高压下岩浆凝固对岩石圈力学状态的影响

Effect of Magma Solidification under High Pressure on Mechanical State of Lithosphere

板块构造活动与岩石圈密切相关,是地震等重大地质活动的物理源,但其动力机制尚不清楚。为此,通过分析地球内部处于高压环境的岩浆凝固对岩石圈力学状态的影响,探究板块运动的力源机制。地球作为一个整体不断向外太空散发热量,内部是处于高压高温下的液-固共存状态。自地球形成以来,熔融岩浆的凝固过程持续至今,液-固转变将导致地球内部的密度变化和潜热释放,从而降低刚性岩石圈底部的压力及其支撑力。研究发现,岩石圈的强度不足以支撑其自重,底部的压力(强)波动会使其力学结构失稳。受刚性、脆性岩石圈的约束,地球内部处于高压环境的岩浆凝固必然导致岩石圈力学状态发生变化,在重力作用下,板块之间的相互作用加剧,局部应力积累会超过岩石的强度极限,导致岩石圈内部发生破裂,所积累的应力通过地震等地质活动形式在岩石圈薄弱地带释放,并自我调整以达到新的力学平衡,而板块边界就是岩石圈的最薄弱区域,所以该区域的地震活动频繁发生。上述过程是不断重复的,这就是板块运动驱动力的来源。

Plate tectonic activity is closely related to the lithosphere and is the physical source of major geological activities such as earthquakes,but its dynamic mechanism is not clear.This paper will explore the force source mechanism of plate movement by analyzing the influence of magma solidification in a highpressure environment inside the Earth on the mechanical state of the lithosphere.The Earth as a whole is constantly radiating heat into outer space,and its interior is in a state of liquid-solid coexistence under high pressure and high temperature.The solidification process of molten magma has continued since the formation of the Earth,and this liquid-solid transition will result in density changes and latent heat release in the Earth’s interior,reducing the pressure and supporting force at the bottom of the rigid lithosphere.We found that the lithosphere is not strong enough to support its dead weight,and any pressure fluctuations at the bottom destabilize its mechanical structure.Due to the constraint of rigid and brittle lithosphere,the solidification of magma under high pressure in the Earth will inevitably lead to the change of the mechanical state of the lithosphere.Under the action of gravity,the interaction between plates intensifies,and local stress accumulation exceeds the strength limit of rocks,leading to fracture in the lithosphere.The accumulated stress is released in the weak zone of the lithosphere through geological activities such as earthquakes and adjusts itself to reach a new mechanical equilibrium.And plate boundaries are the weakest parts of the lithosphere,so there’s a lot of seismic activity.The above process is repeated over and over again,and this is where the driving force of plate movement comes from.