Kabba
Geology and Mineralization
Arizona is one of the world's premier copper-producing regions, but broad regions of the state lie buried beneath shallow alluvial cover, making exploration difficult. The recent discovery of the giant Resolution orebody served as a reminder that undiscovered porphyry copper deposits still exist in Arizona, and that they are worth finding.
The large Arizona porphyry systems and their alteration and mineralization halos, zoned from proximal potassic alteration with Cu-Mo-W-U mineralization to distal propylitic alteration with Pb-V-Zn-Ag-Au mineralization, provide an indirect method to peer laterally beneath Arizona's alluvial cover. The fringing V-Pb-As-Mo-Au mineralization exposed in the erosional window at Kabba provided the Compay such an opportunity.
Previous mining in the Maynard District during the early twentieth century produced small quantities of vanadium-molybdenum ore with gold and lead credits. A mine located on patented mining claims, which are not held by Bell, were the source of vanadium ore hosted in breccia and quartz veinlets associated with porphyry dikes and sills. A 1600 foot inclined shaft servicing 2000 feet of lateral workings produced fifty thousand tons of ore grading 1.5% vanadium oxide, 0.24% molybdenum oxide, 6.3% lead, and one ounce per ton gold.
Mineralization outboard of this mine shows most of the features associated with typical porphyry copper deposits, including stockwork quartz and sulphide veinlets, disseminated indigenous iron oxide minerals after copper-iron sulfides, brecciation, and potassic, sericitic, and propylitic alteration. Much of the surface exposure at Kabba has been attacked by supergene alteration, and now consists of bright red hematitic leached capping (Figue 5).
Known mineralization at Kabba is located within strongly hematitic, sericitized breccias and stockwork zones cutting porphyry dikes and Precambrian granitic wallrocks. Broad, pervasively altered fracture zones extend westerly and disappear beneath a sequence of capping gravels and a basal post-mineral lava flow consisting of olivine basalt.
Ten miles to the west and twelve miles to the northeast, Siwiec (2003) and Beardman (1993), respectively, have mapped the same post-mineral basal olivine basalt lavas that are exposed at Kabba. A geologic cross section shows the implications of reconstructing this faulted basal layer of olivine basalt: the Kabba prospect should contain the down-faulted, copper-rich top of this porphyry copper system. The deduced fault offset along the west side of the Kabba prospect is about 3000 meters, and the missing part of this porphyry deposit is expected to lie within 1 kilometer of the surface.
The erosional bedrock windows at Kabba demonstrate that the down-faulted, probably supergene-enriched, top of this giant porphyry copper deposit is not deeply buried by valley-filling detritus.