缘形成的大陆弧的岩浆产物。北祁连缝合带内的寒武纪安第斯型弧、寒武纪-奥陶世马里亚纳型洋内弧和多个早古生代增生杂岩共同证明了原特提斯洋从寒武纪到中海发生的各种俯冲-增生过程大陆末期碰撞前的奥陶纪时间。