Zircon saturation model in silicate melts:a review and update

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.

Mathematical Viscosity Models for Ternary Metallic and Silicate Melts

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.

Surface roughness affects metastable non-wetting behavior of silicate melts on thermal barrier coatings

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.

Application of Hydrothermal Diamond Anvil Cell to Homogenization Experiments of Silicate Melt Inclusions

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.

Intermediate-acidic silicate melt found in continental mantle of East China

CO2-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（CO2 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.

Experimental constraints on trace element partitioning between coesite and hydrous silicate melt at 5 GPa and 1500-1750℃

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.

Experiments on the Saturation of Fluorite in Magmatic Systems: Implications for Maximum F Concentration and Fluorine-Cation Bonding in Silicate Melt

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.