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sulphide mounds commonly consist of pyrite and chalcopyrite together with pyrrhotite,
isocubanite, and locally bornite.
The outer portions of chimneys and mounds are commonly composed of lower
temperature precipitates such as sphalerite/wurtzite, marcasite, and pyrite, which are
also the principal sulphide minerals of low-temperature white smoker chimneys.
Anhydrite is important in the high-temperature assemblages, but is typically replaced by
later sulphides, amorphous silica, or barite at lower temperatures.
Sulphide mineralisation at back-arc spreading centres has some mineralogical
characteristics that are similar to hydrothermal precipitates at volcanic-dominated midocean
ridges. Commonly, pyrite and sphalerite are the dominant sulphides. Chalcopyrite
is common in the higher temperature assemblages, but pyrrhotite is rare. Barite and
amorphous silica are the most abundant non-sulphides.
Many of the deposits forming in back-arc rifts are characterised by a variety of
minor and trace minerals such as galena, tennantite, tetrahedrite, cinnabar, realgar,
orpiment, and complex, non-stoichiometric Pb-As-Sb sulphosalts. The first examples of
visible primary gold in seafloor sulphides were documented in samples of lower
temperature (