[S-MP29] 鉱物の物理化学

[SMP29-01] カルサイトの衝撃変形における転位組織変化

★招待講演

*富岡 尚敬¹、黒澤 耕介²、三宅 亮³、伊神 洋平³、永冶 方敬^4,5、野口 高明³、松本 徹³、宮原 正明⁶、瀬戸 雄介⁷ (1.海洋研究開発機構高知コア研究所、2.神戸大学人間発達環境学学研究科、3.京都大学大学院理学研究科、4.東京学芸大学環境科学分野、5.早稲田大学教育・総合科学学術院、6.広島大学大学院先進理⼯系科学研究科、7.大阪公立大学理学研究科)

キーワード：カルサイト、衝撃変形、転位、透過電子顕微鏡

Shock recovery experiments were performed using a two-stage light gas gun to clarify the progressive deformation microstructures of calcite at the submicron scale concerning pressure. Decaying compression pulses were produced using a projectile that was smaller than the natural marble target. In two experiments, natural marble samples were shocked to 13 and 18 GPa at the epicenters of the targets. Calcite grains shocked in the pressure range of 1.1–18 GPa were examined using polarized light microscopy and (scanning) transmission electron microscopy. The density of free dislocations in the grains shocked at 1.1–2.2 GPa [10^8–9 (cm^-2)] is comparable to that of unshocked Carrara calcite grains. Subparallel bands of entangled dislocations less than 1 µm are formed at 4.2 GPa, and strongly entangled dislocations spread throughout the focused ion beam (FIB) sections at 7.3–18 GPa pressures. Dislocations selectively nucleate and entangle near the slip planes at pressures above ~3 GPa, corresponding to the transition from sharp extinction to undulatory extinction, according to the microstructural evolution with shock pressure. Above approximately 6 GPa, the dislocations nucleated homogeneously throughout the calcite crystals.