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1.
An experimental and theoretical investigation of the effect of pressure on the solubility of FeO in molten iron has been carried out. Analyses of shock-wave compression data on iron oxides combined with measurements of the FeO bond length in “metallic” oxides suggest that the partial molar volume of FeO(V*) dissolved in molten iron is substantially smaller than that of molten wüstite. Hence the effect of high pressure should be to increase the solubility of FeO in molten iron at a given temperature. This inference is confirmed by an experimental investigation of the effect of pressure on the position of the FeFeO eutectic. Thermodynamic calculations based on these experiments yield an estimate forV* which is in reasonable agreement with the theoretical estimates. The experimental value ofV* is used to calculate the effect of high pressure upon the FeFeO phase diagram. Solubility of FeO in molten iron increases sharply with pressure, the liquid immiscibility region contracts and disappears around 20 GPa and it is predicted that the FeFeO phase diagram should resemble a simple eutectic system above about 20 GPa. Analogous calculations predict that the solubility of FeO in molten iron in equilibrium with magnesiowüstite (Mg0.8Fe0.2)O at 2500°C increase from 14 mol.%(P = 0) to above 25 mol.% at 20 GPa. If the core formed by segregation of metallic iron originally dispersed throughout the earth, it seems inevitable that it would dissolved large amounts of FeO, thereby accounting for the observation that the density of the outer core is substantially smaller than that of pure iron under correspondingP, T conditions.  相似文献   

2.
The system iron-enstatite-water was investigated at pressures around 5 GPa and at temperatures ranging from 1000 to 1200°C, using several different kinds of starting materials. Quenched samples showed the coexistence of iron, olivine and pyroxene. Synthesis of the Fe-containing olivine in the run products proves that a series of reactions, Fe + H2O → FeHx + FeO and FeO + MgSiO3 → (Mg, Fe)2SiO4, have taken place. Spherical “balls of iron” were observed in the 1200°C run. This strongly indicates that the melting temperature of iron decreased by ~ 500 K by the possible dissolution of hydrogen. Following geophysical implications are derived from these experimental results. If water was retained in the hydrous minerals in the primordial material, the iron-water reaction is expected to occur throughout the core-formation process. The reaction product FeHx will melt and then sink to form a proto-core and iron oxide will be dissolved in the Earth's mantle. The dissolution of hydrogen in the Earth's core is a natural consequence of the core-formation process.  相似文献   

3.
We present new shock devolatilization recovery data for brucite (Mg(OH)2) shocked to 13 and 23 GPa. These data combined with previous data for serpentine (Mg3Si2O5(OH)4) are used to constrain the minimum size terrestrial planet for which planetesimal infall will result in an impact-generated water atmosphere. Assuming a chondritic abundance of minerals including 3–6%, by mass water, in hydrous phyllosilicates, we carried out model calculations simulating the interaction of metallic iron with impact-released free water on the surface of the accreting Earth. We assume that the reaction of water with iron in the presence of enstatite is the prime source of the terrestrial FeO component of silicates and oxides. Lower and upper bounds on the terrestrial FeO budget are based on mantle FeO content and possible incorporation of FeO in the outer core. We demonstrate that the iron-water reaction would result in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed. In order to obtain1025g of atmospheric water by the end of accretion, slightly heterogeneous accretion with initially 36% by mass iron planetesimals, as compared to a homogeneous value of 34% is required. Such models yield final FeO budgets, which either require a higher FeO content of the mantle (17 wt.%) or oxygen as a light element in the outer core of the Earth.  相似文献   

4.
The outer core is assumed to consist of iron and sulfur, with a small amount of potassium that generates heat by radioactive decay of sim||pre|40 K. Two cases are considered, corresponding respectively to a high rate of heat production (Q = 2 · 1012 cal./sec, about 0.1% K), and to a low rate (Q = 2 · 1011 cal./sec). The temperature at a depth of 2800 km in the mantle is taken to be 3300°K (Wang, 1972). The temperature Tc at the core-mantle boundary depends on whether or not a density gradient in the lowermost layer D″ of the mantle prevents convection in that layer. In the first case, and for high Q, Tc = 4500–5000°K. In the second case, or for low Q, Tc ≈ 3500°K.The heat-conduction equation is used to calculate the temperature Ti at the inner-core boundary in the absence of convection. For high Q, Ti ? Tc ≈ 1600°K; for low Q, Ti ? Tc ≈ 160°K. Corresponding temperature gradients at r = rc and r = ri are listed in Table I.The adiabatic gradient at the top of the core is calculated by the method of Stewart (1970). It strongly depends on the parameters (ρ0, c0, γ0, etc.) that characterize core material at low pressure. Stewart has drawn graphs that allow the selection of sets of parameters that are consistent with seismic velocities and a given density distribution in the core. Some acceptable sets of parameters are listed in Table II. Many sets yield temperatures Tc in the range 3500–5000°K; some give an adiabatic gradient steeper than the conductive gradient and are compatible with convection; others do not. Since properties of FeS melts remain unknown, there is at present no way of selecting any set in preference to another.Properties of the FeS system at low pressure suggest the possible appearance of immiscibility at high temperature in liquids of low sulfur content; accordingly, the inner-core boundary is thought to represent equilibrium between a solid (FeNi) inner core and a liquid layer containing only a small amount of sulfur; layer F in turn is in equilibrium with another liquid (forming layer E) containing more sulfur, and slightly less dense, than F. The temperature Ti at the inner-core boundary is about 6000–6500°K for high Q and Tc ≈ 4500–5000°K. It is consistent with Alder's (1966) and Leppaluoto's (1972) estimates of the melting point of iron at 3.3 Mbar, but not with that of Higgins and Kennedy (1971).  相似文献   

5.
The electrical conductivity of liquid (Fe90Ni10)3S2 saturated with 2.6 weight percent carbon averages 2.7·105 mho/m at 1000°C and zero pressure. This may imply a slightly lower electrical conductivity for the earth's core than that obtained by extrapolating the properties of pure liquid iron and solid iron alloys to core pressures and temperatures. Although a sulphur-rich core would have a smaller proportion of sulphur, the effect of lowering the sulphur content of the FeNiSC liquid to about 15 weight percent would be unlikely to increase the conductivity above 5·105 mho/m.  相似文献   

6.
Tholeiitic basalt glasses from the FAMOUS area of the Mid-Atlantic Ridge are among the most primitive basaltic liquids reported from the ocean basins. One of the more primitive of these[Mg/(Mg+Fe2+) = 0.68;Ni= 232ppm;TiO2 = 0.61] glasses (572-1-1) was selected for an experimental investigation. This study found olivine to be the liquidus phase from 1 atm to 10.5 kbar where it is replaced by clinopyroxene. The sequence of appearance of phases at 1 atm pressure is olivine (1268°C), plagioclase (1235°C) and clinopyroxene (1135°C). The sample is multiply saturated at 10.5 kbar with olivine (Fo88), clinopyroxene (Wo32En60Fs9), and orthopyroxene (Wo5En83Fs12). From the 1-atm data we have measured (FeO/MgO) olivine/(FeO*/MgO) liquid (K′D) for olivine-melt pairs equilibrated at 12 temperatures in the range 1268–1205°C.K′D varies from 0.30 at 1205°C to 0.27 at 1268°C. Analysis of high-pressure olivine melt pairs indicates a systematic increase inK′D with pressure.Evaluation of the 1-atm experiments reveals that fractionation of olivine followed by olivine + plagioclase can generate much of the variation in major element chemistry observed in the FAMOUS basalt glasses. However, it cannot account for the entire spectrum of glass compositions — particularly with respect to TiO2 and Na2O. The variations in these components are such as to require different primary liquids.Comparison of clinopyroxene microphenocrysts/xenocrysts found in oceanic tholeiites with experimental clinopyroxenes reveal that the majority of those in the tholeiites may have crystallized from the magma at pressures greater than ~ 10 kbar and are not accidental xenocrysts. Clinopyroxene fractionation at high pressures may be a viable mechanism for fractionating basaltic magmas.The major and minor element mineral/meltK′d's from our experiments have been used to model the source region residual mineralogy for given percentages of partial melting. These data suggest that ~20% partial melting of a lherzolite source containing 0–10% clinopyroxene can generate the major and minor element concentrations in the parental magmas of the Project FAMOUS basalt glasses.  相似文献   

7.
Experimental data on the differential travel time t BCt DF of seismic waves PKPDF and PKPBC in the Earth’s core under Africa and Australia are analyzed. The differential travel-time residuals beneath Africa in a narrow range of angles from 21° to 25° between the direction of the seismic ray in the core and the Earth’s rotation axis exhibit a scoop-shaped peculiarity not accounted for by cylindrical anisotropy in the inner core. A model with a 0.2–0.8% P-wave velocity anomaly with a radius of 1375 km in the cylindrical region in the outer core is proposed, which closely fits the experimental data. We suggest that the velocity anomaly is generated by the dynamical processes occurring in the outer core, namely, the growth of the inner core and the convection in the outer core, both leading to the formation of a low-density anomaly in the outer core.  相似文献   

8.
Entrapped biogenic gas in peat can greatly affect peatland biogeochemical and hydrological processes by altering volumetric water content, peat buoyancy, and ‘saturated’ hydraulic conductivity, and by generating over‐pressure zones. These over‐pressure zones further affect hydraulic gradients which influence water and nutrient flow direction and rate. The dynamics of entrapped gas are of global interest because the loss of this gas to the atmosphere via ebullition (bubbling) is likely the dominant transport mechanism of methane (CH4) to the atmosphere from peatlands, which are the largest natural terrestrial source per annum of atmospheric CH4. We investigated the relationship between atmospheric pressure and temperature on volumetric gas content (VGC) and CH4 ebullition using a laboratory peat core incubation experiment. Peat cores were incubated at three temperatures (one core at 4 °C, three cores at 11 °C, and one core at 20 °C) in sealed PVC cylinders, instrumented to measure VGC, pore‐water CH4 concentrations, and ebullition (volume and CH4 concentrations). Ebullition events primarily occurred (71% of the time) during periods of falling atmospheric pressure. The duration of the drop in atmospheric pressure had a larger control on ebullition volume than the magnitude of the drop. VGC in the 20 °C core increased from the onset of the experiment and reached a fluctuating but time‐averaged constant level between experiment day 30 and 115. The change in VGC was low for the 11 °C cores for the initial period of the experiment but showed large increases when the growth chamber temperature increased to 20 °C due to a malfunction. The core maintained at 4 °C showed only a small increase in entrapped gas content throughout the experiment. The 20 °C core showed the largest increase in VGC. The increases in VGC occurred despite pore‐water concentrations of CH4 being below the equilibrium solubility level. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
The paper continues a cycle of petromagnetic investigations of epicontinental deposits at the Mesozoic-Cenozoic (K/T) boundary and is devoted to the study of the Gams section (Austria). Using thermomagnetic analysis, the following magnetic phases are identified: goethite (T C = 90–150°C), hemoilmenite (T C = 200?300°C), metallic nickel (T C = 350–360°C), magnetite and titanomagnetite (T C = 550–610°C), Fe-Ni alloy (T C = 640–660°C), and metallic iron (T C = 740–770°C). Their concentrations are determined from M(T). In all samples, ensembles of magnetic grains have similar coercivity spectra and are characterized by a high coercivity. An exception is the lower coercivity of the boundary clay layer due to grains of metallic nickel and iron. With rare exceptions, the studied sediments are anisotropic and generally possess a magnetic foliation, which indicates a terrigenous accumulation of magnetic minerals. Many samples of sandy-clayey rocks have an inverse magnetic fabric associated with the presence of acicular goethite. The values of paramagnetic and diamagnetic components in the deposits are calculated. According to the results obtained, the K/T boundary is marked by a sharp increase in the concentration of Fe hydroxides. The distribution of titanomagnetite reflects its dispersal during eruptive activity, which is better expressed in the Maastrichtian and at the base of the layer J. The along-section distribution of metallic iron, most likely of cosmic origin, is rather uniformly chaotic. The presence of nickel, most probably of impact origin, is a particularly local phenomenon as yet. The K/T boundary is not directly related to an impact event.  相似文献   

10.
The conductivity of four igneous rocks with, 49, 65, 77, and 84% SiO2 was measured as a function of temperature in the interval from 20° to 1280°C; measurements were made in a vacuum of 10?3 torr. No simple relationships were found between conductivity and SiO2 content or versus major element groupings such as Na2O=K2O=CaO and TiO2=Cr2O3=Al2O3=Fe2O3=FeO. An analytical expression was obtained between conductivity and the albite-quartz ratio, valid for temperatures between 300° and 1200°C. It was necessary to compute the CIPW norm in order to obtain the albite and quartz percentages. The onset of melting apparently occurred between 600° and 700°C. Petrography performed on two samples after cooling showed 70 and 85% partial melting. Three conduction regions were identified: 1) below 300°C, 2) between 300°C and 600°C, and 3) above 600°C. Different activation energies obtained for the heating and cooling intervals confirm that the sample undergoes textural changes in the heating-cooling cycle. Activation energy increments of 0.1 and 0.2 eV per decade of albite-quartz ratio were obtained.  相似文献   

11.
Boninite is an unusual, plagioclase-free magnesian andesite, occurring as vesicular pillow lavas and hyaloclastites, accompanied by andesites and dacites in Chichi-jima, Bonin Islands. The Bonin Islands belong to the Izu-Mariana arc and consist of dominant volcanic rocks and subordinate sedimentary rocks of late Oligocene-early Miocene age. The chemistry of boninite is characterized by high contents of MgO. Cr and Ni similar to primitive basalts, but apparently in ill accord with its relatively high SiO2 content of ? 55%. The relation of SiO2 to total FeO/MgO ratio indicates that boninite belongs to the cale-alkalic rock suite. The mineralogy of boninite consists of olivine (Fo87-90), orthopyroxene (En87-90), clinopyroxene (Wo38-35En37-44Fs25-21), hydrous glass and Cr-spinel, Experimental studies show that the magma of boninite composition could be in equilibrium with upper mantle peridotite at pressures less than 17 kb and temperatures of 1200–1050°C under high PH2O. It is suggested that boninite is a sea-floor quenched product (900°C) of a direct partial melt of the upper mantle. Related andesites and dacites are considered to be probably fractional crystallization products from the same magma.  相似文献   

12.
The solubility of fluorapatite in a wide variety of basic magmatic liquids was experimentally determined over a range of upper mantle P-T conditions (8–25 kbar, 1275–1350°C). Fluorapatite is stable over the entire range of conditions investigated, but its solubility in melts is variable, depending negatively on SiO2 content of the melt and positively upon temperature, with relatively little sensitivity to pressure above 8 kbar. At upper mantle pressures and a temperature of 1250°C, molten basalt (50% SiO2) will dissolve 3–4 wt.% P2O5 before saturation in apatite is reached. For a magma 100°C cooler or containing 10 wt.% more SiO2, apatite saturation occurs at less than 2 wt.% dissolved P2O5. The observed high solubility of apatite in basic magmas at their normal near-liquidus temperatures virtually precludes the occurrence of residual apatite in mantle source regions. If relatively low-temperature melting conditions prevail (e.g., 1100°C), as might be possible in H2O-bearing regions of the upper mantle, apatite could remain in the residue, but only in amounts too small to have significant effects on the rare earth patterns of the liquids.Because of the high solubility of apatite in basic magmas, phosphorus can be confidently treated as an incompatible element in peridotite melting models. Such models, in combination with observed characteristics of basic lavas, indicate that the upper mantle contains ~200 ppm of phosphorus, much less than the chondritic abundance of ~900 ppm.  相似文献   

13.
The electrical conductivity of a single crystal of San Carlos olivine (Fo92, 0.16 wt.% Fe2O3) has been measured as a function of temperature and oxygen fugacity (fO2). After heating to 1338°C at fO2 = 10?12 atm., the conductivity at 950°C was 10?5 (ohm-m)?1, almost 3 orders of magnitude less than that measured in air. This decrease is due to the reduction of Fe3+ to Fe2+. Further heating to 1500°C at fO2 = 10?14 atm., decreased the electrical conductivity at 950°C to 10?6 (ohm-m)?1. When recovered at room temperature, the speciment had Fo96 composition and contained small, opaque blebs distributed throughout the crystal. Derivations of temperature profiles for the earth's mantle from conductivity-depth models must take account of the important role played by iron oxidation state in the electrical conductivity of olivine.  相似文献   

14.
The trajectory of the North Atlantic Deep Water is traced from 65°N to 20°N latitude. Along this track the dissolved O2 decreases, theδ18O of the dissolved O2 increases, and the14C content of the water decreases. From these observations the rate of in-situ O2 utilization in the deep water is calculated to be 0.10 μmol kg?1 yr?1. As was observed previously in the Pacific, theδ18O data presented here indicate that the utilization is probably caused by bacterial respiration. Carbon dioxide is being added to the water at the rate of 0.07 μmol kg?1 yr?1 from the oxidation of this organic matter. An additional 0.12 μmol kg?1 yr?1 of CO2 is derived from the dissolution of particles of CaCO3.  相似文献   

15.
The extensive gneisses in the high‐pressure and ultrahigh‐pressure metamorphic terrane in the Dabie‐Sulu orogen usually show no evidence of eclogite‐facies metamorphism. The garnet‐mica‐plagioclase gneisses from the Qiliping region in the western Dabie Orogen, comprise garnet, phengite, biotite, plagioclase, quartz, rutile, ilmenite, chlorite, epidote, and hornblende. The garnet porphyroblasts, with inclusions of quartz, epidote, and rutile, exhibit slight compositional zonations, from core to mantle with an increase in pyrope and a decrease in spessartine, and from mantle to rim with a decrease in pyrope and grossular and an increase in spessartine. The high‐Si phengite indicates that the gneisses may be subjected to a high‐pressure metamorphism. By the P–T pseudosections calculated in a system NCKMnFMASHTO (Na2O‐CaO‐K2O‐MnO‐FeO‐MgO‐Al2O3‐SiO2‐H2O‐TiO2‐O) for two representative samples, the metamorphic P–T path, reconstructed by the compositionally zoned garnet, shows that the prograde metamorphism is characterized by a temperature increase with a slight pressure increase from the conditions of 17.6 ± 1.5 kbar at 496 ± 15°C to the peak‐pressure ones of 21.8 ± 1.5–22.7 ± 1.5 kbar at 555 ± 15–561 ± 15°C; the early retrograde stage is dominated by decompression with a temperature increase to the maximum of 608 ± 15–611 ± 18°C at 10.3 ± 1.5–11.0 ± 1.5 kbar; and the late retrograde one is predominated by pressure and temperature decreases. The mineral assemblages in the prograde metamorphism are predicted to contain garnet, glaucophane, jadeite, lawsonite, phengite, quartz, rutile, and/or chlorite, which is different from those observed at present. Such high‐pressure metamorphism can partly be reconstructed by the P–T pseudosection in combination with the high‐Si phengite and garnet compositions in the core and mantle. This provides an important constraint on the subduction and exhumation of the terrane during the continent–continent collision between the Yangtze and Sino‐Korean cratons.  相似文献   

16.
Thermal experiment on the pumice at atmospheric pressure shows that welding begins at about 900° C and complete melting occurs at 1350° C. It is noticed that FeO content of pumice decreases first with increasing temperature, attaining minimum value at 1100° C, and then again increases with increasing temperature. Therefore, an equilibrium is expected in the presence of liquid phase as follows:
$$4FeO + O_2 = 2Fe_2 O_3 .$$  相似文献   

17.
Origin of the troodos and other ophiolites: A reply to hynes   总被引:1,自引:0,他引:1  
Geologic and tectonic evidence on the origin of the Troodos ophiolitic complex is ambiguous, being compatible with its creation in an island arc or a continent as well as in a mid-oceanic ridge. However, there is decisive petrologic and chemical evidence against its origin in a mid-oceanic ridge (and in a marginal sea). A large proportion (about half) of volcanic rocks in the sheeted complex and lower pillow lavas of Troodos have SiO2 > 52.5% and FeO*/MgO > 2.0 in contrast to mid-oceanic ridge volcanics which are almost entirely basic (SiO2 < 52.5%) with FeO*/MgO < 2.0. (FeO* means total iron as FeO.) A considerable proportion of volcanic rocks in Troodos belong to the calc-alkalic series. These facts indicate that the Troodos massif was formed probably in an island arc or a continental region.In order to rebut the above chemical evidence, Hynes resorts to an assumption of thorough compositional change of the Troodos volcanic rocks by metasomatism. However, this assumption is not plausible.  相似文献   

18.
Gallium arsenide (GaAs) has both high saturated electron velocity and high electron mobility, making it useful as a semiconductor material in a variety of applications, including light‐emitting diodes (LEDs), integrated circuits (ICs), and microwave appliances. A side effect of the use of gallium (Ga) is the production of a relatively large amount of hazardous waste. This study aimed at the recovery of Ga and arsenic (As) from GaAs waste using hydrometallurgical methods involving leaching and coagulation and a dry annealing process that involves annealing, vacuum separation, and sublimation by heating. Our research has shown that GaAs can be leached using nitric acid (HNO3) to obtain 100% Ga and As with a leaching solution at pH 0.1, with subsequent adjustment of the leaching solution to pH 3 with sodium hydroxide (NaOH). Another method used a leaching solution at pH 2, then adjusting to pH 11 using NaOH. Ferric hydroxide (FeO(OH)) was added at 90°C after NaOH was added to the leaching solution. At pH 2 and 11, 55.5 and 21.9% of the As could be removed from the hazardous waste, respectively. The Ga could also be precipitated. When GaAs powder was heated to 1000°C over 3 h, 100% As removal was achieved, and 92.6% of the Ga was removed by formation of 99.9% gallium trioxide (Ga2O3). Arsenic was vaporized when the temperature was elevated to 1000°C, allowing arsenic trioxide (As2O3) to condense with 99.2% purity. The Ga2O3 powder produced was then dissolved and electrolyzed, allowing for 95.9% recovery of Ga with a purity of 99.9%.  相似文献   

19.
Palaeomagnetic results are reported from the predominantly green sediments of the Upper Permian to Lower Triassic Sakamena Group and the Upper Carboniferous to Lower Permian Sakoa Group of Madagascar. Secondary magnetizations could only be removed successfully through thermal demagnetization procedures and then only if the cleaning process was completed by 450°C. Heating in air caused extensive magnetochemical changes to occur above this temperature. Coercivity spectrum analysis and low-temperature characteristics of the heated and unheated green sediments indicate that considerable amounts of fine-grained single-domain magnetite are formed at 500°C or more from some non-magnetic mineral, probably the iron silicates. For this reason consistent palaeomagnetic data could only be obtained from about half the samples collected. Results from 4 sites (19 samples) of the Lower Sakamena Group give a palaeomagnetic pole at 64.9S, 113.9E (A95 = 5.6°) and 3 sites (16 samples) from the Glacial Series of the Sakoa Group give a pole at 47.9S, 84.1E (A95 = 8.1°). When compared with corresponding data from Africa these results confirm and strengthen our previous conclusions from the Triassic-Jurassic Isalo Group regarding the palaeoposition of Madagascar. All three poles are only consistent with the Smith and Hallam reconstruction which places Madagascar off the eastern coast of Africa adjacent to Kenya and Tanzania.  相似文献   

20.
Abstract Recent geological investigations of the Isua Supracrustal Belt (3.8 Ga), southern West Greenland, have suggested that it is the oldest accretionary complex on earth, defined by an oceanic plate‐type stratigraphy and a duplex structure. Plate history from mid‐oceanic ridge through plume magmatism to subduction zone has been postulated from analysis of the reconstructed oceanic plate stratigraphy in the accretionary complex. Comparison between field occurrence of greenstones in modern and ancient accretionary complexes reveals that two types of tholeiitic basalt from different tectonic settings, mid‐oceanic ridge basalt (MORB) and oceanic island basalt (OIB), occur. This work presents major, trace and rare earth element (REE) compositions of greenstones derived from Isua MORB and OIB, and of extremely rare relict igneous clinopyroxene in Isua MORB. The Isua clinopyroxenes (Cpx) have compositional variations equivalent to those of Cpx in modern MORB; in particular, low TiO2 and Na2O contents. The Isua Cpx show slightly light (L)REE‐depleted REE patterns, and the calculated REE pattern of the host magma is in agreement with that of Isua MORB. Analyses of 49 least‐altered greenstones carefully selected from approximately 1200 samples indicate that Isua MORB are enriched in Al2O3, and depleted in TiO2, FeO*, Y and Zr at the given MgO content, compared with Isua OIB. In addition, Isua MORB show an LREE‐depleted pattern, whereas Isua OIB forms a flat REE pattern. Such differences suggest that the Early Archean mantle had already become heterogeneous, depending on the tectonic environment. Isua MORB are enriched in FeO compared with modern MORB. Comparison of Isua MORB with recent melting experiments shows that the source mantle had 85–87 in Mg? and was enriched in FeO. Potential mantle temperature is estimated to be approximately 1480°C, indicating that the Early Archean mantle was hotter by at most approximately 150°C than the modern mantle.  相似文献   

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