Analysis of Zn–Fe isotopes reveals a common mantle source for diverse magmas in kimberlites, suggesting implications for magma formation.
• Zn–Fe isotopes measured in 55 kimberlites worldwide. • Kimberlites show a strong positive global Zn–Fe isotopic trend. • Heavy Zn–Fe signatures reflect low-degree melting of asthenospheric mantle. • Variable melting of a common source yields diverse mantle melt types. Kimberlites contain distinct asthenospheric and lithospheric mantle components. Disentangling their relative contributions is a challenging yet important goal to constrain the kimberlite sources. We analyzed the Zn-Fe isotope compositions of 55 globally distributed kimberlites. The Zn-Fe isotopes of kimberlites define a strong positive correlation from isotopically light compositions akin to cratonic peridotites to heavy compositions that are similar to those of melilitites and nephelinites globally. This covariation can be explained by mixing between cratonic mantle peridotites and isotopically similar uncontaminated kimberlite melts, with the observed heavy Zn-Fe isotopic signatures potentially originating from low-degree partial melting of asthenospheric sources. The similarities of trace elements and isotopes between uncontaminated kimberlite melts, nephelinites and melilitites reveal that these strongly silica-undersaturated magmas tap similar mantle sources in the convective mantle. Partial melting of this common source under different melting conditions can produce the spectrum of mantle melts from kimberlitic to silica-undersaturated basaltic melts without necessarily invoking compositional variations in the mantle source.
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Cai et al. (2026) studied this question.
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