Description: Regular changes in solution composition were observed experimentally during granite reaction with dilute NaCl (+CaCl/sub 2/) solutions; these changes closely follow the empirical Na-K-Ca geothermometer relationship. Initial minerals forming the granite (quartz, plagioclase, K-feldspar, and biotite) were etched by the reactions. Alteration phases formed include calcium-zeolite at <300/sup 0/C, feldspar overgrowths at >300/sup 0/C, and minor amounts of clay and calcsilicate at all temperatures. Amphibole overgrowths were also found at 340/sup 0/C. Quartz is near saturation in all experiments, and preliminary calculations of aqueous species distributions and mineral affinities indicate that the solutions achieve super-saturation with feldspars as the temperature increase. A consistent variation attributable to pH differences was observed in the empirical geothermometer relationship for all experimental data. At 340/sup 0/C, the experimental solutions appear to have deviated slightly from the empirical Na-K-Ca relationship. Such deviations may also be found in natural systems that attain such temperatures.
Date: August 1, 1986
Creator: Janecky, D.R.; Charles, R.W.; Bayhurst, G.K. & Benjamin, T.M.
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