东特提斯板块会聚边缘与岛弧造山作用

PLATE CONVERGENT MARGINS AND ISLAND-ARC OROGENESIS IN EASTERN TETHYS

关键词:  东特提斯  会聚边缘  岛弧造山

Key words:  eastern Tethys  convergent margin  island-arc orogenesis

摘要:

本文重点简述了特提斯构造域内古、中、新三个演化阶段的蛇绿混杂岩与岛弧带的时空展布及其沟一弧一盆体系,所识别出的蛇绿混杂岩、洋中脊拉斑玄武岩、大洋沉积物和岛弧带等地质记录,提供了东特提斯早期大洋岩石圈板块运动的有力证据。同时,与岛弧有关的不同时期不同阶段的各种弧前盆地、弧间盆地和弧后盆地成为造山带板块会聚边缘特征的标志。这些类型多样的沉积盆地的形成与演化也颇有特色,它们受制子东特提斯构造域内复杂的地质构造背景的影响和控制。很明显,盆地均经历了断陷拉张一稳定沉降一挤压隆升的演化过程。断陷拉张阶段多以火山活动强烈与发育扇三角洲沉积为典型特征;稳定沉降阶段主要碳酸盐与陆源的混合和低密度浊流沉积;挤压阶段早期发育海底扇。需要强调的是,普遍存在于各种盆地中的石英质糜棱岩岩屑物源是确定再旋回造山带的重要因素。典型的义敦岛弧与沙鲁里山岩浆弧之间的弧一弧碰撞模式及其外延到整个东特提斯构造域内都是很普遍的。义敦岛弧的成长是一个从早期裂谷基础上由不成熟到成熟的阶段发展起来的过程。沙鲁里山岩浆弧在一个古老陆块基础上发展而形成。它们之间的俯冲、碰撞,造成柯鹿洞-亚金带的造山井抬升。这种造山作用不仅向西提供了大量的麋棱岩岩屑,而且在它们的西侧产生了措交玛-措莫隆滞后型花岗岩类;并形成了锡多金属矿化带。此外,弧一陆碰撞也是常见的另一种造山作用模式。文章的最后,指出了东特提斯构造域内板块会聚边缘盆地与岛弧遣山的一般特征。

Abstract:

The spatio-temporal distribution of the ophiolitic melanges and island-arc zones is emphasized in combination with the trench-arc-basin systems in the eastern Tethyan tectonic domain,for which three evolutionary stages of Eo-Tethys,Mid-Tethys and Neo-Tethys have been distinguished.The geological records of the ophiolitic melanges,mid-ocean ridge basalts,oceanic sediments and island-arc zones,which are recognized,have provided essential evidences for plate movement in the early oceanic lithosphere.The plate convergent margins in orogenic zones are characterized by all kinds of fore-arc,inter-arc and back-arc basins which are related with island arcs and formed in varying times and stages.Moreover,the formation and evolution of the distinctive basins are sujected to the effects and controls of different geological settings.It is obvious that most of the basins have experienced three stages of evolution,including rifting and extensional,steady sinking,and compressional and uplifting processes.The first stage is characterized by intense volcanic activities and well-developed fan-deltaic sediments;the second stage by mixed and low-density turbidity current deposits of carbonates and siliciclastics,and the early time of the third stage by the development of submarine fans.It is important that the features of recycling orogenesis in many basins are indicated by the terrigenous clastic sediments of quartzitic mylonite.There is a typical example for arc-arc collision between the Yidun island arc and Shalulishan magmatic arc,or even throughout eastern Tethys.The growth of the Yidun island arc records the transition from immature to mature arc on the basis of the early rift, whereas the Shalulishan magmatic arc was developed on an ancient landmass.The subduction and collision of the two arcs stimulated the uplifting of the Korlondo-Yajin zone.The ovogenesis not only brought westwards about a vast amount of mylonite clasts,but also resulted in the formation of the lag-type granitoids in the Cuojiaoma-Cuomolong zone and of Sn polymetatlic metallogenic zones in the west of Yidun.Besides,the arc-continent collision may be served as an additional model for orogenesis.Finally,the common features are also described for the basins and island arcs on the plate convergent margins in the eastern Tethyan tectonic domain.