Geology and mineralization of the southeastern Gillis Range, Mineral County, Nevada

Abstract

Geological studies in the eastern part of the Fitting District, which is located in the southern Gillis Range, Mineral County, Nevada, revealed the presence of Upper Triassic Luning Formation sediments, Jurassic Dunlap Formation sediments (which are thrust upon Luning Formation rocks), Cretaceous dioritic to granitic rocks, and assorted Cenozoic volcanic and sedimentary rocks. Several types of mineralization were observed, including significant skarn deposits, and minor quartz-sulphide veins and thorium/uranium-bearing pegmatite-like occurrences. Tungsten- and copper-bearing bedding-controlled skarn veins occur at the White Hills claims. The tungsten skarns replace potassically altered andesitic tuffs; up to two discontinuous meta- somatic zones are present: an early formed scapolite zone and a later grandite (Ad10_25) zone. Tungsten mineralization is confined to the grandite zone. The copper-bearing skarn veins replace calc-silicate hornfels; up to four metasomatic zones are present: the later-formed zones contain more andraditic grandite and more diopsidic pyroxene than early-formed zones.