Isotope-calibrated hydrothermal models: Geothermal implications of a model of the Skaergaard intrusion

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:175619

Brikowski, T H ^[1]

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1. Desert Research Institute, Reno, NV (United States)

Hydrothermal circulation models can be greatly refined by including isotopic alteration of multiple mineral phases, and calibrating predicted alteration to field observations. Analysis of predicted alteration in physical and chemical ({delta}-{delta}) space yields tight constraints on model parameters, especially permeability and isotope exchange rate constant. Applying this technique at a mafic rifting site (the Eocene Skaergaard Intrusion, eastern Greenland) yields an accurate model of the hydrothermal system, from which the geothermal aspects of the system can be estimated with considerable confidence. To match field observations of {delta}{sup 18}O alteration patterns at the Skaergaard, low average permeabilities are required (10{sup -16} m{sup 2} for basalt host rock). This results in a narrow depth range of convection-dominated beat transport, and mild surficial anomalies in fluid {delta}{sup 18}O (max. {delta}{sup 18}O{sub f} = +2%). The shallow temperature gradient reaches a maximum of 130{degrees} C/km, but average convective beat flux at the surface is 11 MW for the entire intrusion. Erosion and lack of appropriate isotopic data for host rocks above the Skaergaard preclude refinement of the geothermal model but this pluton-alteration-calibrated model indicates a much more conduction-dominated cooling history than expected at this site.

• OSTI ID: 175619
• Report Number(s): CONF-951037--
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
GEOLOGIC MODELS
GEOTHERMAL RESOURCES
GREENLAND
HYDROTHERMAL SYSTEMS
PLUTONIC ROCKS
TEMPERATURE GRADIENTS