Geologic and geophysical investigations of Climax Stock intrusive, Nevada

Abstract

The Climax stock is a composite granitic intrusive of Cretaceous age, composed of quartz monzonite and granodiorite, which intrudes rocks of Paleozoic and Precambrian age. Tertiary volcanic rocks, consisting of ashflow and ash-fall tuffs, and tuffaceous sedimentary rocks overlie the sedimentary rocks and the stock. Erosion has removed much of the Tertiary volcanic rocks. Hydrothermal alteration of quartz monzonite and granodiorite is found mainly along joints and faults and varies from location to location. The Paleozoic carbonate rocks have been thermally and metasomatically altered to marble and tactite as much as 457 m (1,500 ft) from the contact with the stock, although minor discontinuous metasomatic effects are noted in all rocks out to 914 m (3,000 ft). Three major faults which define the Climax area structurally are the Tippinip, Boundary and Yucca faults. North of the junction of the Boundary and Yucca faults, the faults are collectively referred to as the Butte fault. The dominant joint sets and their average attitudes are N. 32? W., 22? NE; N. 60? W., vertical and N. 35? E., vertical. Joints in outcrop are weathered and generally open, but in subsurface, the joints are commonly filled and healed with secondary mineral s. The location of the water table and the degree of saturation of the granitic rocks are presently unknown. Measurement from drill holes indicated that depth to perched water levels ranges from 30 to 244 m (100-800 ft). Recent field investigations have shown the contact between the Pogonip marble and the granodiorite is a contact rather than a fault as previously mapped. The thickness of the weathered granodiorite is estimated to be 8 to 46 m (25 to 150 ft).