Tschauner et al. (Reports, 11 November 2021, p. 891) present evidence that diamond GRR-1507 formed in the lower mantle. Instead, the data support a much shallower origin in cold, subcratonic lithospheric mantle. X-ray diffraction data are well matched to phases common in microinclusion-bearing lithospheric diamonds. The calculated bulk inclusion composition is too imprecise to uniquely confirm CaSiO3 stoichiometry and is equally consistent with inclusions observed in other lithospheric diamonds.

Tschauner et al. (Reports, 11 November 2021, p. 891) present evidence that diamond GRR-1507 formed in the lower mantle. Instead, the data support a much shallower origin in cold, subcratonic lithospheric mantle. X-ray diffraction data are well matched to phases common in microinclusion-bearing lithospheric diamonds. The calculated bulk inclusion composition is too imprecise to uniquely confirm CaSiO3 stoichiometry and is equally consistent with inclusions observed in other lithospheric diamonds.

Harzburgites and dunites forming the base of the Late Cretaceous-Paleocene Papuan Ultramafic Belt (PUB) and Marum ophiolites of Papua New Guinea (PNG) are among the most refractory mantle peridotites on Earth. We present a new integrated dataset of major element, bulk plus mineral trace element and Re-Os isotopic analyses aimed at better understanding the genesis of these peridotites. The PUB harzburgites contain olivine (Fo(92-93)), low-Al enstatite (less than or equal to 0.5 wt. % Al2O3 and CaO), and Cr-rich spinel (Cr#= 0.90-0.95). The Marum harzburgites are less refractory with olivine (Fo(91.9)-(92.7)), enstatite (similar to 0.5-1.0 wt. % Al2O3 and CaO), minor clinopyroxene (diopside), and spine! (Cr# = 0.71-0.77). These major element characteristics reflect equivalent or greater levels of melt depletion than that experienced by Archean cratonic peridotites. Whereas bulk-rock heavy rare earth element (HREE) abundances mirror the refractory character indicated by the mineral chemistry and major elements, large-ion lithophile elements indicate a more complex melting and metasomatic history. In situ olivine and orthopyroxene REE measurements show that harzburgites and dunites have experienced distinct melt-rock interaction processes, with dunite channels/lenses, specifically, showing higher abundances of HREE in olivine. Distinctive severe inter-element fraction of platinum group elements and Re result in complex patterns that we refer to as 'M-shaped'. These fractionated highly siderophile element (HSE) patterns likely reflect the dissolution of HSE-rich phases in highly depleted peridotites by interaction with subduction-related melts/fluids, possibly high-temperature boninites. Osmium isotope compositions of the PNG peridotites are variable (Os-187/Os-188 = 0.1204 to 0.1611), but fall within the range of peridotites derived from Phanerozoic oceanic mantle, providing no support for ancient melt depletion, despite their refractory character. This provides further evidence that highly depleted peridotites can be produced in the modern Earth, in subduction zone environments. The complex geochemistry indicates a multi-stage process for the formation of the PNG mantle peridotites in a modern geodynamic environment. The first stage involves partial melting at low-pressure (<2 GPa) and high-temperature (similar to 1250 degrees C-1350 degrees C) to form low-K, low-Ti tholeiitic magmas that formed the overlying cumulate peridotite-gabbro and basalt (PUB only) sequences of the ophiolites. This is inferred to have occurred in a fore-arc setting at the initiation of subduction. Later stages involved fluxing of the residual harzburgites with hydrous fluids and melts to form replacive dunites and enstatite dykes and interaction of the residual peridotites in the overlying mantle wedge with high-temperature hydrous melts from the subducting slab to generate the extremely refractory harzburgites. This latter stage can be linked to the eruption of low-Ca boninites at Cape Vogel, and other arc-related volcanics, in a nascent oceanic island arc. Both ophiolites were emplaced shortly after when the embryonic oceanic island arc collided with the Australian continent.

Tschauner et al. (Reports, 11 November 2021, p. 891) present evidence that diamond GRR-1507 formed in the lower mantle. Instead, the data support a much shallower origin in cold, subcratonic lithospheric mantle. X-ray diffraction data are well matched to phases common in microinclusion-bearing lithospheric diamonds. The calculated bulk inclusion composition is too imprecise to uniquely confirm CaSiO3 stoichiometry and is equally consistent with inclusions observed in other lithospheric diamonds.

The Earth could have experienced sulfide segregation during its differentiation due to sulfur (S) saturation within a magma ocean. The relative timing of sulfide saturation during magma ocean crystallisation is strongly dependent on the solubility of S at sulfide saturation (SCSS). Here, we present SCSS data directly relevant for a deep terrestrial magma ocean obtained from laser heated diamond anvil cell experiments. Our new data, along with existing SCSS data obtained for similar compositions, was parameterised to derive a new predictive equation. Our parameterisation predicts that existing models strongly underestimate the SCSS over the P-T range of a deep magma ocean. Our SCSS models provide the S abundances required at any given stage of terrestrial accretion, and imply that sulfide saturation is much less efficient at stripping the Earth's mantle of S during accretion than previously predicted. Applying our results to the most recent mantle S evolution models shows that the SCSS would be far too high to achieve sulfide saturation, until only perhaps the final stages of magma ocean crystallisation. To satisfy highly siderophile element systematics, either the S content of the magma ocean was considerably higher than currently assumed, or highly siderophile element abundances were affected by other processes, such as iron disproportionation.

How and when Earth's volatile content was established is controversial with several mechanisms postulated, including planetesimal evaporation, core formation and the late delivery of undifferentiated chondrite-like materials. The isotopes of volatile elements such as sulfur can be fractionated during planetary accretion and differentiation and thus are potential tracers of these processes. Using first-principles calculations, we examine sulfur isotope fractionation during core formation and planetesimal evaporation. We find no measurable sulfur isotope fractionation between silicate and metallic melts at core-forming conditions, indicating that the observed light sulfur isotope composition of the bulk silicate Earth relative to chondrites cannot be explained by metal-silicate fractionation. Our thermodynamic calculations show that sulfur evaporates mostly as H2S during planetesimal evaporation when nebular H-2 is present. The observed bulk Earth sulfur isotope signature and abundance can be reproduced by evaporative loss of about 90% sulfur mainly as H2S from molten planetesimals before nebular H-2 is dissipated. The heavy sulfur isotope composition of the Moon relative to the Earth is consistent with evaporative sulfur loss under 94-98% saturation condition during the Moon-forming giant impact. In summary, volatile evaporation from molten planetesimals before Earth's formation probably played a key role in establishing Earth's volatile element content.

An Excel spreadsheet compiling published major and trace element data for all important sublithospheric (upper mantle, transition zone and lower mantle) inclusion phases in diamond. Major element data are obtained by EPMA, trace element data by SIMS (ion microprobe) and LA-ICPMS. For additional details, please refer to Chapter 7: Geochemistry of Silicate and Oxide Inclusions in Sublithospheric Diamonds by Walter et al. in the RiMG volume "Diamond - Genesis, Mineralogy, and Geochemistry ", https://doi.org/10.2138/rmg.2022.88.07

The HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) of the Magellanic Clouds will use dust emission to investigate the life cycle of matter in both the Large and Small Magellanic Clouds (LMC and SMC). Using the Herschel Space Observatory's PACS and SPIRE photometry cameras, we imaged a 2 degrees x 8 degrees strip through the LMC, at a position angle of similar to 22.5 degrees as part of the science demonstration phase of the Herschel mission. We present the data in all 5 Herschel bands: PACS 100 and 160 mu m and SPIRE 250, 350 and 500 mu m. We present two dust models that both adequately fit the spectral energy distribution for the entire strip and both reveal that the SPIRE 500 mu m emission is in excess of the models by similar to 6 to 17%. The SPIRE emission follows the distribution of the dust mass, which is derived from the model. The PAH-to-dust mass (f(PAH)) image of the strip reveals a possible enhancement in the LMC bar in agreement with previous work. We compare the gas mass distribution derived from the HI 21 cm and CO J = 1-0 line emission maps to the dust mass map from the models and derive gas-to-dust mass ratios (GDRs). The dust model, which uses the standard graphite and silicate optical properties for Galactic dust, has a very low GDR = 65(-18)(+15) making it an unrealistic dust model for the LMC. Our second dust model, which uses amorphous carbon instead of graphite, has a flatter emissivity index in the submillimeter and results in a GDR = 287(-42)(+25) that is more consistent with a GDR inferred from extinction.

We demonstrate the unique capabilities of Herschel to study very young luminous extragalactic young stellar objects (YSOs) by analyzing a central strip of the Large Magellanic Cloud obtained through the HERITAGE science demonstration program. We combine PACS 100 and 160, and SPIRE 250, 350, and 500 mu m photometry with 2MASS (1.25-2.17 mu m) and Spitzer IRAC and MIPS (3.6-70 mu m) to construct complete spectral energy distributions (SEDs) of compact sources. From these, we identify 207 candidate embedded YSOs in the observed region, similar to 40% never-before identified. We discuss their position in far-infrared color-magnitude space, comparing with previously studied, spectroscopically confirmed YSOs and maser emission. All have red colors indicating massive cool envelopes and great youth. We analyze four example YSOs, determining their physical properties by fitting their SEDs with radiative transfer models. Fitting full SEDs including the Herschel data requires us to increase the size and mass of envelopes included in the models. This implies higher accretion rates (>= 10(-4)M(circle dot)yr(-1)), in agreement with previous outflow studies of high-mass protostars. Our results show that Herschel provides reliable longwave SEDs of large samples of high-mass YSOs; discovers the youngest YSOs whose SEDs peak in Herschel bands; and constrains the physical properties and evolutionary stages of YSOs more precisely than was previously possible.

In the year following the end of the 2009 eruption of Redoubt Volcano, Alaska, four significant swarms of low-frequency, low-magnitude (M-L < 0.1) earthquakes occurred at shallow depths beneath the summit. Because swarms of low-frequency (LF) earthquakes preceded eruptions in 1989 and 2009, the posteruption swarms caused considerable concern and prompted the Alaska Volcano Observatory to raise the monitoring levels on three occasions. None of these swarms led to eruptions, however, and most observers (including us) initially concluded that the swarms had been caused by minor stress adjustments in the new lava dome or in the surrounding summit glaciers. New observations reveal that the shallow LF swarms were accompanied by 2 families of repeating earthquakes at depths between 3 km and 6 km below sea level, where the magma storage region is thought to be. These mid-crustal volcano-tectonic (VT) type earthquakes were identical to earthquakes recorded during the 2009 Redoubt eruption more than 6 months earlier. Focal mechanisms demonstrate that these earthquakes have thrust mechanisms inconsistent with the strike-slip nature of regional faulting. Based on these observations, we conclude that they are generated through processes occurring within the magma storage region. The concurrence of the repeating VT earthquakes with the shallow LF swarms indicates that the shallow LF earthquakes were also magmatically driven. Our results emphasize that even brief episodes of low-amplitude earthquake activity, such as the LF swarms observed at Redoubt following the 2009 eruption, can be indicative of magmatic activity. Perhaps more significant, however, is the demonstration that the conduit system at Redoubt remained active, intact, and capable of transporting heat and fluids to the surface months after the eruption was considered over.