950℃、1.0～3.5GPa下斜长角闪岩脱水熔融--压力和时间对结构的影响  

Textural development of dehydration-melting in amphibolite at 1.0-3.5 GPa and 950 ℃—Effect of pressure and time

作　　者：周文戈[1] 范大伟[1,2] 万方[1,2] 邢印锁[1,2] 刘永刚[1] 谢鸿森[1] 

机构地区：[1]中国科学院地球化学研究所地球深部物质与流体作用地球化学实验室,贵州贵阳550002 [2]中国科学院研究生院,北京100049

出　　处：《地学前缘》2009年第1期146-154,共9页Earth Science Frontiers

基　　金：国家自然科学基金项目(40873052);中国科学院知识创新工程重要方向项目(KJCX2-SW-N20);西部之光联合学者项目(2008年度)

摘　　要：利用YJ-3000t和JL-3600t多顶砧压力机,以哀牢山造山带南部红河县大白能—乐育剖面上的天然块状斜长角闪岩为初始样品,在950℃、1.0～3.5GPa、恒温20～300h条件下进行了两个系列的斜长角闪岩块状样品脱水部分熔融实验:(1)保持温度T=950℃,加热时间t=100h不变,改变压力(1.0～3.5GPa)的实验;(2)保持温度T=950℃,压力p=3.0GPa不变,改变加热时间(20～300h)的实验。结果表明,1.0～3.5GPa、950℃、恒温100h的条件下,随压力升高,斜长角闪岩中依次生成了单斜辉石+石榴石+熔体的矿物组合(1.0～1.5GPa)和单斜辉石+石榴石+熔体+硬玉+SiO2矿物+蓝晶石(2.0～3.5GPa)的矿物组合。3.0GPa、950℃条件下,随加热时间增加,实验产物中依次生成了单斜辉石+石榴石+熔体+硬玉+SiO2矿物+蓝晶石的矿物组合(20～100h)和单斜辉石+石榴石+熔体的矿物组合(150～300h)。斜长角闪岩的原岩结构决定了实验产物中新生矿物和熔体的分布。依据实验产物的矿物组合和新生矿物的分布特征,讨论了950℃、1.0～3.5GPa、恒温(20～300h)条件下,斜长角闪岩部分熔融过程的结构变化、变质反应以及石榴石冠状体的成因。Two sets of dehydration-melting with a natural solid amphibolite（56vol.% hornblende, 43vol.% plagioclase）, collected from the Dabaineng-Leyu profile in the southern Ailaoshan orogenic belt, Honghe County, Yunnan Province, have been carried out in multi-anvil apparatus（YJ-3000t and JL-3600t） at 1.0-3.5 GPa and 950 ℃ for 20-300 h. One is keeping the temperature at 950 ℃ and the annealing time of 100 h, varying the pressure （1.0-3.5 GPa）. The other is keeping the pressure at 3.0 GPa and temperature at 950 ℃, varying the annealing time （20-300 h）. The products are inspected with microscope and electron probe. The results indicate that at 950 ℃, annealing time of 100 h, as the pressure in the range of 1.0-1.5 GPa, the min eral assemblage in the products is clinopyroxene＋ garnet ＋ melt. As the pressure larger than 1.5 GPa, the mineral assemblage in the products is clinopyroxene ＋ garnet ＋ melt ＋ Jadeite ＋ SiO2 ± kyanite. However, at 3.0 GPa and 950 ℃, as the annealing time in the range of 20-100 h, the mineral assemblage of clinopyroxene ＋garnet＋melt＋Jadeite＋SiO2 ±kyanite appears successively with time in the products. As the annealing time longer than 100 h, the mineral assemblage of clinopyroxene＋garnet＋melt appears in the products. The distribution of the newly-formed minerals and melt is restricted by the texture of the started amphibolite. Based on the mineral distribution and assemblage in the run products at 1.0-3.5 GPa and 950 ℃ for 20-300 h, the textural development of amphibolite during the partial melting process, the metamorphic reaction, and the garnet corona generation are discussed.

关 键 词：高温高压 斜长角闪岩脱水熔融 结构变化 变质反应 石榴石冠状体 

分 类 号：P589.1[天文地球—岩石学] O52[天文地球—地质学]