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Geochemistry of surface water in alpine catchments in central Colorado, USA: Resolving host-rock effects at different spatial scales

Applied Geochemistry

By:
, , , , , , ,
DOI: 10.1016/j.apgeochem.2008.12.012

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Abstract

The US Geological Survey is conducting a study of surface-water quality in the Rocky Mountains of central Colorado, an area of approximately 55,000 km2. Using new and existing geologic maps, the more than 200 rock formations represented in the area were arranged into 17 groups based on lithologic similarity. The dominant regional geologic feature affecting water quality in central Colorado is the Colorado mineral belt (CMB), a NE-trending zone hosting many polymetallic vein or replacement deposits, and porphyry Mo deposits, many of which have been mined historically. The influence of the CMB is seen in lower surface-water pH (<5), and higher concentrations of SO42 - (>100 mg/L) and chalcophile metals such as Cu (>10 ??g/L), Zn (>100 ??g/L), and Cd (>1 ??g/L) relative to surface water outside the CMB. Not all streams within the CMB have been affected by mineralization, as there are numerous catchments within the CMB that have no mineralization or alteration exposed at the surface. At the regional-scale, and away from sites affected by mineralization, hydrothermal alteration, or mining, the effects of lithology on water quality can be distinguished using geochemical reaction modeling and principal components analysis. At local scales (100 s of km2), effects of individual rock units on water chemistry are subtle but discernible, as shown by variations in concentrations of major lithophile elements or ratios between them. These results demonstrate the usefulness of regional geochemical sampling of surface waters and process-based interpretations incorporating geologic and geochemical understanding to establish geochemical baselines.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geochemistry of surface water in alpine catchments in central Colorado, USA: Resolving host-rock effects at different spatial scales
Series title:
Applied Geochemistry
DOI:
10.1016/j.apgeochem.2008.12.012
Volume
24
Issue:
4
Year Published:
2009
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Applied Geochemistry
First page:
600
Last page:
610
Number of Pages:
11