Hot-spring sinter deposits in the Alvord-Pueblo Valley, Harney County, Oregon
- Portland State Univ., OR (United States). Dept. of Geology
Silica sinter deposits occur at Borax Lake, Alvord Hot Springs, and Mickey Springs in the Alvord-Pueblo Valley. Although the sinter deposits occur in areas of active hot springs, sinter is not being deposited. Hot springs are localized along faults that have been active since the Pleistocene. The sinter deposits formed after the drying of glacial Lake Alvord, but before and during extensive wind deflation of glacial-lacustrine sediments. At Mickey Springs, sinter rests directly on unaltered, unconsolidated lithic-rich sand. At Borax Lake, sinter overlies unaltered diatomite, but some armoring, presumably by silica, of the 30 m vent has developed. Field relations suggest rapid dumping of silica from solution without alteration of the country rock at the vent. Discharge of thermal fluids and cold groundwater along the same structure may have produced colloidal silica carried in a solution stripped of dissolved silica. Sinter is composed of opal-a, traces of detrital feldspar and quartz, and evaporation-related boracite. The concentration of Sb is similar among the three sinter deposits (20 to 70 ppm); however, As, Cs, and Br are highest at Borax Lake (5 to 560 ppm; 26 to 118 ppm; 5 to 1,040 ppm) while Hg is highest at Mickey Springs (1.0 to 5.2 ppm).
- OSTI ID:
- 5290826
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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