Figure F37. Visual estimation of olivine alteration in thin sections from Hole 735B vs. depth. A. Average degree of alteration of olivine. B. Percentage of talc after olivine in the secondary mineral assemblage. Magnetite is generally associated with talc. C. Percentage of smectite after olivine in the secondary mineral assemblage. Variable amounts of sulfide minerals or carbonate + oxyhydroxide are commonly intergrown with smectite. D. Percentage of amphibole after olivine in the secondary mineral assemblage. Amphibole forms microcrystalline reaction rims around olivine.