论全球岩石圈板块构造的动力学机制

On the dynamic mechanics of global lithosphere plate tectonics

全球板块构造的动力学机制问题是一个热门但至今尚未解决的难题。本文首先回顾了近百年来大地构造学的各种主要假说和近四十年来板块构造学说的许多新进展。在上述研究的基础上,受Rampino和Stothers关于陨击作用可引起地表重大灾变事件思想的启发,笔者提出了一个新的假说。基于中、新生代(200 Ma以来)每隔33 Ma太阳系就会穿越一次银河系星际物质密集的银道面,诱发太阳系内部引力场的巨变,使部分小行星失稳,从而撞击地球。笔者根据用以描述中生代以来全球板块构造的七种不同的运动模式,提出了巨大陨星在不同地点、以不同角度撞击地表岩石圈,可能诱发地幔底辟的形成,从而推动板块呈放射状或单向运移的假说,也即在200、170、100、65和0.78Ma等时期的陨击事件基本上是垂直地表面而撞击的,从而诱发地幔底辟的形成和岩石圈板块的放射状张裂和运移;138 Ma的陨击事件可能是指向印度板块的斜向撞击;而35 Ma时期的微玻璃陨石撞击事件则是陨石以极低角度撞击地球表面的表现。陨石撞击地球,这是太阳系内部各星体之间引力作用变化的表现,因而此假说不是什么外因作用论。

The dynamic mechanics of global plate tectonics, a hot topic in Earth Science, is a difficult and unsolved problem. This paper reviewed the main plate tectonics hypotheses of the last hundred years as well as critical new knowledges of the past forty years. Drawing inspiration from Rampino ＆ Stothers＇ hypothesis of 1984, which relates periodic comet impacts to global change, the author proposed here a new plate tectonic dynamics hypothesis. As record shows, during the Mesozoic - Cenozoic of the last 200 Ma, the solar system penetrated the Milky Way galactic plane every 33 Ma. The events greatly altered the gravitational field in the solar system, causing destabilization of some asteroids that could then impact the Earth. Based on the seven different orientation-migration models for the global plate tectonics of the last 200 Ma, the author proposed the following hypothesis： giant meteorites impact the lithosphere surface with different impact angles at different locations; such impacts could then sometimes induce mantle diapirs, causing plates to migrate radially or in one orientation depending on the impact angle. Thus, giant meteorite impacts in the periods of 200, 170, 100, 65 and 0.78 Ma were all near vertical impacts to Earth＇s surface, as they induced mantle diapirs and led to radiating extension and migrations of the lithosphere plates. In contrast, the 138 Ma giant meteorite impact event could be an oblique impact to the Indian Plate; and in the period of 35 Ma, the microtektites event exhibited a very low impact angle to the Earth＇s surface. According to this new hypothesis, meteorite impact on Earth is a result of interplanetary gravity change within the solar system.