Geology of the Paradox No. 3 Mine Area

Citation

Peck, Dallas Lynn (1953) Geology of the Paradox No. 3 Mine Area. Master's thesis, California Institute of Technology. doi:10.7907/5H20-J918. https://resolver.caltech.edu/CaltechETD:etd-05082003-103136

Abstract

The Paradox No. 3 mine, Atolia, California, was mapped and thin sections of the vein minerals and wall rock were examined. Veins containing quartz, scheelite and carbonate occur along faults and fractures in Atolia quartz monzonite (Upper Jurassic ?), which is an orthoclase-biotite tonalite in the mine area. The mineralization occurs along three principle veins, named for convenience the main vein, north vein and west vein. Both the main and north veins occupy steeply dipping, northwest trending faults and fractures which dip 50 to 60 degrees southward from the surface and upper levels, but the main vein changes dip to the north near the 100 level, and the north vein changes dip to the north near the 200 level. Upward branching and changes in dip of the veins are common and are believed to be the result of nearly equal pressures on the different fracture surfaces at the time of mineralization. The west vein occupies a west to northwest trending thrust fault, which dips northward at 30 to 45 degrees, and an east trending strike-slip fault. The forces causing the faulting and fracturing are believed to be local vertical forces followed by regional compression oriented north to northeast. Localization of ore seems to occur at the junction of the thrust and strike-slip faults and at and above changes in dip of the north and main veins. The vein matter consists of coarse grained scheelite, quartz, and calcite, deposited in that order as open space filling in the fractures. Crustification, comb textures and small filled cavities are common. Wall rock alteration in the quartz monzonite resulted in pervasive alteration of biotite to chlorite and, feldspar to white mica, carbonate and clays. Adjacent to the veins the wall rock consists of illite, calcite, quartz and minor clays, chlorite, pyrite and locally albite. The deformation and mineralization are believed to have occurred during Miocene times at shallow depths. The ore forming fluids were probably hot carbonated aqueous solutions carrying minor quantities of sulphur and tungsten and possibly silica and potash. Suggested sites for exploration for ore are on the north vein at the 100 and 150 levels end the main vein at the east end of the 100 level.

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