Location:

Great Gossan Lead, Virginia, USA

A massive synsedimentary sulphide deposit has suffered lower amphibolite facies metamorphism accompanied by deformation. The final mineral assemblage records both prograde and retrograde metamorphic effects. Gangue phases include actinolitic and tremolitic hornblende, biotite, muscovite, chlorite, quartz and calcite.

Major Minerals:

Hexagonal pyrrhotite, sphalerite, chalcopyrite, local pyrite

Minor Minerals:

Galena, arsenopyrite

Trace Minerals:

Include cubanite, mackinawite, tetrahedrite, stannite, native bismuth, rutile, ilmenite, graphite

Textures:

The injection of sphalerite, chalcopyrite and galena into silicate fractures and cleavage is extensive. Durchbewegung and ball textures are common. Deformation kink-banding is developed in pyrrhotite. Pyrrhotite has recrystallized with dihedral angles of 120°

References:

Henry et al., 1979; Craig, 1983