Arsenic geochemistry in geothermal systems

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

OSTI ID:6897889

Ballantyne, J M; Moore, J N; Adams, M C

Arsenic plays an important role in exploration for both active geothermal systems and the epithermal gold deposits which are their fossil analogs. Arsenic is also an environmentally hazardous byproduct of production from many of these systems. The authors ongoing study of As geochemistry aims to refine existing exploration methodologies and mitigate environmental problems. Arsenic concentrations in fluids from producing geothermal systems generally range from 1 to 10 ppm although concentrations as high as 50 ppm have been reported. Variation within individual fields is related to both chloride content and temperature of the fluids. Similarities of regression line slopes for data from different systems suggest that As concentration in fluids is controlled by fluid-mineral equilibria. The decrease in aqueous As concentration with decreasing temperature is consistent with the observed enrichment of As in rocks in the upper, cooler portions of hydrothermal systems. Oxidation also plays a role in the precipitation of As. Arsenic in deep fluids is present mostly as As(III), oxidizing to As(V) at surface. Chemical analyses of geothermally altered rocks indicate that As is incorporated primarily in pyrite or in iron oxides after pyrite. Available data indicate that upward enrichment of As in rock in venting systems correlates with both pyrite abundance and the concentration of As in pyrite.

• Research Organization: Univ. of Utah, Salt Lake City (USA)
• OSTI ID: 6897889
• 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
150302* -- Geothermal Exploration & Exploration Technology-- Geochemical Techniques & Surveys
58 GEOSCIENCES
580400 -- Geochemistry-- (-1989)
ARSENIC
ARSENIC COMPOUNDS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
ELEMENTS
EXPLORATION
FLUIDS
GEOCHEMISTRY
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
GOLD ORES
IRON COMPOUNDS
IRON SULFIDES
MINERALS
ORES
OXIDATION
PYRITE
SEMIMETALS
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS