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<jats:title>Abstract</jats:title> <jats:p>Electron backscatter diffraction (EBSD) investigation of strain mainly uses polycrystalline samples to study fabric development. We extend the use of EBSD for the analysis of large single mineral grains by measuring the apparent surficial subdomain boundary density per unit area, reported here as unit segment length (USL). We apply this USL technique to examine and quantify the plastic deformation recorded by naturally shocked olivine in the low to moderately shocked ureilite meteorite Northwest Africa 2221 and the highly shocked martian dunitic cumulate meteorite Northwest Africa 2737, by assessing the types of subdomain boundaries and the increase of subdomain misorientation with increasing shock metamorphism. We further compare USL results for the shocked olivine in the meteorites with those for the terrestrial deformation of Hawaiian olivine. USL of olivine increases with shock level, and USL from shocked olivine is significantly greater than that of terrestrially deformed olivine. USL is a promising tool for the quantification of plastic deformation in large single crystals from shock as well as terrestrial deformation. The results derived from USL measurements along with local EBSD maps are complementary with quantitative 2D X-ray diffraction analysis of crystal deformation and disruption, leading to a more comprehensive understanding of characteristic shock deformation recorded by large single crystals.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The origin of Libyan Desert Glass (LDG) found in the western parts of Egypt close to the Libyan border is debated in planetary science. Two major theories of its formation are currently competing: (1) melting by airburst and (2) formation by impact-related melting. While mineralogical and textural evidence for a high-temperature event responsible for the LDG formation is abundant and convincing, minerals and textures indicating high shock pressure have been scarce. This paper provides a nanostructural study of the LDG, showing new evidence of its high-pressure and high-temperature origin. We mainly focused on the investigation of Zr-bearing and phosphate aggregates enclosed within LDG. Micro- and nanostructural evidence obtained with transmission electron microscopy (TEM) are spherical inclusions of cubic, tetragonal, and orthorhombic (Pnma or OII) zirconia after zircon, which indicate high-pressure, high-temperature decomposition of zircon and possibly, melting of ZrO2. Inclusions of amorphous silica and amorphous Al-phosphate with berlinite composition (AlPO4) within mosaic whitlockite and monazite aggregates point at decomposition and melting of phosphates, which formed an emulsion with SiO2 melt. The estimated temperature of the LDG melts was above 2750 °C, approaching the point of SiO2 boiling. The variety of textures with different degrees of quenching immediately next to each other suggests an extreme thermal gradient that existed in LDG through radiation cooling. Additionally, the presence of quenched orthorhombic OII ZrO2 provides direct evidence of high-pressure (&amp;gt;13.5 GPa) conditions, confirming theory 2, the hypervelocity impact origin of the LDG.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The first-row transition element (FRTE) and high field strength element (HFSE) systematics are powerful tools for tracking the source and evolution of mantle-derived magmas. Clinopyroxene is generally considered a key fractionating mineral controlling the partitioning of trace elements between melt and residual solid during mantle melting. Although partitioning of FRTE and HFSE between clinopyroxene and basaltic melts has been well-studied, experimental constraints on their partitioning behavior in the presence of siliceous, aluminous, and alkali-rich melts are still lacking. Here we present clinopyroxene-silicic melt (67–69 wt% SiO2) partitioning experiments at 1 bar pressure and 1070–1100 °C for Co, Mn, Ni, Cu, Zn, Fe, Sc, Cr, V, Ti, Zr, Hf, Nb, and Ta. Run products consist of diopsidic clinopyroxene coexisting with various melt compositions with non-bridging oxygen to tetrahedral cation ratio (NBO/T) ranging from 0.10 to 0.22. Using our new partition coefficients (Ds) and combined with literature data, we assess some of the effects of crystal chemistry and the melt composition on the partitioning of FRTE and HFSE in this simple system.</jats:p> <jats:p>We show that partitioning of FRTE varies from mildly incompatible (e.g., D = ~0.1−1 for V, Cu, and Zn) to highly compatible (e.g., D &amp;gt; 10 for Cr and Ni), with the highest compatibilities observed for Ni (DNi = 13−34). The partitioning of HFSE varies from highly incompatible (D = 0.01−0.08) for Nb and Ta to mildly incompatible (D = 0.18−0.82) for Zr, Hf, and Ti. Our measured clinopyroxene-melt Ds are consistent with the theoretical predictions of the lattice strain model. Ds data for most tri-, tetra-, and pentavalent elements tend to increase with increasing tetrahedrally coordinated Al content, in agreement with those anticipated from crystal-chemical considerations. In contrast to ivAl concentrations, the clinopyroxene Na concentration has very little effect on trace element partitioning due to its low concentrations in clinopyroxene at relatively low-pressure conditions. These data further support a significant control of melt composition/structure on partitioning for highly polymerized melts. In general, measured Ds roughly increase to different extents with increasing polymerization of the melt (i.e., lower NBO/T or higher ASI). For our equilibrium melt compositions, Ds for several FRTE, such as Co and Ni, correlate well with the melt molar Mg2+/(M+ + M2+), whereas Ds for HFSE vary as a function of the melt alkali concentration. These well-defined trends support the role of melt NBO species (e.g., Mg2+) or complexing ligands (e.g., Na+ and K+) in controlling the partitioning of these elements.</jats:p> <jats:p>Overall, our new Ds data demonstrate that even very small changes in melt major-element compositions can greatly affect element partitioning in strongly polymerized silicic systems. These findings have important implications relevant to petrogenetic studies of the interaction between silicic melt and peridotite that occurs at shallow mantle conditions in various tectonic settings.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Microbially induced formation and transformation of clay minerals are known to be ubiquitous in nature. This work investigated the smectite-to-kaolinite transformation by Bacillus mucilaginosus, a kind of silicate-weathering bacterium. Results showed that the microbe-smectite system doubled protein production compared with the abiotic controls and enhanced dissolved 1.6% of total Si and 0.9% of total Al from smectite after the 25 days experiment. The formation of kaolinite was verified through its distinguished d(001)-spacing of 0.710 nm revealed by synchrotron radiation X-ray diffraction (SR-XRD) and high-resolution transmission electron microscope (HR-TEM). HR-TEM analysis indicated some mixed layers of smectite and kaolinite appeared in the form of a super-lattice structure. Moreover, the compositional and morphological changes of the solids suggested the emergence of kaolinite was associated with the formation of amorphous SiO2 and fragmented clay particles with lower Si/Al ratio and exposed crystal edge. Based on the detection of –C=O species on the smectite surface and the decrease of pH from 8.5 to 6.5, we inferred the organic ligands secreted by Bacillus mucilaginosus complexed with cations, especially for Si, which stripped the tetrahedral sheets and promoted the kaolinization of smectite. To our knowledge, this is the first report of microbially induced smectite-to-kaolinite transformation under ambient conditions in a highly-efficient way. This work could shed light on a novel pathway of microbe-promoted weathering of smectite to kaolinite at the Earth surface conditions. Such a robust and efficient transformation from expansive smectite to non-expansive clays as kaolinite may be of great potential in enhancing oil recovery in reservoirs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Hydroxylation of wadsleyite, β-(Mg,Fe)2SiO4, is associated with divalent cation defects and well known to affect its physical properties. However, an atomic-scale understanding of the defect structure and hydrogen bonding at high pressures is needed to interpret the influence of water on the behavior of wadsleyite in the mantle transition zone. We have determined the pressure evolution of the wadsleyite crystal symmetry and structure, including all O∙∙∙O interatomic distances, up to 32 GPa using single-crystal X-ray diffraction on two well-characterized, Fe-bearing (Fo90) samples containing 0.25(4) and 2.0(2) wt% H2O. Both compositions undergo a pressure-dependent monoclinic distortion from orthorhombic symmetry above 9 GPa, with the less hydrous sample showing a larger increase in distortion at increased pressures due to the difference in compressibility of the split M3 site in the monoclinic setting arising from preferred vacancy ordering at the M3B site. Although hydrogen positions cannot be modeled from the X-ray diffraction data, the pressure evolution of the longer O1∙∙∙O4 distance in the structure characterizes the primary hydrogen bond length. We observe the hydrogen-bonded O1∙∙∙O4 distance shorten gradually from 3.080(1) Å at ambient pressure to about 2.90(1) Å at 25 GPa, being still much longer than is defined as strong hydrogen bonding (2.5–2.7 Å). Above 25 GPa and up to the maximum pressure of the experiment at 32.5 GPa, the hydrogen-bonded O1∙∙∙O4 distance decreases no further, despite the fact that previous spectroscopic studies have shown that the primary O-H stretching frequencies continuously drop into the regime of strong hydrogen bonding (&amp;lt;3200 cm–1) above ~15 GPa. We propose that the primary O1-H∙∙∙O4 hydrogen bond in wadsleyite becomes highly nonlinear at high pressures based on its deviation from frequency-distance correlations for linear hydrogen bonds. One possible explanation is that the hydrogen position shifts from being nearly on the long O1-O4 edge of the M3 site to a position more above O1 along the c-axis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Diverse fluid sources and complex fluid flow paths in skarn systems appear to be well documented. Nevertheless, in situ microanalysis of oxygen isotopes by secondary ion microprobe (SIMS) in skarn minerals can provide further high spatial resolution information on this complexity and the formation of skarns and associated ore deposits. In this study, we investigated the Haobugao skarn Zn-Fe-Sn deposit (0.36 M tonnes Zn) in the southern Great Xing’an Range, northeast (NE) China, and the associated Early Cretaceous Wulanba biotite granite. Based on drill hole logging, four early skarn phases are recognized: proximal red-brown garnet-hedenbergite exoskarn, central green garnet exoskarn, light brown garnet-diopside exoskarn, and distal pyroxene skarn. Oxygen isotope analyses of garnet, pyroxene, and other minerals from skarn, oxide, and quartz-sulfide stages were carried out using SIMS to determine the origin and evolution of the skarn-forming hydrothermal system. Garnet from exoskarn has a much wider range in δ18OVSMOW, between –8.1 and +6.0‰, than other stages and minerals. The estimated δ18O values of fluids in equilibrium with the Haobugao skarn vary widely from –5.1‰ to +8.9‰, suggesting that the skarn formed via episodic flux of magmatic fluid and meteoric water. Low δ18O values of cassiterite and quartz from quartz-sulfide stage rocks are +1.2 to +3.6‰, and +5.7 to +5.9‰, respectively, indicating significant contributions of meteoric water during deposition of Pb-Zn sulphides. Therefore, meteoric fluids were periodically present throughout most of the stages of skarn formation at Haobugao.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Crocobelonite, CaFe23+(PO4)2O, is a new natural oxyphosphate discovered in the pyrometamorphic complexes of the Hatrurim Formation in Israel and Jordan. Crocobelonite-bearing assemblages contain a series of anhydrous Fe-Ni phosphates, hematite, diopside, anorthite, and phosphides—barringerite Fe2P, transjordanite Ni2P, murashkoite FeP, halamishite Ni5P4, and negevite NiP2. Crocobelonite forms submillimeter-sized aggregates of prismatic to acicular crystals of saffron-red to pinkish-red color. There are two polymorphic modifications of the mineral whose structures are interrelated by the unit-cell twinning. Crocobelonite-2O is orthorhombic, Pnma, a = 14.2757(1), b = 6.3832(1), c = 7.3169(1) Å, V 666.76(1) Å3, Z = 4. This polymorphic modification is isotypic with synthetic oxy-phosphates AV23+(PO4)2O where A = Ca, Sr, Cd. The crystal structure has been refined to RB = 0.71% based on powder XRD data, using the Rietveld method and the input structural model obtained from the single-crystal study. Chemical composition (electron microprobe, wt%) is: CaO 16.03, MgO 0.56, Fe2O3 43.37, Al2O3 0.33, SiO2 0.32, P2O5 39.45, Total 100.06. The empirical formula based on O = 9 apfu is Ca1.02(V1.943+Mg0.05Al0.02)2.01(P1.98Si0.02)2.00O9.00 with Dcalc = 3.555 g/cm3. The strongest lines of powder XRD pattern [d(Å)(I)(hkl)] are: 6.54(16)(200), 5.12(26)(201), 3.549(100)(102), 3.200(50) (401), 2.912(19)(220), 2.869(40)(411), 2.662(21)(501). Crocobelonite-1M is monoclinic, P21/m, a = 7.2447(2), b = 6.3832(1), c = 7.3993(2) Å, β = 106.401(2)°, V = 328.252(14) Å3, Z = 2. This polymorphic modification does not have direct structural analogs. Its crystal structure has been solved and refined based on the single-crystal data to R1 = 1.81%. Chemical composition is: CaO 15.56, MgO 0.16, NiO 0.78, Fe2O3 41.28, Al2O3 0.45, V2O3 0.42, Cr2O3 0.23, TiO2 0.79, P2O5 39.94, Total 99.61, corresponding to the empirical formula (O = 9 apfu) Ca0.99(V1.853+Ni0.04Ti0.04Al0.03V0.023+Cr0.01Mg0.01)2.00P2.01O9.00 with Dcalc = 3.604 g/cm3. The strongest lines of powder XRD pattern [d(Å)(I)(hkl)] are 6.98(17)(100), 4.40(22)(101), 3.547(100)(201), 3.485(21)(200), 3.195(50)(020), 2.855(38)(102), 2.389(33)(122). Crocobelonite represents a novel type of phosphate mineral formed by oxidation of phosphide minerals at temperatures higher than 1000 °C and near-atmospheric pressure (pyrolytic oxidation).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Tetrahedrite-(Ni) (IMA2021-031), ideally Cu6(Cu4Ni2)Sb4S13, is the first natural Ni-member of tetrahedrite group mineral found in Luobusa chromite deposit, Tibet, China. The new species occurs as anhedral grains 2 to 20 μm in size, associated with gersdorffite, vaesite, and chalcostibite, which are disseminated in a matrix of dolomite, magnesite, quartz, Cr-rich mica, and Cr-bearing clinochlore. Tetrahedrite-(Ni) is black in color with a reddish-black streak and metallic luster. It is brittle with uneven fractures and has a calculated density of 5.073 g·cm–3. The mean values of 9 electron microprobe analyses (wt%) are Cu 39.83, Ni 5.67, Fe 1.45, Sb 21.69, As 5.45, S 25.39, total 99.48, and the empirical formula calculated on the basis of cation = 16 apfu is M(2)Cu6.00M(1)[Cu4.03(Ni1.55Fe0.42)Σ1.97]Σ6.00X(3)(Sb2.85As1.16)Σ4.01S12.67. Tetrahedrite-(Ni) is cubic, with space group I43m, a = 10.3478(4) Å, V = 1108.00(14) Å3, and Z = 2. Its crystal structure has been solved by X-ray single-crystal diffraction on the basis of 188 independent reflections, with a final R1 = 0.0327. Tetrahedrite-(Ni) is isostructural with tetrahedrite group minerals. It represents the first natural tetrahedrite-group mineral with a Ni-dominated charge-compensating constituent. Tetrahedrite-(Ni) may be the product of late-serpentinization at moderately high-temperature conditions around 350 °C. In this case, tetrahedrite-(Ni) and its mineral paragenesis record an entire geological process of nickel enrichment, migration, activation, precipitation, and alteration from deep mantle to shallow crust.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This issue of New Mineral Names summarizes new species that contain toxic heavy metals and rare earth elements with a partial focus on new minerals found in China. All these new minerals have potential uses for environmental and technological applications, and their origins reflect historical mining or cultural significance. Here we look at fluorbritholite-(Nd), napoliite, scenicite, evseeite, haitaite-(La), dongchuanite, liguowuite, and gysinite-(La).</jats:p>