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1.
The melting curves of CaCO3 and MgCO3 have been extended to pressures of 36 kb by experiments in piston-cylinder apparatus. At 30 kb, the melting temperatures of calcite and magnesite are 1610°C and 1585°C, respectively. New data for the magnesite dissociation reaction permit the location of an invariant point for the assemblage magnesite + periclase + liquid + vapor near 26 kb-1550°C. New data are also presented for the calcite-aragonite transition at 800°C, 950°C and 1100°C. At pressures above 36–50 kb, calcite and magnesite melt at temperatures lower than the solidus of dry mantle peridotite. Natural and experimental evidence suggests that carbon dioxide in the Earth's mantle could be present in a variety of forms: (a) a free vapor phase, (b) vapor dissolved in silicate magma, (c) crystalline carbonate, (d) carbonatite liquid, (e) carbon-bearing silicate analogs, or (f) carbonato-silicates (such as scapolite, spurrite, tilleyite, and related compounds). 相似文献
2.
An extensive laboratory study was conducted to measure the interfacial tension (IFT) between CO2 and brine consisting in equal molal concentrations of NaCl and CaCl2. The experiments were repeated at various pressures, temperatures and salinities that are representative of conditions prevailing during CO2 storage in deep saline aquifers. The dependence of CO2/brine IFT on pressure and temperature is similar to that previously reported for the systems: CO2/NaCl solution and CO2/CaCl2 solution. CO2/brine IFT increases linearly with water salinity and the magnitude of this increase was found equal to the sum of the individual CO2/NaCl solution and CO2/CaCl2 solution IFT increments, indicating a strong additive effect on IFT when the brine is composed of various salts. 相似文献
3.
Lin-Gun Liu 《Earth and Planetary Science Letters》1975,24(3):357-362
Samples of Ni2SiO4 in both olivine and spinel phases have been compressed to pressures above 140 kbar in a diamond-anvil cell and heated to temperatures of 1400–1800°C using a continuous YAG laser. After quenching and releasing pressure, X-ray diffraction examination indicates that the samples disproportionate to a mixture of stishovite (SiO2) and bunsenite (NiO) at pressures between 140 and 190 kbar. The exact disproportionation pressure is not certain due to transient increases in pressure during the local and rapid heating. However, thermodynamic calculations suggest that the transition pressure is about 192 ± 4 kbar at 1545°C and that the equation of the spinel-mixed oxides phase boundary isP(kbar) = 121 + (0.046 ± 0.020) T (°C). 相似文献
4.
Leonie E.A. Jones 《Physics of the Earth and Planetary Interiors》1977,15(1):77-89
The elastic moduli of single-crystal CaF2, SrF2 and BaF2 have been determined by the ultrasonic pulse superposition technique as a function of temperature from T = 298 to T = 650°K. These new data are consistent with other data obtained by ultrasonic pulse techniques in the region of room temperature and are superior to previous high-temperature data from resonance experiments. The elastic moduli (c) are represented by quadratic functions in T over the experimental temperature range with the curvature in the same sense for all the moduli. Evaluation of the temperature derivatives of the elastic moduli at constant volume indicates that the dominant temperature effect is extrinsic for (?KS/?T)P and intrinsic for (?μ/?T)P, where KS and μ are the isotropic bulk and shear moduli, respectively. For the series CaF2SrF2BaF2, |(?c/?T)p| decreases with increasing molar volume for all moduli; however there are no theoretical or empirical grounds on which to derive a simple relationship between (?c/?T)P and crystallographic parameters. 相似文献
5.
The melting curve of forsterite has been studied by static experiment up to a pressure of 15 GPa. Forsterite melts congruently at least up to 12.7 GPa. The congruent melting temperature is expressed by the Kraut-Kennedy equation in the following form: Tm(K)=2163 (1+3.0(V0 ? V)/V0), where the volume change with pressure was calculated by the Birch-Managhan equation of state with the isothermal bulk modulus K0 = 125.4 GPa and its pressure derivative K′ = 5.33. The triple point of forsterite-β-Mg2SiO4-liquid will be located at about 2600°C and 20 GPa, assuming that congruent melting persists up to the limit of the stability field of forsterite. The extrapolation of the previous melting data on enstatite and periclase indicates that the eutectic composition of the forsterite-enstatite system should shift toward the forsterite component with increasing pressure, and there is a possibility of incongruent melting of forsterite into periclase and liquid at higher pressure, although no evidence on incongruent melting has been obtained in the present experiment. 相似文献
6.
7.
Eric Dowty 《Earth and Planetary Science Letters》1977,35(2):347-351
Extraterrestrial calcium phosphates (“whitlockites”) have the anhydrous β-Ca3(PO4)2 structure, which is different from that of hydrous terrestrial whitlockite. This has been confirmed by X-ray refinement of the structure of a phosphate from the achondrite Angra dos Reis. In the β-Ca3(PO4)2 structure, there is one crystallographic site, Ca(IIA), which is half-occupied by calcium, and which seems to have an energetically unfavorable configuration; natural phosphates with this configuration (including Angra dos Reis) have composition Ca19(Mg,Fe)2(PO4)14. Stability of the structure is probably increased by substitution of Na for Ca in Ca(IIA) giving composition Ca18 (Mg,Fe)2Na2(PO4)14, which occurs in chondrites; by vacancy of Ca(IIA), with rare earths and yttrium substituting for calcium in other sites for charge balance, giving composition Ca16(Y,RE)2(Mg,Fe)2(PO4)14, found in lunar rocks; or by replacing Ca with hydrogen, giving composition Ca18(Mg,Fe)2H2(PO4)14, which is terrestrial whitlockite. Lack of the favorable substitutions of Na, (Y, RE) or H in Angra dos Reis phosphate implies that these elements were relatively scarce in its environment of formation. 相似文献
8.
Ian Jackson 《Physics of the Earth and Planetary Interiors》1977,14(1):86-94
Solvi and liquidi for various LiFMgF2 mixtures have been determined at pressures up to 40 kbar by differential-thermal-analysis in a piston-cylinder high-pressure device. The melting curves of pure LiF and MgF2 were also studied and the initial slopes (dTm/dP)P = 0 were found to be 11.2 and 8.3°C/kbar, respectively. The eutectic composition (LiF)0.64(MgF2)0.36 is independent of pressure to 35 kbar and the eutectic temperature rises approximately 6.3°C per kbar. Initial slopes of 11°C/kbar and 35°C/kbar are inferred for the melting curves of MgO and SiO2 (stishovite) respectively, on the basis of data for their structural analogue compounds. The observed solid solution of LiF in MgF2 and other evidence suggest the possibility of solid solution in the system (Mg,Fe)OSiO2 (stishovite) under mantle conditions which may have important consequences for the elastic properties of a “mixed-oxide” zone of the earth's mantle. 相似文献
9.
Pyroxene-garnet solid-solution equilibria have been studied in the pressure range 41–200 kbar and over the temperature range 850–1,450°C for the system Mg4Si4O12Mg3Al2Si3O12, and in the pressure range 30–105 kbar and over the temperature range 1,000–1,300°C for the system Fe4Si4O12Fe3Al2Si3O12. At 1,000°C, the solid solubility of enstatite (MgSiO3) in pyrope (Mg3Al2Si3O12) increases gradually to 140 kbar and then increases suddenly in the pressure range 140–175 kbar, resulting in the formation of a homogeneous garnet with composition Mg3(Al0.8Mg0.6Si0.6)Si3O12. In the MgSiO3-rich field, the three-phase assemblage of β- or γ-Mg2SiO4, stishovite and a garnet solid solution is stable at pressures above 175 kbar at 1,000°C. The system Fe4Si4O12Fe3Al2Si3O12 shows a similar trend of high-pressure transformations: the maximum solubility of ferrosilite (FeSiO3) in almandine (Fe3Al2Si3O12) forming a homogeneous garnet solid solution is 40 mol% at 93 kbar and 1,000°C.If a pyrolite mantle is assumed, from the present results, the following transformation scheme is suggested for the pyroxene-garnet assemblage in the mantle. Pyroxenes begin to react with the already present pyrope-rich garnet at depths around 150 km. Although the pyroxene-garnet transformation is spread over more than 400 km in depth, the most effective transition to a complex garnet solid solution takes place at depths between 450 and 540 km. The complex garnet solid solution is expected to be stable at depths between 540 and 590 km. At greater depths, it will decompose to a mixture of modified spinel or spinel, stishovite and garnet solid solutions with smaller amounts of a pyroxene component in solution. 相似文献
10.
Experimental data on the stability of titan-phlogopite [K2Mg4TiAl2Si6O20(OH)4] are presented which show it to be stable to substantially higher temperatures than normal phlogopite [K2Mg6Al2Si6O20(OH)4]. A qualitative model to explain the role of titan-phlogopite during magma generation is put forward. Breakdown of titan-phlogopite during melting at depth (> 150km) on subducted lithospheric slabs is believed responsible for the concomitant increase of K and Ti observed in magmas erupted during orogenic volcanism. At lower pressures (up to about 10 kbar) beneath mid-oceanic ridges, titan-phlogopite is predicted to behave as a refractory phase during partial melting in the mantle, especially if H2O-excess conditions pertain, although at higher pressures in this environment it would almost certainly behave as a low-melting component. 相似文献
11.
I. Kushiro 《Earth and Planetary Science Letters》1978,41(1):87-90
Viscosity of anhydrous albite melt, determined by the falling-sphere method in the solid-media, piston-cylinder apparatus, decreases with increasing pressure from 1.13 × 105 P at 1 atm to 1.8 × 104 P at 20 kbar at 1400°C. The rate of decrease in viscosity is larger between 12 and 15 kbar than in other pressure ranges examined. The density of the quenched albite melt increases with increasing pressure of quenching from 2.38 g/cm3 at 1 atm to 2.53 g/cm3 at 20 kbar. The rate of increase in density is largest at pressures between 15 and 20 kbar. The melting curve of albite shows an inflexion at about 16 kbar. These observations strongly suggest that structural changes of albite melt would take place effectively at pressures near 15 kbar. Melt of jadeite (NaAlSi2O6) composition shows very similar changes in viscosity and density and a melting curve inflexion at pressures near 10 kbar. Difference in pressure for the suggested effective structural changes of albite and jadeite melts is 5–6 kbar, which is nearly the same as that between the subsolidus reaction curves nepheline + albite= 2jadeite and albite=jadeite + quartz. The structural changes of the melts are, however, continuous and begin to take place at pressures lower than those of the crystalline phases. 相似文献
12.
Ian Jackson 《Physics of the Earth and Planetary Interiors》1977,14(2):143-164
The melting curves of the fluorides ZnF2 and NiF2 (rutile structure), CaF2, SrF2 and BaF2 (fluorite structure), and of the fluoroberyllates Na2BeF4 and Li2BeF4 have been studied at pressures ? 40 kbar by differential thermal analysis in a piston-cylinder high-pressure device. The initial slopes (dTm/dP)0 of these melting curves are respectively 7.2, 5.8, 16.7, 15.2, 15.7, 15.1 and <0°C/kbar. A new Li2BeF4 polymorph, apparently of the olivine structure type, is stable at pressures > 10 kbar and its melting curve has an average slope of ~6.7°C/kbar. These new data and those for SiO2, BeF2, GeO2, LiF and MgF2, recently studied by Jackson, are combined with existing data for elements, ionic compounds and silicates to assess the influence of crystal structure, molar volume and the nature of interatomic bonding on the initial slopes of melting curves. It is found that the entropy of fusion (ΔSm) is primarily a function of crystal structure while the volume change on fusion (ΔVm) is controlled by crystal molar volume within each isostructural series. Such systematics have recently facilitated estimation of the initial slopes of the melting curves of periclase and stishovite. New and existing melting data for silicates and their analogues have been analysed and a systematic dependence of (dTm/dP)0 on SiO2 concentration has been demonstrated. Possible implications of this trend for partial melting of upper-mantle garnet lherzolite are illustrated. Finally, the use of the traditional silicate-germanate and oxide-fluoride modelling schemes is reviewed in the light of information from this present study. 相似文献
13.
Kristian McConville Claudia Halsband Elaine S. Fileman Paul J. Somerfield Helen S. Findlay John I. Spicer 《Marine pollution bulletin》2013
Some planktonic groups suffer negative effects from ocean acidification (OA), although copepods might be less sensitive. We investigated the effect of predicted CO2 levels (range 480–750 ppm), on egg production and hatching success of two copepod species, Centropages typicus and Temora longicornis. In these short-term incubations there was no significant effect of high CO2 on these parameters. Additionally a very high CO2 treatment, (CO2 = 9830 ppm), representative of carbon capture and storage scenarios, resulted in a reduction of egg production rate and hatching success of C. typicus, but not T. longicornis. In conclusion, reproduction of C. typicus was more sensitive to acute elevated seawater CO2 than that of T. longicornis, but neither species was affected by exposure to CO2 levels predicted for the year 2100. The duration and seasonal timing of exposures to high pCO2, however, might have a significant effect on the reproduction success of calanoid copepods. 相似文献
14.
The system Mg2SiO4MgOH2O was investigated at pressures between 85 and 160 kbar and at temperatures between 750 and 1200°C. In runs for a gel with Mg/Si ratio of 3 and with 4.0 wt.-percent H2O, a dense hydrous magnesian silicate, denoted phase B by Ringwood and Major, was found at pressures from about 100 kbar to at least 160 kbar in the whole temperature range studied. In the following table the crystallographic parameters and chemical formula of phase B, determined in this study, are compared with those of the other dense hydrous silicates in Mg2SiO4MgOH2O.
Phase | Composition | Space group | Cell parameters | Density (g cm?3) | |||
β | |||||||
(Å) | (Å) | (Å) | (°) | ||||
Chondrodite | Mg5Si2O10H2 | 7.914 | 4.752 | 10.350 | 108.71 | 3.06 | |
Clinohumite | Mg9Si4O18H2 | 13.695 | 4.747 | 10.284 | 100.64 | 3.14 | |
Phase A | Mg7Si2O14H6 | 7.860 | 9.573 | 2.96 | |||
Phase B | Mg23Si8O42H6 | 10.600 | 14.098 | 10.092 | 104.05 | 3.32 |