“全新特提斯洋”概念与广义特提斯构造域

The proposition of Holo-Tethys Ocean and the generalized Tethyan tectonic domain

特提斯最初是指欧亚大陆南缘的古海洋,后逐渐引申出从元古宙、古生代到中生代的一系列位于劳亚大陆与冈瓦纳大陆之间的古大洋,如原特提斯洋、古特提斯洋和新特提斯洋,不同大洋在时间上前后交叠。如今横亘在冈瓦纳大陆(南极洲)和欧亚大陆之间的是印度洋,是新特提斯洋的继承者,可以另称为“全新特提斯洋”。这一概念的引申直接体现了印度洋与特提斯构造域一脉相承的关系,有助于将今论古、由此及彼,更直观地了解特提斯构造域的演化过程。本文按时间序列梳理了印度洋的大地构造演化和岩浆作用过程,识别了印度洋在155 Ma、120Ma、90~84Ma、76Ma、65Ma、52Ma、45Ma、38Ma等关键时期的异常海底扩张记录,这些扩张事件将为标定新特提斯构造域的演化提供参照。其中155Ma可能指示了新特提斯洋的鼎盛期,90Ma指示了新特提斯洋的洋中脊俯冲,76~52Ma是非洲-阿拉伯大陆与欧亚大陆初始碰撞-主碰撞(即新特提斯洋西部关闭)的时期,65~45Ma是印度次大陆与欧亚大陆初始碰撞-主碰撞(即新特提斯洋中部关闭)的时期,38Ma是澳大利亚北部大洋开始净俯冲(即新提斯洋东部开始消减)的时间。印度洋扩张历史的研究为理解新特提斯洋消亡提供参考标尺。站在“后方”印度洋的角度,可以更清晰地透视“前线”特提斯构造域的演化过程,为理解板块构造活动规律提供支撑。

The Tethys originally refers to the ancient ocean in the southern margin of Eurasia,but gradually extends to a series of ancient oceans from the Proterozoic,Paleozoic to Mesozoic,such as the Proto-Tethys,the Paleo-Tethys and the Neo-Tethys,in which different oceans overlap in time.Now what is stretching between Gondwana(Antarctica)and Eurasia is the Indian Ocean,the successor to the Neo-Tethys,namely the“Holo-Tethys”.The extension of this concept literally reflects the continuous relationship between the Indian Ocean and the Tethyan tectonic domain,which is helpful to understand the evolution process of the Tethyan tectonic domain more intuitively by studying the present process.In this paper,the tectonic evolution and magmatic processes of the Indian Ocean are summarized according to the time series,and the key seafloor spreading events at 155Ma,120Ma,90~84Ma,76Ma,65Ma,52Ma,45Ma and 38Ma are identified.These spreading events will provide references for the evolution of the Neo-Tethyan tectonic domain.The width of Neo-Tethys Ocean may culminate around 155Ma,while 90 Ma may indicate the subduction of the mid-ocean ridge of Neo-Tethys.76~52Ma is the time of initial collision and the main collision between African-Arab and Eurasia(i.e.,the western Neo-Tethys was closed),while 65~45Ma is time for the initial collision and the main collision between India and Eurasia(i.e.,the central Neo-Tethys was closed).And the eastern part of Neo-Tethys north of Australia may initiate its subduction at 38 Ma.The study of Indian Ocean spreading history provides a reference for understanding the extinction of the Neo-Tethys Ocean and the process of the India-Asia collision.From the perspective of the“rear”Indian Ocean,the evolution process of the“front”Tethyan tectonic domain can be more clearly understood.The movement of plates and the mechanism of plate tectonics can be further constrained by the study of generalized Tethyan tectonic domain.