Distinguishing significant from false copper and nickel anomalies in soil overlying the Gladesville norite, Jasper County, Georgia

Abstract

Abstract Distinct anomalies of Cu and Ni in stream alluvium and soil are associated with the Gladesville norite, but are generally not related to significant mineralization. The origin of one of the soil anomalies was investigated by determining partitioning relationships of Cu and Ni in outcrop samples, B-horizon soil samples, and a soil profile sample utilizing selective leaching techniques and electron microprobe analyses. Silicate minerals and spinel are important controls of both Cu and Ni distribution in the outcrop samples. Sulfides are a minor residence site of Ni but an important residence site of Cu. In soil, scavenging of Cu by montmorillonite has been important. Disintegration of montmorillonite in the B-horizon leaves residual minerals as an important and probably dominant control of Cu distribution in the upper part of the soil. Iron oxide particle coatings contain more Ni (46%) than any other single material in the B-horizon soil samples but contain only 21% of the Cu. Certain characteristics of the investigated Cu and Ni soil anomaly may be significant in future exploration as indicators of “false” anomalies. These include areal anomaly distribution patterns, soil/bedrock metal ratios, and the tendency of each metal to reside principally in a single soil component.