Figure F10. Downhole profiles of volume expansion during hydrothermal alteration for Sites 1188 and 1189. Symbols denote the petrographic categories set out in Table T1. Circled symbols ("exact") denote altered samples with measured specific gravity (SG) (from Binns, Barriga, Miller, et al., 2002); for others the SGs of nearby analogous samples were used in calculations. Volume expansion = SGparent/SGsample/X, where X = ratio of immobile element content in the altered sample to that of its presumed parent (averaged for Zr and Ti). The plots do not account for precursor vesicularity. Vuggy altered andesites (Category A and one Y-K) and a vuggy bleached dacite (69.1 mbsf) in Hole 1188A show exceptional expansion, reflecting high fluid pressures during alteration. Precursor SGs obtained by reference to measurements on Pual Ridge glasses and microlitic glasses (unpublished CSIRO data), using Zr/TiO2 to compute precursor composition.

Figure F10. Downhole profiles of volume expansion during hydrothermal alteration for Sites 1188 and 1189. Symbols denote the petrographic categories set out in Table T1. Circled symbols ("exact") denote altered samples with measured specific gravity (SG) (from Binns, Barriga, Miller, et al., 2002); for others the SGs of nearby analogous samples were used in calculations. Volume expansion = SG_parent/SG_sample/X, where X = ratio of immobile element content in the altered sample to that of its presumed parent (averaged for Zr and Ti). The plots do not account for precursor vesicularity. Vuggy altered andesites (Category A and one Y-K) and a vuggy bleached dacite (69.1 mbsf) in Hole 1188A show exceptional expansion, reflecting high fluid pressures during alteration. Precursor SGs obtained by reference to measurements on Pual Ridge glasses and microlitic glasses (unpublished CSIRO data), using Zr/TiO₂ to compute precursor composition.