GEOPHYSICAL STUDIES OF THE CRIPPLE CREEK MINING DISTRICT, COLORADO

Abstract

Integrated geophysical, geochemical, and geological interpretations expand the knowledge about the localization of the ore deposits in the Cripple Creek district, Colorado. The principal gold deposits occur in a Tertiary volcanic subsidence basin within Precambrian granite, gneiss, and schist. The basin is filled with volcanic breccia and is intruded by dikes and irregular masses of phonolite, latite‐phonolite, syenite, trachydolerite, and basalt. The volcanic complex gives rise to a broad 10 mgal gravity minimum anomaly upon which are superimposed local minima believed to be related to deep mineralized fissure zones. A negative magnetic anomaly over the volcanic subsidence basin probably reflects the degree of alteration of rocks in the subsurface. Two local closed magnetic lows may represent highly altered volcanic centers in the bottom of the basin. The gravity and magnetic anomalies of the basin correlate geographically with positive geochemical anomalies for gold, silver, and tellurium. Just east of the volcanic basin, a prominent negative magnetic anomaly and a corresponding gravity low may represent an altered zone in the granite subsurface.