高温高压下辉闪岩的部分熔融与弹性波速  

Partial Melting and Compressional Wave Velocities of Tebinite at High Temperature and Pressure

作　　者：蒋玺[1] 安邦[1,2] 唐波[1] 

机构地区：[1]贵州大学资源与环境工程学院,贵阳550025 [2]贵州大学研究生院,贵阳550025

出　　处：《地质科技情报》2013年第2期1-7,共7页Geological Science and Technology Information

基　　金：国家自然科学基金项目(40804019);矿床地球化学国家重点实验室开放研究基金项目(201013);贵州省科学技术基金项目(黔科合J字[2008]2251号)

摘　　要：在YJ-3000t高压装置上,利用超声波脉冲透射-反射法,测量了压力0.6～2.0GPa、室温至1 091℃条件下辉闪岩的纵波波速(vp),并对实验中间产物进行了取样和详细的显微观测统计。结果显示,0.6GPa压力下,室温至763℃,样品的vp下降了3.7%,vp的温度系数vp/T为-0.3×10-3 km/(s.℃),而763～1 025℃,vp快速下降了36.1%,vp/T达-9.7×10-3 km/(s.℃);1.0GPa压力下,室温至808℃,vp下降了3.2%,vp/T=-0.3×10-3 km/(s.℃),808～1 091℃时vp快速下降了41.5%,vp/T为-9.9×10-3 km/(s.℃);2.0GPa压力下,室温至927℃,vp下降了4.3%,vp/T为-0.2×10-3 km/(s.℃),927～1 087℃时,vp下降了20.9%,vp/T达-9.6×10-3 km/(s.℃)。实验产物观测表明,恒压下辉闪岩的vp首先随温度近线性缓慢降低,后由于岩石的脱水和部分熔融作用,导致vp急剧下降。随温度升高,实验产物中熔体的含量增加;同时形态上从封闭囊状逐渐向连通管状或薄膜状演化,连通程度增加。从角闪石一侧向斜长石一侧,熔体颜色变浅。样品初熔阶段,低黏度的熔体在矿物颗粒边界和裂隙中形成的微细薄膜,导致岩石vp随熔体含量增加急剧下降。研究证实,含水矿物脱水和岩石部分熔融是中、下地壳低速层的重要成因。With the pulse transmission-reflection method,ultrasonic measurements of compressional wave velocities（vp） for a tebinite were carried out in YJ-3000t multi-anvil apparatus up to 1 091℃ at the pressures of 0.6 GPa,1.0 GPa and 2.0 GPa.The testing products were investigated by microscope and electron-probe,which were obtained at different temperatures and pressures.The results show that the vp of tebinite decrease slowly with temperature up to 763℃（0.6 GPa）,808℃（1.0 GPa） and 927℃（2.0 GPa）.At the temperatures higher than these temperatures,because of dehydration of hornblende and epidote and partial melting of the rock,the vp decreases quickly with increasing temperature.The volume percentage of melt increases obviously,and its shape transforms to more connective film with increasing temperature.At the beginning of dehydration and partial melting,the melt with low viscosity moves into the microfissure and boundary of minerals to form into melt film,which results in the sharp decrease of vp of tebinite.It is proved that the dehydration and partial melting of rocks are important explanations for the seismic low velocity layer in crust.

关 键 词：高温高压 辉闪岩 矿物脱水 部分熔融 纵波波速 

分 类 号：P588.12[天文地球—岩石学]