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Introduction: Metal-rich achondrites include a variety of types, and likely have a variety of origins. Models range from gravitational mixing at the core-mantle boundaries of differentatiated asteroids, to complex impact mixing scenarios. We describe a new type of metal-rich achondrite that might be the first metal-rich ureilite. Sample: Tin-Essako (TE) 001 (~4.3 kg) was found in Mali in 2020 and purchased by Jay Piatek in 2021. It was classified as a metal-rich ungrouped achondrite, with olivine and oxygen isotope (avg. δ18O=8.281‰, δ17O=3.718 ‰, Δ17O=-0.654‰) compositions suggesting affinity to ureilites [1]. We studied one polished section (~188 mm²). Petrography: TE 001 consists of ~60% metal and 40% silicates, heterogeneously distributed (Fig. 1a). The metal is largely fresh, but iron oxides (presumably terrestrial) occur along one edge and in some patches and veins. The silicates are ≥90% olivine, plus melt-textured areas of plagioclase + Si-rich glass. Minor phases are chromite and carbon. Olivine occurs as rounded grains (≤2.5 mm) in metal, commonly with rims of melt-textured plagioclase + glass. Olivine also occurs in massive areas having a "honeycomb" texture (Fig. 1b), with olivine "cells" surrounded by a network of interstitial reduced olivine (full of tiny metal grains) plus melt-textured plagioclase + Sirich glass (Fig. 1c). Chromite occurs as subhedral to rounded grains (~30-500 μm) included in olivine or metal. A carbon phase occurs as lacy-textured (fibrous) rims around olivine grains or patches within metal. Mineral Compositions: The olivine (excluding interstitial areas) is Fo 73.9±0.5, with 0.25±0.02 wt.% CaO, 0.31±0.01 wt.% Cr2O3, 0.01 wt.% NiO, and molar Fe/Mn=49.8±2.2 (53 analyses). Olivine in interstitial areas has Fo up to at least 91. Smaller chromite grains have Fe# (molar Fe/[Fe+Mg]) = 0.54±0.01, Cr# (molar Cr/[Cr+Al]) = 0.52±0.01, 0.52±0.02 wt.% V2O3 and 0.21±0.04 wt.% ZnO (28 analyses). One larger grain is zoned from Fe# = 0.45, Cr# = 0.52 to Fe# = 0.40, Cr# = 0.57, and contains thin Al-rich lamellae not resolved by EMPA. One irregularly shaped patch of chromite in olivine has Fe# = 0.26 and contains no ZnO. Plagioclase laths are An ~53-60, with ≤0.01 wt.% K2O. Glass contains 75-76 wt.% SiO2 and ~16 wt.% Al2O3. The metal contains 5.2±0.2 wt.% Ni, 0.46±0.02 wt.% Co, and 0.01±0.01 wt.% Cr, with Si and P below detection (168 analyses). Discussion: The olivine + chromite assemblage in TE 001 is suggestive of the most ferroan ureilites (Fo ~75-77 [2]), as are the oxygen isotopes [1]. The presence of a carbon phase supports this, though the identity of this phase (graphite as in ureilites?) remains to be determined. The "honeycomb" textured areas, in particular, the presence of "reduction rims," resemble shock-smelted olivine in ureilites [3], but melt-textured areas of plagioclase laths + glass like those in TE 001 have not been reported in such (or any) ureilites. Olivine in TE 001 is marginally more ferroan than in the most ferroan ureilite, with Fe/Mg-Fe/Mn offset from the trend of olivine + low-Ca pyroxene ureilites (similar to augite-bearing ureilites) [2]. CaO and Cr2O3 contents are in the range of those in ureilite olivine [4], though Cr2O3 is at the extreme low end of the range [5]. Chromites (except the unusual one) have similar Fe# to the most ferroan chromites in ureilites [2], but lower Cr# (0.52 vs. 0.71). Metal compositions are in the range for metal in ureilites [6]. The absence of pyroxene and sulfide, and high abundance of metal, in TE 001, are unlike ureilites. One possibility is that a ferroan, chromite-bearing, pyroxene-poor ureilite was invaded (possibly due to impact) by a metallic liquid (the low S content suggests very high temperature), resulting in complete melting of pyroxene and smelting of olivine, with rapid recrystallization of melted silicate as plagioclase + glass. Alternatively, a preexisting metal-rich ureilite assemblage may have been impact melted. Additional types of data will be obtained to evaluate these and other hypotheses (i.e., is the metal indigenous?) and assess affinity to ureilites. [ABSTRACT FROM AUTHOR]

Introduction: Vesta is one of the largest bodies in the asteroid belt and has long been known to have similar absorption features in the visible and near-infrared wavelength regions to the HED (howardite, eucrite, diogenite) meteorites. Eucrites are basalts and gabbros that are mostly composed of pyroxene and anorthite-rich plagioclase while diogenites are predominantly composed of magnesian orthopyroxene. Howardites are polymict breccias that contain mineral and lithic fragments of both eucritic and diogenitic materials. Vesta was one of the targets of NASA's Dawn mission, which spectrally and chemically mapped its surface. Vesta's surface is primarily composed of eucritic and howarditic material with diogenitic regions being much less common [1]. Numerous smaller bodies (Vestoids) in the Vesta family and throughout the inner asteroid belt also have reflectance spectra similar to HEDs [2]. Vestoids have also been identified far from Vesta in the middle and outer part of the asteroid belt. A few eucrites have been found to have oxygen isotopic values that differ from "typical" HEDs [3] and appear to be more evidence that other differentiated parent bodies besides Vesta existed. Using previously derived formulas [4], we calculated the bulk pyroxene mineralogies of forty-nine main-belt and Mars-crossing V-types using band centers derived from their reflectance spectra. Our goal is to see what we can tell about Vesta from analyzing the Vestoids. Vesta is a relatively unique body since it has been orbited by a spacecraft and can be linked to both large (Vestoids) and small (HED) fragments. Data: We analyzed publicly available main-belt and Mars-crossing V-type bodies that had spectra in the visible and near-infrared. The near-infrared reflectance spectra were all taken using SpeX at the NASA Infrared Telescope Facility (IRTF). Visible spectra were spliced to the near-infrared spectra when necessary so the reflectance peak located at ~0.7-0.8 µm would be part of each analyzed spectrum. Analysis: Band I and Band II centers, respectively, were calculated from seventy-one V-type reflectance spectra taken of forty-nine bodies. Fs and Wo contents were then calculated from the band centers. A temperature correction was applied to all band centers since all the asteroids have surface temperatures lower than room temperature. We then determined bulk pyroxene compositions using previously derived formulas. For objects with multiple spectra, we averaged the calculated bulk pyroxene compositions. One object, (10537) 1991 RY16, had a Band I center consistent with a significant olivine component [5]. Results: Consistent with other studies [6], we find that diogenitic Vestoids are rare. Approximately half of the Vtypes had interpreted bulk pyroxene mineralogies consistent with eucrites. Most of the remaining V-types had bulk pyroxene mineralogies consistent with eucrites/howardites or howardites. Only one body, (3155) Lee, had a bulk pyroxene mineralogy consistent with howardites/diogenites. However, diogenites are much more common among HED falls and finds since diogenites comprise approximately twenty percent of known HEDs. To explain the absence of diogenitic Vestoids, we propose that the diogenitic regions in Vesta's crust were relatively thin. Modeling by Wilson & Keil [7] suggested that "deep" intrusions on Vesta would have had thicknesses of only 3 meters or less. If the diogenitic regions in the eucritic crust were not very thick then the formation of craters on Vesta would have only produced "small" diogenite fragments that could have only come to Earth as meteorites. Diogenitic bodies would not be observed since diogenitic Vestoids would not be large enough to be characterized from Earth. These "thin" diogenitic intrusions must have formed as part of an extensive network on Vesta for diogenites to consistently fall to Earth and also be abundant components of howardites. Conclusions: Diogenitic Vestoids appear extremely rare whereas eucritic and howarditic Vestoids appear much more common. One possibility for this discrepancy is that diogenitic intrusions are extremely "thin" but widespread in Vesta's eucritic crust. Diogenitic material can be ejected as small fragments from Vesta but not as multi-kilometer diogenitic bodies that are observable from Earth. [ABSTRACT FROM AUTHOR]

Low concentrations (tens to hundreds of parts per million) of water in nominally anhydrous minerals (NAMs) of the mantle have been shown to significantly affect the rheology, depth of depressurization melting, and many other properties of the mantle. In this contribution, we evaluate the effect of trace concentrations of water in NAMs on melting of lower continental crust. Water locked in structural sites and in fluid inclusions in nominally anhydrous minerals in lower crustal granitoids may act as a flux for partial melting of these source rocks. Water concentrations of 3000 ppm in minerals that make up large volumes of crustal rocks (K-feldspar, plagioclase, quartz) would lower the dry solidus of granite by 273 °C at 1 GPa. Measurements and maps of water concentration in variably deformed samples of the Stevenson Granite from northern Saskatchewan (Canada) show that, during deformation and recrystallization of K-feldspar mega-crysts, water migrated from the interior of megacrysts to finer-grained matrix material. Dark, fine-grained, water-richer matrix material consisting of quartz, plagioclase, alkali feldspar, and fine iron oxides are interpreted to be former melt films that resulted, at least in part, from fluxing by NAM-derived water. Deformation may play a role in moving water from NAMs to phase boundaries where generation of partial melt may lead to further rock weakening and further release of water from NAMs. [ABSTRACT FROM AUTHOR]