Geology and mineralization of the Marietta area, Mineral County Nevada

Abstract

Pre-Tertiary layered rocks dominate the study area at Marietta, Nevada, in the central Excelsior Mountains. In stratigraphic order these include andesite volcanics and volcaniclastic sediments, calcareous siltstone, conglomerate with interbedded arkosic wacke and silt- stone with interbedded conglomerate. They range from Permian through Lower Jurassic in age and are about 2,900 meters thick. Tertiary volcanics cap the range to the north, with a quartz monzonite intrusion bordering the area to the southwest. The rocks strike northeast and dip to the southeast. This has been complicated in the southern portion of the area by northwest trending faults and a fold resulting from the forceful quartz monzonite intrusion. Mineralization consists of argentiferous galena veins which are hosted by conglomerate. The veins have a preferred strike of N60 to 80 W with steep dips. They can be divided into coarse grained galena veins and veins of more varied sulfide mixtures. Other mineralization includes occurrences of copper and gold.