Oxygen isotope fractionation between analcime and water: An experimental study

Journal Article · Tue May 01 00:00:00 EDT 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90161-D· OSTI ID:6014161

Karlsson, H R; Clayton, R N ^[1]

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1. The University of Chicago, IL (USA)

The fractionation of oxygen isotopes between natural analcime ({approximately}100 {mu}m) and water has been determined at 300, 350, and 400{degree}C at fluid pressures ranging from 1.5 to 5.0 kbar. Isotope ratios were obtained for the analcime framework, the channel water, and bulk water. Analcimes from Surtsey (145{degree}C), DSDP Hole 417A (30 to 55{degree}C), and Guam (25{degree}C) were used to constrain the fractionation factors below 300{degree}C. Analcime channel water exchanged completely with external water in all runs. Although some retrograde exchange may have occurred during quenching, the results indicate that the channel water is depleted in {sup 18}O relative to bulk water by a constant value of {approximately}5{per thousand}, nearly independent of temperature. Analcime is the first hydrated mineral found to have water of hydration depleted in {sup 18}O. Analcime framework oxygen exchanged 80, 90, and 96% at 300{degree}C for 412 h, 350{degree}C for 178 h, and 400{degree}C for 120 h, respectively. Equilibrium {Delta}{sup 18}O ({per thousand}) are as follows: 2.9 (400{degree}C), 4.5 (350{degree}C), and 5.8 (300{degree}C) for the experimental runs and 12.2 (145{degree}C) and 24.2 to 28.2 (30-55{degree}C) for the empirical data. The analcime-water fractionation curve is within experimental error of that of calcite-water. The exchange had little effect on grain morphology and does not involve recrystallization. This is the fastest exchange observed for a silicate. The rapid exchange rates indicate that zeolites in active high-temperature geothermal areas are in oxygen isotopic equilibrium with ambient fluids. Once calibrated, zeolites may be among the best low-temperature oxygen isotope geothermometers.

• OSTI ID: 6014161
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 54:5; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
58 GEOSCIENCES
ANALCIME
GEOCHEMISTRY
ISOTOPE RATIO
ISOTOPIC EXCHANGE
GEOTHERMAL SYSTEMS
GEOTHERMOMETERS
ROCK-FLUID INTERACTIONS
GEOTHERMAL FLUIDS
GEOTHERMOMETRY
OXYGEN ISOTOPES
CHEMISTRY
FLUIDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
ISOTOPES
MATERIALS
MEASURING INSTRUMENTS
MINERALS
SILICATE MINERALS
THERMOMETERS
ZEOLITES
152004* - Geothermal Data & Theory- Isotope & Trace Element Studies
580000 - Geosciences