Figure F7. SEM images of hydrothermal clay mineral assemblages (freshly broken surfaces). A. Altered glass (showing undulose anisotropism in thin section) from the upper cristobalite zone of Hole 1188A, composed chiefly of very fine grained pyrophyllite (Pyroph) with a crystal of disseminated anhydrite (Anhy), a mass of cristobalite (Crist), and a patch of coarser pyrophyllite flakes intergrown with cristobalite (Sample 193-1188A-9R-2 [Piece 1, 0–5 cm]; 69.10 mbsf; CSIRO 142653). B, C. Sample 193-1188F-26Z-1 (Piece 4, 62–64 cm); 300.72 mbsf; CSIRO 142684; (B) typical illite-chlorite quartz kernel assemblage from the quartz domain of Hole 1188F. Quartz (Qtz) grains and chlorite (Chlor) flakes are labeled; most other flakes are illite. Pyrite occurs elsewhere; (C) pale selvage composed principally of illite; quartz and anhydrite occur outside the field of view. D. Hydrothermal potassium feldspar (Kspar) intergrown with flakes of illite (majority of view) and grains of quartz. Pyrite and chlorite occur nearby (Sample 193-1189B-8R-1 [Piece 9, 33–36 cm]; 98.73 mbsf; CSIRO 142709).