岩浆脉动结晶的实例:山东伟德山岩体

伟德山花岗岩体位于胶东半岛的东部。燕山运动晚期,地下深处形成的岩浆由于重力不稳性和构造减压而发生上升,并侵入于地壳上层,结晶成岩。早期结晶的是熔点较高,暗色矿物较多的组分,因对流及扩散作用发生分异,形成边缘岩带;由于脉动作用,岩浆冲破早先结晶的岩石,岩浆体一方面上升,一方面扩大体积,并继续结晶,从而形成过渡岩带;进而又一次岩浆脉动,形成中心岩带。由于这种脉动作用,形成成分、结构、构造都呈近同心分带的伟德山岩体。

WEIDESHAN PLUTONIC COMPLEX,AN EXAMPLE OF MAGMATIC PULSATING CRYSTALLIZATION

The Weideshan complex located at the eastern edge of Jiaodong Peninsular. At the late stage of Yanshan movement, the rocks at the deep crust level were partially melted.The melt uplifted and filled the preexisted fractures at shallow level of crust.Because of the instablity of gravity and the decreasing of pressure,in situ crystallization took place.The magma,with the decreasing of temperature,solidified from the'margins inward.The relatively mafic-rich high-temperature assemblages.This solidification was interrupted twice by the surges of fluid core magma and the magma eroded the adjacent solidifying or solidified rocks.Then,the volume of the magma chamber was expanded at the exposed level by crowding the wall rocks.It is the surge or pulse that formed the circular-like distributions of composition,texture and structure.