Compositional variability of San Carlos olivine

Lambart, Sarah; Hamilton, Sarah; Lang, Otto I.

doi:10.1016/j.chemgeo.2022.120968

“…Both secondary standards define a narrow range in the Fe/Mg contents calculated from repeat measurements in the analytical sessions where equilibration experiments were measured: CIT-SC, Fo = 89.89 ± 0.05 (n = 85) and CIT-GI, Fo = 89.95 ± 0.05 (n = 90). Note that published analyses of San Carlos olivines (Jarosewich et al 1979;Houlier et al 1990;Spandler and O'Neill 2010;Batanova et al 2015;Tollan et al 2018;Lambart et al 2022) range from Fo = 88.4-91.5, with a mean of 90.5; repeat measurements of the same chip in the CIT-SC olivine mount are slightly more Fe-rich than the mean value above, but are well within the reported range.…”

Section: Secondary Glass and Olivine Standardssupporting

confidence: 72%

Fe2+–Mg partitioning between olivine and liquid at low oxygen fugacity: an experimental and thermodynamic framework

Saper

¹

,

Baker

²

,

Stolper

³

2022

Contrib Mineral Petrol

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A set of 1-atm gas-mixing experiments (n = 31) was run using Re wire loops at low-oxygen fugacity (ƒO2, within one half-log unit of the Fe–FeO buffer) and temperatures of 1175–1400 °C to explore the compositional dependence of the Fe2+–Mg olivine–liquid exchange coefficient, $${\mathrm{K}}_{\mathrm{D},{\mathrm{Fe}}^{2+}-\mathrm{Mg}}^{\mathrm{ol}/\mathrm{liq}}$$ K D , Fe 2 + - Mg ol / liq , under conditions where corrections for liquid Fe3+ are small. The bulk compositions used for these experiments include a picrite, a high-alumina basalt, and a suite of three MORB compositions with variable Fe/Mg. The $${\mathrm{K}}_{\mathrm{D},{\mathrm{Fe}}^{2+}-\mathrm{Mg}}^{\mathrm{ol}/\mathrm{liq}}$$ K D , Fe 2 + - Mg ol / liq values from the n = 14 experiments run on pre-saturated Re wire loops were fit to a regular solution model that relates $${\mathrm{K}}_{\mathrm{D},{\mathrm{Fe}}^{2+}-\mathrm{Mg}}^{\mathrm{ol}/\mathrm{liq}}$$ K D , Fe 2 + - Mg ol / liq to temperature, melt composition, and olivine composition. Fe2+–Mg exchange in the experiments is well-described using two parameters: the SiO2 content of the liquid and the coexisting olivine composition. Combining our experiments with a literature compilation of low-pressure, low-ƒO2 experiments (largely on non-terrestrial bulk compositions) produced a combined data set spanning a broad region of composition space (e.g., liquid TiO2 and Na2O + K2O contents up to 18.4 wt% and 8.4 wt%, respectively). Fitting this expanded experimental database required two additional liquid compositional terms: Ti, and a Si-(Na + K) cross-term. Because the Fe3+ content of all of the experimental liquids is low, the compositional variation seen in $${\mathrm{K}}_{\mathrm{D},{\mathrm{Fe}}^{2+}-\mathrm{Mg}}^{\mathrm{ol}/\mathrm{liq}}$$ K D , Fe 2 + - Mg ol / liq is effectively independent of the compositional effects on liquid Fe3+/Fe2+ ratios. Given olivine–liquid Mg or Fe2+ partition coefficient information, it is possible to eliminate the explicit dependence of $${\mathrm{K}}_{\mathrm{D},{\mathrm{Fe}}^{2+}-\mathrm{Mg}}^{\mathrm{ol}/\mathrm{liq}}$$ K D , Fe 2 + - Mg ol / liq on olivine composition, enabling a simple iterative approach for calculating the composition of coexisting olivine given only the bulk composition (and Fe3+/Fe2+ ratio) of an olivine-saturated liquid.

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“…This suggests that very extensive refertilization could be at the origin of some websterite and pyroxenites, and that harzburgites, lherzolites and pyroxenites may form a continuum rather than distinct groups. Such a continuum is commonly reported in mantle series and mainly explained by melt-rock reactions (e.g., from clinopyroxenite to orthopyroxenite in Kornprobst, 1969; from dunite to lherzolite in Morgan and Liang, 2005; from dunite to websterite in Denis et al, 2018, or from harzburgite to websterite in Lambart et al, 2022). The simple impregnation model presented here however, is unlikely to explain the scatter in the most refractory lithologies (i.e., olivine-rich harzburgite and dunite).…”

Section: Natural Datamentioning

confidence: 53%

“…This likely is because the addition of volatiles in the melt increases the reactivity and disequilibrium degree of the melt, resulting in a highly dynamic dissolution-precipitation process (e.g., Keller and Katz, 2016;Lambart et al, 2022;Mallmann et al, 2009;Shaw et al, 2018). Additionally, in comparison to CO 2 -free experiments, Mallik and Dasgupta (2013) observed an increase in orthopyroxene (and garnet) in the residual solid after reaction at the expense of olivine and clinopyroxene.…”

Section: Other Parametersmentioning

confidence: 99%

Thermodynamic modeling of melt addition to peridotite: Implications for the refertilization of the non-cratonic continental mantle lithosphere

¹

,

France

²

,

Lambart

³

et al. 2022

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“…Comparison of the mean concentrations from 11 NIST612 analyses with the GeoReM preferred values (Jochum et al., 2011) shows that the relative error on the trace element contents in quartz is 6.7% for Ti and lies between 1.0% and 12.1% for the other analyzed elements (Table S1 in Supporting Information ). We also performed six analyses on the reference material San Carlos Olivine NMNH 111312/42 for comparison with data published in the literature (Lambart et al., 2022). The measured Ti concentration in olivine San Carlos reference material overlaps with the published values within two standard deviations (Table S1 in Supporting Information ).…”

Section: Methodsmentioning

confidence: 99%

Evidence for Low‐Pressure Crustal Anatexis During the Northeast Atlantic Break‐Up

Morris,

Lambart,

Stearns

et al. 2024

Geochem Geophys Geosyst

0

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While basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (<5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U‐Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post‐dates the Paleocene‐Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low‐pressure, high‐temperature crustal anatexis preceding the main phase of magmatism.

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Compositional variability of San Carlos olivine

Cited by 15 publications

References 56 publications

Fe2+–Mg partitioning between olivine and liquid at low oxygen fugacity: an experimental and thermodynamic framework

Fe2+–Mg partitioning between olivine and liquid at low oxygen fugacity: an experimental and thermodynamic framework

Thermodynamic modeling of melt addition to peridotite: Implications for the refertilization of the non-cratonic continental mantle lithosphere

Evidence for Low‐Pressure Crustal Anatexis During the Northeast Atlantic Break‐Up

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