Geology of the Monte Cristo Mining Area

Citation

Phipps, Rodney Thirsk (1951) Geology of the Monte Cristo Mining Area. Master's thesis, California Institute of Technology. doi:10.7907/VG4N-GV19. https://resolver.caltech.edu/CaltechTHESIS:03312010-154632812

Abstract

The Monte Cristo mining area was discovered in the early days of mining in California, and intermittent attempts have been made to work it to the present time. The gold is localized in lenticular quartz veins replacing fractured country rock along north-south fault zones. Pyrite is the principal ore mineral with magnetite and minor amounts of sphalerite, pyrrhotite, and chalcopyrite also present. Anorthosite is the principal country rock in the areas apparently intruded into diorite. Hornblendite dikes cut the anorthosite before the time of gold mineralization, and late lamprophyre dikes were injected after the vein quartz. Some pegmatite and late aplite dikes are also present. The area on the whole has undergone little metamorphism. Several stages and patterns of faulting are present and an attempt was made to work out their relative ages and the ages of the dikes and veins with respect to them. Joint patterns were mapped but no relation was found between them and the ore control. Economically the mine is considered a bad risk for any sizeable operation. Small scale mining of high grade ore shoots with a minimum of investment capital is believed to offer the best chance of success. The most favorable aspect of the property is the amount of development work done on the Monte Cristo North area where short crosscuts would open up a possible downward extension of the vein exposed at the surface.

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