深部地壳镁铁质岩石波速的研究  

INVESTIGATIoN ON COMPRESSIONAL WAVE VELOCITIES OF MAFIC ROCKS IN DEEP CRUST

作　　者：张友南[1] 马瑾[1] 

机构地区：[1]国家地震局地质研究所,北京100029

出　　处：《地球物理学报》1997年第2期221-230,共10页Chinese Journal of Geophysics

基　　金：国家自然科学基金

摘　　要：镁铁质、超镁铁质岩石波速实验测量在高压700-800MPa、高温800-1100℃下进行．波速-温度曲线的斜率以温度系数dVp／dT表示，大体在700℃以内，8个标本的温度系数平均为-1．86×10-4km·S-1／℃，比资料值小得多，即在此温度范围内，波速随温度的降幅不大．在这一温度限以上，大多岩石开始脱水出溶，相组合发生变化，同时波速大幅度下降．曲线发生转折的机制是岩石中液相的产生．角闪岩波速曲线斜率也从700℃开始发生改变，950℃后速度直线下降，到1008℃时，岩石中液量达30％，波速Vp值下降到487km／s．最后，依岩类不同以及岩石出溶和相变对波速的影响划分出5个速度-温度区，讨论了华北断块内构造隆起区和沉降区下地壳可能存在的岩石及其状态．Experimental measurements of wave velodhes Vp of mafic and ultromafic rocks wer carried out at condihons of P=700-80MPa, T=80-1100℃.At theperabo roughly be low 700℃, the slopes of velodty-temperature curves in this paper are much smaller than that in the othe materials. And above that temperature dehydrahon-exsolution reaction occurs with which the veloicties of the rocks have a sharply dropping down. Itis suggested that as pressure reaches the value in this paper, mechamism to take the curve a turn is liquid to develop in the rocks, instead of microfracture to open. The slope of the velocity curve in the amphibolite also begins to change at 700℃ in temperature' The velocity from 6.80km /s near 700℃ drops down to 4.87 km /s at 1008℃ while the amount of liquid in the rock is about 30% in volume. Fnally, 5 velocity-temperature areas are divided according to different kind of rocks and to the effect of exsolution and transition of the rocks on wave velocity, and with this division probable rocks and their states existed in the lower crust of structural rising zone and sinking zone in the Chinese Northern fault block are discussed.

关 键 词：地壳 镁铁质岩石 波速 

分 类 号：P588.242[天文地球—岩石学]