Oxygen isotope and fluid inclusion study of the Mineral Point area, Eureka Graben, Colorado

Oxygen and hydrogen isotope studies have established that certain fractured, highly permeable volcanic piles have undergone extensive interaction with heated meteoric ground waters (Taylor, 1971, 1973, 1974a; Forester and Taylor, 1972, 1980). The western San Juan caldera complex in southwestern Colorado is an area where such regional hydrothermal activity took place in the late Tertiary. This paper details an oxygen isotope and fluid inclusion study of rocks and veins within the Eureka graben, which lies in the center of the complex (Fig. 1). Use of these two complementary tracers elucidates the nature of the hydrothermal fluids present during mineralization and places some constraints on the thermal regime of the hydrothermal system.