Abstract:
The author have already investigated the interrelationship of processes of subsolidus metasomatic preparation of rocks and fluid interaction in the mafic-ultramafic-alkalic series. The results presented below describe experiments run at 600° and PH(2)O = 100 MPa in a cold-sealed reactor. In the experiments with basalt glass, in a purely aqueous medium montmorillonite developed as the metastable phase, together with clinopyroxene, plagioclase and magnetite. Amphibole, talc, plagioclase and magnetite crystallize from such glass when the solution-charge ratio is 0.3, but frea silica appears when it equals 0.7. Under purely aqueous conditions, andesite glass is transformed into a mixture of amphibole, trioctahedral mica, quartz, plagioclase and magnetite. In acid media, amphibole and magnetite disappear, but mica is more stable and is formed in very small amounts when the solution-charge ratio equals unity. When this ratio is further increased, the only newly formed minerals are plagioclase and quartz. Comparison of the components obtained in the experiments shows, on the whole, that the order in which minerals disappear with increasing intensity of acid attack is as follows: clinopyroxene + and/or amphibole + magnetite + mica + plagioclase + quartz.