Crystal chemical controls on rare earth element partitioning between epidote-group minerals and melts: an experimental and theoretical study

Frei, Dirk; Liebscher, Axel; Wittenberg, Antje; Shaw, Cliff S. J.

doi:10.1007/s00410-003-0493-7

Cited by 32 publications

(15 citation statements)

References 45 publications

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“…Therefore, the decreasing whole-rock concentration in LREE of the eclogitic selvage is not balanced despite the high modal abundance of omphacite in this domain. The influence of clinozoisite cannot be verified due to the lack of trace-element data, but epidote-group minerals and especially allanite (Hermann, 2002) are generally important LREE hosts in eclogites (e.g., Tribuzio et al, 1996;Frei et al, 2003;John et al, 2004). As noted above, since clinozoisite in the blueschist host rock generally occurs as inclusions in garnet, it is rather unlikely that the observed mobilization of LREE is caused by breakdown of clinozoisite.…”

Section: Rare Earth Elementsmentioning

confidence: 93%

Trace-element mobilization during Ca-metasomatism along a major fluid conduit: Eclogitization of blueschist as a consequence of fluid–rock interaction

Beinlich

Klemd

John

et al. 2010

Geochimica et Cosmochimica Acta

156

113

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Section: Rare Earth Elementsmentioning

confidence: 93%

Trace-element mobilization during Ca-metasomatism along a major fluid conduit: Eclogitization of blueschist as a consequence of fluid–rock interaction

Beinlich

Klemd

John

et al. 2010

Geochimica et Cosmochimica Acta

156

113

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“…The model has been applied to a large number of minerals such as clinopyroxene (Wood and Blundy 1997), garnet (e.g. van Westrenen et al 1999, 2000a, b, 2001, titanite (Prowatke and Klemme 2005), zoisite (Frei et al 2003) and apatite . In addition, the lattice strain model was successfully applied to Opx-melt partitioning data by Green et al (2000), Adam and Green (2006), Bédard (2007) and Frei et al (2009).…”

Section: Lattice Strain Modelmentioning

confidence: 99%

Experimental and computational study of trace element distribution between orthopyroxene and anhydrous silicate melt: substitution mechanisms and the effect of iron

Parker¹,

Liebscher

Frei

et al. 2009

Contrib Mineral Petrol

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Although orthopyroxene (Opx) is present during a wide range of magmatic differentiation processes in the terrestrial and lunar mantle, its effect on melt trace element contents is not well quantified. We present results of a combined experimental and computational study of trace element partitioning between Opx and anhydrous silicate melts. Experiments were performed in air at atmospheric pressure and temperatures ranging from 1,326 to 1,420°C in the system CaO-MgO-Al 2 O 3 -SiO 2 and subsystem CaOMgO-SiO 2 . We provide experimental partition coefficients for a wide range of trace elements (large ion lithophile: Li, Be, B, K, Rb, Sr, Cs, Ba, Th, U; rare earth elements, REE: La, $ 0:058, and are all virtually independent of temperature. Cr and Co are the only compatible trace elements at the studied conditions. To elucidate charge-balancing mechanisms for incorporation of REE into Opx and to assess the possible influence of Fe on Opx-melt partitioning, we compare our experimental results with computer simulations. In these simulations, we examine major and minor trace element incorporation into the end-members enstatite (Mg 2 Si 2 O 6 ) and ferrosilite (Fe 2 Si 2 O 6 ). Calculated solution energies show that R 2? cations are more soluble in Opx than R 3? cations of similar size, consistent with experimental partitioning data. In addition, simulations show charge balancing of R 3? cations by coupled substitution with Li ? on the M1 site that is energetically favoured over coupled substitution involving Al-Si exchange on the tetrahedrally coordinated site. We derived best-fit values for ideal ionic radii r 0 , maximum partition coefficients D 0 , and apparent Young's moduli E for substitutions onto the Opx M1 and M2 sites. Experimental r 0 values for R 3? substitutions are 0.66-0.67 Å for M1 and 0.82-0.87 Å for M2. Simulations for enstatite result in r 0 = 0.71-0.73 Å for M1 and *0.79-0.87 Å for M2. Ferrosilite r 0 values are systematically larger by *0.05 Å for both M1 and M2. The latter is opposite to experimental literature data, which appear to show a slight decrease in r M2 0 in the presence of Fe. Additional systematic studies in Febearing systems are required to resolve this inconsistency and to develop predictive Opx-melt partitioning models for use in terrestrial and lunar magmatic differentiation models.

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“…However, it is the absolute concentration of Nd (and not just Nd/La) that increases during crystallization of zoned allanite grains. Because K d values for all REE in allanite are )1 (Frei et al, 2004), this process cannot yield an absolute increase in any REE. (Table 1) The third and, in our opinion, most reasonable explanation is that the allanite/melt K d values for REEs can and do change during the crystallization of zoned allanite.…”

Section: Zoningmentioning

confidence: 99%

“…Furthermore, K d vlaues for REE vary substantially within the epidote family of minerals. For example, although allanite shows a strong preference for La, zoisite preferentially incorporates Nd (Frei et al, 2003).…”

Section: Zoningmentioning

confidence: 99%

“…At the outset, however, we emphasize that this study is not designed to provide K d values for use in petrological modelling, but to describe and propose a mechanism for producing chemical zoning in natural allanites. Experiments and data from glassy volcanic rocks (see Frei et al (2004), for a review) provide the best absolute partition coefficient numbers for purposes of petrological modelling.…”

Section: Introductionmentioning

confidence: 99%

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REE zoning in allanite related to changing partition coefficients during crystallization: implications for REE behaviour in an epidote-bearing tonalite

2006

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Allanite is present in most samples of the tonalitic Bell Island Pluton, with an average mode near 0.05 wt.%. Allanite occurs as cores in igneous epidote-clinozoisite and exhibits characteristic and consistent zoning patterns. REE-rich cores (All40-70) grade out towards epidote-clinozoisite with REE below electron microprobe detection limits. La, Ce and Pr contents are highest in the REE-rich cores of zoned crystals. Nd and Sm contents both initially increase as total REE decreases and are highest in intermediate zones. Y contents are generally low throughout, but tend to be highest in analyses with A115-20. The zoning behaviour exhibited by the allanite, specifically the rimward increases in Nd, Sm, and Y, cannot be accounted for by simple fractionation and are best explained by increases in allanite/ melt partition coefficients (Kd values) for these elements during crystallization. We propose that the variation in Kd values reflects modification of the allanite structure with changing REE content. These modifications are manifested by changes in colour, extinction, and pleochroism within the zoned crystals and include changes in unit-cell volume and dimensions. The changes in Kd values are large enough to result in crossing REE patterns within single allanite crystals. Fractional crystallization of zoned allanite can have noticeable effects on LREE contents and La/Sm (and almost certainly La/Lu) in magmas. In the Bell Island pluton, 80% of La, but <3% of Y is contained in allanite. Although some of the variation in the LREE chemistry of the pluton is attributable to statistical sampling error, much of it appears to reflect petrogenetic processes that controlled LREE abundance and, ultimately, allanite mode. One sample of Bell Island tonalite is depleted in LREE and has low La/Lu and La/Sm. These chemical features can be modelled by fractionation of zoned allanite.

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Crystal chemical controls on rare earth element partitioning between epidote-group minerals and melts: an experimental and theoretical study

Cited by 32 publications

References 45 publications

Trace-element mobilization during Ca-metasomatism along a major fluid conduit: Eclogitization of blueschist as a consequence of fluid–rock interaction

Trace-element mobilization during Ca-metasomatism along a major fluid conduit: Eclogitization of blueschist as a consequence of fluid–rock interaction

Experimental and computational study of trace element distribution between orthopyroxene and anhydrous silicate melt: substitution mechanisms and the effect of iron

REE zoning in allanite related to changing partition coefficients during crystallization: implications for REE behaviour in an epidote-bearing tonalite

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