The closure of the Mongol-Okhotsk Ocean (MOO) marks the final suturing of the Central Asian Orogenic Belt, one of the largest accretionary orogens on Earth and a region that is considered an archetype for crustal growth during the Phanerozoic. Abundant Permian to Triassic magmatism in Mongolia extended into the Jurassic on the eastern side of the Mongol-Okhotsk Belt (MOB), the orogenic belt produced by the closure of the MOO. Magmatic belts formed north and south of the suture along the MOB provide insight into the dynamics of the subduction system and the magmatic, crustal, and mantle processes pre-, syn- and post- collision within this accretionary margin. One of the main questions regarding the magmatism in the region is: Was the magmatism formed during active subduction or during the collision and closure of the basin? Here we compile geochemical data (major and trace elements, and isotopes) from the Permian to Jurassic magmatic rocks in the MOB and analyze their spatiotemporal characteristics. Our goal is to assess how magmatism changed in time and space during the closure of the Mongol-Okhotsk Ocean and how those changes relate to first-order tectono-magmatic processes right before or during the collisional event that closed the basin. Our results show a general enrichment in fluid mobile elements, LILE, and LREE and depletion in HFSE, and HREE in mafic and felsic rocks, which indicates a mantle metasomatized by subduction-related fluids regardless of crustal contamination. Our analysis supports higher enrichment in sediment melts, especially along its western and older extent, and the assimilation of juvenile crustal components without producing abundant S-type peraluminous magmatism which indicates mantle and crustal contributions. Thus, we conclude that magmatism formed above a sediment-rich retreating margin was able to recycle and stabilize young and compositionally evolved crustal material in the Central Asian Orogenic Belt.

中文翻译：

---

从增生边缘到富含沉积物的碰撞：蒙古-鄂霍茨克洋闭合期间岩浆作用的时空演化


蒙古-鄂霍茨克洋（MOO）的闭合标志着中亚造山带的最终缝合，中亚造山带是地球上最大的增生造山带之一，被认为是显生宙地壳生长的原型区域。蒙古境内丰富的二叠纪至三叠纪岩浆活动延伸至蒙古-鄂霍次克带（MOB）东侧的侏罗纪，该带是由MOO闭合产生的造山带。沿 MOB 缝合线以北和以南形成的岩浆带可以深入了解俯冲系统的动力学以及该增生边缘内碰撞前、同碰撞和碰撞后的岩浆、地壳和地幔过程。关于该地区岩浆作用的主要问题之一是：岩浆作用是在主动俯冲过程中形成的还是在盆地碰撞闭合过程中形成的？在这里，我们收集了MOB中二叠纪至侏罗纪岩浆岩的地球化学数据（主量元素、微量元素和同位素），并分析了它们的时空特征。我们的目标是评估蒙古-鄂霍茨克洋闭合期间岩浆作用在时间和空间上如何变化，以及这些变化与闭合盆地的碰撞事件之前或期间的一级构造岩浆过程有何关系。我们的结果表明，镁铁质和长英质岩石中流体流动元素、LILE 和 LREE 普遍富集，HFSE 和 HREE 普遍贫化，这表明无论地壳污染如何，地幔都会被俯冲相关流体交代。我们的分析支持沉积物熔体的富集度较高，特别是沿其西部和更古老的范围，以及新生地壳成分的同化，但没有产生丰富的 S 型过铝岩浆作用，这表明地幔和地壳的贡献。 因此，我们得出的结论是，在富含沉积物的后退边缘上方形成的岩浆作用能够回收和稳定中亚造山带年轻且成分演化的地壳物质。