Contact-metasomatic magnetite deposit, Medfra Quadrangle, Alaska

A small contact-metasomatic magnetite deposit was discovered in the Medfra quadrangle, Alaska, in 1976. It occurs at the contact between a Cretaceous or early Tertiary quartz monzonite stock and Paleozoic limestone and dolomite. The ore is a magnetite-clinohumite-hematite rock that contains up to 60 volume percent magnetite and 76 weight percent total iron expressed as FeO. Computer modelling of data derived from a ground-level magnetometer survey yielded an estimate of the shape and volume of the deposit. The volume is grossly estimated at 11,600³m .