Experimental Alteration of a Granodiorite in a Circulation System
- Key words
- Hot Dry Rock; USA; New Mexico; Fenton Hill; Heat Exchangers; Chemical Analysis; Rock Alteration; Quartz; Microcline
- Location
- Fenton Hill, New Mexico; Valles Caldera, New Mexico
- Conference
- Geothermal Resources Council Transactions
- Year
- 1978
- Session
- HDR/EGS; Granodiorite; Hydrothermal alteration; Brine chemis
- Language
- English
Abstract
Reaction of granodiorite from Fenton Hill Hot Dry Rock Geothermal Site with distilled water at 300°C and 345 bars total pressure for 8 months has produced many morphological and chemical effect. Eight polished rock disks were mounted on a tantalum pedestal inside a 500ml autoclave. The autoclave is part of a circulation system designed for operation to 400°C and 345 bars. Solution samples were taken at 32, 56, 176, 368, 752, 1544, 3104 and 5816 hr. Rock disks were removed also at a latter four times. The reactivity of phases was shown to be quartz>>microcline>plagioclase>mafica, opaque's and trace phases. Quartz was removed congruently. The albite component of the plagioclase was dissolved essentially congruently changing plagioclase from oligoclase (fresh) to bytownite (8 mo.). Microcline showed congruent dissolution. Other phases were inert. Secondary mineralization included phillipsite, thomosonite and vermiculite.
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