R3: High-pressure science and deep Earth's material

[R3-12] Mineralogical characteristics of nano-polycrystalline diamond in pseudotachylyte from Nishisonogi metamorphic rock

*Hiroaki Ohfuji¹, Tadao Nishiyama² (1. GRC, Ehime Univ., 2. Kumamoto Univ., Sci)

Keywords:Nano-polycrystalline diamond, Pseudotachylyte, Microtexture, TEM

Here we report the mineralogical characteristics of nano-polycrystalline diamond grains included in quartz-carbonate pseudotachylyte in Nishisonogi metamorphic rock. The diamond grains are 1-2 μm and show angular to pseudo-euhedral shapes surrounded by amorphous carbon. They consist of very well-sintered diamond crystals of <5 - 20 nm and contain no pores simialr to nano-polycrystalline diamond synthesized by the HPHT direct conversion of graphite.