The latter include perlitic-textured and vesicular lavas and likely volcaniclastic sediment. Hydrothermal breccias abound. Silica is largely cristobalite with minor to subordinate quartz. A thin, laminated unit at 136.9 to 137.8 mbsf, interpreted as sedimentary, marks a change in alteration. Below the sedimentary unit quartz is the dominant silica form and the rocks contain noticeable magnetite, while anhydrite seems restricted to late vein fillings.
Alteration varies from intense to extreme.
Preservation of the original rock textures varies from excellent to nil. Veins, stockworks and breccias are common. At the time of writing this report, the shipboard chemical and mineralogical data needed to resolve lateral variations between sites is just starting to flow. Initial measures of microbe abundance indicate rapidly decreasing abundance with depth. No live cells have been detected beyond 50 mbsf.