Ni, Co, and Fe K-edge X-ray absorption fine structure (XAFS) measurements were performed, revealing an unexpected local structure around Co in well-known iron and stony-iron meteorites. Cobalt is enriched in kamacite but remains in taenite at concentrations of at least 0.3 atom%. The Co K-edge X-ray absorption near-edge structure (XANES) spectra of taenite with a face-centered cubic (FCC) structure in all examined iron meteorites exhibited an unexpected body-centered cubic (BCC)-type local coordination, with Co showing a coordination number of 8 + 6. The local FCC and BCC structures can be clearly distinguished based on their XANES patterns. In taenite, up to 20% of the local structure is inferred to be BCC in regions where three-dimensional periodicity is maintained. Moreover, local BCC structures are likely to predominate in subregions that do not contribute to three-dimensional periodicity. Co transforms into a locally ordered BCC structure within the high-temperature parent FCC phase of iron meteorites. In this phase, Co appears to have a stronger affinity for Fe than for Ni, leading to the formation of Co-Fe clusters with a regular BCC arrangement.

The fusion crusts of meteorites indicate the quenched high temperature layers, but few studies are known due to the complicated process at the time of formation. We focused on the redox reactions in the outermost of fusion crusts of typical stony meteorites to investigate the dynamic formation process of rapid heating and quenching through interactions with atmosphere. We used X-ray absorption fine structure (XAFS) method to estimate the valence states of three transition elements of Ti, Fe, and Mn. The results showed a range of valence state between 3.7 and 4.0 in Ti and 2.0 and 3.0 in Fe, and about 2.5 in Mn. The close relationship between the valence states between Ti and Fe is not recognized apparently although the valence of Mn is nearly constant. If the redox reaction occurs at extreme high temperature, reduction is expected thermodynamically. Oxidation also is expected at the late stage of formation near the Earth surface when the observed meteorites keep high temperatures. The present results on the valence states of Ti, Fe, and Mn in the outermost fusion crusts of stony meteorites imply Ti effectiveness as a good indicator for redox reaction at extreme high temperatures, as supported in tektites formation.

The local structures and chemical states of Se and Br atoms in the Cretaceous-Paleogene (KPg) boundary sediments from Stevns Klint in Denmark were studied to obtain information on the concentration processes of both elements using Se and Br K-edge x-ray absorption fine structure (XAFS) spectroscopy. The Se K-edge x-ray absorption near-edge structure (XANES) spectra, radial structural functions (RSFs) around Se, and Se-O distance of 1.73(1) & Aring; revealed that Se in the KPg boundary sediments exists as a ferric selenite structure intimately associated with the ferrihydrite. Se was incorporated into ferrihydrite through precipitation and diagenesis caused by the sedimentation of Fe-rich impact ejecta. A high concentration of Se occurs through a process similar to that of As and Sb in the KPg sediments. The XANES spectra, RSFs and Br-C distance of 1.87(2) & Aring; showed that Br in the KPg boundary sediments is covalently bonded with carbon in highly polymerised aromatic groups. The stability and long-term persistence of organobromine in the KPg boundary sediments are attributed to the strong C-C and C-Br bonds in the polymerised aromatic groups. Because no iodine enrichment was observed, Br-C bond formation in the KPg boundary sediments likely had little biological involvement. The formation of Br-C bonds in organobromine compounds may be promoted by the redox activity of the abundant Fe and other transition metals. The existence of abundant Fe from impact ejecta leads to unusually high concentrations of As, Se and Sb by coprecipitation and of Br by its redox activity, causing Br-C bonding.

The chemical composition of swedenborgite sample obtained from the type locality, L & aring;ngban, V & auml;rmland, Sweden, was determined using scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was observed that swedenbolgite crystals possess both Ca-free and Ca-containing zones. The crystal structures of swedenborgite [space group P6(3)mc, a = 5.4402(10) & Aring; c = 8.8690(9) & Aring;, Z = 2] was refined to R1 = 0.012 using 1573 unique reflections. In addition, the threshold energy of the Sb K-edge XANES spectrum of swedenborgite was found to be higher than that of Sb2O3, but almost the same as that of Sb2O5. These results indicated that the oxidation state of Sb in swedenborgite was almost pentavalent, although the presence of a small amount of trivalent Sb is also suggested. It was therefore assumed that the following substitution relationship exists: 2Na(+) + Sb5+ -><- 2Ca(2+) + Sb3+, and that the charge balance of Ca occupation is achieved by reduction of some Sb5+ ions in the Ca-containing zone. The general formula of swedenborgite was therefore expressed as (Na1-xCax)Be4Sb1-0.5x5+Sb0.5x3+O7 (x = 0.0 or 0.05-0.07). The distortions of the Be-O distances along the c-axis and O-Be-O angles of BeO4 trigonal pyramid in swedenborgite were significantly larger than those in BeO bromellite. Opposite coordinate shifts between cations and anions along the c-axis occur because of the asymmetric arrangement around the NaO12 tetradecahedra with upper face sharing and lower edge sharing. The structure of swedenborgite therefore exhibits a biased arrangement of cations and anions parallel to the c-axis, which induces spontaneous polarization.

Single crystals of CaW1-xMoxO4 scheelite-powellite solid solutions (x = 0.0, 0.03, 0.08, 0.2, 0.3, 0.5, 0.8, and 1.0) were synthesized using a melting method. The light emission spectra of the solid solutions were measured using a JASCO FP-8300 fluorescence spectrometer. The maximum fluorescence peak at 419 nm in the CaWO4 scheelite end-member greatly decreases in intensity and shifts its peak position to 451 nm with only 3% Mo substitution. The change in near-ultraviolet light emission intensity at 292 and 301 nm are more moderate than those in the strong peak at 419 nm. The tendency of change in intensity and wavelength shift due to the Mo substitution differs among these fluorescence peaks. Single crystal X-ray diffraction experiments for the CaW1-xMoxO4 solid solutions (x = 0.0, 0.2, 0.3, 0.5, 0.8, and 1.0) were carried out using a Rigaku Super-Nova Single source at offset/far HyPix3000 diffractometer. The R1 index for CaW1-xMoxO4 solid solutions were convergent to 1.22-1.71% using anisotropic temperature factors. The expansion of the c-axis and shrinkage of the unit cell volume were induced with an increase in Mo content. The significant increase in the angle ]Ocloser-Ca-Ocloser was directly related to the expansion of the c-axis. The Debye temperature Theta D for Ca, W, and O atoms in CaWO4 were 381, 198, and 534 K, respectively. The obtained Theta D for Ca, Mo, and O atoms in CaMoO4 were 363, 257, and 503 K, respectively. The phonon density of states estimated from the lattice dynamics calculations coincided with the observed Theta D values.

AbstractRh-rich and Ir-poor erlichmanite–laurite OsS2–RuS2 solid solutions have been discovered at placers in Haraigawa, Misato-machi, Kumamoto, Japan. Microprobe analysis was performed to identify solid solutions containing few sub-components other than Rh. Approximately 10 at.% Rh was found to be present in the solid-solution samples. Structural refinement was performed using four natural samples: Os0.32Ru0.61Rh0.07S2, Os0.49Ru0.43Rh0.08S2, Os0.58Ru0.33Rh0.08S2 and Os0.81Ru0.09Rh0.10S2. The unit-cell parameters for the solid solutions containing Rh from Haraigawa varied from 5.61826(6) to 5.63142(8) Å. The (Os, Ru, Rh)–S distances in the Os1–x–yRuxRhyS2 system were almost constant with a small variation of 0.001 Å. Conversely, the S–S distances varied significantly, with variations approaching 0.1 Å. Rh substitution of Os rather than Ru had a larger impact on the crystal structure. The atomic displacement ellipsoid of both cations and anions was almost spherical, and no elongation along the M–S and S–S bond directions was observed. The bulk Debye temperatures were estimated from the Debye–Waller factor for the sulfide site. The bulk Debye temperatures of pure OsS2 and RuS2 were 688 K and 661 K, respectively, which suggests that the melting point of erlichmanite is higher than that of laurite. The high Debye temperature of OsS2 is inconsistent with the crystallisation of laurite prior to erlichmanite from the primitive magma, which suggests that $f_{\rm S_2}$, rather than temperature, is the main cause of the known crystallisation order. The presence of several percent Rh has a significant effect on the thermal stability of OsS2 and lowers the melting point of the erlichmanite solid solution compared to that of the laurite solid solution.

Heavy meteorite impacts on Earth's surface produce melt and vapor that are quenched rapidly and scattered over wide areas as natural glasses with various shapes and characteristic chemistry, which are known as tektites and impact glasses. Their detailed formation conditions have long been debated using mineralogical and geochemical data and numerical simulations of impact melt formations. These impact processes are also related to the formation and evolution of planets. To unravel the formation conditions of impact-induced glasses, we performed shock recovery experiments on a tektite. Recovered samples were characterized by X-ray diffraction, Raman spectroscopy, and X-ray absorption fine structure spectroscopy on the Ti K-edge. Results indicate that the densification by shock compression is subjected to post-shock annealing that alters the density and silicate-framework structures but that the local structures around octahedrally coordinated Ti ions remain in the quenched glass. The relationship between the average Ti-O distance and Ti K pre-edge centroid energy is found to distinguish the valance state of Ti ions between Ti4+ and Ti3+ in the glass. This relationship is useful in understanding the formation conditions of impact-derived natural glasses. The presence of Ti3+ in tektites constrains the formation conditions at extremely high temperatures or reduced environments. However, impact glasses collected near the impact sites do not display such conditions, but instead relatively mild and oxidizing formation conditions. These different formation conditions are consistent with the previous numerical results on the crater size dependence.

Abstract The stabilities of the minerals that can hold water are important for understanding water behavior in the Earth’s deep interior. Recent experimental studies have shown that the incorporation of aluminum enhances the thermal stabilities of hydrous minerals significantly. In this study, the phase relations of hydrous aluminosilicates in the AlOOH-AlSiO3OH system were investigated at 22 GPa and 1400–2275 K using a multi-anvil apparatus. Based on the X-ray difraction measurements and composition analysis of the recovered samples, we found that the AlSiO4H phase Egg forms a solid solution with δ-AlOOH above 1500 K. Additionally, at temperatures above 1800 K, two unknown hydrous aluminosilicates with compositions Al2.03Si0.97O6H2.03 and Al2.11Si0.88O6H2.11 appeared, depending on the bulk composition of the starting materials. Both phases can host large amounts of water, at least up to 2275 K, exceeding the typical mantle geotherm. The extreme thermal stability of hydrous aluminosilicates suggests that deep-subducted crustal rocks could be a possible reservoir of water in the mantle transition zone and the uppermost lower mantle.

Single crystals of Ir2S3 (diiridium trisulfide) and Rh2S3 (dirhodium trisulfide) were grown in evacuated silica-glass tubes using a chemical transport method and their crystal structures were determined by single-crystal X-ray diffraction analysis. These compounds have a unique sesquisulfide structure in which pairs of face-sharing octahedra are linked into a three-dimensional structure by further edge- and vertex-sharing. Ir2S3 and Rh2S3 had similar unit-cell parameters and bond distances. The atomic displacement parameter (MSD: mean-square displacement) of each atom in Ir2S3 was considerably smaller than that in Rh2S3. The Debye temperatures (ΘD) estimated from the observed MSDs for the Ir, S1 and S2 sites in Ir2S3 were 259, 576 and 546 K, respectively, and those for Rh, S1 and S2 in Rh2S3 were 337, 533 and 530 K, respectively. The bulk Debye temperature for Ir2S3 kashinite (576 K) was found to rank among the higher values reported for many known sulfides. The bulk Debye temperature for Rh2S3 bowieite (533 K) was lower than that for Ir2S3 kashinite, which crystallizes in the early sequences of mineral crystallization differentiation from the primitive magma in the Earth's mantle.

The stabilities of the minerals that can hold water are important for understanding the water behavior in 22 the Earth’s deep interior. Recent experimental studies have shown that the incorporation of aluminum 23 enhances the thermal stabilities of hydrous minerals significantly. In this study, the phase relations of 24 hydrous aluminosilicates in the AlOOH-AlSiO 3 OH system were investigated at 22 GPa and 1400–2275 25 K using a multi-anvil apparatus. Based on the X-ray diffraction measurements and composition analysis 26 of the recovered samples, we found that the AlSiO 4 H phase Egg forms a solid solution with δ-AlOOH 27 above 1500 K. Additionally, at temperatures above 1800 K, two unknown hydrous aluminosilicates with 28 compositions Al 2.03 Si 0.97 O 6 H 2.03 and Al 2.11 Si 0.88 O 6 H 2.11 appeared, depending on the bulk composition of 29 the starting materials. Both the phases can host large amount of water at least up to 2275 K, exceeding the 30 typical mantle geotherm. The extreme thermal stability of hydrous aluminosilicates suggests that deep- 31 subducted crustal rocks could be a possible reservoir of water in the mantle transition zone and the 32 uppermost lower mantle.

The mechanisms of hematite spherule formation on Mars have been widely evaluated to understand the Martian surface conditions and their history. These Martian hematite spherules was suggested to have a sedimentary origin, with the spherules predicted to have formed in solutions through precipitation. In this study, we investigated the formation mechanism of hematite spherules on Mars by performing oxidative hydrothermal alteration experiments using reproduced I-type cosmic spherules. Our results suggest that Martian hematite spherules were formed by oxidation of Ni-bearing metallic spherules produced by ablation of iron meteorites during their entry into the Martian atmosphere. After long-term exposure on the surface of Mars, most spherules were pulverized because of oxidation. Some hematite fine grains blended into the Martian soil and were moved by storms, whereas others maintained their initial spherical shape with a high content of Ni. Notably, the precursor of Martian hematite spherules may be metallic spherules derived from iron meteorites.

The structure refinement and XANES study of two gold-silver-tellurides [Au1+xAgxTe2, krennerite (x = 0.11-0.13) and sylvanite (x = 0.29-0.31)] are presented and the structures are compared with the prototype structure of calaverite (x = 0.08-0.10). Whereas the latter is well known for being incommensurately modulated at ambient conditions, neither krennerite nor sylvanite present any modulation. This is attributed to the presence of relatively strong Te-Te bonds (bond distances < 2.9 Å) in the two minerals, which are absent in calaverite (bond distances > 3.2 Å). In both tellurides, trivalent gold occurs in slightly distorted square planar coordination, whereas monovalent gold, partly substituted by monovalent silver, presents a 2+2+2 coordination, corresponding to distorted rhombic bipyramids. The differentiation between bonding and non-bonding contacts is obtained by computation of the Effective Coordination Number (ECoN). The CHARge DIstribution (CHARDI) analysis is satisfactory for both tellurides but suggests that the Te-Te bond in the [Te3]2- anion is not entirely homopolar. Both tellurides can therefore be described as Madelung-type compounds, despite the presence of Te-Te in both structures.

Parasymplesite and vivianite specimens were obtained from Kiura Mine, Ohita, Japan and Tomigaoka, Nara, Japan, respectively. Empirical chemical formulas of the specimens determined by energy-dispersive X-ray spectroscopy on the scanning electron microscopy were Fe-3(AsO4)(2)center dot 8H(2)O, and (Fe0.93Mn0.06Mg0.01)(3)(PO4)(2)center dot 8H(2)O, respectively. The crystal structures of parasymplesite and vivianite determined by single-crystal X-ray diffraction method were monoclinic, space group C2/m, with unit-cell parameters: a = 10.3519(10), b = 13.6009(13), c = 4.7998(4) angstrom, beta = 104.816(2)degrees, V= 653.32(11) angstrom(3) (Z= 4), and monoclinic, space group C2/m, with unit-cell parameters: a = 10.1518(6), b = 13.4327(7), c = 4.7005(3) angstrom, beta = 104.692(2)degrees, V = 620.03(6) angstrom(3) (Z = 4), respectively. The crystal structure of parasymplesite solved with the ideal chemical formula was refined to the R1 value of 0.0301 (wR2 = 0.0788) for 722 independent reflections with vertical bar Fo vertical bar > 4 sigma(vertical bar Fo vertical bar), whereas that of vivianite was refined to the R1 value of 0.0272 (wR2 = 0.0832) for 664 independent reflections. The hydrogen atom positions determined by the difference Fourier method coincided with the positions where residual electron density peaks appeared. In the edge-sharing Fe2O6(H2O)(4) double octahedra in parasymplesite and vivianite, the bond distance of Fe2-O5, where O5 is the oxygen atom of the H2O molecule, is shorter than that of Fe2O2. In each arsenate and phosphate phase, only the M2-O2 bond distance shows an increase trend with the increase in the average ionic radii of the M2 site, but the M2-O3 bond distance never shows a clear average M2 ionic radius dependence. In vivianite group minerals, a distortion at the isolated M1O(2)(H2O)(4) octahedra increases as a function of the average M1 ionic radius. The respective complex sheets consisting of the TO4 tetrahedra, isolated M1 octahedra, and edge-sharing M2 double octahedra are connected only by the hydrogen bond O5-H52 center dot center dot center dot O4. In the arsenate phases, the donor-acceptor distance between O5 and O4 exhibits an increase trend as increase of the average M ionic radius, but in the phosphate phases, there is no clear correlation between donor-acceptor distances and the average M ionic radius.

Structural analysis of Ce- and Nb-perovskites containing Fe, Zr, Nb, and rare earth elements (REEs) in CaTiO3 perovskite was performed using single-crystal X-ray diffraction and X-ray absorption near-edge structure (XANES) analyses. Based on chemical analysis results, XANES measurements and the site-occupation of elements at A- and B-sites showed the chemical formula: (Ca-0.817(2+) REE0.0873+Na0.081+Sr0.0052+Th0.0034+)(0.993)1(.998+) (Ti-0.941(4+))Na0.0205+La0.0153+Sr0.0032+)(0.996)(2.008+) (Ti0.7304+Nb0.1225+Fe0.1083+Al0.0203+Zr0.0094+V0.0085+)(0.997)(3.990+) O-3 for Nb-perovskite. In Ce- and Nbperovskites, the total charges at the A- and B-sites achieved near-ideal divalent and tetravalent states such as Ca2+ Ti4+ O-3, respectively, due to complex elemental substitutions. Local distortions around Ti in the perovskite solid solutions were greater, and the pre-edge features of the Ti atoms in Ce- and Nb-perovskites were different from those in pure CaTiO3. The valence states and local structures of Fe in Ce- and Nb-perovskites were significantly different. The existence of divalent Fe2+ at the B-site in Ce-perovskite was confirmed. It is presumed that the displacement ellipsoids of all atoms and local irregularities in Ce-perovskite increase owing to the radiative decay of the actinoid element Th. We reconfirmed that the composition and three-dimensional structure of perovskite-type structures were flexible and caused various electrical, structural changes.

Iron meteorites record the evolutionary and cosmochemical processes of their parent bodies. Fe–Ni phases in iron meteorites show complex textures from various thermal histories of parent bodies as well as the phase relationships and crystal chemistry of Fe–Ni metal. Synchrotron radiation-based X-ray absorption fine structure spectra and X-ray diffraction were applied herein to the study of iron meteorite NWA 859 Fe, Ni, and Ge contents at the K-edge, since they are effective techniques in identifying crystal structures in iron meteorites. The bond distances of Fe and Ni in tetrataenite and kamacite were detected. Field-emission scanning electron microscopy and energy-dispersive spectroscopy were used to observe the petrological and chemical characteristics of the main minerals, kamacite and tetrataenite, and the trace mineral schreibersite. The tetrataenite phase and body-centered cubic kamacite formed a Widmanstätten pattern and cloudy zone. The extended X-ray absorption fine structure (EXAFS) analyses of NWA 859 and a single-crystal diffraction of tetrataenite show that it has a near-face-centered cubic (FCC) tetragonal structure with 12 nearest-neighboring Ni, Fe, and Ge atoms at distances of rNi-(Ni, Fe) = 2.5170(13) Å, rFe-(Ni, Fe) = 2.534(3) Å, and rGe-(Ni, Fe) = 2.524(5) Å, respectively. Moreover, the X-ray absorption near-edge structure (XANES) spectra suggest that the Ge in tetrataenite exhibits a specific local structure with coordination number 12, suggesting that a new local structure of Ge-(Ni, Fe) was first discovered in extraterrestrial material, forming a stable tetragonal structure at approximately 688–618 K. X-ray absorption fine structure (XAFS) is an efficient technique that could provide us further information about local atomic structures and forming conditions in extraterrestrial materials without damage.

Single crystals of Ni3Se2 (trinickel diselenide) and NiSe (nickel selenide) with stoichiometric chemical compositions were grown in evacuated silica-glass tubes. The chemical compositions of the single crystals of Ni3Se2 and NiSe were determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). The crystal structures of Ni3Se2 [rhombohedral, space group R32, a = 6.02813 (13), c = 7.24883 (16) Å, Z = 3] and NiSe [hexagonal, space group P63/mmc, a = 3.66147 (10), c = 5.35766 (16) Å, Z = 2] were analyzed by single-crystal X-ray diffraction and refined to yield R values of 0.020 and 0.018 for 117 and 85 unique reflections, respectively, with Fo > 4σ(Fo). R32 is a Sohncke type of space group where enantiomeric structures can exist; the single-domain structure obtained by the refinement was confirmed to be correct by a Flack parameter of -0.05 (2). The existence of Ni-Ni bonds was confirmed in both compounds, in addition to the Ni-Se bonds. The value of the atomic displacement parameter (mean-square displacement) of each atom in NiSe was larger than that in Ni3Se2. The larger amplitude of the atoms in NiSe corresponds to longer Ni-Se and Ni-Ni bond lengths in NiSe than in Ni3Se2. The Debye temperatures, θD, estimated from observed mean-square displacements for Ni and Se in Ni3Se2, were 322 and 298 K, respectively, while those for Ni and Se in NiSe were 246 and 241 K, respectively. The existence of large cavities in the structure and the weak bonding force are likely responsible for the brittle and soft nature of the NiSe crystal.

Single crystals of pyrite-type PdSb2 were grown by sealing a stoichiometric proportion of the elements in an evacuated silica glass tube and heating the tube in a furnace at 930 K for 20 days. The crystal structure of PdSb2 [space groupPa3, a = 6.4659(2) angstrom, u = 0.37331(3), Z = 4] was refined to R1 = 0.0171 for 374 unique reflections obtained by single-crystal X-ray diffraction experiments. The lattice constant, a, and anion-anion distance of 2.8677(3) angstrom are slightly different from the previously reported values. The single crystal diffraction method has excellent advantages such that the Debye temperature can be determined for each crystallographically independent site. The obtained Theta D values for Pd and Sb in PdSb2 are 258 K and 214 K, respectively. Characteristically, the Debye temperatures, Theta D, of both atoms in PdSb2 were found to be very low among the pyrite-type transition metal pnictides and chalcogenides. Certain regularities between the cation-anion bonding distances and Debye temperatures were found in pyrite-type compounds. The vibration of anion contributes to the highest energy part of the normal mode of thermal vibration, when the cation-anion bonding distances in pyrite-type compounds are shorter than 2.6 angstrom.