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The independently measured pressure and temperature evolution of Ca3V2O8 is characterized by X-ray diffraction and DFT calculations. A pressure-induced phase transition is discovered and the crystal structure for the HP phase reported.

The Traspena meteorite fell on 2021 January 18 about 20 km south-east of the city of Lugo (Galiza, Spain), shortly after a huge and bright fireball crossed the sky for 4.84 s. Astrometric measurements obtained from the fireball cameras of the Universidade de Santiago de Compostela (USC) as well as from many casual videos were used to determine the atmospheric trajectory of this meteoroid which penetrated the atmosphere and generated sound waves that were detected at three seismic stations. The original meteoroid had a diameter of about 1.15 m and a mass around 2620 kg. It impacted the Earth’s atmosphere with a steep entry angle of about 76 . ◦7 from a height of 75.10 km until fading away at 15.75 km with a velocity of 2.38 km s −1 . Before the impact, this small asteroid was orbiting the Sun with a semimajor axis of 1.125 au, a moderate eccentricity of 0.386, and a low inclination of 4 . ◦55. A weak evidence of dynamic link with the PHA (Potential Hazardous Asteroid) Minos was investigated. During the atmospheric entry, two major fragmentation events occurred between heights of 35 and 29 km at aerodynamic pressures between 1 and 5 MPa. The strewn field was computed after calculating the individual dark flights of the main body along with two smaller fragments. For- tunately, 2 month after the superbolide, a 527-g meteorite was found. It was examined using several geochemical and petrographic analyses which allowed us to classify it as a moderately shocked (S3) L5 ordinary chondrite with a bulk density of 3.25 g cm −3 ., This paper was supported by the Xunta de Galicia (Spain) under the ED431B 2020/38 grant.

Karstic bauxite deposits are the main resource of aluminum in Europe and are formed through a combination of weathering, leaching, and deposition processes known as bauxitization. Bauxites have recently been proposed as unconventional resources of rare-earth elements (REE) as well. The studied karstic bauxite deposits are located on the salt-detached Serres Marginals thrust sheet, at the external most unit of the south-central Pyrenees (Catalonia, NE Spain). The Pyrenean bauxites are found overlaying and filling karstic surfaces forming aligned pockets up to several meters thick. These deposits have been mined for more than 20 years and present high variability in SiO2, Al2O3 and Fe2O3 contents. Here, we characterize these deposits for the first time by a combination of field geology, XRD, FTIR and XRF to determine their formation, mineralogy, and geochemistry and to understand the causes affecting their compositional variations. Field data indicate that the bauxite deposits fill a paleokarst system affecting Dogger dolostones and/or Tithonian-Berriasian limestones. XRD data indicate that the studied karstic bauxites are mainly composed of Al-rich minerals kaolinite and boehmite, in addition to the Fe-oxide hematite, and lesser amounts of the Ti-oxides rutile and anatase. The detailed study of the FTIR spectra also confirmed the presence of diaspore and dickite. XRF data confirm the presence of varying amounts of Al, Fe and Si in addition to varying low contents of REE. These results suggest that boehmite was formed first during bauxitization and later transformed to diaspore, kaolinite and finally to dickite upon metasomatism. The presence of dickite in faults and fractures provides a direct proof for such fluid circulation. Our results suggest that the mechanisms responsible of the compositional variations in karstic bauxites are rather complex and fall beyond the standard bauxitization processes. The observed metasomatism should be further assessed, since the inferred fluid-rock interactions are susceptible to affect and mobilize REE not only in the south-central Pyrenees karstic bauxites but elsewhere in similar geological settings.

Carbonaceous chondrites (CCs) can beconsidered cosmic aggregates containingprotoplanetary disk components. Modern analytical techniques allow us to identify CCsunaffected by thermal or aqueous alterationprocesses, having a pristine nature. Such ahighly unequilibrated meteorites allow us toget clues on the early Solar System (ESS), astheir components are ancient materials retentive of chemical clues on their formation.The information they contain is valuable to beapplied to better understand protoplanetary disks.

Altres ajuts: acords transformatius de la UAB Altres ajuts: Departament de Cultura of the Generalitat de Catalunya and the CERCA Program - ARQ001SOL-173-2022 The lithographic limestone of La Pedrera de Meià (LPM) in south-Central Pyrenees (NE Spain) is considered one of the best preserved lacustrine-coastal successions of the Early Cretaceous in Europe, hosting a taxonomically diverse record of Barremian biota. While this Konservat-Lagerstätte has been extensively surveyed for paleontological purposes, little is known about the paleoenvironmental and depositional conditions prevailing during the formation of this fossil lagerstätte deposit. LPM limestone is made up of a homogeneous, dark gray to pale brown, faintly laminated 50 m-thick succession of micrite-rich intervals. To shed light on the environmental conditions of deposition, 303 rock samples were studied using a multiproxy approach based on different techniques including petrography, SEM-EDX, XRD, ICP-MS, XRF, Rare Earth Element distributions and C and O stable isotope geochemistry. The combination of sedimentological and geochemical data reveals a vertical shift of facies from littoral to profundal environments and then returning to littoral conditions. Profundal facies are made up of filament-rich mudstones originated from in situ precipitation of micrite either through biotically mediated or physico-chemical processes in undisturbed low energy settings, under anoxic conditions, characterized by the presence of transported terrestrial and lacustrine organisms that are exquisitely well-preserved. Littoral areas are characterized by the presence of in situ charophytes, smooth ostracods, and miliolid foraminifera that accumulated in mud-rich facies indicating low/moderate-energy, shallow-water, and relatively oxygenated conditions. Stable isotopic data and elemental geochemistry suggest a hydrologically closed to semi-closed lacustrine system with a restricted water circulation encouraging dysoxic to anoxic conditions in profundal sediments. Paleoproductivity proxies suggest a good correlation between catchment-derived siliciclastic discharge to the lake and primary productivity peaks. Furthermore, a decline interrigenous input coupled with a reduction of meteoric water entrance to the lake is interpreted based on elemental proxies derived from paleosalinity and paleoredox analysis. Collectively, the strontium/barium (Sr/Ba) ratios, the sparse presence of miliolid foraminifera, and the isotopic signatures indicate an increase in salinity toward the younger intervals of the lake infilling, although their ultimate causes are unclear (i.e., increased evaporation, or a combination of reduced meteoric input and sporadic marine inputs might explain our data). The present work shows the importance of performing detailed multiproxy geochemical-sedimentological studies to better constrain the unique paleoenvironmental and paleohydrological conditions associated with the exceptional preservation of fossil biotas in Konservat-Lagerstätte deposits in analogous depositional settings.

Raman scattering (RS) in bulk hafnium disulfide (HfS$_2$) is investigated as a function of temperature (5 K $-$ 350 K) with polarization resolution and excitation of several laser energies. An unexpected temperature dependence of the energies of the main Raman-active (A$_{\textrm{1g}}$ and E$_{\textrm{g}}$) modes with the temperature-induced blueshift in the low-temperature limit is observed. The low-temperature quenching of a mode $\omega_1$ (134 cm$^{-1}$) and the emergence of a new mode at approx. 184 cm$^{-1}$, labeled Z, is reported. The optical anisotropy of the RS in HfS$_2$ is also reported, which is highly susceptible to the excitation energy. The apparent quenching of the A$_{\textrm{1g}}$ mode at $T$=5 K and of the E$_{\textrm{g}}$ mode at $T$=300 K in the RS spectrum excited with 3.06~eV excitation is also observed. We discuss the results in the context of possible resonant character of light-phonon interactions. Analyzed is also a possible effect of the iodine molecules intercalated in the van der Waals gaps between neighboring HfS$_2$ layers, which inevitably result from the growth procedure., Comment: 9 pages, 7 figures +SI

The structural, vibrational and electronic properties of the compressed beta-Sb2O3 polymorph, a.k.a. mineral valentinite, have been investigated in a joint experimental and theoretical study up to 23 GPa. The compressibility of the lattice parameters, unit-cell volume and polyhedral unit volume as well as the behaviour of its Raman- and IR-active modes under compression have been interpreted on the basis of ab initio theoretical simulations. Valentinite shows an unusual compressibility up to 15 GPa with four different pressure ranges, whose critical pressures are 2, 4, and 10 GPa. The pressure dependence of the main structural units, the lack of soft phonons, and the electronic density charge topology address the changes at those critical pressures to isostructural phase transitions of degree higher than 2. In particular, the transitions at 2 and 4 GPa can be ascribed to the changes in the interaction between the stereochemically-active lone electron pairs of Sb atoms under compression. The changes observed above 10 GPa, characterized by a general softening of several Raman- and IR-active modes, point to a structural instability prior to the 1st-order transition occurring above 15 GPa. Above this pressure, a tentative new high-pressure phase (s.g. Pcc2) has been assigned by single-crystal and powder X-ray diffraction measurements., This research was partially supported by the MINECO (FIS2017-83295-P, MAT2016-75586-C4-1/2/3-P, PGC2018- 097520-A-100, RED and PID2019-106383GB-41/42/43), by the MALTA-CONSOLIDER TEAM network (RED2018-102612-T) and by the EU-FEDER. JAS acknowledges the Ramon y Cajal fellowship (RYC-2015-17482) for financial support. VM thanks the Juan de la Cierva Program (FJCI-2016-27291) and Beatriz Galindo Fellowship (BG20/00077) for financial support. We also thank the ALBA (2016091901 experiment) and DIAMOND light source (CY22223 experiment) for providing beamtime, and Mark Warren, Sarah Barnett and Dominik Daisenberger for their help in the single-crystal X-ray diffraction experiment under pressure.

We report a joint experimental and theoretical study of the structural, vibrational, and electronic properties of layered monoclinic arsenic sulfide crystals (α-As2S3), aka mineral orpiment, under compression. X-ray diffraction and Raman scattering measurements performed on orpiment samples at high pressure and combined with ab initio calculations have allowed us to determine the equation of state and the tentative assignment of the symmetry of many Raman-active modes of orpiment. From our results, we conclude that no first-order phase transition occurs up to 25 GPa at room temperature; however, compression leads to an isostructural phase transition above 20 GPa. In fact, the As coordination increases from threefold at room pressure to more than fivefold above 20 GPa. This increase in coordination can be understood as the transformation from a solid with covalent bonding to a solid with metavalent bonding at high pressure, which results in a progressive decrease of the electronic and optical bandgap, an increase of the dielectric tensor components and Born effective charges, and a considerable softening of many high-frequency optical modes with increasing pressure. Moreover, we propose that the formation of metavalent bonding at high pressures may also explain the behavior of other group-15 sesquichalcogenides under compression. In fact, our results suggest that group-15 sesquichalcogenides either show metavalent bonding at room pressure or undergo a transition from p-type covalent bonding at room pressure towards metavalent bonding at high pressure, as a precursor towards metallic bonding at very high pressure., Authors thank the financial support from Spanish Ministerio de Economia y Competitividad (MINECO) through MAT2016-75586-C4-2/3-P and FIS2017-83295-P and from Generalitat Valenciana under project PROMETEO/2018/123-EFIMAT. ELDS acknowledges the European Union Horizon 2020 research and innovation programme under Marie Sklodowska-Curie for grant agreement No. 785789-COMEX. JAS also acknowledges Ramón y Cajal program for funding support through RYC-2015-17482. AM, SR and ELDS thank interesting discussions with J. Contreras-García who taught them how to analyze the ELF. Finally, authors thank ALBA Light Source for beam allocation at beamline MSPD (Experiment No. 2013110699) and acknowledge computing time provided by MALTA-Cluster and Red Española de Supercomputación (RES) through computer resources at MareNostrum with technical support provided by the Barcelona Supercomputing Center (QCM-2018-3-0032).

A wide band gap is one of the essential requirements for metal iodates to be used as nonlinear optical materials. Usually, the band gap of these materials decreases under the application of pressure. Herein, we introduce a case in which the band-gap energy of a hydrated metal iodate, namely Ca(IO3)2 center dot H2O, has been successfully increased, from 4.52 to 4.92 eV, by applying external pressure without showing signs of saturation upon increasing pres-sure. The pressure-induced nonlinear band-gap opening correlates with the pressure-induced shortening of the I-O bond distances, as obtained from x-ray diffraction measurements. In addition, two pressure-induced isostructural phase transitions are observed in the pressure regions of 6.6-8.0 and 13.0-15.5 GPa. These two isostructural phase transitions cause a nonlinear pressure-induced evolution of the band-gap energy and crystal lattice parameters, as well as the occurrence of several extra peaks and peak splitting in Raman spectra., This study was supported by project MALTA Consolider Team network (RED2018‐102612‐T), financed by MINECO/AEI/10.13039/501100003329, I+D+i project PID2019‐106383GB‐41/42 financed by MCIN/AEI/10.13039/501100011033; as well as by projects PROMETEO CIPROM/2021/075 (GREENMAT) and MFA/2022/007 financed by Generalitat Valenciana. A.L. and D.E. thank the Generalitat Valenciana for the Ph.D. Fellowship No. GRISOLIAP/2019/025. R.T. and D.E. thank the Generalitat Valenciana for the postdoctoral Fellowship No. CIAPOS/2021/20. The authors also thank ALBA synchrotron light source for funded experiment under proposal number AV-2021095390 at the MSPD-BL04 beamline.

We acknowledge Víctor Fondevilla, who cooperated with sedimentology and was co-advisor for the master’s thesis of A.G. The funding of this research, together with the associated permission to conduct the field study, was provided by the ‘General Research Project of the Junta de Andalucía, First human occupations and paleoecological context from the Plio-Pleistocene deposits of the Guadix-Baza basin, Archaeological zone of the Orce basin (Granada, Spain)’. Servicio General de Análisis de Isótopos Estables (Nucleus, Salamanca University) is acknowledged for the quick delivery of isotopic data. Soledad Alvarez, from the XRD Service at GEO3BCN-CSIC, is acknowledged for technical support with the XRD measurements. O.O. is a member of the 2017SGR-1666 research group. A.K. was funded by the Academy of Finland. We are very grateful to L. Melim and an anonymous reviewer for their constructive and detailed review of this manuscript. Roy Siddall (Univ. Helsinki Language Centre) did an excellent revision of English language., Despite the paleontological relevance of the terrestrial Early Pleistocene Venta Micena bonebed (Baza Basin, Spain), it lacks a comprehensive geochemical/sedimentological study. Here, we demonstrate that the 1.5-m-thick Venta Micena limestone formed in a relatively small freshwater wetland/pond located at the periphery of the large saline Baza paleolake. Two microfacies are observed, with high and low contents of invertebrate fossils, and which originated in the centre and margin of the wetland, respectively. X-ray diffraction (XRD) mineralogy and paleohydrological characterization based on ostracod and bulk-rock geochemistry (δ13C and δ18O) indicate that the limestone reflects a general lowstand of the Baza lake, permitting the differentiation of freshwater wetlands that were fed by adjacent sources. Conversely, during highstands, the Baza lake flooded the Venta Micena area and the freshwater fauna was replaced by a saline one. Bulk-rock isotopic data indicate that the lower interval C1 of the limestone (bone-rich in marginal settings) displays general negative values, while the upper interval C2 (bone free) displays less negative values. The bones of predated mammals accumulated in the marginal areas, which were flooded and buried by recurring water-table fluctuations. Lake dynamics played a critical role in bone accumulation, which was previously considered as representing a hyena den., Academy of Finland, Junta de Andalucía

The sedimentary record of the maar lake succession at Camp dels Ninots (Pliocene, NE Spain) reflects mineralogical shifts that correlate with orbitally forced climate changes. X-ray powder diffraction was obtained from a 47 m-long core collected from a borehole drilled in the centre of the paleolake. The results show compositional variations in terms of allogenic/authigenic mineral assemblages which, in turn, correlate with climate proxies such as pollen. Intervals that are dominantly composed of allogenic minerals (quartz, feldspar, smectite) correlate with wet periods. These periods are characterised by an increase in the percentage of Abies pollen. Conversely, intervals enriched in carbonates correlate with dry periods, with decreased amounts of Abies pollen. This cyclicity is attributed to rainfall variations leading to hydrologically open lake conditions during periods of relative high precipitation (when clastic input is enhanced) and hydrologically closed lake conditions during drier periods (when precipitation of authigenic carbonates is enhanced). It is concluded that the mineralogy of maar paleolakes may be highly sensitive to record climate changes., We would like to thank the land owners for their permission to work in the area, and the Town Council of Caldes de Malavella and the Departament de Cultura de la Generalitat de Catalunya for the economic funding of the excavation under the project CLT009/18/00052. This study was partially funded by project of the Spanish Government and the SGR2017-859 and SGR-2017-1666 of the Generalitat de Catalunya. The research of B.G.S. and G.C. is funded by the CERCA Programme/Generalitat de Catalunya. The Institut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA) has received financial support from the Spanish Ministry of Science and Innovation through the ‘María de Maeztu’ program for Units of Excellence (CEX2019-000945-M). XRD technical assistance was provided by Soledad Álvarez and José J. Elvira at the XRD Laboratory of GEO3BCN-CSIC (former ICTJA-CSIC), and by Laura Burrel.

Ladle furnace slag (LFS) has been proposed as partial cement replacement due to its similar chemical composition with Portland cement. However, its mineralogical composition needs to be considered due to problems with expansive reactions and lower cementing activity. The objective of this study is to investigate the effect of particle size and mineralogical composition of LFS in cement-slag systems. The obtained results show a correlation between microstructural changes and macroscopic properties, lower mechanical performance and volumetric instability problems, although within the established limits in normal curing conditions. Therefore, it is concluded that LFS presents an interesting potential as cement replacement., This work was funded by the National Agency for Research and Development (ANID) DOCTORADO EN EL EXTRANJERO, BECAS CHILE/2019 – 72200568.

Ronchi et al. (in press) comment on the stratigraphic, sedimentological, mineralogical and palaeontological analyses performed in the recently described Coll de Terrers Permian–Triassic terrestrial succession from the Catalan Pyrenees by Mujal et al. (2017a). The comment debates our interpretation of a succession of red-beds as Permian (Upper Red Unit, URU). Instead, the comment infers that the analysed succession is part of the regional upper Buntsandstein facies unit (Triassic), debating the proposed stratigraphic scheme by using the tectonic evolution as the main argument. Here, we clarify and present more details on the interpretation published in Mujal et al. (2017a). Based on this clarification and taking into account the comment, we arrive to the conclusion that the interpretation and inferences presented in Mujal et al. (2017a) are sound and justified. © 2018 Elsevier B.V.

The Las Minas Gypsum Unit consists of more than 100 m of alternations of gypsum, carbonates and marls in Las Minas Basin (Betic Cordillera). Although this unit has been previously described as lacustrine, a marine influence in the basin has been suggested. This study provides new geochemical and paleontological data supporting the marine influence during the interevaporitic episodes, allowing to refine the palaeogeography of the eastern Betic Seaway during the Late Tortonian. Sr-87/Sr-86 ratios in gypsum (0.70797 to 0.70825) suggest recycling of Triassic evaporites. The sulphate isotopic values in gypsum (11.5 < delta S-34(VCDT) < 21.9 parts per thousand; 16.6 < delta O-18(VSMOW) < 28.1 parts per thousand) are indicative of microbial sulfate-reduction activity. Carbonates are mainly composed of dolomite formed by subspherical crystal aggregates related to bio-mediated processes. The Sr-87/Sr-86 values in the interevaporitic carbonates (0.70823 to 0.70851) are higher than those expected for Triassic marine authigenic carbonates but lower than expected for the Late Miocene ones, suggesting a mixing of continental and marine water contributions. The 'non-marine' isotopic values in gypsum and carbonates contrast with an abundant content of marine siliceous fossils (radiolarians, diatoms, porifera, etc.) in the marls and carbonates that reveals marine incursions into the basin between periods of gypsum precipitation. A tephra layer identified in Las Minas and in the nearby El Cenajo Basin, located in a more inland position, allows a precise correlation between both basins, showing marine fossils in Las Minas and lacustrine in El Cenajo. In El Cenajo Basin, marine microfossils have been found but only in some levels, while others show lacustrine diatoms. A new palaeogeographic model of evaporitic lakes with temporal marine connections is proposed for the latest Tortonian in this region, when the uplift of the Betic Cordillera was very active accelerating the palaeogeographic evolution., Funding was provided by Spanish Government grants CGL-2013-42689 and CGL-2016-79458, and by the Catalan Government action 217-SGR-829.

We report a joint experimental and theoretical study of the low-pressure phase of α′-Ga2S3 under compression. Theoretical ab initio calculations have been compared to X-ray diffraction and Raman scattering measurements under high pressure carried out up to 17.5 and 16.1 GPa, respectively. In addition, we report Raman scattering measurements of α′-Ga2S3 at high temperature that have allowed us to study its anharmonic properties. To understand better the compression of this compound, we have evaluated the topological properties of the electron density, the electron localization function, and the electronic properties as a function of pressure. As a result, we shed light on the role of the Ga–S bonds, the van der Waals interactions inside the channels of the crystalline structure, and the single and double lone electron pairs of the sulphur atoms in the anisotropic compression of α′-Ga2S3. We found that the structural channels are responsible for the anisotropic properties of α′-Ga2S3 and the A′(6) phonon, known as the breathing mode and associated with these channels, exhibits the highest anharmonic behaviour. Finally, we report calculations of the electronic band structure of α′-Ga2S3 at different pressures and find a nonlinear pressure behaviour of the direct band gap and a pressure-induced direct-to-indirect band gap crossover that is similar to the behaviour previously reported in other ordered-vacancy compounds, including β-Ga2Se3. The importance of the single and, more specially, the double lone electron pairs of sulphur in the pressure dependence of the topmost valence band of α′-Ga2S3 is stressed., The authors thank the financial support from the Spanish Research Agency (AEI) under projects MALTA Consolider Team network (RED2018-102612-T) and projects MAT2016-75586-C4-2/3-P, FIS2017-83295-P, PID2019-106383GB-42/43, and PGC2018-097520-A-100, as well as from Generalitat Valenciana under Project PROMETEO/2018/123 (EFIMAT). A. M. and P. R.-H. acknowledge computing time provided by Red Espa?ola de Supercomputaci?n (RES) and MALTA-Cluster and E. L. D. S. acknowledges Marie Sklodowska-Curie Grant No. 785789-COMEX from the European Union's Horizon 2020 research and innovation program. J. A. S. also wants to thank the Ramon y Cajal fellowship (RYC-2015-17482) for financial support. We also thank the ALBA synchrotron light source for funded experiment 2017022088 at the MSPD-BL04 beamline.

Rhenium disulfide (ReS2), known in nature as the mineral rheniite, is a very interesting compound owing to its remarkable fundamental properties and great potential to develop novel device applications. Here we perform density functional theory (DFT) calculations to investigate the structural properties and compression behavior of this compound and also of the (Re,Mo)S-2 solid solution as a function of Re/Mo content. Our theoretical analysis is complemented with high-pressure X-ray diffraction (XRD) measurements, which have allowed us to reevaluate the phase transition pressure and equation of state of 1T-ReS2. We have observed the 1T-to-1T' phase transition at pressures as low as similar to 2 GPa, and we have obtained an experimental bulk modulus, B-0, equal to 46(2) GPa. This value is in good agreement with PBE+D3 calculations, thus confirming the ability of this functional to model the compression behavior of layered transition metal dichalcogenides, provided that van der Waals corrections are taken into account. Our experimental data and analysis confirm the important role played by van der Waals effects in the high-pressure properties of 1T-ReS2., J.I. and C.P. acknowledge the Spanish Ministry of Science, Innovation and Universities via Grant FIS2017-2017-83295-P. T.W. acknowledges financial support from Polish Ministry of Science and Higher Education via Diamond Grant no. D\2015 002645.

This study aims to assess the feasibility of delineating and identifying mineral ores from hyperspectral images of tin–tungsten mine excavation faces using machine learning classification. We compiled a set of hand samples of minerals of interest from a tin–tungsten mine and analyzed two types of hyperspectral images: (1) images acquired with a laboratory set-up under close-to-optimal conditions, and (2) a scan of a simulated mine face using a field set-up, under conditions closer to those in the gallery. We have analyzed the following minerals: cassiterite (tin ore), wolframite (tungsten ore), chalcopyrite, malachite, muscovite, and quartz. Classification (Linear Discriminant Analysis, Singular Vector Machines and Random Forest) of laboratory spectra had a very high overall accuracy rate (98%), slightly lower if the 450–950 nm and 950–1650 nm ranges are considered independently, and much lower (74.5%) for simulated conventional RGB imagery. Classification accuracy for the simulation was lower than in the laboratory but still high (85%), likely a consequence of the lower spatial resolution. All three classification methods performed similarly in this case, with Random Forest producing results of slightly higher accuracy. The user’s accuracy for wolframite was 85%, but cassiterite was often confused with wolframite (user’s accuracy: 70%). A lumped ore category achieved 94.9% user’s accuracy. Our study confirms the suitability of hyperspectral imaging to record the spatial distribution of ore mineralization in progressing tungsten–tin mine faces., EIT RawMaterials supported this research within the framework of the iTARG3T (Innovative targeting & processing ofW–Sn–Ta–Li ores: towards EU’s self-supply) project nb. 18036.

Numerous and extensive 'Stone Walled Sites' have been identified in southern African Iron Age landscapes. Appearing from around 1200 CE, and showing considerable variability in size and form, these settlements are named after the dry-stone wall structures that characterize them. Stone Walled Sites were occupied by various Bantu-speaking agropastoral communities. In this paper we test the use of pXRF (portable X-ray fluorescence analysis) to generate a 'supplementary' archaeological record where evident stratigraphy is lacking, survey conditions may be uneven, and excavations limited, due to the overall site size. We propose herein the application of portable X-ray fluorescence analysis (pXRF) coupled with multivariate exploratory analysis and geostatistical modelling at Seoke, a southern African SWS of historical age (18th century CE). The aim of the paper is twofold: to explore the potential of the application of a low cost, quick, and minimally invasive technique to detect chemical markers in anthropogenic sediments from a Stone Walled Site, and to propose a way to analyse the results in order to improve our understanding of the use of space at non-generalized scales in such sites., This research is funded by Fundación Palarq, calls 2019 and 2020, project ”Geo-EtnoArqueologia y uso del espacio (GEA)” entrusted to SB. SM and FM received financial support from the Office of Research and Development at the University of Botswana. The work of SGA was funded by the European Union’s MapDung project funded by the EU Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No H2020-MSCA-IF-2017-794823. SB, JAM, ARG, CL and SGA are members of CaSEs Research Group of the Catalan Research Agency (AGAUR SGR-212), which is an associated unit (Unidad Asociada) to the Institucion Mila Y Fontanals of the Spanish Research National Council (CSIC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

14th Europlanet Science Congress, The Moon is no longer a goal in itself but a necessary step for the conquest of space. In this work we focus in the composition of Lunar meteorites as the only objects alongside Apollo, and Luna collected samples, that the scientific community has available to first-hand analyze the Moon. Future Artemis sample return missions will provide new samples to continue learning from our satellite. Given its proximity to our planet, our satellite is an ideal planetary body to use it as a space camp for new technology, to establish a space base, and to test space mining. The continuous depletion of Earth resources put special importance on the exploration of extraterrestrial natural resources potential and the feasibility of its exploitation. After many robotic and manned missions, the utilization of lunar resources has been studied for a long time. In-Situ Resources Utilization (ISRU) refers to the generation of materials (for construction, life support, or as propellants) from the available resources on a celestial body that otherwise, would have needed to be brought from Earth, The authors acknowledge financial support from the Spanish Ministry (PGC2018-097374-B-I00).

We report a study of the high-pressure structural behavior of ZnV2O6, Zn2V2O2, and Zn3V2O8, which has been explored by means of synchrotron powder x-ray diffraction. We found that ZnV2O6 and Zn3V2O8 remain in the ambient-pressure structure up to 15 GPa. In contrast, in the same pressure range, Zn2V2O2 undergoes three phase transitions at 0.7, 3.0, and 10.8 GPa, respectively. Possible crystal structures for the first and second high-pressure phases are proposed. Reasons for the distinctive behavior of Zn2V2O2 are discussed. The compressibility of the different polymorphs has been determined. The response to pressure is found to be anisotropic in all the considered compounds and the room-temperature equations of state have been determined. The bulk moduli of Zn2V2O6 (129(2) GPa) and Zn2V2O8 (120(2) GPa) are consistent with a structural framework composed of compressible ZnO6 octahedra and uncompressible VO4 tetrahedra. In contrast, Zn2V2O2 is highly compressible with a bulk modulus of 58(9) GPa, which is almost half of the bulk modulus of the other two vanadates. The large compressibility of Zn2V2O2 and its sequence of structural transitions are related to the fact that this material is less dense than the other zinc vanadates and to the penta-coordination of Zn atoms by oxygen atoms in Zn2V2O2. A comparison to the high-pressure behavior of related compounds is presented. (C) 2020 Elsevier B.V. All rights reserved., This work was supported by the Spanish Ministry of Science, Innovation and Universities under Grants MAT2016-75586-C4-1-P and PGC2018-097520-A-I00, and by Generalitat Valenciana under Grant Prometeo/2018/123 (EFIMAT). D.S.-P. also acknowledges the financial support of Spanish MINECO for the RyC2014-15643 Ramón y Cajal Grant. CP thanks the financial support from Spanish MINECO under FIS2017-83295-P project. The authors thank ALBA synchrotron for providing beam-time for the XRD experiments (Projects 2016081779 and 2019023362).

We report a joint experimental and theoretical investigation of the high pressure structural and vibrational properties of terbium sesquioxide (Tb2O3). Powder X-ray diffraction and Raman scattering measurements show that cubic Ia3̅ (C-type) Tb2O3 undergoes two phase transitions up to 25 GPa. We observe a first irreversible reconstructive transition to the monoclinic C2/m (B-type) phase at ∼7 GPa and a subsequent reversible displacive transition from the monoclinic to the trigonal P3̅m1 (A-type) phase at ∼12 GPa. Thus, Tb2O3 is found to follow the well-known C → B → A phase transition sequence found in other cubic rare earth sesquioxides with cations of larger atomic mass than Tb. Our ab initio theoretical calculations predict phase transition pressures and bulk moduli for the three phases in rather good agreement with experimental results. Moreover, Raman-active modes of the three phases have been monitored as a function of pressure, while lattice-dynamics calculations have allowed us to confirm the assignment of the experimental phonon modes in the C- and A-type phases as well as to make a tentative assignment of the symmetry of most vibrational modes in the B-type phase. Finally, we extract the bulk moduli and the Raman-active mode frequencies together with their pressure coefficients for the three phases of Tb2O3. These results are thoroughly compared and discussed in relation to those reported for rare earth and other related sesquioxides as well as with new calculations for selected sesquioxides. It is concluded that the evolution of the volume and bulk modulus of all the three phases of these technologically relevant compounds exhibit a nearly linear trend with respect to the third power of the ionic radii of the cations and that the values of the bulk moduli for the three phases depend on the filling of the f orbitals., High pressure powder X-ray diffraction and Raman scattering measurements show that cubic Tb2O3 undergoes a phase transition to a monoclinic phase at ∼7 GPa and to a trigonal phase above ∼12 GPa. The measured bulk modulus and the pressure dependence of the phonon modes for the 3 phases are supported by density functional theory calculations. The obtained results are compared to those reported for other rare earth and related sesquioxides.

Fracture-filling rose-like clusters of bladed calcite crystals are found in the northern sector of the Cad&iacute, thrust sheet (SE Pyrenees). This unusual calcite crystal morphology has been characterized by using optical and electron microscope, X-ray diffraction, Raman spectroscopy, &delta, 18O, &delta, 13C, 87Sr/86Sr, clumped isotopes, and major and rare earth elements + yttrium (REEs + Y) analysis. Petrographic observations and powder X-ray diffraction measurements indicate that these bladed crystals are mainly made of massive rhombic crystals with the conventional (104) faces, as well as of possibly younger, less abundant, and smaller laminar crystals displaying (108) and/or (108) rhombic faces. Raman analysis of liquid fluid inclusions indicates the presence of aromatic hydrocarbons and occasionally alkanes. Clumped isotopes thermometry reflects that bladed calcite precipitated from meteoric fluids at ~60&ndash, 65 &deg, C. The 87Sr/86Sr ratios and major elements and REEs content of calcite indicate that these fluids interacted with Eocene marine carbonates. The presence of younger &lsquo, nailhead&rsquo, calcite indicates later migration of shallow fresh groundwater. The results reveal that rose-like calcite clusters precipitated, at least in the studied area, due to a CO2 release by boiling of meteoric waters that mixed with benzene and aromatic hydrocarbons. This mixing decreased the boiling temperature at ~60&ndash, C. The results also suggest that the high Sr content in calcite, and probably the presence of proteins within hydrocarbons trapped in fluid inclusions, controlled the precipitation of bladed crystals with (104) rhombohedral faces.

We report a joint experimental and theoretical investigation of the high pressure structural and vibrational properties of terbium sesquioxide (Tb2O3). Powder X-ray diffraction and Raman scattering measurements show that cubic Ia3̅ (C-type) Tb2O3 undergoes two phase transitions up to 25 GPa. We observe a first irreversible reconstructive transition to the monoclinic C2/m (B-type) phase at ∼7 GPa and a subsequent reversible displacive transition from the monoclinic to the trigonal P3̅m1 (A-type) phase at ∼12 GPa. Thus, Tb2O3 is found to follow the well-known C → B → A phase transition sequence found in other cubic rare earth sesquioxides with cations of larger atomic mass than Tb. Our ab initio theoretical calculations predict phase transition pressures and bulk moduli for the three phases in rather good agreement with experimental results. Moreover, Raman-active modes of the three phases have been monitored as a function of pressure, while lattice-dynamics calculations have allowed us to confirm the assignment of the experimental phonon modes in the C- and A-type phases as well as to make a tentative assignment of the symmetry of most vibrational modes in the B-type phase. Finally, we extract the bulk moduli and the Raman-active mode frequencies together with their pressure coefficients for the three phases of Tb2O3. These results are thoroughly compared and discussed in relation to those reported for rare earth and other related sesquioxides as well as with new calculations for selected sesquioxides. It is concluded that the evolution of the volume and bulk modulus of all the three phases of these technologically relevant compounds exhibit a nearly linear trend with respect to the third power of the ionic radii of the cations and that the values of the bulk moduli for the three phases depend on the filling of the f orbitals., The authors are thankful for the financial support of Generalitat Valenciana under Project PROMETEO 2018/ 123-EFIMAT and of the Spanish Ministerio de Economiá y Competitividad under Projects MAT2015-71035-R, MAT2016-75586-C4-2/3/4-P, and FIS2017-2017-83295-P as well as MALTA Consolider Team research network under project RED2018-102612-T. J.A.S. also acknowledges the Ramón y Cajal program for funding support through RYC- 2015-17482. A.M. and P.R.-H. acknowledge computing time provided by Red Española de Supercomputación (RES) and the MALTA Consolider Team cluster. HP-XRD experiments were performed at MPSD beamline of Alba Synchrotron (experiment no. 2016071772).

© 2019 by the authors., Pressure is an important thermodynamic parameter, allowing the increase of matter density by reducing interatomic distances that result in a change of interatomic interactions. In this context, the long range in which pressure can be changed (over six orders of magnitude with respect to room pressure) may induce structural changes at a much larger extent than those found by changing temperature or chemical composition. In this article, we review the pressure-induced phase transitions of most sesquioxides, i.e., A2O3 compounds. Sesquioxides constitute a big subfamily of ABO3 compounds, due to their large diversity of chemical compositions. They are very important for Earth and Materials Sciences, thanks to their presence in our planet’s crust and mantle, and their wide variety of technological applications. Recent discoveries, hot spots, controversial questions, and future directions of research are highlighted., This research was funded by Spanish Ministerio de Ciencia, Innovación y Universidades under grants MAT2016-75586-C4-1/2/3-P, FIS2017-83295-P, PGC2018-094417-B-100, and RED2018-102612-T (MALTA-Consolider-Team network) and by Generalitat Valenciana under grant PROMETEO/2018/123 (EFIMAT). J. A. S. also acknowledges Ramón y Cajal Fellowship for financial support (RYC-2015-17482).

In this work, the relation between the photovoltaic and resistive switching (RS) properties of metal-oxide-semiconductor devices containing Si nanocrystal (Si NC) superlattices is investigated. A first approximation concludes that the low resistance state achieved by the RS process allows for enhanced photogenerated carrier extraction when compared to the high resistance state and pristine devices. By using different current compliance values during the electroforming process, the low resistance state is further modified, improving its conductivity and the collection probability of photogenerated carriers. Conversion efficiency is enhanced by at least one and up to five orders of magnitude by applying different electroforming processes. In addition to promoting the RS properties in these devices, spectral response measurements demonstrate that Si NCs are partially responsible for the optical absorption, and that their contribution is maintained after electroforming. We thus conclude that the proposed methodology can improve the conversion efficiency of this and other multijunction solar cells or structures that also exhibit RS properties. Through RS, a dense network of conductive filaments is promoted in the insulating region, which reduces the travel distance of photocarriers for their collection., This work was financially supported by the Spanish Ministry of Economy, Industry and Competitiveness (TEC2016-76849-C2-1-R) and the German Research Foundation (ZA191/27-3 and ZA191/33-1). J.L.F. acknowledges financial support from the subprogram “Ayudas para la Formación de Profesorado Universitario” (FPU16/06257) from the Spanish Ministry of Education, Culture and Sports.

High-pressure X-ray diffraction studies on nanocrystals of the GdBO3 and YBO3 rare-earth orthoborates are herein reported up to 17.4(2) and 13.4(2) GPa respectively. The subsequent determination of the room-temperature pressure-volume equations of state is presented and discussed in the context of contemporary publications which contradict the findings of this work. In particular, the isothermal bulk moduli of GdBO3 and YBO3 are found to be 170(13) and 163(13) GPa respectively, almost 50% smaller than recent findings. Our experimental results provide an accurate revision of the high-pressure compressibility behaviour of GdBO3 and YBO3 which is consistent with the known systematics in isomorphic borates and previous ab initio calculations. Finally, we discuss how experimental/analytical errors could have led to unreliable conclusions reported elsewhere. © 2021 Elsevier B.V., The authors thank the financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades , Spanish Research Agency (AEI) , Generalitat Valenciana , and European Fund for Regional Development (ERDF, FEDER) under grants nos. FIS2017-83295-P , MAT2016-75586-C4-1/2/3-P , RTI2018-101020-BI00 , PID2019-106383 GB-C41/C42/C43 , RED2018-102612-T ( MALTA Consolier Team ), and Prometeo/2018/123 ( EFIMAT ). R.T. acknowledges funding from the Spanish MINECO via the Juan de la Cierva Formación program ( FJC2018-036185-I ), and J.Á.S. acknowledges funding from the Ramón y Cajal Fellowship Program ( RYC-2015-17482 ). We also thank ALBA synchrotron light source for funded experiments 2016021648 and 2016021668 at the MSPD-BL04 beamline.

It is shown that portable X-ray fluorescence (pXRF) is a powerful tool for the identification and geochemical characterization of prospective Cretaceous–Paleogene (K–Pg) boundary sites. Field measurements in two well-known K–Pg boundary sequences, located at Agost and Caravaca, SE Spain, have been performed. A sizable enrichment around the K–Pg horizon of several elements such as K, Ti, Fe, Ni, Cr, Cu, Zn, As or Pb, together with a strong reduction in the Ca content, is found with the pXRF instrument. These observations represent a primary geochemical signature of the K–Pg boundary in distal marine sections such as those of Agost and Caravaca. Also, the intensities of the pXRF peaks correlate well with elemental composition data obtained by inductively coupled plasma-mass spectrometry (ICP-MS) on collected samples. Hence, the pXRF field measurements are shown to provide fast and useful quantitative information about K–Pg boundary sequences., Work co-funded by ERDF-EU Ref. CSIC10-4E-141 (XRD-pXRF laboratory) and by ERDF-EU Ref. CSIC08-516 4E-001 (LabGEOTOP infrastructure). This study was carried out within the framework of the Research Consolidated Group GEOPAM (Generalitat de Catalunya, 2014SGR869). VF and JP-C acknowledge support from the Spanish Ministerio de Economía, Industria y Competitividad (FPI grants BES-2012-052366 and BES-2016-076469, respectively).

Controlling the size and shape of metallic colloids is crucial for a number of nanotechnological applications ranging from medical diagnosis to electronics. Yet, achieving tunability of morphological changes at the nanoscale is technically difficult and the structural modifications made on nanoparticles generally are irreversible. Here, we present a simple nonchemical method for controlling the size of metallic colloids in a reversible manner. Our strategy consists of applying hydrostatic pressure on a Ca cationic sublattice embedded in the irradiated matrix of CaF2 containing a large concentration of defects. Application of our method to CaF2 along with in situ optical absorption of the Ca plasmon shows that the radii of the Ca nanoparticles can be reduced with an almost constant rate of −1.2 nm/GPa up to a threshold pressure of ∼9.4 GPa. We demonstrate recovery of the original nanoparticles upon decompression of the irradiated matrix. The mechanisms for reversible nanocolloid-size variation are analyzed with first-principles simulations. We show that a pressure-driven increase in the binding energy between fluorine centers is responsible for the observed nanoparticle shrinkage. We argue that the same method can be used to generate other metallic colloids (Li, K, Sr, and Cs) with tailored dimensions by simply selecting an appropriate matrix., J.R.-F. and V.M. acknowledge the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva program IJCI-2014-20513 and FJCI-2016-27921, respectively. C.C. acknowledges support from the Australian Research Council under the Future Fellowship funding scheme (No. FT140100135). Computational resources and technical assistance were provided by the Australian Government and the Government of Western Australia through the National Computational Infrastructure (NCI) and Magnus under the National Computational Merit Allocation Scheme and The Pawsey Supercomputing Centre. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 829161.

Geological Society of American Annual Meeting 2019 in Phoenix, Arizona, USA, 22-25 september

Localized cutaneous argyria is a rare condition secondary to skin deposition of silver following exposure to substances containing this metal. The clinical appearance and dermoscopy findings require deep melanocytic lesions and particularly melanoma metastasis to be ruled out. Silver deposits are usually confirmed by scanning electron microscopy and/or energy-dispersive X-ray spectroscopy. Herein we describe the in vivo reflectance confocal microscopy (RCM) features observed in one case of localized cutaneous argyria. These features include the presence of a hyperrefractile network in the papillary dermis and a periadnexal dotted bright pattern. In vivo RCM might be a useful tool for an early diagnosis of this uncommon entity.

Inorganic chemistry 57(21), 14005 - 14012 (2018). doi:10.1021/acs.inorgchem.8b01808, The zircon to scheelite phase boundary of ErVO$_4$ has been studied by high-pressure and high-temperature powder and single-crystal X-ray diffraction. This study has allowed us to delimit the best synthesis conditions of its scheelite-type phase, determine the ambient-temperature equation of state of the zircon and scheelite-type structures, and obtain the thermal equation of state of the zircon-type polymorph. The results obtained with powder samples indicate that zircon-type ErVO$_4$ transforms to scheelite at 8.2 GPa and 293 K and at 7.5 GPa and 693 K. The analyses yield bulk moduli K$_0$ of 158(13) GPa for the zircon phase and 158(17) GPa for the scheelite phase, with a temperature derivative of dK$_0$/dT = −[3.8(2)] × 10$^{–3}$ GPa K$^{–1}$ and a volumetric thermal expansion of $α_0$ = [0.9(2)] × 10$^{–5}$ K$^{–1}$ for the zircon phase according to the Berman model. The results are compared with those of other zircon-type vanadates, raising the need for careful experiments with highly crystalline scheelite to obtain reliable bulk moduli of this phase. Finally, we have performed single-crystal diffraction experiments from 110 to 395 K, and the obtained volumetric thermal expansion $(α_0 )$ for zircon-type ErVO$_4$ in the 300–395 K range is [1.4(2)] × 10$^{–5}$ K$^{–1}$, in good agreement with previous data and with our experimental value given from the thermal equation of state fit within the limits of uncertainty., Published by American Chemical Society, Washington, DC

The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300K up to the melting temperature. The pressure at which c/a reaches root 3 (approximate to 10GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple poly-crystals. In addition, a noticeable change in the pressure dependence of c/a takes place at the same pressure. Both phenomena could be caused by an isomorphic second-order phase transition induced by pressure in Zn. The reported melt curve extends previous results from 24 to 135 GPa. The pressure dependence obtained for the melting temperature is accurately described up to 135 GPa by using a Simon-Glatzel equation: T-m = 690 K(1 + P/10.5 GPa)(0.76), where P is the pressure in GPa. The determined melt curve agrees with previous low-pressure studies and with shock-wave experiments, with a melting temperature of 5060(30) K at 135 GPa. Finally, a thermal equation of state is reported, which at room-temperature agrees with the literature., The authors are thankful for the financial support to this research from the Spanish Ministerio de Economía y Competitividad, the Spanish Research Agency, and the European Fund for Regional Development under Grant Nos. MAT2016- 75586-C4-1-P, and MAT2015-71070-REDC (MALTA Consolider). British Crown Owned Copyright 2018/AWE.