Onset of slab mantle melting in Earth’s lower mantle: Evidence from ferropericlase in superdeep diamonds

Science Advances · 2025-10-15

Ferropericlase ([Mg x ,Fe 1-x ]O), the most common inclusion in sublithospheric diamonds, has a poorly understood crystallization history and depth of origin. Nineteen microscopic ferropericlase grains with different Mg#s were released from Juína and Kankan diamonds with mantle-like carbon, for Mg and Fe isotopic analysis. Two groups of ferropericlase inclusions can be distinguished with respect to diamond growth: high-Mg# inclusions with mantle-like Mg and Fe (δ 26 Mg = −0.23 ± 0.22‰; δ 56 Fe = 0.00 ± 0.14‰) inferred to be preexisting and lower Mg# inclusions with non–mantle-like heavy Fe (δ 56 Fe up to +0.3‰) and light Mg (δ 26 Mg down to −1.4‰) inferred to be coeval. We propose that coeval ferropericlase inclusions formed by melting of hydrated and carbonated peridotitic slab components subducted to lower mantle depths. Continuous reaction of these melts with surrounding reduced, dry slab harzburgite can produce the large range in Mg# and Ni contents of our ferropericlase suite—a heretofore unexplained feature of global ferropericlase data.

Iron isotope systematics of the lithospheric mantle investigated by a magnesiochromite inclusion in diamond

2025-01-01

High-energy impact and vapor recondensation history of the angrite parent body revealed by nickel isotopes

Proceedings of the National Academy of Sciences · 2025-11-10 · 2 citations

The angrite parent body (APB) is the most volatile-depleted among known differentiated bodies in the Solar System, yet the mechanisms responsible remain poorly constrained. Here, we present high-precision nickel (Ni) isotope data from a suite of angrite samples to reconstruct the APB’s volatile depletion history. Plutonic angrites contain unusually high proportions of metallic iron and exhibit chondritic δ 60/58 Ni values (0.202 ± 0.028‰; per mille mass-dependent 60 Ni/ 58 Ni deviation relative to National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 986). These observations are consistent with a homogeneous Ni isotope composition of the APB after core formation and the subsequent incorporation of endogenous core material in plutonic angrites. In contrast, a dunite and megacrystic olivines from volcanic angrites, derived from the mantle, display suprachondritic δ 60/58 Ni values (0.4 to 0.7‰). We argue that these values are consistent with Ni loss via evaporation during a high-energy impact that follows an initial stage of volatile loss from a magma ocean generated by 26 Al heating. Thermodynamic modeling confirms Ni to be more volatile than Mn, Fe, Si, and Mg during evaporation from silicate liquids, in agreement with the observed relative magnitude of isotopic fractionation. Volcanic angrite matrices show variable and often subchondritic δ 60/58 Ni values (down to −0.5‰), reflecting mixing with isotopically heavy megacrystic olivines and recondensation of light Ni vapor onto the crust. These findings imply that volatile elements are stratified (core–mantle–crust) in the APB and provide direct isotopic evidence for impact-driven vapor loss and recondensation on a differentiated planetary body.

Equilibrium Fe isotope fractionation between olivine, pyroxene, spinel and MORB glass: Implications for mantle partial melting to generate MORBs

Geochimica et Cosmochimica Acta · 2025-06-19 · 3 citations

17 Endogenous Lunar Volatiles

2024-04-22 · 1 citations

Despite all of the new data generated on endogenous lunar volatiles since the publication of New Views of the Moon, many important questions remain unanswered or only partially resolved. This abstract looks to the future and discusses several of those important remaining questions on the topic of endogenous lunar volatiles.

CONSTRAINTS ON DIAMOND DEPTHS OF ORIGIN FROM Fe-Mg PARTITIONING

Abstracts with programs - Geological Society of America · 2024-01-01

Volatile degassing during fire fountain eruptions on the Moon

2024-01-01

Understanding diamond-forming fluids and parental lithologies using Fe, Mg, and K isotopes

2024-07-08

Copper isotope fractionation by diffusion in a basaltic melt

Earth and Planetary Science Letters · 2023-11-09 · 7 citations

Copper shows limited isotopic variation in equilibrated mantle-derived silicate rocks, but large isotopic fractionation during kinetic processes. For example, lunar and terrestrial samples that have experienced evaporation were found to have an isotopic fractionation of up to 12.5‰ in their 65Cu/63Cu ratios, while komatiites, lherzolites, mid-ocean ridge and ocean island basalts show negligible Cu isotope fractionation as a result of equilibrium partial melting and crystal fractionation. The contrast between the observed magnitudes of equilibrium and kinetic isotope fractionation for Cu calls for a better understanding of kinetic Cu isotope fractionation. One of the mechanisms for creating large kinetic isotopic fractionation even at magmatic temperatures is diffusion. In this study, we performed Cu isotopic measurements on Cu diffusion couple experiments to constrain the beta factor for Cu isotopic fractionation by diffusion. We demonstrate a Monte Carlo approach for the regression and error estimation of the measured isotope profiles, which yielded beta values of 0.16 ± 0.03 and 0.18 ± 0.03 for the two experimental charges measured. Our results are subsequently applied to a quantitative model for the evaporation of a molten sphere to discuss the role of diffusion in affecting the bulk Cu isotopic fractionation between liquid and vapor during evaporation. We apply the model to Cu evaporation experiments and tektite data to show that convection primarily governs mass transport for evaporation during tektite formation. In addition, we show that Cu isotopes can be used as a tool to test the role of kinetics during various magmatic processes such as magmatic sulfide ore deposit formation, porphyry-type ore deposit formation, and fluid-rock interactions.

Ni stable isotope fractionation during core crystallization

2023-01-01

As one of the most significant stages during planetary formation, core formation and crystallization usually cause important redistributions of siderophile elements and their isotope compositions.Core crystallization occurs with equilibrium processes between solid metal (sulfur-poor) and liquid metal (sulfur-rich) phases [1].Ni is a major and siderophile element in planetary/asteroidal cores, and significant, large Ni stable isotope fractionations (~1) have been found in sulfides [2].The stable isotopes of Ni may therefore provide a means of tracing core crystallization.However, due to lack of Ni isotope data of magmatic iron meteorites from a same group [3], we hope to reconstruct this process from high-temperature experiments.Experimental samples of solid metal and liquid metal were produced at the Johns Hopkins University Applied Physics Lab, in a one-atmosphere vertical furnace at 1,260-1,470 C for durations of 1-7 days [4].Ni stable isotope measurements were performed at University of Bristol, using a double spike technique, with long-term 60/58 Ni data reproducibility better than 0.03 (2SD).No Ni isotope differences (-0.02 0.02, 2SD) between solid metal and liquid metal were found for the samples that were conducted at 1,470 C.However, at 1,260 C, Ni isotopes are not equilibrated until seven days, which is not the case for Fe isotope system [4].Isotopic fractionation between solid and liquid metal ( 60/58 Ni solid-liquid = 0.05 0.02 2SD, N = 6) was observed for experiments made at 1,260 -1,380 C.These data suggest limited Ni stable isotope fractionation during asteroidal core crystallization.The relatively large 60/58 Ni variation (~0.4) in iron meteorites [3] could be caused by other processes, e.g., Ni diffusion and kinetic isotope fractionation between kamacite and taenite.Similarly, Ni stable isotope variation in ureilites [5] and enstatite achondrites [6] cannot be caused by equilibrium Ni stable isotope fractionation between metal and sulfur-rich phases.