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Plagioclase properties

Fig. 2.37. Phase diagram for Ca0-Na20 Si02-(Al203)-H20 system in equilibrium with quartz at 400°C and 400 bars. Plagioclase solid solution can be represented by the albite and anorthite fields, whereas epidote is represented by clinozoisite. Note that the clinozoisite field is adjacent to the anorthite field, suggesting that fluids with high Ca/(H+) might equilibrate with excess anorthite by replacing it with epidote. The location of the albite-anorthite-epidote equilibrium point is a function of epidote and plagioclase composition and depends on the model used for calculation of the thermodynamic properties of aqueous cations (Berndt et al., 1989). Fig. 2.37. Phase diagram for Ca0-Na20 Si02-(Al203)-H20 system in equilibrium with quartz at 400°C and 400 bars. Plagioclase solid solution can be represented by the albite and anorthite fields, whereas epidote is represented by clinozoisite. Note that the clinozoisite field is adjacent to the anorthite field, suggesting that fluids with high Ca/(H+) might equilibrate with excess anorthite by replacing it with epidote. The location of the albite-anorthite-epidote equilibrium point is a function of epidote and plagioclase composition and depends on the model used for calculation of the thermodynamic properties of aqueous cations (Berndt et al., 1989).
Chemical potentials for the constituents of minerals are defined in a similar manner. All minerals contain substitutional impurities that affect their chemical properties. Impurities range from trace substitutions, as might be found in quartz, to widely varying fractions of the end-members of solid solutions series. Solid solutions of geologic significance include clay minerals, zeolites, and plagioclase feldspars, which are important components in most geochemical models. [Pg.34]

Part of this program was realized at the Survey. Between 1901 and 1907, the chemist Allen, the physicist Day, and the petrographer, Iddings, completed a rigorous study of the thermal properties of the plagioclase feldspars, the most abundant rockforming minerals. This study was important in several respects. [Pg.27]

Carpenter M. A. and Ferry I M. (1984). Constraints on the thermodynamic mixing properties of plagioclase feldspars. Contrib. Mineral Petrol, 87 138-148. [Pg.823]

Intact soil cores (6.7 cm i.d.) were taken with spilt spoon at depths of 1 to 2 meters from a field test site located approximately 50 km east of Cincinnati, Ohio. The soil in this interval consists mainly of quartz (60%) and clay minerals (35%) with minor amounts of plagioclase and potassium feldspar. The majority of clay is illite and smectite, with minor amount of kaolinite. Soil chemical properties were analyzed prior to, and after, electroosmosis, in order to evaluate the effects of electroosmosis on the distribution of elements within the soil column. Sampled cores were wrapped in aluminum foil and stored at 12°C until the EO cell was assembled. [Pg.94]

Thus far, we have shown that the large cation sites in clinopyroxene and plagioclase have elastic properties which follow, quite closely, the oxygen polyhedral trend of Equation (14). Their best-fit ... [Pg.1103]

Ryzhova, T. V. 1964. Elastic properties of plagioclase. Bulletin of the Academy of Sciences of the USSR, Geophysics Series, English Translation, 7,633-635. [Pg.133]

Carpenter MA, McCoimell JDC, Navrotsky A (1985) Enthalpies of ordering in the plagioclase feldspar solid solution. Geochim Cosmochim Acta 49 947-966 Carpenter MA, Salje EKH, Graeme-Barber A, Wmck B, Dove MT, Kiught KS (1998) Calibration of excess thermodynamic properties and elastic constant variations associated with the a< p phase transition in quartz. Am Mineral 83 2-22... [Pg.168]

Properties Smectite 93%, quartz 2%, cristobalite 2%, plagioclase 3%, total surface area 725 rn 7g, BET (external) specific surface area 33 m7g, particle radius 250 nm, specific density 2700 kg/in [36]. [Pg.578]

The suite of minerals found in the Uinta Sandstone collected from Parachute Creek reflects the unique geochemical environment provided by Lake Uinta. The dominant minerals in the fresh sandstone are quartz, sodium plagioclase feldspars, and potassic feldspars as indicated by X-ray diffraction analysis (Ij. Important accessory minerals are caldte, nahcolite, dolomite-ankerite, and talc. Tlace minerals include iron-enriched magnesite in the siderite-magnesite series, pyrite, pyrrhotite, and hematite. Chemical properties of representative samples of the Uinta San tone are summarized in Thble I. [Pg.141]


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See also in sourсe #XX -- [ Pg.127 ]




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