The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of fiv...The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Qi from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Qi were obtained, denoted as Qi-Ca-Qj and Qi-[Ob]-Qj, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.展开更多
Airborne silicate pollutants in flight corridors pose a serious threat to aviation safety whose severity is directly linked to the wettability of molten silicates on thermal barrier coatings(TBCs)at high temperatures(...Airborne silicate pollutants in flight corridors pose a serious threat to aviation safety whose severity is directly linked to the wettability of molten silicates on thermal barrier coatings(TBCs)at high temperatures(1200–2000℃).Despite its importance,the wettability of silicate melt on TBCs has not been well investigated.In particular,the surface morphology characteristics of TBCs can be expected to have a first-order effect on the wettability of silicate melt on such TBCs.Here,a series of atmospheric plasma spray(APS)yttria-stabilized zirconia(YSZ)TBCs with varying surface roughness were generated through the application of mechanical polishing.The metastable nonwetting behavior of three representative types of airborne silicate ash(volcanic ash,fly ash and a synthetic calcium–magnesium–aluminum–silicates(CMAS)powder)on these TBCs with varying surface roughness was investigated.It was observed that the smoother the surface of TBCs was,the larger the contact angle was with the molten silicate melts,and consequently,the smaller the area of damage was on the TBCs.Thus,the reduction in TBCs surface roughness(here via mechanical polishing)led to an improvement in the wetting and spreading resistance of TBCs to silicate melts at high temperature.In support of these observations and conclusions,the surface morphology of the TBC(both before and after polishing)had been characterized,and the mechanism of the surface roughness-dependence of wettability had been discussed.These results should contribute to reducing the deposition rate of silicate melt on TBCs,thus extending the lifetime of turbine blades and reducing maintenance costs.展开更多
Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation ...Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation model proposed by Watson and Harrison(Earth Planet Sci Lett 64(2):295-304,1983) is widely cited and has been updated recently,the three main models currently in use may generate large uncertainties due to extrapolation beyond their respective calibrated ranges.This paper reviews and updates zircon saturation models developed with temperature and compositional parameters.All available data on zircon saturation ranging in composition from mafic to silicic(and/or peralkaline to peraluminous)at temperatures from 750 to 1400℃ were collected to develop two refined models(1 and 2) that may be applied to the wider range of compositions.Model 1 is given by lnCZr(melt)=(14.297±0.308)+(0.964 ± 0.066).M-(11113±374)/r,and model 2 given by lnCZr(melt)=(18.99±0.423)-(1.069±0.102)·lnG-(12288±593)/T,where CZr(melt) is the Zr concentration of the melt in ppm and parameters M [=(Na+K+2 Ca)/(Al·Si)](cation ratios) and G [=(3·Al2 O3+SiO2)/(Na2-O+K2 O+CaO+MgO+FeO)](molar proportions)represent the melt composition.The errors are at one sigma,and T is the temperature in Kelvin.Before applying these models to natural rocks,it is necessary to ensure that the zircon used to date is crystallized from the host magmatic rock.Assessment of the application of both new and old models to natural rocks suggests that model 1 may be the best for magmatic temperature estimates of metaluminous to peraluminous rocks and that model 2 may be the best for estimating magmatic temperatures of alkaline to peralkaline rocks.展开更多
The mathematical viscosity models for metallic melts were discussed. The experimental data of Ag-Au-Cu systems were used to verify the models based on Chou′s general geometric thermodynamic model and the calculated r...The mathematical viscosity models for metallic melts were discussed. The experimental data of Ag-Au-Cu systems were used to verify the models based on Chou′s general geometric thermodynamic model and the calculated results are consistent with the reported experimental data. A new model predicting the viscosity of multi-component silicate melts was established. The CaO-MnO-SiO 2,CaO-FeO-SiO 2 and FeO-MnO-SiO 2 silicate slag systems were used to verify the model.展开更多
Carbonated silicate melts transport oxidized carbon from the deep to shallow mantle,and thus play an important role in the deep carbon cycle.However,it is unclear how carbonated silicate melts are formed.Here,we repor...Carbonated silicate melts transport oxidized carbon from the deep to shallow mantle,and thus play an important role in the deep carbon cycle.However,it is unclear how carbonated silicate melts are formed.Here,we report whole-rock major and trace element,and Mg-Zn-Fe isotope,and in situ olivine and clinopyroxene Mg isotope data for peridotites and pyroxenites in Cenozoic alkaline basalts from Shulan and Yitong,Northeast China,to reveal the formation mechanisms of carbonated silicate melts.As residues of the primitive mantle,most of the Shulan and Yitong(spinel)harzburgite and lherzolite have relatively lower δ26Mg and higher δ66Zn than the mantle values,and show LREE-enriched patterns.These features indicate that these peridotites have been modified by carbonated silicate melt,transforming them into carbonated peridotites.The Shulan websterites exhibit metasomatic textures,and most of their whole-rock and in situ δ26Mg values are lower than the mantle values,which also supports the presence of a carbonated lithospheric mantle.The Yitong cumulate orthopyroxenites,representing silica-rich melts,have lower δ26Mg and higher δ66Zn values than mantle peridotites,implying that recycled carbonate has been involved in these silica-rich melts.The Yitong cumulate wehrlites and(olivine)websterites display major element compositions similar to those of carbonated peridotite melts,coupled with low whole-rock and clinopyroxene δ26Mg values,high δ66Zn and δ57Fe values,indicating the occurrence of carbonated silicate melts.The transition from orthopyroxenites to(olivine)websterites is marked by the decreasing of their whole-rock δ26Mg,δ57Fe values and Zn/Fe ratios and increasing of their δ66Zn values,along with decreasing of their crystallization temperatures,suggesting that silica-rich melts were gradually transformed into carbonated silicate melts via continuous interaction with carbonated peridotite.Our findings demonstrate that silica-rich melts from the stagnant slab can extract carbon from pre-existing carbonated mantle within the big mantle wedge.展开更多
The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous sil...The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous silicate melts and aqueous fluids is sensitive to composition, temperature, and pressure, making it useful for understanding partial melting and fluid activity at great depths. This study presents a review on the experimental studies of electrical conductivity of silicate melts and aqueous fluids, and introduces some important applications of experimental results. For silicate melts, electrical conductivity increases with increasing temperature but decreases with pressure. With a similar Na^+ concentration, along the calc-alkaline series electrical conductivity generally increases from basaltic to rhyolitic melt, accompanied by a decreasing activation enthalpy. Electrical conductivity of silicate melts is strongly enhanced with the incorporation of water due to promoted cation mobility. For aqueous fluids, research is focused on dilute electrolyte solutions. Electrical conductivity typically first increases and then decreases with increasing temperature, and increases with pressure before approaching a plateau value. The dissociation constant of electrolyte can be derived from conductivity data. To develop generally applicable quantitative models of electrical conductivity of melt/fluid addressing the dependences on temperature, pressure, and composition, it requires more electrical conductivity measurements of representative systems to be implemented in an extensive P-T range using up-to-date methods.展开更多
The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experime...The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experiments on SMIs use microscope-mounted heating stages capable of producing high temperatures at 1 atm and cold-seal high-pressure vessels.Heating stages are generally used for SMIs with low internal pressures and allow in situ observations of the homogenization processes.In contrast,cold-seal high-pressure vessels are generally used to heat SMIs that have high internal pressures,although the homogenized SMIs can only be observed after quenching in this approach.Here we outline an alternative approach that uses a hydrothermal diamond anvil cell （HDAC） apparatus to homogenize SMIs.This is the only current method wherein phase changes in high-internal-pressure SMIs can be observed in situ during homogenization experiments,which represents an advantage over other conventional methods.Using an HDAC apparatus prevents high-internal-pressure SMIs from decrepitating during heating by elevating their external pressure,in addition to allowing in situ observations of SMIs.The type-V HDAC that is currently being used has a shorter distance between the sample chamber and the observation window than earlier types,potentially enabling continuous observation of the processes involved in heating and SMI homogenization through an objective lens with a long working distance.Homogenization experiments using HDAC require that a number of steps,including HDAC preparation,sample preparation,sample loading,preheating,and formal heating,be carefully followed.Homogenization experiments on SMIs within granite samples from the Jiajika pegmatite deposit （Sichuan,China） are best performed using an HDAC-based approach,because the elevated proper external pressure of these SMIs,combined with a short heating duration,helps to suppress material leakage and any reactions within the SMIs,in addition to allowing in situ observations during homogenization experiments.Furthermore,using the HDAC approach has other benefits：heating rates can be precisely controlled,wafer oxidization can be prevented,and samples can be subjected to in situ microbeam analysis.In summary,homogenization using HDAC provides more reliable results than those obtained using conventional heating equipment.Future developments will include improvements to the quenching method and temperature controls for the HDAC apparatus,thereby improving the utility of this approach for SMI homogenization experiments.展开更多
Experiments on the partitioning of Cu between different granitic silicate melts and the respective coexisting aqueous fluids have been performed under conditions of 850 ℃, 100 MPa and oxygen fugacity （fO2） buffered...Experiments on the partitioning of Cu between different granitic silicate melts and the respective coexisting aqueous fluids have been performed under conditions of 850 ℃, 100 MPa and oxygen fugacity （fO2） buffered at approaching Ni-NiO （NNO）. Partition coefficients of Cu （Dcu = Cfluid/Cmelt） were varied with different alumina/alkali mole ratios [Al2O3/（Na2O ＋ K2O）, abbreviated as Al/ Alk], Na/K mole ratios, and SiO2 mole contents. The DCu increased from 1.28 ± 0.01 to 22.18 ±0.22 with the increase of Al/Alk mole ratios （ranging from 0.64 to 1.20） and Na/K mole ratios （ranging from 0.58 to 2.56）. The experimental results also showed that Dcu was positively correlated with the HCl concentration of the starting fluid. The Dcu was independent of the SiO2 mole content in the range of SiO2 content considered. No Dcu value was less than 1 in our experiments at 850 ℃ and 100 MPa, indicating that Cu preferred to enter the fluid phase rather than the coexisting melt phase under most conditions in the melt-fluid system, and thus a significant amount of Cu could be transported in the fluid phase in the magmatichydrothermal environment. The results indicated that Cu favored partitioning into the aqueous fluid rather than the melt phase if there was a high Na/K ratio, Na-rich, peraluminous granitic melt coexisting with the high Cl^- fluid.展开更多
The effects of melt composition,temperature and pressure on the solubility of fluorite(CaF2),i.e.,fluorine concentration in silicate melts in equilibrium with fluorite,are summarized in this paper.The authors present ...The effects of melt composition,temperature and pressure on the solubility of fluorite(CaF2),i.e.,fluorine concentration in silicate melts in equilibrium with fluorite,are summarized in this paper.The authors present a statistic study based on experimental data in literature and propose a predictive model to estimate F concentration in melt at the saturation of fluorite(CFin melt^Fl-sat).The modeling indicates that the compositional effect of melt cations on the variation in can be expressed quantitatively as one parameter FSI(fluorite saturation index):FSI=(3Al^NM+Fe^2++6Mg+Ca+1.5Na-K)/(Si+Ti+Al^NF+Fe^3+),in which all cations are in mole,and Al^NF and Al^NM are A1 as network-forming and network-modifying cations,respectively.The dependence of CFin melt^Fl-sat on FSI is regressed as:CFin melt^Fl-sat=1.130-2.014·exp(1000/T)+2.747·exp(P/T)+0.111·CmeltH2O+17.641·FSI,in which T is temperature in Kelvin,P is pressure in MPa,CmeltH2O is melt H2O content in wt.%,and CFin melt^Fl-sat is in wt.%(normalized to anhydrous basis).The reference dataset used to establish the expression for conditions within 540-1010℃,50-500 MPa,0-7 wt.%melt H2O content,0.4 to 1.7 for A/CNK,0.3 wt.%-7.0 wt.%for CFin melt^Fl-sat.The discrepancy of CFin melt^Fl-sat between calculated and measured values is less than±0.62 wt.%with a confidence interval of 95%.The expression of FSI and its effect on CFin melt^Fl-sat indicate that fluorine incorporation in silicate melts is largely controlled by bonding with network-modifying cations,favorably with Mg,Al^NM,Na,Ca and Fe^2+in a decreasing order.The proposed model for predicting CFin melt^Fl-sat is also supported by our new experiments saturated with magmatic fluorite performed at 100-200 MPa and 800-900℃.The modeling of magma fractional crystallization emphasizes that the saturation of fluorite is dependent on both the compositions of primary magmas and their initial F contents.展开更多
Subduction-related Cu-(Au) deposits which represent giant geochemical anomalies of metals and S in the upper crust are commonly associated with arc magmas. However, the fundamental differences between barren and ferti...Subduction-related Cu-(Au) deposits which represent giant geochemical anomalies of metals and S in the upper crust are commonly associated with arc magmas. However, the fundamental differences between barren and fertile magma producing these deposits still remain highly controversial. In this study, we report the chemical compositions of zircon and silicate melt inclusions(SMIs) from barren arc lavas at eastern Taiwan Island aiming to increase our knowledge on the factors that affect the mineralization potential of arc magma systems. The zircon U-Pb dating shows the magmatism occurred at ~0.7 Ma and the andesitic lava formed at ~900–950℃ with a reduced magmatic environment. The plagioclase-hosted SMIs show an andesitic melt composition and variable Cu content features. The calculated H_(2)O content of parental melt is ~3–4 wt.%. The evidence presented above suggests that oxidation state(f O_(2)) and H_(2)O content are probably the key controls of Cu-(Au) fertility of arc magmas. We interpret that a reduced and relatively dry magma may be a potential hinderance to cause the absence of porphyry Cu deposits at the eastern Taiwan Island.展开更多
CO<sub>2</sub>-RICH fluid inclusions have been found in 6 anhydrous peridotite xenolith minerals in Ceno-zoic basalts of 5 areas in East China.Electron probe backscattering electron image reveals thatsever...CO<sub>2</sub>-RICH fluid inclusions have been found in 6 anhydrous peridotite xenolith minerals in Ceno-zoic basalts of 5 areas in East China.Electron probe backscattering electron image reveals thatseveral inclusions appear in all the rock sections,completely filled with glass or with cavities attheir center part（CO<sub>2</sub> has escaped）.Some inclusions show devitrification and daughter miner-als appear.We have carried out the analysis on the non-devitrification glass in the inclusions.展开更多
Trace element partitioning between coesite and hydrous silicate melt has been investigated at 5 GPa and 1500-1750℃.High-P experiments successfully produced large coesite crystals in equilibrium with large silicate me...Trace element partitioning between coesite and hydrous silicate melt has been investigated at 5 GPa and 1500-1750℃.High-P experiments successfully produced large coesite crystals in equilibrium with large silicate melt pools(plus kyanite and corundum crystals in some cases).Scanning electron microscopy and micro-Raman spectroscopy were employed to characterize the phases and the textures.Wavelength-dispersive electron microprobe analyses were performed to quantify conventional major elements,and laser ablation-inductively coupled plasma-mass spectrometry analyses were successfully conducted to quantify trace elements.Eventually,high-P partition coefficients were obtained for 33 elements.In general coesite is a very pure phase.With a few possible exceptions like Sc,Ti,and V,nearly all other trace elements are incompatible in coesite.Moreover,the partitioning behaviors of nearly all trace elements except some 4+cations cannot be readily described by the lattice strain model,presumably implying a minor role for the cation size in the trace-element partitioning.Combining our experimental results with the results in the literature,some T and P effects on the element partitioning behavior have been observed:T seemingly has different effects on different trace elements,but P might negatively correlate with the partition coefficients in all cases.Due to its large modal fraction in some subducted materials such as the continental crustal material,coesite might play an important role in the distributions of some trace elements,Ti for example.展开更多
Water diffusion in silicate melt is an important process modulating magmatic water content and facilitating bubble growth and volcanic eruption.The increase of water diffusivity with increasing water content was ascri...Water diffusion in silicate melt is an important process modulating magmatic water content and facilitating bubble growth and volcanic eruption.The increase of water diffusivity with increasing water content was ascribed to a dominant role played by molecular H_(2)O(H_(2)O_(m)),but the contribution of hydroxyl(OH),especially at water content < 2 wt%,was recently recognized for intermediate to mafic melts.The mechanisms of water diffusion in felsic melts therefore also require reexamination.In this study,we carried out two series of water diffusion experiments in low-H_(2)O rhyolitic melts:(1) diffusion couple experiments at 1473 K and 1 GPa in piston cylinder apparatus for melts with 0–2 wt% total water(H_(2)O_t);(2) hydration experiments at 773–1873 K and 0.1–1 GPa in cold-seal pressure vessel and piston cylinder apparatus for melts with < 0.15 wt%H_(2)O_t.The diffusion profiles in the quenched products measured with FTIR microspectroscopy were fitted with both error function and speciation-based diffusion models.The diffusion couple profiles indicated an increase in water diffusivity with increasing water content.At H_(2)O_t< 0.15 wt%,a change in slope at ~1373 K was found in the Arrhenius plot of water diffusivity,and the data at 1373–1873 K were in line with fluorine diffusivity.These observations indicate that while H_(2)O_(m) dominates water diffusion in rhyolitic melt at H_(2)O_t> 0.3 wt% or T<1273 K,OH diffusion makes a huge contribution to water diffusivity at H_(2)O_t<0.15 wt% and T>1373 K,despite that a vast majority of OH is attached to the silicate network.We provide an updated quantitative model for water diffusivity in rhyolitic melt with the incorporation of OH contribution.Oxygen diffusion boosted by OH can explain the discrepancy between experimental O diffusivity in “dry” rhyolitic melt(with actually a few hundred μg g-1water) and the value prescribed by the Eyring relation.展开更多
Water plays a crucial role in the melting of Earth's mantle. Mantle magmatisms mostly occur at plate boundaries(including subduction zones and mid-ocean ridges) and in some intraplate regions with thermal anomaly....Water plays a crucial role in the melting of Earth's mantle. Mantle magmatisms mostly occur at plate boundaries(including subduction zones and mid-ocean ridges) and in some intraplate regions with thermal anomaly. At oceanic subduction zones, water released by the subducted slab may induce melting of the overlying mantle wedge or even the slab itself, giving rise to arc magmatism, or may evolve into a supercritical fluid. The physicochemical conditions for the formation of slab melt and supercritical fluid are still under debate. At mid-ocean ridges and intraplate hot zones, water and CO_2 cause melting of the upwelling mantle to occur at greater depths and in greater extents. Low degree melting of the mantle may occur at boundaries between Earth's internal spheres, including the lithosphere-asthenosphere boundary(LAB), the upper mantletransition zone boundary, and the transition zone-lower mantle boundary, usually attributed to contrasting water storage capacity across the boundary. The origin for the stimulating effect of water on melting lies in that water as an incompatible component has a strong tendency to be enriched in the melt(i.e., with a mineral-melt partition coefficient much smaller than unity), thereby lowering the Gibbs free energy of the melt. The partitioning of water between melt and mantle minerals such as olivine, pyroxenes and garnet has been investigated extensively, but the effects of hydration on the density and transport properties of silicate melts require further assessments by experimental and computational approaches.展开更多
基金Project(2012CB722805)supported by the National Basic Research Program of ChinaProjects(50504010,50974083,51174131,51374141)supported by the National Natural Science Foundation of China+1 种基金Project(50774112)supported by the Joint Fund of NSFC and Baosteel,ChinaProject(07QA4021)supported by the Shanghai"Phosphor"Science Foundation,China
文摘The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Qi from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Qi were obtained, denoted as Qi-Ca-Qj and Qi-[Ob]-Qj, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.
基金This study was financially supported by the National Science and Technology Major Project(No.2017-VI-0010-0081)the Program of the Ministry of Education of China for Introducing Talents of Discipline to Universities(No.B17002)+2 种基金the National Natural Science Foundation of China(No.51901011)the“Freigeist”Fellowship of the Volkswagenstiftung on“Volcanic Ash Deposition in Jet Engines”(VADJEs,No.89705)China Scholarship Council(CSC).
文摘Airborne silicate pollutants in flight corridors pose a serious threat to aviation safety whose severity is directly linked to the wettability of molten silicates on thermal barrier coatings(TBCs)at high temperatures(1200–2000℃).Despite its importance,the wettability of silicate melt on TBCs has not been well investigated.In particular,the surface morphology characteristics of TBCs can be expected to have a first-order effect on the wettability of silicate melt on such TBCs.Here,a series of atmospheric plasma spray(APS)yttria-stabilized zirconia(YSZ)TBCs with varying surface roughness were generated through the application of mechanical polishing.The metastable nonwetting behavior of three representative types of airborne silicate ash(volcanic ash,fly ash and a synthetic calcium–magnesium–aluminum–silicates(CMAS)powder)on these TBCs with varying surface roughness was investigated.It was observed that the smoother the surface of TBCs was,the larger the contact angle was with the molten silicate melts,and consequently,the smaller the area of damage was on the TBCs.Thus,the reduction in TBCs surface roughness(here via mechanical polishing)led to an improvement in the wetting and spreading resistance of TBCs to silicate melts at high temperature.In support of these observations and conclusions,the surface morphology of the TBC(both before and after polishing)had been characterized,and the mechanism of the surface roughness-dependence of wettability had been discussed.These results should contribute to reducing the deposition rate of silicate melt on TBCs,thus extending the lifetime of turbine blades and reducing maintenance costs.
基金financially supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB18010402)the National Natural Science Foundation of China (Grant No. 41702224)the Pearl River Talent Plan of Guangdong Province
文摘Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation model proposed by Watson and Harrison(Earth Planet Sci Lett 64(2):295-304,1983) is widely cited and has been updated recently,the three main models currently in use may generate large uncertainties due to extrapolation beyond their respective calibrated ranges.This paper reviews and updates zircon saturation models developed with temperature and compositional parameters.All available data on zircon saturation ranging in composition from mafic to silicic(and/or peralkaline to peraluminous)at temperatures from 750 to 1400℃ were collected to develop two refined models(1 and 2) that may be applied to the wider range of compositions.Model 1 is given by lnCZr(melt)=(14.297±0.308)+(0.964 ± 0.066).M-(11113±374)/r,and model 2 given by lnCZr(melt)=(18.99±0.423)-(1.069±0.102)·lnG-(12288±593)/T,where CZr(melt) is the Zr concentration of the melt in ppm and parameters M [=(Na+K+2 Ca)/(Al·Si)](cation ratios) and G [=(3·Al2 O3+SiO2)/(Na2-O+K2 O+CaO+MgO+FeO)](molar proportions)represent the melt composition.The errors are at one sigma,and T is the temperature in Kelvin.Before applying these models to natural rocks,it is necessary to ensure that the zircon used to date is crystallized from the host magmatic rock.Assessment of the application of both new and old models to natural rocks suggests that model 1 may be the best for magmatic temperature estimates of metaluminous to peraluminous rocks and that model 2 may be the best for estimating magmatic temperatures of alkaline to peralkaline rocks.
文摘The mathematical viscosity models for metallic melts were discussed. The experimental data of Ag-Au-Cu systems were used to verify the models based on Chou′s general geometric thermodynamic model and the calculated results are consistent with the reported experimental data. A new model predicting the viscosity of multi-component silicate melts was established. The CaO-MnO-SiO 2,CaO-FeO-SiO 2 and FeO-MnO-SiO 2 silicate slag systems were used to verify the model.
基金financially supported by the National Natural Science Foundation of China(Grants Nos.42572064 and 42422203)the Program for Jilin University Science and Technology Innovative Research Team(Grant No.2021-TD-05)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.45124031D045)the Graduate Innovation Fund of Jilin University.
文摘Carbonated silicate melts transport oxidized carbon from the deep to shallow mantle,and thus play an important role in the deep carbon cycle.However,it is unclear how carbonated silicate melts are formed.Here,we report whole-rock major and trace element,and Mg-Zn-Fe isotope,and in situ olivine and clinopyroxene Mg isotope data for peridotites and pyroxenites in Cenozoic alkaline basalts from Shulan and Yitong,Northeast China,to reveal the formation mechanisms of carbonated silicate melts.As residues of the primitive mantle,most of the Shulan and Yitong(spinel)harzburgite and lherzolite have relatively lower δ26Mg and higher δ66Zn than the mantle values,and show LREE-enriched patterns.These features indicate that these peridotites have been modified by carbonated silicate melt,transforming them into carbonated peridotites.The Shulan websterites exhibit metasomatic textures,and most of their whole-rock and in situ δ26Mg values are lower than the mantle values,which also supports the presence of a carbonated lithospheric mantle.The Yitong cumulate orthopyroxenites,representing silica-rich melts,have lower δ26Mg and higher δ66Zn values than mantle peridotites,implying that recycled carbonate has been involved in these silica-rich melts.The Yitong cumulate wehrlites and(olivine)websterites display major element compositions similar to those of carbonated peridotite melts,coupled with low whole-rock and clinopyroxene δ26Mg values,high δ66Zn and δ57Fe values,indicating the occurrence of carbonated silicate melts.The transition from orthopyroxenites to(olivine)websterites is marked by the decreasing of their whole-rock δ26Mg,δ57Fe values and Zn/Fe ratios and increasing of their δ66Zn values,along with decreasing of their crystallization temperatures,suggesting that silica-rich melts were gradually transformed into carbonated silicate melts via continuous interaction with carbonated peridotite.Our findings demonstrate that silica-rich melts from the stagnant slab can extract carbon from pre-existing carbonated mantle within the big mantle wedge.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41402041 & 41322015)the Fundamental Research Funds for the Central Universities of China
文摘The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous silicate melts and aqueous fluids is sensitive to composition, temperature, and pressure, making it useful for understanding partial melting and fluid activity at great depths. This study presents a review on the experimental studies of electrical conductivity of silicate melts and aqueous fluids, and introduces some important applications of experimental results. For silicate melts, electrical conductivity increases with increasing temperature but decreases with pressure. With a similar Na^+ concentration, along the calc-alkaline series electrical conductivity generally increases from basaltic to rhyolitic melt, accompanied by a decreasing activation enthalpy. Electrical conductivity of silicate melts is strongly enhanced with the incorporation of water due to promoted cation mobility. For aqueous fluids, research is focused on dilute electrolyte solutions. Electrical conductivity typically first increases and then decreases with increasing temperature, and increases with pressure before approaching a plateau value. The dissociation constant of electrolyte can be derived from conductivity data. To develop generally applicable quantitative models of electrical conductivity of melt/fluid addressing the dependences on temperature, pressure, and composition, it requires more electrical conductivity measurements of representative systems to be implemented in an extensive P-T range using up-to-date methods.
基金supported by the Chinese SinoProbe Project (SinoProbe-03-01)the National Natural Science Foundation of China (41372088)the China Geological Survey Program (1212011220805)
文摘The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experiments on SMIs use microscope-mounted heating stages capable of producing high temperatures at 1 atm and cold-seal high-pressure vessels.Heating stages are generally used for SMIs with low internal pressures and allow in situ observations of the homogenization processes.In contrast,cold-seal high-pressure vessels are generally used to heat SMIs that have high internal pressures,although the homogenized SMIs can only be observed after quenching in this approach.Here we outline an alternative approach that uses a hydrothermal diamond anvil cell （HDAC） apparatus to homogenize SMIs.This is the only current method wherein phase changes in high-internal-pressure SMIs can be observed in situ during homogenization experiments,which represents an advantage over other conventional methods.Using an HDAC apparatus prevents high-internal-pressure SMIs from decrepitating during heating by elevating their external pressure,in addition to allowing in situ observations of SMIs.The type-V HDAC that is currently being used has a shorter distance between the sample chamber and the observation window than earlier types,potentially enabling continuous observation of the processes involved in heating and SMI homogenization through an objective lens with a long working distance.Homogenization experiments using HDAC require that a number of steps,including HDAC preparation,sample preparation,sample loading,preheating,and formal heating,be carefully followed.Homogenization experiments on SMIs within granite samples from the Jiajika pegmatite deposit （Sichuan,China） are best performed using an HDAC-based approach,because the elevated proper external pressure of these SMIs,combined with a short heating duration,helps to suppress material leakage and any reactions within the SMIs,in addition to allowing in situ observations during homogenization experiments.Furthermore,using the HDAC approach has other benefits：heating rates can be precisely controlled,wafer oxidization can be prevented,and samples can be subjected to in situ microbeam analysis.In summary,homogenization using HDAC provides more reliable results than those obtained using conventional heating equipment.Future developments will include improvements to the quenching method and temperature controls for the HDAC apparatus,thereby improving the utility of this approach for SMI homogenization experiments.
文摘Experiments on the partitioning of Cu between different granitic silicate melts and the respective coexisting aqueous fluids have been performed under conditions of 850 ℃, 100 MPa and oxygen fugacity （fO2） buffered at approaching Ni-NiO （NNO）. Partition coefficients of Cu （Dcu = Cfluid/Cmelt） were varied with different alumina/alkali mole ratios [Al2O3/（Na2O ＋ K2O）, abbreviated as Al/ Alk], Na/K mole ratios, and SiO2 mole contents. The DCu increased from 1.28 ± 0.01 to 22.18 ±0.22 with the increase of Al/Alk mole ratios （ranging from 0.64 to 1.20） and Na/K mole ratios （ranging from 0.58 to 2.56）. The experimental results also showed that Dcu was positively correlated with the HCl concentration of the starting fluid. The Dcu was independent of the SiO2 mole content in the range of SiO2 content considered. No Dcu value was less than 1 in our experiments at 850 ℃ and 100 MPa, indicating that Cu preferred to enter the fluid phase rather than the coexisting melt phase under most conditions in the melt-fluid system, and thus a significant amount of Cu could be transported in the fluid phase in the magmatichydrothermal environment. The results indicated that Cu favored partitioning into the aqueous fluid rather than the melt phase if there was a high Na/K ratio, Na-rich, peraluminous granitic melt coexisting with the high Cl^- fluid.
基金This study was supported by the National Natural Science Foundation of China(No.41902052)the German Research Foundation(DFG)(No.BE 1720/40).
文摘The effects of melt composition,temperature and pressure on the solubility of fluorite(CaF2),i.e.,fluorine concentration in silicate melts in equilibrium with fluorite,are summarized in this paper.The authors present a statistic study based on experimental data in literature and propose a predictive model to estimate F concentration in melt at the saturation of fluorite(CFin melt^Fl-sat).The modeling indicates that the compositional effect of melt cations on the variation in can be expressed quantitatively as one parameter FSI(fluorite saturation index):FSI=(3Al^NM+Fe^2++6Mg+Ca+1.5Na-K)/(Si+Ti+Al^NF+Fe^3+),in which all cations are in mole,and Al^NF and Al^NM are A1 as network-forming and network-modifying cations,respectively.The dependence of CFin melt^Fl-sat on FSI is regressed as:CFin melt^Fl-sat=1.130-2.014·exp(1000/T)+2.747·exp(P/T)+0.111·CmeltH2O+17.641·FSI,in which T is temperature in Kelvin,P is pressure in MPa,CmeltH2O is melt H2O content in wt.%,and CFin melt^Fl-sat is in wt.%(normalized to anhydrous basis).The reference dataset used to establish the expression for conditions within 540-1010℃,50-500 MPa,0-7 wt.%melt H2O content,0.4 to 1.7 for A/CNK,0.3 wt.%-7.0 wt.%for CFin melt^Fl-sat.The discrepancy of CFin melt^Fl-sat between calculated and measured values is less than±0.62 wt.%with a confidence interval of 95%.The expression of FSI and its effect on CFin melt^Fl-sat indicate that fluorine incorporation in silicate melts is largely controlled by bonding with network-modifying cations,favorably with Mg,Al^NM,Na,Ca and Fe^2+in a decreasing order.The proposed model for predicting CFin melt^Fl-sat is also supported by our new experiments saturated with magmatic fluorite performed at 100-200 MPa and 800-900℃.The modeling of magma fractional crystallization emphasizes that the saturation of fluorite is dependent on both the compositions of primary magmas and their initial F contents.
基金supported by the National Natural Science Foundation of China (Grant No. 41921003)the National Key R&D Program of China (Grant No. 2022YFC2903301)+1 种基金the National Natural Science Foundation of China (Grant No. 42003031)financial support from the China Scholarship Council program (CSC) during the stay at McGill University。
文摘Subduction-related Cu-(Au) deposits which represent giant geochemical anomalies of metals and S in the upper crust are commonly associated with arc magmas. However, the fundamental differences between barren and fertile magma producing these deposits still remain highly controversial. In this study, we report the chemical compositions of zircon and silicate melt inclusions(SMIs) from barren arc lavas at eastern Taiwan Island aiming to increase our knowledge on the factors that affect the mineralization potential of arc magma systems. The zircon U-Pb dating shows the magmatism occurred at ~0.7 Ma and the andesitic lava formed at ~900–950℃ with a reduced magmatic environment. The plagioclase-hosted SMIs show an andesitic melt composition and variable Cu content features. The calculated H_(2)O content of parental melt is ~3–4 wt.%. The evidence presented above suggests that oxidation state(f O_(2)) and H_(2)O content are probably the key controls of Cu-(Au) fertility of arc magmas. We interpret that a reduced and relatively dry magma may be a potential hinderance to cause the absence of porphyry Cu deposits at the eastern Taiwan Island.
文摘CO<sub>2</sub>-RICH fluid inclusions have been found in 6 anhydrous peridotite xenolith minerals in Ceno-zoic basalts of 5 areas in East China.Electron probe backscattering electron image reveals thatseveral inclusions appear in all the rock sections,completely filled with glass or with cavities attheir center part（CO<sub>2</sub> has escaped）.Some inclusions show devitrification and daughter miner-als appear.We have carried out the analysis on the non-devitrification glass in the inclusions.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFC0600408)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB42000000)the Program of the National Mineral Rock and Fossil Specimens Resource Center from MOST,China。
文摘Trace element partitioning between coesite and hydrous silicate melt has been investigated at 5 GPa and 1500-1750℃.High-P experiments successfully produced large coesite crystals in equilibrium with large silicate melt pools(plus kyanite and corundum crystals in some cases).Scanning electron microscopy and micro-Raman spectroscopy were employed to characterize the phases and the textures.Wavelength-dispersive electron microprobe analyses were performed to quantify conventional major elements,and laser ablation-inductively coupled plasma-mass spectrometry analyses were successfully conducted to quantify trace elements.Eventually,high-P partition coefficients were obtained for 33 elements.In general coesite is a very pure phase.With a few possible exceptions like Sc,Ti,and V,nearly all other trace elements are incompatible in coesite.Moreover,the partitioning behaviors of nearly all trace elements except some 4+cations cannot be readily described by the lattice strain model,presumably implying a minor role for the cation size in the trace-element partitioning.Combining our experimental results with the results in the literature,some T and P effects on the element partitioning behavior have been observed:T seemingly has different effects on different trace elements,but P might negatively correlate with the partition coefficients in all cases.Due to its large modal fraction in some subducted materials such as the continental crustal material,coesite might play an important role in the distributions of some trace elements,Ti for example.
基金supported by the National Natural Science Foundation of China (Grant Nos.42330301,42241124)the National Key R&D Program of China (Grant No.2018YFA0702700)the Fundamental Research Funds for the Central Universities of China(Grant No.WK3410000019)。
文摘Water diffusion in silicate melt is an important process modulating magmatic water content and facilitating bubble growth and volcanic eruption.The increase of water diffusivity with increasing water content was ascribed to a dominant role played by molecular H_(2)O(H_(2)O_(m)),but the contribution of hydroxyl(OH),especially at water content < 2 wt%,was recently recognized for intermediate to mafic melts.The mechanisms of water diffusion in felsic melts therefore also require reexamination.In this study,we carried out two series of water diffusion experiments in low-H_(2)O rhyolitic melts:(1) diffusion couple experiments at 1473 K and 1 GPa in piston cylinder apparatus for melts with 0–2 wt% total water(H_(2)O_t);(2) hydration experiments at 773–1873 K and 0.1–1 GPa in cold-seal pressure vessel and piston cylinder apparatus for melts with < 0.15 wt%H_(2)O_t.The diffusion profiles in the quenched products measured with FTIR microspectroscopy were fitted with both error function and speciation-based diffusion models.The diffusion couple profiles indicated an increase in water diffusivity with increasing water content.At H_(2)O_t< 0.15 wt%,a change in slope at ~1373 K was found in the Arrhenius plot of water diffusivity,and the data at 1373–1873 K were in line with fluorine diffusivity.These observations indicate that while H_(2)O_(m) dominates water diffusion in rhyolitic melt at H_(2)O_t> 0.3 wt% or T<1273 K,OH diffusion makes a huge contribution to water diffusivity at H_(2)O_t<0.15 wt% and T>1373 K,despite that a vast majority of OH is attached to the silicate network.We provide an updated quantitative model for water diffusivity in rhyolitic melt with the incorporation of OH contribution.Oxygen diffusion boosted by OH can explain the discrepancy between experimental O diffusivity in “dry” rhyolitic melt(with actually a few hundred μg g-1water) and the value prescribed by the Eyring relation.
基金supported by the National Natural Science Foundation of China(Grant Nos.41590622&41473058)the 111 Project of Ministry of Education,China+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe Recruitment Program of Global Experts(Thousand Talents),China
文摘Water plays a crucial role in the melting of Earth's mantle. Mantle magmatisms mostly occur at plate boundaries(including subduction zones and mid-ocean ridges) and in some intraplate regions with thermal anomaly. At oceanic subduction zones, water released by the subducted slab may induce melting of the overlying mantle wedge or even the slab itself, giving rise to arc magmatism, or may evolve into a supercritical fluid. The physicochemical conditions for the formation of slab melt and supercritical fluid are still under debate. At mid-ocean ridges and intraplate hot zones, water and CO_2 cause melting of the upwelling mantle to occur at greater depths and in greater extents. Low degree melting of the mantle may occur at boundaries between Earth's internal spheres, including the lithosphere-asthenosphere boundary(LAB), the upper mantletransition zone boundary, and the transition zone-lower mantle boundary, usually attributed to contrasting water storage capacity across the boundary. The origin for the stimulating effect of water on melting lies in that water as an incompatible component has a strong tendency to be enriched in the melt(i.e., with a mineral-melt partition coefficient much smaller than unity), thereby lowering the Gibbs free energy of the melt. The partitioning of water between melt and mantle minerals such as olivine, pyroxenes and garnet has been investigated extensively, but the effects of hydration on the density and transport properties of silicate melts require further assessments by experimental and computational approaches.
