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Use of imaging in the 0.46-2.36 [micrometers] spectral region for alteration mapping in the Cuprite mining district, Nevada

Open-File Report 77-585

By:
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Abstract

Color composites of Landsat MSS ratio images that display variations in the intensity of ferric-iron absorption bands are highly effective for mapping limonitic altered rocks, but ineffective for mapping nonlimonitic altered rocks. Analysis of 0.45-2.5 ?m field and laboratory spectra shows that iron-deficient opalites in the Cuprite mining district, Nevada, have an intense OH-absorption band near 2.2 ?m owing to their clay mineral and alunite contents and that this spectral feature is absent or weak in adjacent unaltered tuff and basalt. To evaluate the usefulness of this spectral feature for discriminating between altered and unaltered rocks, we generated color-ratio composite images from multispectral (0.46-2.36 ?m) aircraft data. The altered rocks in the district can be discriminated from unaltered rocks with few ambiguities; in addition, some effects of mineralogical zoning can be discriminated within the altered area. Only variations in amounts of limonite can be discerned in shorter wavelength aircraft data, Landsat MSS bands, and color aerial photographs.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Use of imaging in the 0.46-2.36 [micrometers] spectral region for alteration mapping in the Cuprite mining district, Nevada
Series title:
Open-File Report
Series number:
77-585
Edition:
-
Year Published:
1977
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
ii, 19 leaves :ill., map ;27 cm.