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1.
Property and behaviour of sand–pile interface are crucial to shaft resistance of piles. Dilation or contraction of the interface soil induces change in normal stress, which in turn influences the shear stress mobilised at the interface. Although previous studies have demonstrated this mechanism by laboratory tests and numerical simulations, the interface responses are not analysed systematically in terms of soil state (i.e. density and stress level). The objective of this study is to understand and quantify any increase in normal stress of different pile–soil interfaces when they are subjected to loading and stress relief. Distinct element modelling was carried out. Input parameters and modelling procedure were verified by experimental data from laboratory element tests. Parametric simulations of shearbox tests were conducted under the constant normal stiffness, constant normal load and constant volume boundary conditions. Key parameters including initial normal stress ( $ \sigma_{{{\text{n}}0}}^{\prime } $ ), initial void ratio (e 0), normal stiffness constraining the interface and loading–unloading stress history were investigated. It is shown that mobilised stress ratio ( $ \tau /\sigma_{\text{n}}^{\prime } $ ) and normal stress increment ( $ \Updelta \sigma_{\text{n}}^{\prime } $ ) on a given interface are governed by $ \sigma_{{{\text{n}}0}}^{\prime } $ and e 0. An increase in $ \sigma_{{{\text{n}}0}}^{\prime } $ from 100 to 400 kPa leads to a 30 % reduction in $ \Updelta \sigma_{\text{n}}^{\prime } $ . An increase in e 0 from 0.18 to 0.30 reduces $ \Updelta \sigma_{\text{n}}^{\prime } $ by more than 90 %, and therefore, shaft resistance is much lower for piles in loose sands. A unique relationship between $ \Updelta \sigma_{\text{n}}^{\prime } $ and normal stiffness is established for different soil states. It can be applied to assess the shaft resistance of piles in soils with different densities and subjected to loading and stress relief. Fairly good agreement is obtained between the calculated shaft resistance based on the proposed relationship and the measured results in centrifuge model tests. 相似文献
2.
Equilibrium alumina contents of orthopyroxene coexisting with spinel and forsterite in the system MgO-Al2O3-SiO2 have been reversed at 15 different P-T conditions, in the range 1,030–1,600° C and 10–28 kbar. The present data and three reversals of Danckwerth and Newton (1978) have been modeled assuming an ideal pyroxene solid solution with components Mg2Si2O6 (En) and MgAl2SiO6 (MgTs), to yield the following equilibrium condition (J, bar, K): $$\begin{gathered} RT{\text{ln(}}X_{{\text{MgTs}}} {\text{/}}X_{{\text{En}}} {\text{) + 29,190}} - {\text{13}}{\text{.42 }}T + 0.18{\text{ }}T + 0.18{\text{ }}T^{1.5} \hfill \\ + \int\limits_1^P {\Delta V_{T,P}^{\text{0}} dP = 0,} \hfill \\ \end{gathered} $$ where $$\begin{gathered} + \int\limits_1^P {\Delta V_{T,P}^{\text{0}} dP} \hfill \\ = [0.013 + 3.34 \times 10^{ - 5} (T - 298) - 6.6 \times 10^{ - 7} P]P. \hfill \\ \end{gathered} $$ The data of Perkins et al. (1981) for the equilibrium of orthopyroxene with pyrope have been similarly fitted with the result: $$\begin{gathered} - RT{\text{ln(}}X_{{\text{MgTs}}} \cdot X_{{\text{En}}} {\text{) + 5,510}} - 88.91{\text{ }}T + 19{\text{ }}T^{1.2} \hfill \\ + \int\limits_1^P {\Delta V_{T,P}^{\text{0}} dP = 0,} \hfill \\ \end{gathered} $$ where $$\begin{gathered} + \int\limits_1^P {\Delta V_{T,P}^{\text{0}} dP} \hfill \\ = [ - 0.832 - 8.78{\text{ }} \times {\text{ 10}}^{ - {\text{5}}} (T - 298) + 16.6{\text{ }} \times {\text{ 10}}^{ - 7} P]{\text{ }}P. \hfill \\ \end{gathered} $$ The new parameters are in excellent agreement with measured thermochemical data and give the following properties of the Mg-Tschermak endmember: $$H_{f,970}^0 = - 4.77{\text{ kJ/mol, }}S_{298}^0 = 129.44{\text{ J/mol}} \cdot {\text{K,}}$$ and $$V_{298,1}^0 = 58.88{\text{ cm}}^{\text{3}} .$$ The assemblage orthopyroxene+spinel+olivine can be used as a geothermometer for spinel lherzolites, subject to a choice of thermodynamic mixing models for multicomponent orthopyroxene and spinel. An ideal two-site mixing model for pyroxene and Sack's (1982) expressions for spinel activities provide, with the present experimental calibration, a geothermometer which yields temperatures of 800° C to 1,350° C for various alpine peridotites and 850° C to 1,130° C for various volcanic inclusions of upper mantle origin. 相似文献
3.
Oxygen Fugacity measurements were carried out on chromites from the Eastern Bushveld Complex (Maandagshoek) and are compared with former measurements on chromites from the western Bushveld Complex (Zwartkop Chrome Mine). These results together with those of Hill and Roeder (1974) yield the following conditions of formation for the massive chromitite layers: Western Bushveld Complex (Zwartkop Chrome Mine) $$\begin{gathered} Layer{\text{ }}T(^\circ C) p_{O_2 } (atm) \hfill \\ LG3{\text{ 1160}} - {\text{1234 10}}^{ - {\text{5}}} - 10^{ - 7.6} \hfill \\ LG4{\text{ 1175}} - {\text{1200 10}}^{ - 6.35} - 10^{ - 7.20} \hfill \\ LG6{\text{ 1162}} - {\text{1207 10}}^{ - 6.20} - 10^{ - 7.50} \hfill \\ \hfill \\ \end{gathered} $$ Eastern Bushveld Complex (Farm Maandagshoek) $$\begin{gathered} {\text{LXI 1115}} - {\text{1150 10}}^{ - 7.80} - 10^{ - 8.80} \hfill \\ ( = {\text{Steelpoort Seam)}} \hfill \\ {\text{LX 1125 10}}^{ - 8.25} \hfill \\ {\text{V 1120 10}}^{ - 8.55} \hfill \\ {\text{LII 1120 10}}^{ - 8.0} - 10^{ - 8.60} \hfill \\ \end{gathered} $$ The comparison of the data shows, that the chronitite layers within each particular sequence were formed under approximately identicalp o 2- andT-conditions. The chromites from the western Bushveld Complex, however, were formed at higher temperatures and higher oxygen fugacities than the chromites from the eastern Bushveld Complex. Fromp o 2-T-curves of disseminated chromites and the temperatures derived above, the following conditions of formation for the host rocks were obtained: Western Bushveld Complex $$T = 1200^\circ {\text{C; }}p_{{\text{o}}_{\text{2}} } = 10^{ - 7.25} - 10^{ - 7.50} $$ Eastern Bushveld Complex $$T = 1125^\circ {\text{C; }}p_{{\text{o}}_{\text{2}} } = 10^{ - 8.50} - 10^{ - 9.25} $$ Consequently, the host rocks in the Zwartkop-Chrome-Mine, were formed under higher temperatures and higher oxygen fugacities than the host rocks at Maandagshoek. The rock sequence in the Zwartkop-Chrome-Mine therefore originated in an earlier stage of the differentiation of the Bushveld magma. Comparison of the chromites from the host rocks with the chromites from massive layers supports Ulmer's (1969) thesis that an increase of the oxygen fugacity is responsible for the formation of massive chromitite layers. The values in this investigation show that increases of only about 0.5–1.0 log units are necessary to enhance chromitite layer formation. 相似文献
4.
Detailed analysis of textural and chemical criteria in rocks of the anorthosite-charnockite suite of the Adirondack Highlands suggests that development of garnet in silica-saturated rocks of the suite occurs according to the reaction: $$\begin{gathered} {\text{Anorthite}} {\text{Orthopyroxene}} {\text{Quartz}} \hfill \\ {\text{2CaAl}}_{\text{2}} {\text{Si}}_{\text{2}} {\text{O}}_{\text{8}} + (6 - \alpha )({\text{Fe,Mg}}){\text{SiO}}_{\text{3}} + \alpha {\text{Fe - Oxide + (}}\alpha {\text{ - 2)SiO}}_{\text{2}} \hfill \\ {\text{Garnet}} {\text{Clinopyroxene}} \hfill \\ = {\text{Ca(Fe,Mg)}}_{\text{5}} {\text{Al}}_{\text{4}} {\text{Si}}_{\text{6}} {\text{O}}_{{\text{24}}} + {\text{Ca(Fe,Mg)Si}}_{\text{2}} {\text{O}}_{\text{6}} \hfill \\ \end{gathered} $$ , where α is a function of the distribution of Fe and Mg between the several coexisting ferromagnesian phases. Depending upon the relative amounts of Fe and Mg present, quartz may be either a reactant or a product. Using an aluminum-fixed reference frame, this reaction can be restated in terms of a set of balanced partial reactions describing the processes occurring in spatially separated domains within the rock. The fact that garnet invariably replaces plagioclase as opposed to the other reactant phases indicates that the aluminum-fixed model is valid as a first approximation. This reaction is univariant and produces unzoned garnet. It differs from a similar equation proposed by de Waard (1965) for the origin of garnet in Adirondack metabasic rocks, i.e. 6 Orthopyroxene+2 Anorthite = Clinopyroxene+Garnet+2 Quartz, the principle difference being that iron oxides (ilmenite and/or magnetite) are essential reactant phases in the present reactions. The product assemblage (garnet+clinopyroxene+plagioclase ± orthopyroxene ± quartz) is characteristic of the clinopyroxene-almandine subfacies of the granulite facies. 相似文献
5.
W. Johannes 《Contributions to Mineralogy and Petrology》1968,19(4):309-315
A new determination of the equilibrium reaction: $$\begin{gathered} 2{\text{ Mg}}_{\text{2}} [{\text{SiO}}_{\text{4}} ] + 3{\text{ H}}_{\text{2}} {\text{O}} \rightleftharpoons {\text{1 Mg}}_{\text{3}} [({\text{OH)}}_{\text{4}} |{\text{Si}}_{\text{2}} {\text{O}}_{\text{5}} ] + 1{\text{ Mg(OH)}}_{\text{2}} \hfill \\ \hfill \\ {\text{ forsterite serpentine brucite}} \hfill \\ \end{gathered} $$ yielded equilibrium temperatures which lie (at identical H2O-pressures) about 60° C lower than all previously published data (Bowen and Tuttle, 1949; Yoder, 1952; Kitahara et al., 1966; Kitahara and Kennedy, 1967). It has been shown that the above authors have determined not the stable equilibrium curve but instead a metastable “synthesis boundary”. The actual (stable) equilibrium curve is located at 0,5 kb and 350° C 2,0 kb and 380° C 3,5 kb and 400° C 5,0 kb and 420° C 6,5 kb and 430° C. 相似文献
6.
The temperature-sensitive Fe,Mg exchange equilibrium,
相似文献
7.
M. Cai 《Rock Mechanics and Rock Engineering》2010,43(2):167-184
By applying the Griffith stress criterion of brittle failure, one can find that the uniaxial compressive strength (σc) of rocks is eight times the value of the uniaxial tensile strength (σt). The Griffith strength ratio is smaller than what is normally measured for rocks, even with the consideration of crack closure.
The reason is that Griffith’s theories address only the initiation of failure. Under tensile conditions, the crack propagation
is unstable so that the tensile crack propagation stress (σcd)t and the peak tensile strength σt are almost identical to the tensile crack initiation stress (σci)t. On the other hand, the crack growth after crack initiation is stable under a predominantly compressive condition. Additional
loading is required in compression to bring the stress from the crack initiation stress σci to the peak strength σc. It is proposed to estimate the tensile strength of strong brittle rocks from the strength ratio of
R = \fracs\textc | s\textt | = 8\fracs\textc s\textci . R = {\frac{{\sigma_{\text{c}} }}{{\left| {\sigma_{\text{t}} } \right|}}} = 8{\frac{{\sigma_{\text{c}} }}{{\sigma_{\text{ci}} }}}. The term
\fracs\textc s\textci {\frac{{\sigma_{\text{c}} }}{{\sigma_{\text{ci}} }}} accounts for the difference of crack growth or propagation in tension and compression in uniaxial compression tests.
\fracsc sci {\frac{{\sigma_{c} }}{{\sigma_{ci} }}} depends on rock heterogeneity and is larger for coarse grained rocks than for fine grained rocks. σci can be obtained from volumetric strain measurement or acoustic emission (AE) monitoring. With the strength ratio R determined, the tensile strength can be indirectly obtained from
| s\textt | = \fracs\textc R = \fracs\textci 8. \left| {\sigma_{\text{t}} } \right| = {\frac{{\sigma_{\text{c}} }}{R}} = {\frac{{\sigma_{\text{ci}} }}{8}}. It is found that the predicted tensile strengths using this method are in good agreement with test data. Finally, a practical
estimate of the Hoek–Brown strength parameter m
i is presented and a bi-segmental or multi-segmental representation of the Hoek–Brown strength envelope is suggested for some
brittle rocks. In this fashion, the rock strength parameters like σt and m
i, which require specialty tests such as direct tensile (or Brazilian) and triaxial compression tests for their determination,
can be reasonably estimated from uniaxial compression tests. 相似文献
8.
Partitioning of Mg and Fe between coexisting biotite and orthopyroxene has been experimentally determined at temperatures 700, 750 and 800° C and 490 MPa total pressure in the system KAlO2-MgO-FeO-SiO2-H2O. Oxygen fugacity was controlled by the QFM buffer. Starting materials were synthetic minerals of differing Fe/(Fe+Mg) values. Run products were analyzed for partitioning of components by a microprobe. Orthopyroxene was established to be notably inhomogeneous, whereas biotite was essentially homogeneous. To establish equilibrium relations, statistical treatment of the results of each experiment in addition to the whole complex of experimental data was applied. The regression equations for isotherms of the Fe-Mg partitioning between the minerals studied have been obtained. As a result, the equation for a two-dimensional regression may be written as: $$\begin{gathered} Y = (A + A_1 t + A_2 t^2 )(X - X^4 ) + (B + B_1 t + B_1 t^2 )(X^2 - X^4 ) + \hfill \\ (C + C_1 t + C_1 t^2 )(X^3 - X^4 ) + X^4 {\text{ where }}Y = X_{{\text{Opx}}}^{{\text{Fe}}} ;{\text{ X}} = {\text{X}}_{{\text{Bi}}}^{{\text{Fe}}} ; \hfill \\ t = 1000/T,K, \hfill \\ \begin{array}{*{20}c} {A = {\text{ }}4.59398,} & {A_1 = - {\text{ }}8.29838,} & {A_2 = {\text{ }}4.97316,} \\ {B = - 11.13731,} & {B_1 = {\text{ }}28.19304,} & {B_2 = - 20.98240,} \\ {A = {\text{ }}8.25072,} & {C_1 = - 20.80485,} & {C_2 = {\text{ }}15.35967} \\ \end{array} \hfill \\ {\text{ }}\sigma = 0.0143{\text{ }} \hfill \\ \end{gathered}$$ . This equation enables extrapolation of partitioning isotherms over a wide range of temperatures. 相似文献
9.
J. S. Delaney J. V. Smith J. B. Dawson P. H. Nixon 《Contributions to Mineralogy and Petrology》1979,71(2):157-169
The temperature dependence of the Mn-Mg distribution between garnet and clinopyroxene, originally proposed by Carswell, was confirmed by Shimizu and Allègre (1978) using ion microprobe and electron microprobe data. High precision electron microprobe analyses of a larger set of 52 Iherzolites from S. Africa and Malaita, Solomon Islands show considerable scatter in the temperature dependence of this distribution, and correlation with the CaO content of the garnet is indicated. A new distribution coefficient is based on the reaction: $$\begin{gathered} \operatorname{Mn} _{\text{2}} \operatorname{Si} _2 \operatorname{O} _6 {\text{ + }}\operatorname{CaAl} _{2/3} \operatorname{SiO} _4 {\text{ + }}\operatorname{MgAl} _{2/3} \operatorname{SiO} _4 \hfill \\ {\text{Mn - pyroxene grossular pyrope}} \hfill \\ {\text{ }} \rightleftharpoons \operatorname{CaMgSi} _2 \operatorname{O} _6 {\text{ + }}2\operatorname{MnAl} _{2/3} \operatorname{SiO} _4 \hfill \\ {\text{ diopside spessartine}} \hfill \\ \end{gathered} $$ It was calibrated against temperature determined from two independent thermometers (Wells pyroxene and O'Neill-Wood garnet-olivine) for Iherzolitic assemblages, and shown to to be sensitive to within + 50 °C for most specimens in the range 900 °– 1,300 ° C. This distribution coefficient appears independent of pressure within the uncertainty of the available data, and has the potential to be a third independent thermometer for use in garnet Iherzolites and possibly eclogites. 相似文献
10.
On formation of a bed and distribution of bed thickness, A. N. Kolmogorov presented a mathematical explanation that if repetitive alternations of material accumulation and erosion form a sequence of beds, the resultant bed-thickness distribution curve takes a shape truncated by the ordinate at zero thickness. In this truncated distribution curve, its continuation and extension from positive to negative thickness represents the distribution of beds with negative thickness, that is, the depth of erosion. When a distribution curve, including both positive and negative parts, is expressed by a function f(x),the ratio \(\int_0^\infty {f(x)dx to} \int_{ - \infty }^\infty {f(x)dx} \) ,called Kolmogorov's coefficient and designated as p,is a parameter representing the degree of accumulation in the depositional environment. On the assumption that f(x)is described by the Gaussian distribution function, the coefficient pfor Permian and Pliocene sequences in central Japan was calculated. The coefficients also were obtained from published data for different types of sediments from other areas. It was determined that they are more or less different depending on their depositional environments. The calculated results are summarized as follows: $$\begin{gathered} p = 0.80 - 1.0for{\text{ }}alluvial{\text{ }}or{\text{ }}fluvial{\text{ }}deposits \hfill \\ p = 0.65 - 0.95for{\text{ }}nearshore{\text{ }}sediments \hfill \\ p = 0.55 - 0.95for{\text{ }}geosynclinal{\text{ }}sediments \hfill \\ p = 0.90 - 1.0for{\text{ }}varves \hfill \\ \end{gathered} $$ In addition, a ratio \(q = \int_0^\infty {xf(x)dx/} \int_{ - \infty }^\infty {|x|f(x)dx} \) ,called Kolmogorov's ratio in this paper, is introduced for estimating a degree of total thickness actually observed in the field relative to total thickness once present in a basin. The calculated results of Kolmogorov's ratio are as follows: $$\begin{gathered} q = 0.88 - 1.0for{\text{ }}alluvial{\text{ }}or{\text{ }}fluvial{\text{ }}deposits \hfill \\ q = 0.68 - 0.98for{\text{ }}nearshore{\text{ }}sediments \hfill \\ q = 0.55 - 0.96for{\text{ }}geosynclinal{\text{ }}sediments \hfill \\ q = 0.92 - 1.0for{\text{ }}varves \hfill \\ \end{gathered} $$ The sedimentological significance of these values is discussed. 相似文献
11.
Surendra K. Saxena Alan Benimoff Nicholas E. Pingitore Jr. 《Contributions to Mineralogy and Petrology》1977,60(1):77-90
The chemical composition of 2188 terrestrial igneous rocks ranging from ultrabasic to granitic composition was analyzed statistically using the method of factor analysis (principal components). The resultant first and second factors were: $$\begin{gathered} {\text{ }}F_1 = 0.933{\text{ Na}}_{\text{2}} {\text{O + 0}}{\text{.143 SiO}}_{\text{2}} + 0.206{\text{ K}}_{\text{2}} {\text{O}} - 0.346{\text{ CaO}} - 0.263{\text{ MgO}} - \hfill \\ .203{\text{ FeO}} \pm \cdot \cdot \cdot \hfill \\ {\text{ }}F_2 = 0.979{\text{ Al}}_{\text{2}} {\text{O}}_{\text{3}} - 0.269{\text{ MgO}} - 0.151{\text{ SiO}}_{\text{2}} - 0.112{\text{ FeO}} \pm \cdot \cdot \cdot \hfill \\ \end{gathered} $$ where oxides are in weight percent. A plot of the first factor against the second results in a useful igneous variation diagram. When the compositions of the 2188 terrestrial rocks and 604 lunar rocks are plotted on this diagram, the two groups of rocks are clearly separated within an albite-anorthite-forsterite-fayalite-quartz polygon. None of the terrestrial differentiation trends are significant for lunar rocks. The major difference in the chemistry of lunar and terrestrial rocks lies in the former being albite poor. Removal of most of the albite from the compositions of terrestrial layered intrusives such as the Skaergaard results in an excellent match between the compositions of the two groups of rocks. Albite subtracted compositions of Skaergaard rocks in particular cover the entire range of chemical variation in the lunar rocks. The statistical results prompt us to speculate further on the similarity of the moon and Skaergaard. We note that the average composition of the moon (Wanke et al., 1974) is similar to the albite subtracted composition of the Skaergaard magma. The lunar crust and a significant part of the lunar interior may match the albite subtracted and somewhat Mg enriched Skaergaard magma. 相似文献
12.
Tjerk Peters Hans Schwander Volkmar Trommsdorff 《Contributions to Mineralogy and Petrology》1973,42(4):325-332
Reactions involving the phases quartz-rhodochrosite-tephroite-pyroxmangite-fluid have been studied experimentally in the system MnO-SiO2-CO2-H2O at a pressure of 2 000 bars and resulted in the following expressions
13.
A. Bhattacharya 《Contributions to Mineralogy and Petrology》1986,94(3):387-394
Five geobarometers involving cordierite have been formulated for quantitative pressure sensing in high grade metapelites. The relevant reactions in the FeO-Al2O3-SiO2 (±H2O) system are based on the assemblages (A) cordierite-garnet-sillimanite-quartz, (B) cordierite-spinel-quartz, (C) cordierite-garnet-spinel-sillimanite, (D) cordierite-garnet-orthopyroxene-quartz and (E) cordierite-orthopyroxene-sillimanite-quartz. Application of the barometric formulations to a large number of granulite grade rocks indicates that the cordierite-garnet-sillimanite-quartz equilibrium is widely applicable and registers pressures which are in good agreement with the “consensus” pressure estimates. The dispersion in the computed P values, expressed as one standard deviation, is within ±1.2 kbar. The geobarometers (B) and (C) also yield pressures which are reasonable and compare well with those computed from equilibrium (A). The estimated pressures from (D) and (E), both involving orthopyroxene, are at variance with these estimates. It has been argued that the discrepancy in pressures obtained from these geobarometers stems from an inadequate knowledge of activity-composition relations and/or errors in input thermodynamic data of aluminous orthopyroxene. The convergence of pressure values estimated from the barometric formulations, especially (A), (B) and (C), implies that the present formulations are more dependable than the existing formulations and are also capable of setting limits on P values in response to varying $$\begin{gathered} {\text{1/2Fe}}_{\text{2}} {\text{Al}}_{\text{4}} {\text{Si}}_{\text{5}} {\text{O}}_{{\text{18}}} \hfill \\ {\text{ = 1/3Fe}}_{\text{3}} {\text{Al}}_{\text{2}} {\text{Si}}_{\text{3}} {\text{O}}_{{\text{12}}} {\text{ + 2/3Al}}_{\text{2}} {\text{SiO}}_{\text{5}} {\text{ + 5/6SiO}}_{\text{2}} {\text{. (A)}} \hfill \\ {\text{1/2Fe}}_{\text{2}} {\text{Al}}_{\text{4}} {\text{Si}}_{\text{5}} {\text{O}}_{{\text{18}}} {\text{ = FeAl}}_{\text{2}} {\text{O}}_{\text{4}} {\text{ + 5/2SiO}}_{\text{2}} {\text{. (B)}} \hfill \\ {\text{Fe}}_{\text{2}} {\text{Al}}_{\text{4}} {\text{Si}}_{\text{5}} {\text{O}}_{{\text{18}}} {\text{ + FeAl}}_{\text{2}} {\text{O}}_{\text{4}} \hfill \\ = {\text{Fe}}_{\text{3}} {\text{Al}}_{\text{2}} {\text{Si}}_{\text{3}} {\text{O}}_{{\text{12}}} {\text{ + 2Al}}_{\text{2}} {\text{SiO}}_{\text{5}} {\text{. (C)}} \hfill \\ {\text{1/2Fe}}_{\text{2}} {\text{Al}}_{\text{4}} {\text{Si}}_{\text{5}} {\text{O}}_{{\text{18}}} {\text{ + Fe}}_{\text{2}} {\text{Si}}_{\text{2}} {\text{O}}_{\text{6}} \hfill \\ = {\text{Fe}}_{\text{3}} {\text{Al}}_{\text{2}} {\text{Si}}_{\text{3}} {\text{O}}_{{\text{12}}} {\text{ + 3/2SiO}}_{\text{2}} .{\text{ (D)}} \hfill \\ {\text{1/2Fe}}_{\text{2}} {\text{Al}}{}_{\text{4}}{\text{Si}}_{\text{5}} {\text{O}}_{{\text{18}}} \hfill \\ = 1/2{\text{Fe}}_{\text{2}} {\text{Si}}_{\text{2}} {\text{O}}_{\text{6}} {\text{ + Al}}_{\text{2}} {\text{SiO}}_{\text{5}} {\text{ + 1/2SiO}}_{\text{2}} .{\text{ (E)}} \hfill \\ \end{gathered}$$ . The present communication addresses the calibration, applicability and reliability of these barometers with reference to granulite facies metapelites. 相似文献
14.
T. J. B. Holland 《Contributions to Mineralogy and Petrology》1979,68(3):293-301
Hydrothermal reversal experiments have been performed on the upper pressure stability of paragonite in the temperature range 550–740 ° C. The reaction $$\begin{gathered} {\text{NaAl}}_{\text{3}} {\text{Si}}_{\text{3}} {\text{O}}_{{\text{1 0}}} ({\text{OH)}}_{\text{2}} \hfill \\ {\text{ paragonite}} \hfill \\ {\text{ = NaAlSi}}_{\text{2}} {\text{O}}_{\text{6}} + {\text{Al}}_{\text{2}} {\text{SiO}}_{\text{5}} + {\text{H}}_{\text{2}} {\text{O}} \hfill \\ {\text{ jadeite kyanite vapour}} \hfill \\ \end{gathered}$$ has been bracketed at 550 ° C, 600 ° C, 650 ° C, and 700 ° C, at pressures 24–26 kb, 24–25.5 kb, 24–25 kb, and 23–24.5 kb respectively. The reaction has a shallow negative slope (? 10 bar °C?1) and is of geobarometric significance to the stability of the eclogite assemblage, omphacite+kyanite. The experimental brackets are thermodynamically consistent with the lower pressure reversals of Chatterjee (1970, 1972), and a set of thermodynamic data is presented which satisfies all the reversal brackets for six reactions in the system Na2O-Al2O3-SiO2-H2O. The Modified Redlich Kwong equation for H2O (Holloway, 1977) predicts fugacities which are too high to satisfy the reversals of this study. The P-T stabilities of important eclogite and blueschist assemblages involving omphacite, kyanite, lawsonite, Jadeite, albite, chloritoid, and almandine with paragonite have been calculated using thermodynamic data derived from this study. 相似文献
15.
Eleftheria E. Papadimitriou 《Natural Hazards》1994,9(3):303-321
Earthquake recurrence intervals for large and great shallow mainshocks in 12 seismogenic sources along the North Pacific seismic zone (Alaska-Aleutians-Kamchatka-Kuril Islands) have been estimated and used for the determination of the following relations:
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