Location:

El Salvador, Chile

This deposit is associated with the intrusion of Tertiary porphyritic granodiorite stocks into Cretaceous lavas and sediments and Tertiary volcanics. Hypogene copper mineralization is associated with the X and K porphyries as A-quartz veins and disseminated sulphides, and shows zoning with chalcopyrite-bornite in the centre passing outwards into chalcopyrite-pyrite; and potassic alteration surrounded by propylitic alteration. Molybdenite mineralization (found in B-quartz veins) is associated with a later porphyritic stock. Yet later mineralization is pyrite-dominated and occurs as disseminations in pyrite-bornite or pyrite zones or within D-veins. It is accompanied by phyllic alteration and is the result of remobilization of earlier sulphides and anhydrite.Supergene enrichment, associated with argillic alteration, has replaced primary bornite and chalcopyrite to produce secondary copper sulphides of the chalcocite blanket.

Major Minerals:

Pyrite, chalcopyrite, bornite, molybdenite, supergene chalcocite, djurleite, digenite

Minor Minerals:

Enargite, tennantite, sphalerite, galena, supergene covelline, cuprite, native copper

Trace Minerals:

Include pyrrhotite, magnetite, ilmenite, rutile, haematite

Textures:

Sulphides occur within veinlets and healed veinlets and so look disseminated. Rutile crystals often form the cores to copper sulphides. Bornite-chalcopyrite intergrowths are symplectite-like or occur as crystallographically oriented lamellae due to exsolution or replacement. Pyrite carries minor pyrrhotite and magnetite inclusions. In supergene enrichment zones, chalcocite, digenite, djurleite and covelline form replacement rims about bornite and chalcopyrite

References:

Swayne and Trask, 1960; Gustafson and Hunt, 1975