高温高压下闪长岩的相变与纵波波速  

Phase Transformation and Compressional Wave Velocities of Diorite 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,贵州贵阳550003 [2]贵州大学研究生院,贵州贵阳550025

出　　处：《矿物学报》2012年第4期507-514,共8页Acta Mineralogica Sinica

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

摘　　要：利用脉冲透射-反射法,在YJ-3000 t高压装置弹性波速测量系统上,测量了0.6、1.0和2.0 GPa,最高1141℃条件下闪长岩的纵波波速(vp)。结果显示,高压下闪长岩的vp随温度升高首先缓慢降低,分别到769℃(0.6 GPa)、810℃(1.0 GPa)和925℃(2.0 GPa)后转而快速下降。实验产物观测显示,0.6 GPa下岩石在758℃时发生脱水熔融并有新生单斜辉石生成,1.0 GPa和2.0 GPa下,闪长岩分别在865℃和921℃的实验产物中出现熔体,新生矿物有单斜辉石和石榴子石。温度升高导致闪长岩中熔体含量增加,斜长石、角闪石和绿泥石等逐渐减少直至消失,单斜辉石和石榴子石呈先增加后减少趋势。探针分析显示,熔体含水量较高,且随温度升高熔体成分向基性方向演化。单斜辉石化学成分变化不明显,2.0 GPa下,随温度从1030℃升高到1138℃,新生石榴子石成分逐渐向钙铝榴石变化。vp变化和熔体含量关系表明,熔体含量增加导致了闪长岩在高温阶段波速的持续快速降低。With pulse transmission-reflection combined method, compressional wave velocity （Vp） of diorite was measured at temperatures up to 1141 ℃ and under pressures of 0.6, 1.0 and 2.0 GPa, respectively, by using the YJ-3000t multi-anvil apparatus equipped with ultrasonic measurement system. The vp of diorite decreases slowly with elevating temperature up to 769, 810 and 925℃ under different pressures of 0.6, 1.0 and 2.0 GPa, respectively. And then the velocities of diorite decrease fast. By investigating the products, it is found that diorite is partially molten at 758, 865 and 921 ℃under pressures of 0.6, 1.0 and 2.0 GPa, respectively. With increasing temperatures, the volume percentages of melt increase but the percentages of original minerals decrease obviously, such as plagioclase, hornblende, chlorite and so on. Electron probe inspection indicates that melting in the products has high water content and becomes more rich in basic content with increasing temperatures. Under 2.0 GPa, the new garnets transform toward grossular with increasing temperatures from 1030 to 1138 ℃. The analysis results prove that dehydration and partial melting in diorite are responsible for the nonlinear declines of vp at high temperature under different pressures.

关 键 词：高温高压 相变 部分熔融 闪长岩 纵波波速 

分 类 号：P313[天文地球—固体地球物理学] P579[天文地球—地球物理学]