Trace element and REE geochemistry of Red Butte, Oregon: a gold-bearing hot spring system

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6673547

Evans, C S; Cummings, M L

Red Butte, 60 km south of Vale, Oregon is an Au-bearing hot spring deposit of intercalated lacustrine and fluvial Mio-Pliocene volcaniclastic sediments and basalt flows. Topography of the butte is controlled by a 30-60 m thick cap of silicified sediments which is cut by N and NW-trending faults. Anomalous Au, As, Sb, and Hg occur in fault controlled quartz veins, quartz-adularia veins, silicified sediments and rarely in calcite-quartz veins cutting basalt. Distribution of these elements away from the veins is controlled by permeability of the host rock. REE concentrations were normalized to chondritic abundances for 73 sediment, basalt, and vein samples. Silicified sediments from the butte top and unsilicified sediments from the east slope of the butte have similar LREE enriched patterns with strong negative Eu anomalies reflecting their felsic volcanic source. Silicified sediments are depleted in all REEs relative to fresh sediments indicating dilution by silica deposition. Basalt REE patterns are much closer to chondritic ratios. Patterns of veined basalt mirror those for fresh basalts but are relatively depleted in all REEs. Quartz-adularia and quartz veins have REE abundances 2-3 orders of magnitude lower than fresh sediments, and REE patterns unlike either the sediments or basalts. Mobility of REEs in the hydrothermal fluid is seen in La/Sm and Sa/Yb ratios of the veins. The La/Sm ratio for sediments averages 3.70. In veins this ratio drops to 1.65. The average La/Yb ratio is 9.1 in sediments and falls to 1.65 in quartz veins. Fluids depositing quartz and adularia in veins carried REEs in low abundance and deposited them in ratios that do not reflect the host rock. Any movement of REEs in host rock may have been masked by original high REE content combined with silica dilution.

• Research Organization: Portland State Univ., OR (USA)
• OSTI ID: 6673547
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152002* -- Geothermal Data & Theory-- Properties of Minerals & Rocks
58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
BASALT
CENOZOIC ERA
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENTS
ENERGY SYSTEMS
FEDERAL REGION X
FLUIDS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
GOLD ORES
HOT SPRINGS
HYDROTHERMAL SYSTEMS
IGNEOUS ROCKS
METALS
MINERALOGY
MINERALS
NORTH AMERICA
OREGON
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PERMEABILITY
PLIOCENE EPOCH
QUARTZ
RARE EARTHS
ROCKS
SILICON COMPOUNDS
SILICON OXIDES
TERTIARY PERIOD
THERMAL SPRINGS
TOPOGRAPHY
TRACE AMOUNTS
USA
VOLCANIC ROCKS
WATER SPRINGS