Calcium isotopic fractionation in mantle peridotites by melting and metasomatism and Ca isotope composition of the Bulk Silicate Earth

Kang, Jinting; Ionov, Dmitri A.; Liu, Fang; Zhang, Chen-Lei; Golovin, Alexander V.; Qin, Liping; Zhang, Zhaofeng; Huang, Fang

doi:10.1016/j.epsl.2017.05.035

Cited by 115 publications

(122 citation statements)

References 63 publications

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“…Magnesium isotopic compositions of the Tengchong volcanic rocks (−0.31 to −0.38‰) are slightly beyond the range of typical oceanic basalts (−0.18 to −0.32‰; Teng, Li, Rudnick, et al, ). Similarly, their δ 44/40 Ca values (0.67 to 0.80‰) are systematically lower than the fertile mantle (0.94 ± 0.05‰; Kang et al, ). These isotopic signatures can possibly be attributed to several processes, such as source heterogeneity, magmatic processes, crustal contamination, and alteration.…”

Section: Discussionmentioning

confidence: 91%

“…Gray bar represents the widely accepted δ 26 Mg of the mantle (−0.25 ± 0.07‰; Teng, Li, Rudnick, et al, ). Dashed gray bar represents the δ 44/40 Ca of the fertile mantle (0.94 ± 0.05‰; Kang et al, ). Sm/Yb and Ba/Y are sensitive to partial melting, which will increase when partial melting degree decreases.…”

Section: Discussionmentioning

confidence: 99%

“…The degree of partial melting of Tengchong volcanic rocks, however, has already been demonstrated to be only ~5% (Zhou et al, ), which can only result in shifts in δ 44/40 Ca of less than 0.05‰ (Kang et al, ). In this study, δ 44/40 Ca of Tengchong volcanic rocks have a narrow variation from 0.67 to 0.80‰ with an average of 0.74 ± 0.08‰, lower than the value of fertile mantle (0.94 ± 0.05‰; Kang et al, ) by nearly 0.2‰. This 0.2‰ offset cannot be caused by partial melting but should be related to the mantle source.…”

Section: Discussionmentioning

confidence: 99%

“…Blue line represents the average δ 44/40 Ca of basalts. Gray bars represent the δ 44/40 Ca of the fertile mantle (Kang et al, ). No δ 44/40 Ca variations were observed between Group I and Group II.…”

Section: Discussionmentioning

confidence: 99%

“…As for Ca isotopes, considerable fractionation can also occur during carbonate precipitation, leading to distinctive Ca isotopic compositions between mantle and marine carbonates. Compared with the δ 44/40 Ca of the fertile mantle (0.94 ± 0.05‰; Kang et al, ), ancient marine carbonates have lower δ 44/40 Ca (mostly <0.5‰; e.g., Fantle & DePaolo, ; Farkaš, Böhm, et al, ; Farkaš, Buhl, et al, ). For example, Huang et al () attributed the light Ca isotopic compositions (0.75 to 1.02‰) in Hawaiian basalts to 4% ancient carbonate component in the Hawaii plume.…”

Section: Introductionmentioning

confidence: 99%

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Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

Liu

Wang

et al. 2017

JGR Solid Earth

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Tracing and identifying recycled carbonates is a key issue to reconstruct the deep carbon cycle. To better understand carbonate subduction and recycling beneath the southeastern Tibetan Plateau, high‐K cal‐alkaline volcanic rocks including trachy‐basalts and trachy‐andesites from Tengchong were studied using Mg and Ca isotopes. The low δ26Mg (−0.31 ± 0.03‰ to −0.38 ± 0.03‰) and δ44/40Ca (0.67 ± 0.07‰ to 0.80 ± 0.04‰) values of these volcanic rocks compared to those of the mantle (−0.25 ± 0.07‰ and 0.94 ± 0.05‰, respectively) indicate the incorporation of isotopically light materials into the mantle source, which may be carbonate‐bearing sediments with low δ26Mg and δ44/40Ca values. In addition, no correlations of δ26Mg and δ44/40Ca with either SiO2 contents or trace element abundance ratios (e.g., Sm/Yb and Ba/Y) were observed, suggesting that limited Mg and Ca isotopic fractionation occurred during cal‐alkaline magmatic differentiation. A binary mixing model using Mg–Ca isotopes shows that 5–8% carbonates dominated primarily by dolostone were recycled back into the mantle. Since Tengchong volcanism is still active and probably related to ongoing plate tectonic movement, we propose that the recycled carbonates are derived from oceanic crust related to the ongoing subduction of the Indian plate.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

Liu

Wang

et al. 2017

JGR Solid Earth

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Calcium Isotopic Compositions of Normal Mid‐Ocean Ridge Basalts From the Southern Juan de Fuca Ridge

Zhu

Liu

et al. 2018

JGR Solid Earth

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Mantle peridotites show that Ca is isotopically heterogeneous in Earth's mantle, but the mechanism for such heterogeneity remains obscure. To investigate the effect of partial melting on Ca isotopic fractionation and the mechanism for Ca isotopic heterogeneity in the mantle, we report high‐precision Ca isotopic compositions of the normal Mid‐Ocean Ridge Basalts (N‐MORB) from the southern Juan de Fuca Ridge. δ44/40Ca of these N‐MORB samples display a small variation ranging from 0.75 ± 0.05 to 0.86 ± 0.03‰ (relative to NIST SRM 915a, a standard reference material produced by the National Institute of Standards and Technology), which are slightly lower than the estimated Upper Mantle value of 1.05 ± 0.04‰ and the Bulk Silicate Earth (BSE) value of 0.94 ± 0.05‰. This phenomenon cannot be explained by fractional crystallization, because olivine and orthopyroxene fractional crystallization has limited influence on δ44/40Ca of N‐MORB due to their low CaO contents, while plagioclase fractional crystallization cannot lead to light Ca isotopic compositions of the residue magma. Instead, the lower δ44/40Ca of N‐MORB samples compared to their mantle source is most likely caused by partial melting. The offset in δ44/40Ca between N‐MORB and BSE indicates that at least 0.1–0.2‰ fractionation would occur during partial melting and light Ca isotopes are preferred to be enriched in magma melt, which is in accordance with the fact that δ44/40Ca of melt‐depleted peridotites are higher than fertile peridotites in literature. Therefore, partial melting is an important process that can decrease δ44/40Ca in basalts and induce Ca isotopic heterogeneity in Earth's mantle.

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Effects of Melt Percolation on Zn Isotope Heterogeneity in the Mantle: Constraints From Peridotite Massifs in Ivrea‐Verbano Zone, Italian Alps

et al. 2018

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We determined Zn isotopic compositions of 21 orogenic peridotites from the Baldissero and Balmuccia peridotite massifs in Ivrea‐Verbano Zone, Italian Alps, to investigate Zn isotope behaviors during partial melting and melt percolation in the mantle. The samples include lherzolites, harzburgites, and dunites. Lherzolites are strongly depleted in light rare earth element relative to middle and heavy rare earth element with (La/Sm)PM from 0.009 to 0.265 and (La/Yb)PM from 0.003 to 0.125, which can be explained by 5–15% fractional melting of a primitive mantle source. Harzburgites and dunites with nearly identical Mg# (molar 100 * Mg/(Mg + Fe) = 90.2–91.0) have (La/Sm)PM and (La/Yb)PM higher than but Zn contents similar to or lower than those of the parental lherzolites, suggesting that they were influenced by Zn‐depleted silicate melt percolation. Lherzolites have δ66Zn from 0.13 to 0.27‰ showing no correlations with indicators of melt extraction (e.g., Al2O3, Mg#, and La/Yb) and Zn contents. Three sulfide melt‐affected lherzolites show similar δ66Zn to the other normal ones. These observations indicate that 5–15% partial melting and sulfide melt percolation cause limited Zn isotope variations in the mantle. The metasomatic harzburgites and dunites display high δ66Zn (up to 0.46‰) negatively correlated with Zn contents. Such correlations are attributed to kinetic effect during silicate melt percolation, whereby 64Zn preferentially diffuses out from mantle minerals (e.g., olivine) to the percolating silicate melts. A diffusion model suggests that the negative correlation between δ66Zn and Zn contents in dunites can be explained by an empirical βZn (i.e., βZn‐exponent in D66Zn/D64Zn = (m64Zn/m66Zn)βZn) of 0.05–0.06 in olivine.

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Calcium isotopic fractionation in mantle peridotites by melting and metasomatism and Ca isotope composition of the Bulk Silicate Earth

Cited by 115 publications

References 63 publications

Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

Calcium Isotopic Compositions of Normal Mid‐Ocean Ridge Basalts From the Southern Juan de Fuca Ridge

Effects of Melt Percolation on Zn Isotope Heterogeneity in the Mantle: Constraints From Peridotite Massifs in Ivrea‐Verbano Zone, Italian Alps

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