The Synthesis and Stability of Anthophyllite

"Non-calciferous" orthopyroxene and its bearing on the petrogenesis of ultramafic rocks in Sangun and Joetsu zones.

“…For example, the petro graphical zonation observed in Tari-Misaka ultramafic complex, western Japan, is fairly consistent with experimental results on MgO -SiO2 H2O system (Bowen and Tuttle , 1949;Greenwood, 1963), and can be explained provided that strongly serpentinized wehr litic or lherzolitic peridotite was thermally metamorphosed by granitic masses.…”

“…5; Tari-Misaka complex (Fig. 2) can be well elucidated by experimental results on MgO -SiOaH2O system (Bowen and Tuttle, 1949;Greenwood, 1963). Zonation from the core to the margin is result of progressive ther mal metamorphism of completely or strong ly serpentinized peridotite by granitic mass es.…”

“…This reaction is likely to occur during thermal metamorphism of strongly serpen tinized peridotitic rocks because of the com monness of the mineral assemblage serpen tine+diopside in them. Tremolite may be stable even around the temperature of for mation of orthopyroxene from anthophyllite +olivine (Greenwood, 1963) or from talc+ olivine (Bowen and Tuttle, 1949). In other words, calcium had been excluded from the reaction system which progressively produc ed talc, olivine, and anthophyllite, and "non -calciferous" orthopyroxene was consequent ly formed.…”

Solubility and diffusional uptake of hydrogen in quartz at high water pressures: Implications for hydrolytic weakening

“…Although we applied external confining pressures P, of -1500 MPa during these experiments, we expect that the internal PH,o was still controlled by the Mg(OH) 2 + MgO + H 2 0 buffer yielding an effective contining pressure P. of -600 MPa at T = 800° C, where P. is given by P,-PH,o· Accepting that this assumption, that P, =I= P, 0181 fluid• is uncommon in studies of phase equilibria, the concept of effective pressure has been widely applied in rock mechanics studies [e.g., Hubbert and Willis, 1957; to be rapid, was out of equilibrium, we treat the effective pressure P. as a "partial pressure" of the solid phases [Fyfe et a/., 1978, p. 135]. In addition to these constant strain rate experiments using NaCl assemblies, we repeated mechanical tests of unjacketed Brazilian quartz samples using conventional talc assemblies after annealing (in talc) for times of 4 x 10 4 and 4 x 10 5 s. Because the kinetics of the dehydration reactions talc-+ anthophyllite + quartz + H 2 0 and anthophyllite -+ enstatite + quartz + H 2 0 are relatively slow [e.g., Greenwood, 1963], we expect that the PH,o• and thus P,, must vary with time for these experiments. In addition, as a result of the fluid's contact with the carbon furnace [French, 1966] and temperature gradients within the sample assembly, we cannot be certain of the values of PH,o• Pc"•' Pc 0 , Pc 02 , or P 0 , for these experiments.…”

Stillwater Complex, Montana; rock succession, metamorphism and structure of the complex and adjacent rocks

“…Curve VI, beginning of melting for sanidine-quartz-water (Shaw, 1963). Curve VII, talc+for-sterite=anthophyllite+water (Greenwood, 1963).…”