Aarja, Semail Ophiolite. Oman

The massive sulphides lie between footwall basalts of the Geotimes Unit and hangingwall basalts of the Alley Unit, the latter are interpreted as having formed in a graben-like structure between seamounts. Both mineralogically and texturally, Aarja is different from Lasail and Bayda, for its ore carries few oxide minerals but a greater abundance of bornite and marcasite. It displays abundant collomorphic pyrite and there is little evidence for chalcopyrite replacement of sulphides.

Major Minerals:

Pyrite, chalcopyrite, bornite, sphalerite

Minor Minerals:

Marcasite, tennantite, anomalous bornite

Trace Minerals:

Include bravoite, galena, native gold


Collomorphic textures between the iron, iron-copper and zinc sulphides are dominant. Fine-scale optical (and chemical) zoning of sphalerite is present. There is very little replacement of sphalerite by chalcopyrite, but pyrite is replaced by chalcopyrite and bornite. Sphalerite carries rare tennantite and galena inclusions


Ixer et al., 1984, 1986; Haymon et al., 1984