Modern seafloor sulphides

Chalcopyrite, bornite. chalcocite. East Pacific Rise, Pacific Ocean

A section from the core (right) to margin (left) of a copper-rich chimney. The inner part of the chimney comprises chalcopyrite (yellow, right) which is intergrown with, and rimmed by, bornite (pink-brown, centre). Bornite alters in turn to a blue copper sulphide, chalcocite (left margin), via a series of copper-iron sulphides of intermediate compositions. Black areas are non-sulphides.

Polished block, plane polarized light, x40, air

Chalcopyrite, sphalerite, bornite, pyrite and covelline. East Pacific Rise, Pacific Ocean

Chalcopyrite (yellow, top) is rimmed by bornite (pink brown, centre top) and by euhedral to subhedral sphalerite (light grey, left). Minor amounts of pyrite (white, highest reflectance) occur within chalcopyrite (top left) or within the matrix (bottom, centre). Trace amounts of covelline (blue) have replaced bornite (centre top) but are difficult to see at this magnification.

Polished block, plane polarized light, x 80, air

Bornite, sphalerite, chalcocite, pyrite and chalcopyrite. East Pacific Rise, Pacific Ocean

Bornite (pink-brown, right) passes into an area rich in sphalerite (light grey, left). Bornite contains rare, small pyrite (white, high reflectance, centre right) crystals and is altering to blue copper sulphide, chalcocite (centre right). Sphalerite (centre left) carries very small yellow chalcopyrite inclusions (centre) and also is being replaced by chalcocite. Black areas are non-sulphides.

Polished block, plane polarized light. x 160, oil

Pyrite and sphalerite. East Pacific Rise, Pacific Ocean

A series of roughly linear organic structures (worm tubes?) are associated with the nucleation and crystallization of poorly crystalline pyrite (brown, lower reflectance, centre) and more euhedral pyrite (yellow-white, right), much of which overgrows the poorly crystalline pyrite. Minor amounts of sphalerite (light grey, bottom left) are intergrown with pyrite. Black areas are polishing pits.

Polished block, plane polarized light. x40, air

Pyrite, sphalerite and chalcopyrite. East Pacific Rise, Pacific Ocean

A transverse section through an organic structure (worm tube?) which has poorly crystalline to euhedral pyrite (light yellow-white) associated with it. Euhedral to subhedral sphalerite (light grey, top) is intergrown with minor amounts of chalcopyrite (yellow, top centre). Black areas are polishing pits, dark grey areas are non-sulphides (bottom).

Polished block. plane polarized light, x 40, air

Sphalerite, chalcopyrite and pyrrhotite. East Pacific Rise, Pacific Ocean

The outer margin of a zinc-rich chimney. Sphalerite (grey) is coarse-grained and has inclusion-free cores but minor chalcopyrite (yellow) on its margin. Smaller sphalerite crystals have a hexagonal morphology (centre right) suggesting wurtzite rather than sphalerite was originally precipitated. Fine-grained pyrrhotite laths (brown, left), which have largely altered to pyrite and marcasite, are precipitated 'black smoke'. Black areas are polishing pits.

Polished block, plane polarized light, x 80, air