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Experimentally determined nickel partitioning between mantle minerals and hydrous mafic melts at 1050–1250 °C: Evaluation of pyroxenite contribution to arc magma generation.

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Title: Experimentally determined nickel partitioning between mantle minerals and hydrous mafic melts at 1050–1250 °C: Evaluation of pyroxenite contribution to arc magma generation.
Authors: Sun, Zhongxing1,2 (AUTHOR), Ruan, Mengfei3 (AUTHOR), Xiong, Xiaolin1,2 (AUTHOR), Wang, Yu2 (AUTHOR), Gao, Mingdi1,2 (AUTHOR) gaomingdi@gig.ac.cn
Source: Geochimica et Cosmochimica Acta. Jun2026, Vol. 423, p129-150. 22p.
Subjects: Pyroxenite, Partition coefficient (Chemistry), Petrology, Magmas, Rock-forming minerals, Olivine
Abstract: High-Ni olivine phenocrysts in arc magmas are commonly used to infer the contribution of pyroxenite components during sub-arc mantle melting. However, accurate mantle mineral-melt Ni partition coefficients (D Ni) under conditions relevant to sub-arc mantle melting and early differentiation of arc magmas remain poorly constrained, casting doubt on this interpretation. One principal challenge for determining reliable mineral-melt D Ni by experiments is mitigating the severe Ni loss to experimental capsules. Using the Ni-bearing capsule technique, we here determined D Ni between mantle minerals (olivine, orthopyroxene, clinopyroxene and spinel) and hydrous mafic melt (∼5–12 wt% MgO, ∼1–9 wt% H 2 O) at 1–1.5 GPa and 1050–1250 ℃, corresponding to conditions of arc magma generation and early differentiation. The experimental results show that D Ni values for olivine, orthopyroxene and clinopyroxene increase from 11.4 to 37.6, 3.5 to 11.5 and 3.5 to 6.4, respectively, with decreasing melt MgO content and temperature. These data, combined with screened literature data with limited Ni loss, are used to establish empirical expressions of mineral-melt D Ni as functions of melt MgO content and temperature. These expressions were applied to model Ni contents in melts derived from peridotite and pyroxenite sources, as well as Ni contents in olivine crystallized from these melts. The modeling results show that olivine crystallized from hydrous arc peridotite-derived melts exhibits lower Ni contents than the high-Ni olivine phenocrysts observed in some arc magmas. In contrast, olivine crystallized from pyroxenite-derived melts can reproduce the elevated Ni signatures in these olivine phenocrysts. Our results demonstrate that the pyroxenite contribution to generation of arc magmas might be more widespread than previous expected. [ABSTRACT FROM AUTHOR]
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Abstract:High-Ni olivine phenocrysts in arc magmas are commonly used to infer the contribution of pyroxenite components during sub-arc mantle melting. However, accurate mantle mineral-melt Ni partition coefficients (D Ni) under conditions relevant to sub-arc mantle melting and early differentiation of arc magmas remain poorly constrained, casting doubt on this interpretation. One principal challenge for determining reliable mineral-melt D Ni by experiments is mitigating the severe Ni loss to experimental capsules. Using the Ni-bearing capsule technique, we here determined D Ni between mantle minerals (olivine, orthopyroxene, clinopyroxene and spinel) and hydrous mafic melt (∼5–12 wt% MgO, ∼1–9 wt% H 2 O) at 1–1.5 GPa and 1050–1250 ℃, corresponding to conditions of arc magma generation and early differentiation. The experimental results show that D Ni values for olivine, orthopyroxene and clinopyroxene increase from 11.4 to 37.6, 3.5 to 11.5 and 3.5 to 6.4, respectively, with decreasing melt MgO content and temperature. These data, combined with screened literature data with limited Ni loss, are used to establish empirical expressions of mineral-melt D Ni as functions of melt MgO content and temperature. These expressions were applied to model Ni contents in melts derived from peridotite and pyroxenite sources, as well as Ni contents in olivine crystallized from these melts. The modeling results show that olivine crystallized from hydrous arc peridotite-derived melts exhibits lower Ni contents than the high-Ni olivine phenocrysts observed in some arc magmas. In contrast, olivine crystallized from pyroxenite-derived melts can reproduce the elevated Ni signatures in these olivine phenocrysts. Our results demonstrate that the pyroxenite contribution to generation of arc magmas might be more widespread than previous expected. [ABSTRACT FROM AUTHOR]
ISSN:00167037
DOI:10.1016/j.gca.2026.05.004