The results show that significant reaction rates cause a weakening via the implementation of ductile shear zones that can be preceded by small brittle precursors. A careful analysis of the obtained acoustic signal, combined with an extensive microstructure analysis of the recovered samples, provided major insights into the interplay between transformation and deformation mechanisms. Deformation experiments were carried out in a new-generation Griggs apparatus, where micro-seismicity was recorded in the form of acoustic emissions. Ge-olivine adopts a ringwoodite structure at pressures ~14 GPa lower than its silicate counterpart does, making the transformation accessible with a Griggs rig. In this study, germanium olivine (Ge-olivine) was used as an analogue material to investigate the rheology of samples undergoing the olivine–ringwoodite transformation. These transformations have important rheological consequences, since they may induce weakening, strain localization, and, in some cases, earthquakes. ( E ) Electron diffraction patterns of the gouge and adjacent wall rock display bright olivine spots and numerous spinel spots emanating from the gouge itself.Īs it descends into the Earth’s mantle, the olivine that constitutes the lithosphere of subducting slabs transforms to its high-pressure polymorphs, wadsleyite and ringwoodite, in the so-called transition zone. The fracture walls are intensely deformed. The gouge consists of fully crystalline nanometric material. Dashed lines highlight the main fault, only 100 nm thick. ( D ) Close-up TEM view of the fault zone.
The red line indicates the location of the FIB section (D). ( C ) A narrow band of light gray material highlights the fault. The red box corresponds to the location of (C). The white grains are Ge-enstatite (MgGeO 3 ), and the gray grains are Ge-olivine, the grain size of which are <10 and 150 m m, respectively. ( B ) High-magnification view of one of the fracture planes. The red box corresponds to the location of (B). Horizontal fractures are likely to have been caused during decompression.
#DEEPFOCUS ONLY ITEM CONTENT AREA FULL#
( A ) Full view of the sample ( s 1 is vertical). Electron micrographs of sample D1253, which failed at 5 GPa. Microstructure of the transformed fault zone.
0 kommentar(er)
