The Sierra Nevada Batholith, California, U.S.A. and spatially related mineral deposits

Dodge, F. C. W. and Bateman, P. C. (1977) The Sierra Nevada Batholith, California, U.S.A. and spatially related mineral deposits. Bulletin of the Geological Society of Malaysia, 9. pp. 17-29. ISSN 2637-109X

Abstract

The Sierra Nevada batholith is composed of a great many discrete granitoid plutons of different compositions in sharp contact with one another. Most of these plutons can be assigned to a much smaller number of comagmatic sequences, each representing a single fusion event. Compositional differences between sequences reflect progressive eastward increase in potassium actoss the batholith and less conspicuous decrease in calcium. Uranium, thorium, the oxidation ratio, and 86Sr/87Sr initial ratios also increase eastward. Compositional patterns are independent of the ages of the rocks. The oldest granitoid rocks, of Triassic and Early Jurassic age, are on the east side of the batholith. The next older rocks, chiefly Early Cretaceous, are on the west side. The youngest rocks, of early Late Cretaceous age, are in the core of the batholith. Several workers have pointed out a zonal distribution of mineral deposits in eastern California and have related this zoning to proximity to the Sierra Nevada batholith. Deposits of tungsten, molybdenum, and iron occur within the batholiths, and deposits of gold, silver, copper, zinc, manganese, and chromite are present in the country rocks peripheral to the batholith. Preliminary considerations indicate that the metals that occur within the batholith are the ones most likely to have had their source in the batholith. Chromite is syngenetic with enclosing bodies of ultramafic rock older than the batholith, and the source for most gold, copper, lead, zinc, and manganese probably was also in adjacent country rock where volcanogenic or sedimentary processes had previously produced low-grade concentrations. The batholith may have supplied heat required to mobilize meteoric waters, which reconcentrated these metals in deposits of exploitable grade.

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