Field investigation of airborne radioactivity anomalies in Marquette County, Michigan

The broad radioactivity anomalies recorded by the airborne detector in the vicinity of Republic, Marquette County, Michigan, coincide rather closely with parts of a granitic complex chiefly of Archean age. Ground examination of the rock in these areas of high radioactivity shows that the granitic rock typically yields two to four times the normal background activity. Fissures, shear zones, veins, and pegmatites were tested carefully. None exhibited activity higher than that of the adjacent granitic rock.

It is significant that the zones of more-than-average radio-activity are related to the larger elements of the geology - in fact, the information will be of considerable value in reconsideration of some of the regional problems.