Experimental determination of the partitioning behavior of rare earth and high field strength elements between pargasitic amphibole and natural silicate melts (original) (raw)
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Chemical Geology, 1993
A proton microprobe was used to measure partition coefficients for Rb, Sr, Ba, Y, Zr, Nb and Ta between experimentally produced amphiboles and hydrous basaltic melts. A limited amount of data was also obtained for the distribution of trace elements in clinopyroxene and mica. Partition coefficients for trace elements in amphibole and basanite melts are (at 1 a): Rb 0.34+0.14; Sr 0.33 _+0.07; Ba 0,46+0.16; Y 0.6_+0.2; Ti 0.95_+0.19; Zr 0.25+0.06; Nb 0.08 -+ 0.01; and Ta 0.09 +_0.03. Only small, generally non-systematic differences in these values are observed with variation in pressure ( 10-20 kbar) and temperature ( 1000-1050 ° C ), but large differences accompany changes in melt composition and F content. For a (F-free) basaltic andesite melt, at 20 kbar and 950 ° C, amphibole/melt distribution coefficients are: Rb 0.07 _+ 0.01; Sr 0.35 _+ 0.03; Y 1.3+0.1; Ti 1.75+_0.12; Zr 0.35+0.06; Nb 0.21 _+0.01; and Ta 0.19+0.02. The data support proposals that residual amphibole in mantle source regions for some nephelinites explains their relatively high HFSE/LILE ratios. In contrast, the data do not favour amphibole as the cause of characteristically low HFSE/LILE observed in mantle-derived island arc basalts.
Geochemistry, …, 2000
A new set of partitioning data for rare earth elements (REE: La, Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb), Y, Th, U, and Pb has been obtained for 25 calcic amphiboles (pargasites and kaersutites) crystallized from alkali-basaltic and basanitic bulk rock compositions at f O 2 AˊFMQ−2,pressureP=1.4GPa,andtemperatureTbetween9508and10758C.Thevariationsofamphibole/liquidpartitioncoefficientsandoftheirratiosrelevanttopetrogeneticstudiesarediscussedwithreferencetothemajorelementcompositionoftheamphibolesandofthecoexistingmelt,andtothecrystalchemicalmechanismsfortraceelementincorporation.OurresultssupporttheconclusionsthatREEandactinidesareincorporatedintotheM4cavityincalcicamphibolesanddistributedbetweenthetwoavailablesiteswithinthatcavityandthatPbisincorporatedintotheAsite.Inoursamplepopulation,REEpatternsaresystematicallyenrichedinheavyREE(HREE),asexpectedfromthepresenceofsignificantcummingtonitecomponent.NosignificantfractionationisobservedbetweenThandU.ThemajorfactorcontrollingtheamountoftraceelementincorporationistheSiO2contentofthemelt.ThemajorimplicationofthisstudyisthatHREEcanbecomecompatibleinamphiboleinsystemswithSiO2contentgreaterthanÁFMQ-2, pressure P = 1.4 GPa, and temperature T between 9508 and 10758C. The variations of amphibole/liquid partition coefficients and of their ratios relevant to petrogenetic studies are discussed with reference to the major element composition of the amphiboles and of the coexisting melt, and to the crystal chemical mechanisms for trace element incorporation. Our results support the conclusions that REE and actinides are incorporated into the M4 cavity in calcic amphiboles and distributed between the two available sites within that cavity and that Pb is incorporated into the A site. In our sample population, REE patterns are systematically enriched in heavy REE (HREE), as expected from the presence of significant cummingtonite component. No significant fractionation is observed between Th and U. The major factor controlling the amount of trace element incorporation is the SiO 2 content of the melt. The major implication of this study is that HREE can become compatible in amphibole in systems with SiO 2 content greater than AˊFMQ−2,pressureP=1.4GPa,andtemperatureTbetween9508and10758C.Thevariationsofamphibole/liquidpartitioncoefficientsandoftheirratiosrelevanttopetrogeneticstudiesarediscussedwithreferencetothemajorelementcompositionoftheamphibolesandofthecoexistingmelt,andtothecrystalchemicalmechanismsfortraceelementincorporation.OurresultssupporttheconclusionsthatREEandactinidesareincorporatedintotheM4cavityincalcicamphibolesanddistributedbetweenthetwoavailablesiteswithinthatcavityandthatPbisincorporatedintotheAsite.Inoursamplepopulation,REEpatternsaresystematicallyenrichedinheavyREE(HREE),asexpectedfromthepresenceofsignificantcummingtonitecomponent.NosignificantfractionationisobservedbetweenThandU.ThemajorfactorcontrollingtheamountoftraceelementincorporationistheSiO2contentofthemelt.ThemajorimplicationofthisstudyisthatHREEcanbecomecompatibleinamphiboleinsystemswithSiO2contentgreaterthan50 wt %, whereas LREE always remain incompatible. We use the new D REE amph/l values to calculate the effects of amphibole crystallization during melt migration in the upper mantle by reactive porous flow as well as fractional crystallization of amphibole during melt migration in veined systems. We show that both processes will lead to residual liquids and solids with extremely variable La N /Yb N ratios.
European Journal of Mineralogy, 2007
Amphiboles are rather rare in the volcanics of the whole Etnean succession and commonly are represented by kaersutites to titanian pargasites, mostly found in differentiated products. Titanian Mg-hastingsites have been found in lavas and tephra from the 2001 eruption at Mt. Etna. New major (EMPA) and trace element (LAM-ICP/MS) data on amphiboles from this eruption have been compared with reference data for kaersutites from prehistoric eruptions. The two amphibole groups significantly differ from each other in their Al IV , Al VI , K and Mg# values, which are higher in Mg-hastingsite than in kaersutite. Ti and Na are lower in Mghastingsite than in kaersutite. REE and trace element patterns for all the analysed Mg-hastingsite crystals are quite homogeneous. Kaersutite patterns generally conform to those of Mg-hastingsite but display higher concentrations for most of the trace elements.
Contributions to Mineralogy and Petrology, 2006
Thirty five minor and trace elements (Li, Be, B, Sc, Cu, Zn, Ga, Ge, As, Rb, Nb, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ce, Nd, Sm, Tb, Ho, Tm, Lu, Hf, Ta, W, Tl, Pb, Bi, Th and U) in experimentally produced near-liquidus phases, from a primitive nelpheline basanite from Bow Hill in Tasmania (Australia), were analysed by LAM ICP-MS. A number of halogens (F, Cl and I) were also analysed by electron microprobe. The analyses were used to determine mineral/melt partition coefficients for mica, amphibole, garnet, clinopyroxene, orthopyroxene and olivine for conditions close to multiple saturation of the basanite liquidus with garnet lherzolite (approximately 2.6 GPa and 1,200°C with 7.5 wt% of added H2O). A broader range of conditions was also investigated from 1.0 GPa and 1,025°C to 3.5 GPa and 1,190°C with 5-10 wt% of added H2O. The scope and comprehensiveness of the data allow them to be used for two purposes, these include the following: an investigation of some of the controlling influences on partition coefficients; and the compilation of a set partition coefficients that are directly relevant to the formation of the Bow Hill basanite magma by partial melting of mantle peridotite. Considering clinopyroxene, the mineral phase for which the most data were obtained, systematic correlations were found between pressure and temperature, mineral composition, cation radius and valence, and Δ G coulb (the coulombic potential energy produced by substituting a cation of mismatched valence into a crystallographic site). Δ G coulb is distinctly different for different crystallographic sites, including the M2 and M1 sites in clinopyroxene. These differences can be modelled as a function of variations in optimum valence (expressed as 1 sigma standard deviations) within individual M1 and M2 site populations.
Chemical Geology, 2016
A specific feature of some basaltic lunar rocks is that their TiO 2 contents can reach concentrations as high as 16 wt. %. The High-field strength elements (HFSE) group, which includes Ti, may provide valuable information of the processes that occurred in the lunar mantle to generate high-Ti mare basalts. To assess the effect of such high TiO 2 concentrations on the partitioning of Zr, Hf, Nb, Ta, U, Th, Mo and W between major silicate and oxide phases and silicate melts, we present results from experiments at one atmosphere and 1100 °C-1305 °C, under controlled oxygen fugacity. With the exception of Nb, all ܦ ுிௌா ௫/௧ show a strong negative correlation with the TiO 2 content of the silicate melt. Olivine/silicate melt partition coefficients for Zr, Hf, Nb, Ta and Th decrease slightly from 0 to ca. 5 wt. % TiO 2, above which they remain constant up to ca. 20 wt. % TiO 2 in the silicate glass. In addition, redox sensitive elements, i.e. U, Mo, and W show clearly distinct ܦ ெ ௦௧௦/௧ at different fO 2 , implying that these elements are relatively more compatible at reduced (ca. IW-1.8) than at oxidized (FMQ and air) environments. Iron-rich and Mg-rich armalcolite show contrasting patterns of ܦ ெ ௬௦௧/௧ , with the latter exhibiting slightly higher values of partition coefficient for all analyzed elements, except Th, which is equally incompatible in both end-members. Finally, the new dataset of ܦ ுிௌா ௬௦௧/௧ was used to perform simple melting models of the lunar mantle cumulates. Results
Geochimica Et Cosmochimica Acta, 1992
The effects of composition and temperature on the partitioning behavior of Sc, Y, and the rare earth elements (REEs) between high-Ca clinopyroxene and natural silicate melts were evaluated from doped experiments on natural mafic to intermediate composition lavas at 1 atmosphere pressure. Partition coefficients for these elements were found to be dependent on temperature and composition. The most important compositional parameters controlling clinopyroxene-melt partitioning for Y, Sc, and REEs are Al content of the liquid and pyroxene Ca content. Towards the goal of deriving expressions describing partitioning behavior, approximations were made of equilibrium constants for reactions involving a REE-Al component in the pyroxene. Regression of these equilibrium constants over the experimental temperature range (1180-1050°C) produced expressions which, when applied to the experimental glasses, reproduced the clinopyroxene trace element contents with precisions between 9 and 32% (1σ). The most important conclusion of this work is that pyroxene-melt partition coefficients for trivalent cations have different compositional dependencies than divalent cations because of the participation of Al in paired substitution. Values for high-Ca pyroxene Sc, Y, and REE partition coefficients have a range of over a factor of two between alkali basalts, andesites, and tholeiitic basalts (e.g., 0.2-0.7 for Sm at 1100°C). This represents a large proportion of the total range for D values from all mafic and intermediate magmas. Our contribution is to describe the parameters that control partitioning behavior. This will allow us to more accurately determine REE partitioning for specific systems.
Chemical Geology, 1994
Partition coefficients for the elements Ta, Nb, Hf, Zr, Sc, V, Ga, Zn and Co have been determined by laser ablation ICP-MS and/or electron microprobe between spinel and melt using an alkali olivine basalt at 1 atm. The O sp/Iq for high field strength elements (HFSE) are uniform (O~/lq=0.08, D~Pa/lq=0.06, DrSt°f/Iq=0.05, O~/Iq= 0.06 ), negating the possibility of intra-HFSE fractionation during partial melting or fractional crystallization processes. Results for D~p/Iq continue an approximately linear trend of decreasing D~ TM with increasing fo2 from D~ TM = 68 at IW from previous studies to values of O{fl/Iq = 0.09 at fo2 = air. D~ TM is also fo2 dependent (0.24-0.56 with increasingfo2 ), whereas D~ TM is constant at 3.2. A compositional dependence of partitioning behaviour was found for the Ti-poor solid-solution series between chromite-and magnetite-rich spinels in the log fo2 range from air to FMQ -1 for Co, Zn and Sc. Zn and Co showed deviation from Henry's law behaviour, An approximate value for D~ TM of 4.5 agrees well with the observed partitioning in natural peridotites, but is much larger at lower temperatures. Cobalt partitioning shows a strong negative correlation with temperature and is complicated by fo2 effects.
High-field-strength element partitioning between pyroxene and basaltic to dacitic magmas
Chemical Geology, 1994
The effects of composition and temperature on pyroxene-melt partitioning of the high-field-strength elements (HFSE)-Ti, Zr, Nb and Ta-were evaluated from doped experiments on natural mafic to intermediate composition lavas at pressures from 0.1 MPa to 0.9 GPa (0.001 to 9 kbar). The HFSE partition coefficients (D) maintain similar relative relationships: Dxi > Dzr > DTa > DNb, but vary absolutely as a function of composition and temperature, often exhibiting a range of over a factor of 5 at a single temperature. For example, Dzr ranges from 0.1 in a tholeiitic melt to 0.6 for a dacitic melt at 1100°C, 0.1 MPa. Dzr, DTa and DNb for high-and low-Ca pyroxene can be described as linear functions of Dx,. For high-Ca pyroxenes, the functions are Dzr=0.64Dvi-0.13, Dva=0.14Dv~-0.02 and DNb=0.04DTi-0.01. The low-Ca pyroxene expressions are Dzr=O.6ODTi-O.06, DTa=O.27Dvi-O.O05 and DNb=O.O8Dxi-0.005. This linear relationship suggests similar substitution mechanisms for Ti and the other HFSE in both pyroxene and silicate melts. An expression was derived to calculate the Ti content ofpyroxene based on the melt composition, Ca content of the pyroxene, temperature and pressure. This expression uses an approximation of the equilibrium constant for an exchange reaction of a Ti/Al-bearing component with a Ca-bearing component in the pyroxene. Over the experimental temperature range (1170-1070 °C), the clinopyroxene Ti contents can be reproduced with a precision of +20% (1~).
Experimental determination of F and Cl partitioning between lherzolite and basaltic melt
Contributions to Mineralogy and Petrology, 2012
We experimentally determined F and Cl partition coefficients together with that of 19 trace elements (including REE, U-Th, HFSE and LILE) between basaltic melt and lherzolite minerals: olivine, orthopyroxene, clinopyroxene, plagioclase and garnet. Under conditions from 8 to 25 kbars and from 1,265 to 1,430°C, compatibilities of F and Cl are globally ordered as