河北大麻坪超基性岩包体的岩石组构和地震波速各向异性

Lattice Preffered Orientation and Seismic Anisotropy of Ultramafic Xenoliths in Damaping,Hebei Province

通过系统测定大麻坪尖晶石二辉橄榄岩、尖晶石方辉橄榄岩和含长二辉岩三类超基性岩包体中各主要矿物的晶格优选方位 (LPO) ,并用理论计算和实验测量得出地震波在岩石不同方向上的传播速度。结果表明 :1)大麻坪包体中橄榄石与斜方辉石的LPO方位关系与通常所见的[10 0 ]ol [0 0 1]opx,[0 10 ]ol [10 0 ]opx,[0 0 1]ol [0 10 ]opx不同 ;2 )大麻坪地区幔源包体的波速各向异性显著 ,岩石的波速各向异性特征与其宏观构造和微观组构一致 ,说明岩石组构是造成地震波速各向异性的决定因素 ;3)由地震波速推测的大麻坪地区的上地幔成分与包体出露的情况一致 ,即主体为二辉橄榄岩。

The LPO of main minerals of ultramafic xenoliths including spinel lherzolite,spinel harzburgite and plagioclase bearing websterite which collected from Damaping,Hebei Province is analyzed and the seismic velocities of the rocks in X,Y,Z directions are obtained by two means:calculation and measure.Our investigations are summed as follows: 1) The LPO relations between olivine and orthopyroxene are different from usually situations:[100]ol//[001]opx,[010]ol//[100]opx,[001]ol//[010]opx; 2)The seismic anisotropy of the ultramafic rocks in Damaping is obvious.Their characters are consistent with the structures of the rocks and fabrics of minerals,which means seismic anisotropy is mainly controlled by rocks'fabrics; 3) Seismic velocities suggest that the composition of upper mantle in Damaping region is resemble to the xenoliths,which major component is lherzolite.