冈底斯陆壳属性与显生宙生长演化

Nature and Evolution of Crust in the Southern Lhasa During Phanerozoic

陆壳是孕育人类与高等陆地生命的摇篮,为人类文明的发展和延续提供了最重要的资源,是地球最重要的宜居要素之一。陆壳的形成时间与机制是地球科学研究长期关注的核心科学问题之一。其中,板片构造运动活跃的近10亿年,特别是显生宙以来,陆壳的形成与演化可能不同于太古代时期。因此,板片构造体系主导下陆壳的形成、保存与演化是当代地壳生长研究的重要方向之一。位于青藏高原南部的冈底斯造山带历经了特提斯洋俯冲、印亚大陆碰撞和碰撞后演化等丰富的动力学过程,出露有晚古生代以来的大规模岩浆岩,记录了丰富的地壳生长信息,是开展不同构造环境下地壳生长差异性研究的天然实验室。我们近期的研究指示冈底斯造山带所处的南拉萨地块是具有前寒武纪结晶基底的微陆块,其陆壳主体形成于元古宙。显生宙以来南拉萨地块在特提斯洋演化和大陆碰撞等复杂地质演变过程中经历了强烈的地壳生长和置换再造。研究显示,晚古生代泥盆纪末期前南拉萨陆壳已有50%以上的新生地壳组分,指示存在重要的古生代地壳生长事件。此外,早侏罗世可能是南拉萨地块新生地壳物质增加最重要的时期之一,而大陆碰撞和后碰撞阶段陆壳净生长的评估仍需更多工作验证。

Continental crust is the cradle of human and other advanced terrestrial life,providing resources for the development and continuation of human civilization,and is one of the basic elements of the earth’s habitability.The formation time and mechanism of continental crust is one of the primary scientific issues in earth science.The formation mechanism of primary continental crust in Archean is different from that during the latest 1 billion years,especially since Phanerozoic,when the formation and evolution of continental crust dominated by plate tectonic system.The Gangdese orogenic belt located in the southern Lhasa block of the Tibetan Plateau,experienced geological evolution from the Tethyan ocean subduction to Indo-Asian continental collision and post-collision with abundant magmatic records,and it is regarded as a natural laboratory for studying the plate tectonics dominated crustal growth during Phanerozoic.Our studies suggest that the southern Lhasa block is a microcontinent with Precambrian crystalline basement.The most of continental crust in the southern Lhasa block was mainly formed in Proterozoic and experienced intense crustal growth,reworking and replacement during Tethyan ocean evolution and continental collision.By the end of Devonian,juvenile crustal components in the continental crust in South Lhasa block had reached more than 50%,suggesting the existence of unknown important Paleozoic crustal growth events.In addition,there is an important crustal growth during Early Jurassic,but significant crustal growth in the South Lhasa block during syn-and post-collisional stages lacks robust evidence.All these will promote the understandings on crustal growth and evolution of the southern Lhasa.