岩石の摩擦と流動に対する熱水および化学反応の影響:主要未解決問題  [in Japanese] Effccts of hydrothermal fluids and chemical reactions on friction and flow of rocks : major unsolved problems  [in Japanese]

岩石の摩擦と流動に対する熱水および化学反応の影響に関して, 主要な未解決問題を指摘し, 今後の研究課題を提言した。熱水条件下の岩石の摩擦特性に関しては, 300℃以上の熱水条件下における, 摩擦強度低下および変位速度依存性の起源の解明と, これらが大変位量においても適用可能かどうかの検証が必要である。また, 他の造岩鉱物とは異なる摩擦特性を示す粘土鉱物を含む, 熱水変質ガウジの摩擦特性の解明が必要である。延性剪断変形においては, マイロナイトの基質を構成し, マイロナイトや延性剪断帯の変形特性を支配していると考えられる細粒多相反応生成物の, 試料観察に基づく変形過程の解明に加えて, 変形実験による流動則や変形機構の解明が必要である。

Major unsolved problems on the effects of hydrothermal fluids and chemical reactions on friction and flow of rocks are summarized as below. At hydrothermal conditions, frictional strength of rocks dramatically decreases with creasing temperature at temperatures above 300℃. Accordingly velocity dependence of friction changes from negative to positive at ★300℃. But the origins of the reduced frictional strength and the velocity-dependence change remain unknown. Experiments up to large displacements should also be challenged in order to test the applicability of these frictional properties to seismogenic faulting. Hydrothermally altered fault gouges contain clay minerals whose frictional properties are different from other rock-forming minerals. Frictional properties of clay minerals and their relations to water are, however, poorly understood. Polyphase reaction products composing fine-grained matrix in mylonites likely control the rheology of mylonites and ductile shear zones. But their deformation processes and rheology are not well understood. Both detail micro structural observations of fine-grained polyphase matrix in mylonites and experimental investigations on their flow properties and deformation mechanisms are needed.