Radium-thorium disequilibrium and zeolite-water ion exchange in a Yellowstone hydrothermal environment

Journal Article · Mon May 01 00:00:00 EDT 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90207-X· OSTI ID:5022709

Sturchio, N C; Bohlke, J K ^[1]; Binz, C M ^[2]

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1. Argonne National Laboratory, IL (USA)
2. Loras College, Dubuque, IA (USA)

Whole rock samples of hydrothermally altered Biscuit Basin rhyolite from Yellowstone drill cores Y-7 and Y-8 were analyzed for {sup 226}Ra and {sup 230}Th to determine the extent of radioactive disequilibrium and its relation to the rates and mechanisms of element transport in the shallow portion of an active hydrothermal system. The ({sup 226}Ra/{sup 230}Th) activity ratios range from 0.73 to 1.46 and are generally correlated with Th-normalized Ba concentrations (Ba{sub N}). Compositions of clinoptilolite and mordenite in these samples are consistent with ion exchange equilibrium between zeolites and coexisting thermal waters. Average K{sup Ba}{sub d mineral-water} values are 1.0 {center dot} 10{sup 5} mL/g for clinoptilolite and 1.4 {center dot} 10{sup 4} mL/g for mordenite. Apparent diffusivities through matrix porosity estimated for R and Ba range from {approximately}10{sup {minus}12} to {approximately}10{sup {minus}10} cm{sup 2} s{sup {minus}1} in thoroughly zeolitic rhyolite; these rates of diffusion are too low to account for the observed distance scale of ({sup 226}Ra/{sup 230}Th) disequilibrium. The correlated values of ({sup 226}Ra/{sup 230}Th) disequilibrium and Ba{sub N} represent zeolite-water ion exchange equilibrium that is caused by porous flow of water through the rock matrix and by the relatively rapid diffusion of cations within the zeolite lattices. A water flux of at least {approximately}2.5 (cm{sup 3}{sub water}/cm{sup 3}{sub rock}) yr{sup {minus}1} is required to produce measurable ({sup 226}Ra/{sup 230}Th) disequilibrium, whereas at least {approximately}23 (cm{sup 3}{sub water}/cm{sup 3}{sub rock}) yr{sup {minus}1} is required for the sample exhibiting the most extreme ({sup 226}Ra/{sup 230}Th) disequilibrium; these fluxes are much higher than those that can be inferred from net mass transfers of stable species.

• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 5022709
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:5; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
15 GEOTHERMAL ENERGY
RADIUM ISOTOPES
RADIONUCLIDE MIGRATION
RHYOLITES
CHEMICAL COMPOSITION
HYDROTHERMAL ALTERATION
THORIUM ISOTOPES
YELLOWSTONE NATIONAL PARK
HYDROTHERMAL SYSTEMS
ZEOLITES
ION EXCHANGE
DRILL CORES
EQUILIBRIUM
GEOCHEMISTRY
GEOTHERMAL FLUIDS
IONIC COMPOSITION
RADIUM
ROCK-FLUID INTERACTIONS
THORIUM
WYOMING
ACTINIDE ISOTOPES
ACTINIDES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
CHEMISTRY
ELEMENTS
ENERGY SYSTEMS
ENVIRONMENTAL TRANSPORT
FEDERAL REGION VIII
FLUIDS
GEOTHERMAL SYSTEMS
IGNEOUS ROCKS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
ISOTOPES
MASS TRANSFER
MATERIALS
METALS
MINERALS
NORTH AMERICA
PUBLIC LANDS
ROCKS
USA
VOLCANIC ROCKS
580000* - Geosciences
152003 - Geothermal Data & Theory- Rock-Water-Gas Interactions