A primary objective was to establish the causes of the major compositional differences between the deposits at Middle Valley and Escanaba Trough. A series of shallow RCB exploratory holes was targeted primarily at the exposed mounds of massive sulfide in order to establish the extent, composition, and drillability of the massive sulfide in this area prior to starting a deeper drill hole. No major intersection of massive sulfides was recovered. This is consistent with the lack of chimneys and the general occurrence of high temperature pyrrhotite crusts on the sediment observed during submersible dives.
Massive sulfides consist predominantly of massive pyrrhotite and vuggy pyrite.
Sphalerite is locally abundant and is associated with pyrrhotite.