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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。
The study on two chondrites with different degrees of impact metamorphism shows that the intraocular high-pressure polymorphic transformation of olivine can be produced at lower temperature (<1000 ℃) and larger pressure range (14.5 ~ 23GPa). The high-pressure phase transition in olivine is mainly the formation of laminar forestwood, and no direct olivine-washilite transformation takes place. The thin layer of forestwood composed of a collection of microcrystals distributes along the mid-fault and surface fissures of the olivine and replaces the parent olivine. In some meteorites, olivine produces thin layered washilite and thin-shelled forestwood assemblages. The formation of these washilites is related to retrogressive metamorphism and is an alternative to Wollastonite under pressure release. result. The results of the study are of some reference significance for the exploration of polymorphic transitional environment and temperature-pressure conditions of olivine subducting lithospheric plates.