Regional Report: St. Anthony deposit, Tiger, Mammoth District, Pinal Co., Arizona, USA

The St. Anthony deposit is comprised of the Mammoth-St Anthony Mine (St Anthony Mine, Mammoth Mine, Collins Mine, Mohawk Mine, New Year Mine) and the Ford Mine in nearby Tucson Wash. It has produced intermittently since 1881. Until 1944 gold was the most valuable metal produced, though large amounts of vanadium and molybdenum were recovered. After 1944 Galena and Sphalerite became the chief ore minerals. The rocks in the St. Anthony area are chiefly granitic (Oracle Granite) and volcanic; they range in age from Precambrian to Pleistocene. The deposit is of the vein type, controlled by pre-mineral faulting. The wall rocks ae chiefly rhyolite and quartz monzonite. Both space filling and replacement have been involved in the emplacement of the deposit. The history of the vein can be divided into several stages during which sulphide and associated silicate minerals were introduced. The deposit was oxidized to a depth of about 900 feet and then faulted into two major segments by the Mammoth fault. Each segment was further broken by smaller faults. Molybdenum- and vanadium-bearing solutions were then introduced into the faults and into the oxidized parts of the veins. Presumably reaction with lead carbonate and possibly with lead sulphate produced wulfenite and vanadinite. The deposit has received further oxidation since the formation of these minerals. 2,540,842 pounds V2O5 produced (1934-1944); see Creasey (1950) for total production of Au, Ag, Pb, Zn, Cu, and Mo.

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