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Geology topics

M.A. Chaffee

Publications and source records attributed to M.A. Chaffee.

At least 19 recordsLinked to original sources
USGS1989

Soil geochemistry of Mother Lode-type gold deposits in the Hodson mining district, central California, U.S.A.

The Hodson mining district is in the westernmost foothills of the Sierra Nevada in California, about 17 km west of the town of Angels Camp. This district is part of the West Gold Belt, which lies about 12-16 km west of, and generally parallel to, the better known Mother Lode Gold Belt in central California. The district produced several million dollars worth of Au between about 1890 and 1940. The geologic setting and mineral deposits in the West Gold Belt are generally similar to those in the Mother Lode Gold Belt. Rocks in the study area are of Jurassic age and consist of a mixture of (1) fine-grained, generally thin-bedded, clastic sedimentary rocks that have been metamorphosed to slates, schists, and phyllites, and (2) massive volcanic flows and welded tuffs that have been metamorphosed to metabasalts and metatuffs. All rocks were intensely faulted and folded during the Late Cretaceous Nevadan orogeny; northnorthwest- and northwest-trending faults dominate. Mining in the area was of low-grade gold-pyrite ores occurring principally in the carbonatized wall rocks adjacent to the major northwest-trending Hodson fault and its splays. Minor amounts of other sulfide minerals (principally chalcopyrite, arsenopyrite, sphalerite, and galena) are locally associated with the Au deposits.

California↗
USGS1988

Maps showing distribution of copper, lead, zinc, cadmium, and silver in samples of minus-60-mesh (0.25-MM) stream sediment and nonmagnetic heavy-mineral concentrate, Walker Lake 1 degree by 2 degrees Quadrangle, California and Nevada

This report is part of a folio of maps of the Walker Lake 1 o x 2 o quadrangle, California and Nevada, prepared under the Conterminous United States Mineral Assessment Program. The folio includes geological, geochemical, and geophysical maps, as well as mineral resources assessment maps, which identify selected known or possible mineral-deposit environments in the quadrangle. The geochemical maps show the distributions of selected individual elements (Chaffee and others, 1988 a, b, c) and the distributions of selected groups of elements (Chaffee, 1988a, b, c). Discussions accompanying the individual element maps are restricted to mineral residences of the individual elements as well as to what types of mineral deposits and environments may be represented by anomalies of a particular element. Discussions accompanying the multielemental maps describe the types of mineral deposits that may be related to each element group and indicate the most favorable localities for these deposits.

California, Nevada↗