Shock-produced akimotoite in the Suizhou L6 chondrite

• Published in: Science China. Earth sciences 2015-06, Vol.58 (6), p.876-880
• Main Authors: Chen, Ming, Xie, XianDe
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Geochemistry; Meteors & meteorites; MgSiO3; Minerals; Research Paper; Temperature gradients; Veins (geology); 带状区域; 温度梯度; 玻璃化; 球粒陨石; 缺陷区; 耳鼻喉科; 随州
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-014-5039-5

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 μm 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 MgSiO3-glass as irregular small clumps up to 5 μm 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 MgSiO3-glass （possibly vitrified perovskite） demonstrates a temperature gradi- ent from the vein wall to the unmelted chondritic meteorite.