Hydrogen and oxygen isotope fractionation during crystallization of mirabilite and ice

The equilibrium fractionation factors between mirabilite (Na₂SO₄·10H₂O) and saturated sodium sulphate solution at 25°C and 0°C and between ice and 2·5 molal sodium chloride solution at ?10°C have been measured. For mirabilite, the deuterium factors are 1·017 and 1·019, and the oxygen-18 factors are 1·0014 and 1·0020 at 25°C and 0°C, respectively. For ice, the factors are 1·024 for deuterium and 1·0022 for oxygen-18 at ?10°C. These fractionation factors are used to estimate the fractionation factors between ice and mirabilite and concentrated sea water at ?10°C. It is concluded that the average binding strengths of hydrogen in ice and mirabilite are very similar.     

A single asteroidal source for extraterrestrial Ordovician chromite grains from Sweden and China: High-precision oxygen three-isotope SIMS analysis

We examined oxygen three-isotope ratios of 48 extraterrestrial chromite (EC) grains extracted from mid-Ordovician sediments from two different locations in Sweden, and one location in south-central China. The ages of the sediments (∼470 Ma) coincide with the breakup event of the L chondrite parent asteroid. Elemental compositions of the chromite grains are generally consistent with their origin from L or LL chondrite parent bodies. The average Δ¹⁷O (‰-deviation from the terrestrial mass-fractionation line, measured in situ from 15 μm spots by secondary ion mass spectrometry; SIMS) of EC grains extracted from fossil meteorites from Thorsberg and Brunflo are 1.17 ± 0.09‰ (2σ) and 1.25 ± 0.16‰, respectively, and those of fossil micrometeorites from Thorsberg and Puxi River are 1.10 ± 0.09‰, and 1.11 ± 0.12‰, respectively. Within uncertainty these values are all the same and consistent with the L chondrite group average Δ¹⁷O = 1.07 ± 0.18‰, but also with the LL chondrite group average Δ¹⁷O = 1.26 ± 0.24‰ (Clayton et al., 1991). We conclude that the studied EC grains from correlated sediments from Sweden and China are related, and most likely originated in the same event, the L chondrite parent body breakup. We also analyzed chromites of modern H, L and LL chondrites and show that their Δ¹⁷O values coincide with averages of Δ¹⁷O of bulk analyses of H, L and LL chondrites. This study demonstrates that in situ oxygen isotope data measured by SIMS are accurate and precise if carefully standardized, and can be used to classify individual extraterrestrial chromite grains found in sediments.     

Predicting water contamination during the development of chromite deposits

Physicochemical numerical simulation of the system water-serpentinized ultramafic rocks of the Aganozerskoe deposit (systems closed and open with respect to atmospheric oxygen and carbon dioxide) indicates that wetting and oxygen access to chromite ore and mined processed rock in the open system should result in chromite oxidation and enhance Cr migration. In the closed system, in which the processed rock is stored at the bottom of a water body and is inaccessible to atmospheric gases, the oxidation dissolution of chromite is less intense.     

Group IVA irons: New constraints on the crystallization and cooling history of an asteroidal core with a complex history

We report analyses of 14 group IVA iron meteorites, and the ungrouped but possibly related, Elephant Moraine (EET) 83230, for siderophile elements by laser ablation ICP-MS and isotope dilution. EET was also analyzed for oxygen isotopic composition and metallographic structure, and Fuzzy Creek, currently the IVA with the highest Ni concentration, was analyzed for metallographic structure. Highly siderophile elements (HSE) Re, Os and Ir concentrations vary by nearly three orders of magnitude over the entire range of IVA irons, while Ru, Pt and Pd vary by less than factors of five. Chondrite normalized abundances of HSE form nested patterns consistent with progressive crystal-liquid fractionation. Attempts to collectively model the HSE abundances resulting from fractional crystallization achieved best results for 3 wt.% S, compared to 0.5 or 9 wt.% S. Consistent with prior studies, concentrations of HSE and other refractory siderophile elements estimated for the bulk IVA core and its parent body are in generally chondritic proportions. Projected abundances of Pd and Au, relative to more refractory HSE, are slightly elevated and modestly differ from L/LL chondrites, which some have linked with group IVA, based on oxygen isotope similarities.Abundance trends for the moderately volatile and siderophile element Ga cannot be adequately modeled for any S concentration, the cause of which remains enigmatic. Further, concentrations of some moderately volatile and siderophile elements indicate marked, progressive depletions in the IVA system. However, if the IVA core began crystallization with ∼3 wt.% S, depletions of more volatile elements cannot be explained as a result of prior volatilization/condensation processes. The initial IVA core had an approximately chondritic Ni/Co ratio, but a fractionated Fe/Ni ratio of ∼10, indicates an Fe-depleted core. This composition is most easily accounted for by assuming that the surrounding silicate shell was enriched in iron, consistent with an oxidized parent body. The depletions in Ga may reflect decreased siderophilic behavior in a relatively oxidized body, and more favorable partitioning into the silicate portion of the parent body.Phosphate inclusions in EET show Δ¹⁷O values within the range measured for silicates in IVA iron meteorites. EET has a typical ataxitic microstructure with precipitates of kamacite within a matrix of plessite. Chemical and isotopic evidence for a genetic relation between EET and group IVA is strong, but the high Ni content and the newly determined, rapid cooling rate of this meteorite show that it should continue to be classified as ungrouped. Previously reported metallographic cooling rates for IVA iron meteorites have been interpreted to indicate an inwardly crystallizing, ∼150 km radius metallic body with little or no silicate mantle. Hence, the IVA group was likely formed as a mass of molten metal separated from a much larger parent body that was broken apart by a large impact. Given the apparent genetic relation with IVA, EET was most likely generated via crystal-liquid fractionation in another, smaller body spawned from the same initial liquid during the impact event that generated the IVA body.     

Cr and Al diffusion in chromite spinel: experimental determination and its implication for diffusion creep

Diffusion coefficients of Cr and Al in chromite spinel have been determined at pressures ranging from 3 to 7 GPa and temperatures ranging from 1,400 to 1,700°C by using the diffusion couple of natural single crystals of MgAl₂O₄ spinel and chromite. The interdiffusion coefficient of Cr–Al as a function of Cr# (=Cr/(Cr + Al)) was determined as D _Cr–Al = D ₀ exp {−(Q′ + PV*)/RT}, where D ₀ = exp{(10.3 ± 0.08) × Cr#^0.54±0.02} + (1170 ± 31.2) cm²/s, Q′ = 520 ± 81 kJ/mol at 3 GPa, and V* = 1.36 ± 0.25 cm³/mol at 1,600°C, which is applicable up to Cr# = 0.8. The estimation of the self-diffusion coefficients of Cr and Al from Cr–Al interdiffusion shows that the diffusivity of Cr is more than one order of magnitude smaller than that of Al. These results are in agreement with patterns of multipolar Cr–Al zoning observed in natural chromite spinel samples deformed by diffusion creep.     

Effect of the presence of As,Bi, and Te on the behavior of Pt metals during fractionation crystallization of sulfide magma

The results of study of the chemical and phase compositions of three Ag-, Au-, platinum group element-, As-, Bi-, and Te-bearing samples, which are the product of directed crystallization of the Cu–Fe–Ni sulfide melt, are presented. One sample contained only metals, the second one was additionally doped with As, and the third one was enhanced in As, Bi, and Te. The mechanism of formation of the minerals of the platinum group metals during fractionation crystallization of multicomponent sulfide melts was proposed on the basis of interpretation of experimental data.     

Isotopic fractionation and reaction kinetics between Cr(III) and Cr(VI) in aqueous media

The redox-sensitive stable isotope geochemistry of chromium bears the potential to monitor the attenuation of chromate pollution and to investigate changes in environmental conditions in the present and the past. The use of stable Cr isotope data as a geo-environmental tracer, however, necessitates an understanding of the reaction kinetics and Cr fractionation behaviour during redox transition and isotope exchange. Here, we report stable chromium isotope fractionation data for Cr(VI) reduction, Cr(III) oxidation and isotopic exchange between soluble Cr(III) and Cr(VI) in aqueous media. The reduction of Cr(VI) to Cr(III) with H₂O₂ under strongly acidic conditions shows a near-equilibrium isotope fractionation of Δ^53/52Cr_{(Cr(III)-Cr(VI))} of −3.54 ± 0.35‰. At pH neutrality, however, the reduction experiments show a kinetic isotope fractionation Δ^53/52Cr_{(Cr(III)-Cr(VI))} of −5‰ for the extent of reduction of up to 85% of the chromium. The oxidation of Cr(III) to Cr(VI) in alkaline media, using H₂O₂ as the oxidant, cannot be explained by a single, unidirectional reaction. Our experiments indicate that the involvement of the unstable intermediates Cr(IV) and Cr(V) and their disproportionation during redox reactions between Cr(III) and Cr(VI) influence the overall fractionation factor, depending on the prevailing pH conditions and the reaction rates. No detectable isotope exchange between soluble Cr(VI) and Cr(III) species at pH values of 5.5 and 7 was revealed over a timescale of days to weeks. This means that, at least within such a time frame, the isotopic composition of Cr(VI) in a natural system will not be influenced by equilibration with any Cr(III) and thus reveal the true extent of reduction, given that the Cr isotope composition of the source Cr(VI) and the fractionation factor for the prevailing conditions are known.     

西藏罗布莎铬铁矿中的原位铂族矿物研究:铬铁矿结晶环境的指示

本文对罗布莎三个矿区的铬铁矿进行了详细的原位PGM研究,发现罗布莎各个矿区的铬铁矿中PGM组合和显微结构不同,暗示PGM能够记录铬铁矿形成与演化过程。罗布莎矿区的PGM显微特征显示铬铁矿结晶于高温、低硫逸度的环境中,可能系岩石/熔体反应和结晶分异双重作用下的产物;康金拉矿区的原位PGM主要为组合型包裹体,有少量产于铬铁矿裂隙之间的贱金属硫化物和合金矿物,为不同来源的熔体混合作用的结果,并暗示铬铁矿成矿后还受到热液流体的改造;香卡山矿区的PGM表明铬铁矿成矿之后遭受到还原性流体的交代作用,铬铁矿中早期结晶出来的硫化物或者铂族矿物被还原改造,形成铁镍矿等次生矿物,保存于铬铁矿粒间或者铬铁矿的裂隙中,这个过程可能与蛇纹石化或者晚期构造流体改造作用有关。罗布莎原位PGM研究表明,PGM矿物贯穿于铬铁矿结晶成矿过程的始终,PGM的矿物及其组合能够记录铬铁矿结晶时母熔体的物理化学条件,甚至还能反映铬铁矿成矿后所经历的后期构造热液事件。因此,结合单矿物分选和原位调查两种方法,查明铬铁矿中PGM的赋存类型及微观结构,对全面理解铬铁矿的成矿过程有重要意义。     

Effect of chemical fertilizers on the fractionation of Cu,Cr and Ni in contaminated soil

Effect of chemical fertilizers (urea, NH₄Cl, Ca(NO₃)₂, KCl and KH₂PO₄) on the fractionation of Cu, Cr and Ni was studied by a 4-month incubation experiment. Using sequential extraction procedure, it was found that the application of fertilizers could change the distribution of Cu, Cr and Ni in the fractions of soil. Applying urea (CO(NH₂)₂) significantly decreased the concentrations of Cu, Cr and Ni in water soluble plus exchangeable (WE) fraction, but increased those in Fe–Mn oxides bound (FM) fraction (p < 0.01). However, application of NH₄Cl caused an increase in the WE fraction by 27.7% for Cu, 111.5% for Cr and 20.4% for Ni. The CO(NH₂)₂ raised the soil pH from 4.51 to 4.96, whereas NH₄Cl lowered the pH of soil by 0.44 units. The WE fraction of the three heavy metals was significantly increased, while the FM fraction was significantly decreased by adding KCl (p < 0.01). Moreover, the supply of KH₂PO₄ reduced the WE and carbonate bound (CB) fractions of Cu, Cr and Ni in the soil, however, it raised Cu and Ni in the residual (RS) fraction and Cr in the FM fraction. In addition, the mobility index indicated that KCl and NH₄Cl increased the mobility of Cu, Cr and Ni in the soil, whereas urea and KH₂PO₄ decreased the mobility of the three metals in the soil. These results suggest that applying chemical fertilizers does not only provide plant nutrients, but may also change the speciation and mobility of heavy metals in the soil.     

Al-Mg dating of asteroidal magmatism in the young Solar System

We present high-precision Mg isotope data for most classes of basaltic meteorites including eucrites, mesosiderite silicate clasts, angrites and the ungrouped Northwest Africa (NWA) 2976 measured by pseudo-high-resolution multiple-collector inductively coupled plasma mass spectrometry and utilising improved techniques for chemical purification of Mg. With the exception of the angrites Angra dos Reis, Lewis Cliff (LEW) 86010, NWA 1296 and NWA 2999 and the diogenite Bilanga, which have either been shown to have young ages by other dating techniques or have low Al/Mg ratios, all bulk samples of basaltic meteorites have ²⁶Mg excesses (δ²⁶Mg^∗=+0.0135 to +0.0392‰). The ²⁶Mg excesses cannot be explained by analytical artefacts, cosmogenic effects or heterogeneity of initial ²⁶Al/²⁷Al, Al/Mg ratios or Mg isotopes in asteroidal parent bodies as compared to Earth or chondrites. The ²⁶Mg excesses record asteroidal melting and formation of basaltic magmas with super-chondritic Al/Mg and confirm that radioactive decay of short-lived ²⁶Al was the primary heat source that melted planetesimals. Model ²⁶Al-²⁶Mg ages for magmatism on the eucrite/mesosiderite, angrite and NWA 2976 parent bodies are 2.6-3.2, 3.9-4.1 and 3.5 Myr, respectively, after formation of calcium-aluminium-rich inclusions (CAIs). However, the validity of these model ages depends on whether the elevated Al/Mg ratios of basaltic meteorites result from magma ocean evolution on asteroids through fractional crystallisation or directly during partial melting. Mineral isochrons for the angrites Sahara (Sah) 99555 and D’Orbigny, and NWA 2976, yield ages of and , respectively, after CAI formation. Both isochrons have elevated initial δ²⁶Mg^∗ values. Given the brecciated and equilibrated texture of NWA 2976 it is probable that its isochron age and elevated initial δ²⁶Mg^∗(+0.0175±0.0034‰) reflects thermal resetting during an impact event and slow cooling on its parent body. However, in the case of the angrites the marginally elevated initial δ²⁶Mg^∗(+0.0068±0.0058‰) may reflect either δ²⁶Mg^∗ ingrowth in a magma ocean prior to eruption and crystallisation or in an older igneous protolith with super-chondritic Al/Mg prior to impact melting and crystallisation of these angrites, or partial internal re-equilibration of Mg isotopes after crystallisation. ²⁶Al-²⁶Mg model ages and an olivine + pyroxene + whole rock isochron for the angrites Sah 99555 and D’Orbigny are in good agreement with age constraints from ⁵³Mn-⁵³Cr and ¹⁸²Hf-¹⁸²W short-lived chronometers, suggesting that the ²⁶Al-²⁶Mg feldspar-controlled isochron ages for these angrites may be compromised by the partial resetting of feldspar Mg isotope systematics. Even when age constraints from the ²⁶Al-²⁶Mg angrite model ages or the mafic mineral + whole rock isochron are considered, the relative time difference between Sah 99555/D’Orbigny crystallisation and CAI formation cannot be reconciled with Pb-Pb ages for Sah 99555/D’Orbigny and CAIs, which are ca. 1.0 Myr too old (angrites) or too young (CAIs) for reasons that are not clear. This discrepancy might indicate that ²⁶Al was markedly lower (ca. 40%) in the planetesimal- and planet-forming regions of the proto-planetary disc as compared to CAIs, or that CAI Pb-Pb ages may not accurately date CAI formation, which might be better dated by the ¹⁸²Hf-¹⁸²W and ²⁶Al-²⁶Mg chronometers as 4568.3±0.7 (Burkhardt et al., 2008) and (herein), respectively, when mapped onto an absolute timescale using Pb-Pb ages for angrites.     

Biogenic nano-magnetite and nano-zero valent iron treatment of alkaline Cr(VI) leachate and chromite ore processing residue

Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, was tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR). The performance of this biomaterial, targeting aqueous Cr(VI) removal, was compared to a synthetic alternative, nano-scale zero valent iron (nZVI). Samples of highly contaminated alkaline groundwater and COPR solid waste were obtained from a contaminated site in Glasgow, UK. During batch reactivity tests, Cr(VI) removal from groundwater was inhibited by ∼25% (BnM) and ∼50% (nZVI) when compared to the treatment of less chemically complex model pH 12 Cr(VI) solutions. In both the model Cr(VI) solutions and contaminated groundwater experiments the surface of the nanoparticles became passivated, preventing complete coupling of their available electrons to Cr(VI) reduction. To investigate this process, the surfaces of the reacted samples were analyzed by TEM-EDX, XAS and XPS, confirming Cr(VI) reduction to the less soluble Cr(III) on the nanoparticle surface. In groundwater reacted samples the presence of Ca, Si and S was also noted on the surface of the nanoparticles, and is likely responsible for earlier onset of passivation. Treatment of the solid COPR material in contact with water, by addition of increasing weight % of the nanoparticles, resulted in a decrease in aqueous Cr(VI) concentrations to below detection limits, via the addition of ⩾5% w/w BnM or ⩾1% w/w nZVI. XANES analysis of the Cr K edge, showed that the % Cr(VI) in the COPR dropped from 26% to a minimum of 4–7% by the addition of 5% w/w BnM or 2% w/w nZVI, with higher additions unable to reduce the remaining Cr(VI). The treated materials exhibited minimal re-mobilization of soluble Cr(VI) by re-equilibration with atmospheric oxygen, with the bulk of the Cr remaining in the solid fraction. Both nanoparticles exhibited a considerable capacity for the remediation of COPR related Cr(VI) contamination, with the synthetic nZVI demonstrating greater reactivity than the BnM. However, the biosynthesized BnM was also capable of significant Cr(VI) reduction and demonstrated a greater efficiency for the coupling of its electrons towards Cr(VI) reduction than the nZVI.     

Evidence for large scale fractionation of carbon isotopes and of nitrogen impurity during crystallization of gem quality cubic diamonds from placers of North Yakutia

The spatial distribution of carbon and nitrogen isotopes and of nitrogen concentrations is studied in detail in three gem quality cubic diamonds of variety II according to Orlov’s classification. Combined with the data on composition of fluid inclusions our results point to the crystallization of the diamonds from a presumably oxidized carbonate fluid. It is shown that in the growth direction δ¹³C of the diamond becomes systematically lighter by 2–3‰ (from –13.7 to –15.6‰ for one profile and from –11.7 to –14.1‰ for a second profile). Simultaneously, we observe substantial decrease in the nitrogen concentration (from 400–1000 to 10–30 at ppm) and a previously unrecognized enrichment of nitrogen in light isotope, exceeding 30‰. The systematic and substantial changes of the chemical and isotopic composition can be explained using the Burton-Prim-Slichter model, which relates partition coefficients of an impurity with the crystal growth rate. It is shown that changes in effective partition coefficients due to a gradual decrease in crystal growth rate describes fairly well the observed scale of the chemical and isotopic variations if the diamond-fluid partition coefficient for nitrogen is significantly smaller than unity. This model shows that nitrogen isotopic composition in diamond may result from isotopic fractionation during growth and not reflect isotopic composition of the mantle fluid. Furthermore, it is shown that the infra-red absorption at 1332 сm^-1 is an integral part of the Y-defect spectrum. In the studied natural diamonds the 1290 сm^-1 IR absorption band does not correlate with boron concentration.     

Fractional crystallization and zoning in igneous feldspars: ideal water-buffered liquid fractionation lines and feldspar zoning paths

Diagrams giving plagioclase and sanidine fractionation paths and liquid fractionation lines under conditions of ideal water-buffered fractional crystallization in the ternary feldspar system were constructed graphically using topological reasoning, and experimental data and calculated phase relationships from the literature. The liquidus lines and solidus or solvus paths are unique at constant P and a _{H 2}O. The composition of a liquid evolves with time and moves along a fractionation line by removal of successive crystal fractions, whereas the compositions of each of the crystal fractions lie on and define a solidus or solvus path. Most but not all such water-buffered lines and paths differ only slightly from those in which water is free to build up during crystallization and a _{H 2}O to increase, as in many rocks. Liquid compositions lying along liquidus fractionation lines are not normally preserved, unless erupted as aphyric lavas. The solidus or solvus paths may be preserved either as overgrowth zones in crystals (zoning paths) or as a series of crystal fractions in layered intrusions. The topologies of the lines and paths depend mainly on the nature of the two-feldspar boundary line separating the plagioclase and sanidine fields which is a function of P _{H 2}O or a _{H 2}O at constant P; increases in either progressively lower the liquidi and solidi and cause larger intersections of the solidi with the solvus. One-feldspar solidus paths at high P and a _{H 2}O are simple, whereas they are complex and may bend back on themselves at low P _{H 2}O or low a _{H 2}O at high P. Two-feldspar paths may be simultaneous (cotectic) or sequential (peritectic). The former are simple and do not meet at high P and a _{H 2}O, the critical solution line lying in the gap; they are complex and may bend back or overlap at low P _{H 2}O or low a _{H 2}O at high P, the position of the critical solution line being hard to determine. Liquids which have simultaneously fractionated two feldspars may fractionate only one towards the end, crystallization changing from subsolvus to hypersolvus. Sequential paths may involve overgrowth of an early feldspar by a later one, usually sanidine overgrowths on plagioclase, but plagioclase overgrowths on sanidine occur. These complexities explain in part the difficulties of unravelling the textural and compositional relationships of ternary feldspars in water-poor felsic igneous rocks (even in the absence of alteration or complex magma dynamics) and of trying to deduce phase relationships from natural occurrences of feldspars.C.R.P.G. contribution number 948     

Oxygen isotope fractionation during the dolomitization of calcium carbonate

The oxygen isotope fractionation accompanying the hydrothermal dolomitization of CaCO₃ between 252 and 295°C has been investigated. Dolomitization (which occurs via the crystallization of one or more intermediate magnesian calcite phases) is characterised by a progressive lowering in δ⁸O, which smoothly correlates with the change in the Mg/(Mg + Ca) and the $\text{Sr}\text{(Mg + Ca)}$ ratios and with the sequential phase formation. The data support the proposals of Katz and Matthews (1977) that (a) all reaction occurs by solution and reprecipitation, (b) intermediate phases and dolomite form sequentially and (c) the intermediate phases form within limited solution zones surrounding the dissolving precursor. Calculated volumes of the solution zone for the aragonite → low magnesian calcite transformation are within the range 3.7–6.7 × 10^?5 liters (out of 5 × 10^?3 liters, the volume of the bulk solution used in the present study), and agree well with those calculated from strontium and magnesium partitioning data. Dolomite precipitates in apparent isotopic equilibrium with the bulk solution. The temperature dependence of the fractionation is defined by the equation 1000 Inα_D-H2O = 3.06 × 10⁶T^?2 ? 3.24 Dolomite-water fractionations from this equation are significantly lower than those obtained by extrapolation of the Northrop And Clayton (1966) calibration. The reaction zone model can be applied to explain near zero dolomite-calcite oxygen isotope fractionations reported by Epsteinet al. (1964).     

西藏铬铁矿接替资源航磁勘查及找矿方向探讨

西藏是重要的铬铁矿产地,应用航磁圈定超基性岩,进行铬铁矿资源评价是国内外使用的常规方法,能快速缩小找矿靶区、取得事半功倍的效果。中国国土资源航空物探遥感中心于1969年在西藏中东部地区进行了1∶50万—1∶100万中等精度航磁概查,为早期铬铁矿勘查提供了间接信息;近年来又在中西部和一江两河(雅鲁藏布江、拉萨河和年楚河)及其北部地区进行了1∶100万—1∶20万高精度航磁调查。初步划分为5条强磁异常带和2个强磁异常群,为快速地发现超基性岩体、评价铬铁矿接替资源潜力提供了一批重要的间接找矿线索。     

榴辉岩部分熔融过程中的同位素分馏

本文对榴辉岩部分熔融过程中不同同位素体系是否存在分馏这一当前研究热点进行了综述。榴辉岩作为研究洋陆俯冲、超高压变质以及壳幔相互作用的主要岩石类型,其部分熔融与地壳增生、板片折返过程以及俯冲隧道中元素的迁移分配等具有紧密的联系。作为典型的高压-超高压变质岩石,榴辉岩可通过俯冲带将壳源信息携带至地幔深部,影响地幔的化学组成,并可在大洋玄武岩中得以表现。近些年,随着仪器分析技术的发展,实验研究和理论计算均表明榴辉岩部分熔融过程中稳定同位素可以产生显著的分馏。作为常见的放射性成因子体同位素和传统稳定同位素Sr-Nd-Hf-O被广泛应用于源区示踪、岩浆混合以及结晶分异等过程。但目前有研究指出,在非平衡熔融过程中,熔体和源区的Sr-Nd-Hf-O同位素可发生解耦,导致二者的同位素组成不均一。另外,通过研究榴辉岩及其熔融产物的金属稳定同位素特征,发现榴辉岩部分熔融过程中,由于石榴石效应,会造成Ca、Mg、Fe、Li等金属稳定同位素的分馏。因此,当利用稳定同位素示踪榴辉岩熔体的源区时,需要考虑其分馏的影响。