冲击变质陨石橄榄石晶内高压多形转变特征与条件  

FEATURES AND CONDITIONS FOR THE INTRACRYSTALLINE TRANSFORMATION FROM OLIVINE TO HIGH-PRESSURE POLYMORPHS IN SHOCK-METAMORPHOSED METEORITES

作　　者：陈鸣[1] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640

出　　处：《矿物学报》2009年第1期1-6,共6页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(批准号:40672035);中国科学院知识创新工程项目(批准号:KJCX2-SW-N20))

摘　　要：对2个不同冲击变质程度球粒陨石研究表明,橄榄石晶内高压多形转变可在较低温度(<1000℃)和较大压力范围内(14.5～23GPa)产生。橄榄石晶内高压相转变主要是形成薄层状林伍德石,不发生直接的橄榄石-瓦士利石转变。由微晶集合体组成的薄层状林伍德石多沿着橄榄石中层错和面状裂隙分布并替代母相橄榄石。某些陨石中橄榄石产出薄层状瓦士利石和薄层状林伍德石组合,这些瓦士利石的形成与退变质作用有关,是压力释放过程林伍德石被瓦士利石替代的结果。研究结果对探讨岩石圈俯冲板块橄榄石多形转变环境和温度压力条件具有一定的参考意义。An investigation into two shock-metamorphosed chondritic meteorites indicates that the intracrystalline transformations from olivine to high pressure polymorphs could take place at relatively low temperature （ 〈 1000 ℃ ） in a large pressure regime （14. 5 to 23 GPa）. The intracrystalline transformation of olivine produced lamellar ringwoodite. No direct intracrystalline transformation from olivine to wadsleyite was observed. The lamellar ringwoodite consisting of crystallite aggregates replaced parent olivine along staking faults and planar fractures. An association consisting of wadsleyite and ringwoodite platelets, respectively, has also been observed in olivine of some meteorites. The wadsleyite was produced by replacing ringwoodite during pressure release as a result of retrograde-metamorphism. This study provides information for understanding geological settings and pressure and temperature conditions for the polymorphic transformation of olivine in the Earth＇ s lithospheric subducting slabs.

关 键 词：橄榄石 高压多形 晶内转变 陨石 冲击变质 

分 类 号：P541[天文地球—构造地质学] P571[天文地球—地质学]