Table T1. A simplified petrologic classification of subseafloor alteration styles at PACMANUS, with abbreviations used in the text and figures.
First-order categories:
F Fresh lavas near seafloor
O Opal-bearing altered rocks
X Cristobalite-bearing altered rocks
Y Quartz-bearing altered rocks
Z Altered rocks lacking silica phases, generally occurring as fragments in hydrothermal breccias or between stockwork quartz veins
A Albite-rich altered rocks (andesite precursors)
U Unclassified
Second-order categories:
M Plagioclase (mostly microlites) retained
B Pyrophyllite-bearing "bleached" rocks
Third-order categories:
-K Kernels in samples with fracture-controlled pale selvages
-T Transition zones between kernels and selvages
-S Pale selvages