A 1,800 MILLIVOLT SELF‐POTENTIAL ANOMALY NEAR HUALGAYOC, PERU*

Abstract

ABSTRACT A large self‐potential anomaly was outlined in 1963–64 at Tantahuatay near Hualgayoc in the Andes of northern Peru. Peak value recorded was–1842 millivolts–thus making it one of the strongest, or perhaps the strongest, SP anomaly ever measured. A lack of detailed geological data precludes the formulation of an adequate explanation for the Tantahuatay anomaly, but geological and mineralogical similarities with the well‐documented Venencocha anomaly near Cerro de Pasco, Peru (Kruger and Lacy, 1949), suggest that the anomaly arises from sulfuric acid associated with the mineral alunite. The anomaly obviously cannot be explained by the half‐cell mechanism of Sato and Mooney (1960), who place a limit of 700 millivolts on self‐potential anomalies over sulfide bodies. Further study of the Tantahuatay anomaly would be of interest in understanding self‐potential mechanisms in general.