Discriminating late volcanic differentiates commonly associated with precious metal deposits, using Landsat Thematic Mapper imagery

The magmatic differentiates emplaced late in volcanotectonic cycles (which when highly evolved commonly occur as domes, flow-dome complexes, and shallow intrusive porphyries) are typically more silicic and felsic than their earlier counterparts and exhibit unusually steep spectral curves from about 1.5 to 2.2 microns. This spectral characteristic emerges in the form of relatively high Landsat TM band 7 DN values and low 5/7 values, as well as dark-contrast or enhanced 5/7 images. These evolved late-phase differentiates are commonly associated both temporally and spatially with precious metal deposits, furnishing site-specific exploration targets as well as guides to caldera margins and other late-stage volcanotectonic structures.