Petrographic description and geochemistry of basalts and altered volcanic rocks from ODP Leg 183 sites

In the northern part of the Kerguelen Plateau (Hole 1140A), basalts may have formed from two sources located at different depths.

This is reflected in the presence of both low- and high-titanium basalts. The basalts are variably altered by low-temperature hydrothermal processes (at temperatures up to 120°C), and some are affected by subaerial weathering. The hydrothermal alteration led mainly to the formation of smectites, chlorite minerals, mixed-layer hydromica-smectite and smectite-chlorite minerals, hydromica, serpentine(?), clinoptilolite, heulandite, stilbite, analcime, mordenite, thomsonite, natrolite(?), calcite, quartz, and dickite(?).