Figure F148. Pressure-temperature diagrams showing the possible cooling path for rocks at Site U1309. Reaction numbers correspond to equations in text. A. Reactions in gabbroic rocks. Reaction 1: beginning of hornblende breakdown in amphibolite (Spear, 1981). Reaction 2 = disappearance of epidote in metabasites calculated from TWEEQ program (Berman, 1991), using the database of Berman (1988). Heavy gray line gives approximate low-temperature (T) limit for the stability of olivine + plagioclase after Frost (1976). Blue area gives approximate pressure and temperature conditions for the static hydration seen in gabbroic rocks from Hole U1309B and the upper levels of Hole U1309D. Chl = chlorite, Cz = clinozoisite, Qz = quartz, An = anorthite, Trem = tremolite. B. Reactions found in ultramafic rocks. Location of Reactions 5 through 8 calculated from the database of Berman (1988). Green area shows the temperature range over which reactions proceeded in the ultramafic rocks. Gr = garnet, Pr = prehnite, Di = diopside, Serp = serpentinite, Br = brucite, Fo = forsterite, En = enstatite.
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