冲绳海槽岩浆物理化学性质及其地质意义

The physico-chemical features and their geological implications of magma in the Okinawa Trough

借助冲绳海槽火山岩地球化学分析结果,讨论了海槽不同区段岩浆的温度、压力、密度和黏度等物理化学参数,以确定海槽岩浆的物理性质及其对海槽不同区段岩浆演化过程的影响。海槽北段的岩浆相对于中段表现出高压力、低温度的特征。由于海槽岩浆挥发分含量较高,北段岩浆的密度和黏度要高于中段的。但总的来说,海槽岩浆具有低密度、低黏度的特点,因此岩浆更容易穿透岩石圈,而且有利于岩浆结晶分异作用的进行。对海槽岩浆相对运移速度的研究显示,在外部条件及含水量相同的前提下,在海槽中段岩浆上升速度要大于北段的,这从岩浆物理化学性质的角度解释了为何海槽中段火山活动要强于北段的。

On the basis of geochemical data of volcanic rocks, the variety of physo-chemical parameters, including temperature, pressure, density and viscosity, was studied to understand features and development of magma in the Okinawa Trough. The following conclusions were obtained： （1） the magma under the northern Okinawa Trough held higher pressure and lower temperature than those of magma under the mid- dle Okinawa Trough; （2） the magma of the northern Okinawa Trough had higher value of density and viscosity than that of the middle Okinawa Trough because the magma enriched volatile; （3） the low density and viscosity of magma under the Okinawa Trough were of advantage topentrate lithosphere and played fractional crystallization; and （4） under the same environmental conditions and water content, the uplifted velocity of magma in the middle Okinawa Trough was higher than that in the northern Okinawa Though. It could explain why magmatism in the middle Okinawa Trough was more drastic than in the northern Okinawa Trough.