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Shock-produced akimotoite in the Suizhou L6 chondrite

Science China Earth Sciences 2015年第6期58卷 876-880页

作者： CHEN Ming XIE XianDe State Key Laboratory of Isotope Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Key Laboratory of Mineralogy and Metallogeny Guangzhou Institute of Geochemistry Chinese Academy of Sciences

Shock-produced akimotoite was identified in the Suizhou chondritic meteorite, which occurs in two kinds of occurrence. The first is the irregular layers of akimotoite up to 4 ?m in thickness occurring in fractures and cracks of low-Ca pyroxene enclosed in the shock veins. The second is the zonal polycrystalline aggregates of akimotoite in shocked pyroxene grains close to the shock vein, where akimotoite occurs in a zonal area in between pyroxene and Mg Si O3-glass as irregular small clumps up to 5 ?m in size. This investigation suggests a solid-state transformation mechanism of pyroxene to akimotoite, and that akimotoite should have nucleated and grew in the area with abundant defects caused by shock deformation because the defect significantly enhances the solid-state reactivity and the kinetics of nucleation of high-pressure phase. The spatial relationship among the composed grains of pyroxene, akimotoite and Mg Si O3-glass(possibly vitrified perovskite) demonstrates a temperature gradient from the vein wall to the unmelted chondritic meteorite.

关键词： pyroxene akimotoite perovskite shock vein Suizhou meteorite

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Elastic properties of Fe-bearing akimotoite at mantle conditions: Implications for composition and temperature in lower mantle transition zone

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Fundamental Research 2022年第4期2卷 570-577页

作者： Yajie Zhao Zhongqing Wu Shangqin Hao Wenzhong Wang Xin Deng Jian Song Laboratory of Seismic and Physics of Earth's Interior School of Earth and Space SciencesUniversity of Seience and Technology of ChinaHefei 230026China National Geophysical Observatory at Mengcheng University of Science and Technology of ChinaHefeiChina CAS Center for Excllence in Comparative Planetology UsTcHefei 230026China Institute of Geophysics and Planetary Physics Scripps Institution of OeanographyUniversiy of California San DiegoLa Jolla 92092CAUSA Departnent of Earth Sciences University CollegeLondonLondon WCIE6BTUnited Kingdom Earth and Planets Laboratory Carnegie Instution for ScienceWashingtonDC 20015UsA

The pyrolite model,which can reproduce the upper-mantle seismic velocity and density profiles,was suggested to have significantly lower velocities and density than seismic models in the lower mantle transition zone(MTZ).This argument has been taken as mineral-physics evidence for a compositionally distinct lower ***,previous studies only estimated the pyrolite velocities and density along a one-dimension(1D)geotherm and never considered the effect of lateral temperature *** the majorite-perovskite-akimotoite triple point is close to the normal mantle geotherm in the lower MTz,the lateral low-temperature anomaly can result in the presence of a significant fraction of akimotoite in pyrolitic lower *** this study,we reported the elastic properties of Fe-bearing akimotoite based on first-principles *** with literature data,we found that the seismic velocities and density of the pyrolite model can match well those in the lower MTZ when the lateral temperature heterogeneity is modeled by a Gaussian distribution with a standard deviation of~10o K and an average temperature of dozens of K higher than the triple point of *** suggest that a harzburgite-rich lower MTZ is not required and the whole mantle convection is expected to be more favorable globally.

关键词： akimotoite Pyrolite Elasticmoduli Temperature heterogeneity Gaussian distribution

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