Hasil untuk "Mineralogy"

Akke Corporaal, Toon De Prins, Léa Planquart et al.

Stars and planets form, live, and evolve in unison. Throughout the life of a star, dusty circumstellar discs and stellar outflows influence the further evolution of both the star(s) and their orbiting planet(s). Planet-forming discs, winds of red giant branch (RGB) or asymptotic giant branch (AGB) stars, and post-RGB/post-AGB discs are examples of such host environments where dust physics plays a key role. The physical processes that occur during each of these stages establishes how the Solar System as well as exoplanetary systems were formed, are evolving, and will eventually die. This White Paper aims to bridge the fields of stellar evolution and planet formation by peering into the dust kinematics and macrostructure formation, and its effect on planet-host interaction, in dusty environments from stellar birth to death. Near-future advancements in the 2030s will enable the detection, orbital monitoring and atmospheric/mineralogical characterisation of close-in (proto)planets across diverse stages of stellar evolution. To take full advantage of these developments by the 2040s, we should develop the capabilities required to image the varied dusty environments in which planets are entrained over their lifetime. This will enable extensive testing of current theoretical understandings - from the micro-scales of dust assembly to the deeply interlinked macro-scales of planet-host interactions - across diverse settings often too small, distant, and faint to be resolved in the next decade, simultaneously providing valuable constraints on the two-way interplay of dusty host environments and planetary formation/evolution.

Leonardos Gkouvelis

Theoretical frameworks for reflection and emission spectroscopy of exoplanet surfaces are becoming increasingly important for the characterization of rocky exoplanets, especially with the rapid growth of the detected exoplanet population and observational capabilities. The Hapke theory of reflectance and emittance spectroscopy has been widely adopted in the exoplanet community, yet a key physical effect - the opposition surge enhancement at small phase angles - remains largely neglected. This phenomenon, driven by shadow hiding and coherent backscattering, introduces a significant brightening that depends on wavelength, particle size, and surface morphology. In this paper, I propose an alternative formulation for opposition surge modeling, ensuring a smooth-to-sharp transition at small phase angles, dictated by wavelength-dependent scattering properties. I evaluate the impact of opposition surge on phase curves and surface spectra, comparing a family of models with increasing simplifications, ranging from a full wavelength-dependent opposition effect to its complete omission. My results indicate that neglecting opposition effects can introduce systematic deviations in retrieved albedos, spectral features, and phase curves, with errors reaching up to 20%-30% in certain spectral bands. Upcoming JWST observations will probe phase angles below ~10° for rocky exoplanets around M dwarfs; thus, accounting for opposition effects is crucial for accurate surface characterization. Proper treatment of this effect will lead to improved retrievals of surface albedo, mineralogical composition, and roughness properties. This study establishes a physically consistent framework for exoplanet phase-curve modeling and provides a foundation for future retrieval algorithms aimed at interpreting exoplanet surfaces.

Bernard Marty, Katherine R. Bermingham, Larry R. Nittler et al.

Understanding the origin of comets requires knowledge of how the Solar System formed from a cloud of dust and gas 4.567 Gyr ago. Here, a review is presented of how the remnants of this formation process, meteorites and to a lesser extent comets, shed light on Solar System evolution. The planets formed by a process of collisional agglomeration during the first hundred million years of Solar System history. The vast majority of the original population of planetary building blocks (~100 km-scale planetesimals) was either incorporated into the planets or removed from the system, via dynamical ejection or through a collision with the Sun. Only a small fraction of the original rocky planetesimals survive to this day in the form of asteroids (which represent a total of ~0.05% of Earth's mass) and comets. Meteorites are fragments of asteroids that have fallen to Earth, thereby providing scientists with samples of Solar System-scale processes for laboratory-based analysis. Meteorite datasets complement cometary datasets, which are predominantly obtained via remote observation as there are few cometary samples currently available for laboratory-based measurements. This chapter discusses how analysis of the mineralogical, elemental, and isotopic characteristics of meteorites provides insight into (i) the origin of matter that formed planets, (ii) the pressure, temperature, and chemical conditions that prevailed during planet formation, and (iii) a precise chronological framework of planetary accretion. Also examined is the use of stable isotope variations and nucleosynthetic isotope anomalies as constraints on the dynamics of the disk and planet formation, and how these data are integrated into new models of Solar System formation. It concludes with a discussion of Earth's accretion and its source of volatile elements, including water and organic species.

Jan Erik Rudjord, Mads Huuse

Abstract Oligo-Miocene strata in the northern North Sea comprise hundreds of enigmatic km-scale sand-cored mounds. We investigated these using a basin-scale 3D seismic dataset coupled with petrophysical logs and cuttings mineralogy for hundreds of wells. Here we document the discovery of ‘sinkites’, large-scale sand bodies that have sunk into and underpin low-density bio-silicious ooze rafts, violating the law of superposition. The stratigraphic inversion is attributed to buoyancy instabilities between km-scale rigid low density ooze rafts and liquefied, younger, denser, unconsolidated sand. The sand slurry dislodged the ooze as rafts, delimited by early-stage polygonal faults formed due to volumetric contraction of underlying ooze packages. Akin to load casts, but orders of magnitude bigger, ‘sinkites’ introduce a new large-scale gravitational process into geology. Their discovery and association to fractured low density ooze is important to stratigraphy and assessments of reservoir, seal and fluid flow in petroleum and CO2 storage projects and may have other implications.

Tetsuya Yokoyama, Nicolas Dauphas, Ryota Fukai et al.

The Hayabusa 2 spacecraft sampled ~5.4 g of asteroid material from the Cb-type asteroid Ryugu. Initial analysis of the Ryugu materials revealed a mineralogical, chemical, and isotopic kinship to the CI chondrites. In this study, we have summarized the elemental abundances of Ryugu samples published to date, and evaluated their compositional variability associated with the CI chondrite data. The abundances of some elements (e.g., P, Ca, Mn, and rare earth elements) in individual Ryugu particles were found to show large relative dispersions compared to the other elements, presumably due to the nugget effect of aqueously formed minor secondary minerals (e.g., dolomite, apatite, magnetite, and pyrrhotite). Consequently, the mean abundances of Ryugu for these elements, calculated using currently available Ryugu data, are accompanied by a certain degree of uncertainties. We suggest establishing a consortium to determine the representative elemental abundances of Ryugu by measuring aliquots from a large homogenized powder sample that can mitigate the nugget effect. Our statistical calculation shows that at least 750 and 400 mg of homogenized samples from Chambers A and C, respectively, are needed to achieve within +/-5% compositional heterogeneity. The data obtained throughout the consortium activity complement the scientific objectives of the Hayabusa2 mission. Moreover, we anticipate that the obtained Ryugu data, coupled with the elemental abundances of CI chondrites, provide new insights into the chemical composition of the Solar System, which will be used by multidisciplinary communities, including Earth and planetary sciences, astronomy, physics, and chemistry.

Lotong Laratmase, Sari Bahagiarti Kusumayudha, Agus Harjanto

The research area is located in the Mount Todoko-ranu complex and its surroundings, Sahu District, West Halmahera Regency, North Maluku, Indonesia. This area geologically consists of Quaternary volcanic rocks with various petrochemical composition. On the other hand, natural water found in the research area generally physically appears turbid, while people who take water from this sites actually need clean water. As it is known, groundwater quality is influenced by the geochemistry of the aquifer through which it flows, therefore it is important to conduct a study on the geochemical correlation of volcanic rocks and groundwater quality in the research area. Thus, the aim of this research is to examine the geochemical characteristics of Mount Todoko-Ranu complex volcanic rocks, to analyze groundwater quality, and to study the correlation between the geochemical characteristics of rocks and the quality of groundwater in this volcanic complex. Methodology applied in this study was geological mapping, rock samples testing to determine the mineralogy chemical composition, groundwater, and surface water samples testing to identify their quality, and then correlation analysis. The results show that andesitic and basaltic-andesite of calc-alcaline volcanic rock complex is correlative to no dominant cation, but bicarbonate anion, or mixing type of natural water.

K. Szentpéteri, K. Cutts, S. Glorie et al.

<p>The in situ Lu–Hf geochronology of garnet, apatite, fluorite, and carbonate minerals is a fast-developing novel analytical method. It provides an alternative technique for age dating of accessory minerals in lithium–caesium–tantalum (LCT) rare-element (RE) pegmatites where zircon is often metamict due to alteration or radiation damage. Currently most dates from Finnish LCT pegmatites are based on columbite-group minerals (CGMs), but their occurrence is restricted to mineralised zones within the pegmatites. Accessory minerals such as garnet and apatite are widespread in both mineralised and unmineralised LCT pegmatites. Lu–Hf dating of garnet and apatite provides an exceptional opportunity to better understand the geological history of these highly sought-after sources for battery and rare elements (Li, Nb, Ta, Be) that are critical for the green transition and its technology. In this paper we present the first successful in situ Lu–Hf garnet date of 1801 <span class="inline-formula">±</span> 53 Ma for an LCT pegmatite from the Kietyönmäki deposit in the Somero–Tammela pegmatite region, SW Finland. This age is consistent with previous zircon dates obtained for the region, ranging from 1815 to 1740 Ma with a weighted mean <span class="inline-formula">²⁰⁷</span>Pb <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e653eaf840568ee76bb20ba3bf368ae0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-36-433-2024-ie00001.svg" width="8pt" height="14pt" src="ejm-36-433-2024-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">²⁰⁶</span>Pb age of 1786 <span class="inline-formula">±</span> 7 Ma.</p>

Ivan V. Molchanov, Ilya A. Valiakhmetov, Anastasia O. Bukacheva et al.

The article introduces into scientific discourse eight stone axes and their fragments from the collections of the Regional State Budgetary Institution of Culture “Chelyabinsk State Historical and Archaeological Museum-Reserve “Arkaim”. The materials were discovered at multi-layered archaeological sites, located in several areas of the Chelyabinsk and Orenburg regions: the fortified settlements of Alandskoye, Zhurumbai and Kuisak, the Kalmytskaya Molel’nya burial ground and the settlement of Kamennaya Rechka I. The axes were analyzed in terms of their petrography, typology and functional purpose. As a result, seven objects were classified as axes of the Kabardino-Pyatigorsk type, two of them were models. One of these tools was classified as the axe with a grooved handle. The use of local raw materials indicates local production of axes. The main production techniques were splitting, picketing and grinding with stone abrasive. Items, made of soft material, were worked with a metal blade. Two axes were broken during production, two objects had traces of use after breakage, and there were no signs of utilization of other items.

Alvaro I. Riquelme, Julian M. Ortiz

Multivariate spatial modeling is key to understanding the behavior of materials downstream in a mining operation. The ore recovery depends on the mineralogical composition, which needs to be properly captured by the model to allow for good predictions. Multivariate modeling must also capture the behavior of tailings and waste materials to understand the environmental risks involved in their disposal. However, multivariate spatial modeling is challenging when the variables show complex relationships, such as non-linear correlation, heteroscedastic behavior, or spatial trends. This contribution proposes a novel methodology for general multivariate contexts, with the idea of disaggregating the global non-linear behavior among variables into the spatial domain in a piece-wise linear fashion. We demonstrate that the complex multivariate behavior can be reproduced by looking at local correlations between variables at sample locations, inferred from a local neighborhood, and interpolating these local linear dependencies by using a non-stationary version of the Linear Model of Coregionalization. This mixture of locally varying linear correlations is combined to reproduce the global complex behavior seen in the multivariate distribution. The main challenge is to solve appropriately the interpolation of the known correlation matrices over the domain, as these local correlations defined at sample locations can be endowed with a manifold structure, on which the Euclidean distance is not a suitable metric for interpolation of such correlations. This is addressed by using tools from Riemannian geometry: correlation matrices are interpolated using a weighted Fréchet mean of the correlations inferred at sample locations. An application of the procedure is shown in a real case study with good results in terms of accuracy and reproduction of the reference multivariate distributions and semi-variograms.

Jannik Martens, Carsten W. Mueller, Prachi Joshi et al.

Abstract Ice-rich Pleistocene-age permafrost is particularly vulnerable to rapid thaw, which may quickly expose a large pool of sedimentary organic matter (OM) to microbial degradation and lead to emissions of climate-sensitive greenhouse gases. Protective physico-chemical mechanisms may, however, restrict microbial accessibility and reduce OM decomposition; mechanisms that may be influenced by changing environmental conditions during sediment deposition. Here we study different OM fractions in Siberian permafrost deposited during colder and warmer periods of the past 55,000 years. Among known stabilization mechanisms, the occlusion of OM in aggregates is of minor importance, while 33-74% of the organic carbon is associated with small, <6.3 µm mineral particles. Preservation of carbon in mineral-associated OM is enhanced by reactive iron minerals particularly during cold and dry climate, reflected by low microbial CO2 production in incubation experiments. Warmer and wetter conditions reduce OM stabilization, shown by more decomposed mineral-associated OM and up to 30% higher CO2 production. This shows that considering the stability and bioavailability of Pleistocene-age permafrost carbon is important for predicting future climate-carbon feedback.

Sufyan Alrawi, Lafta Kadhim, Abdulhameed Al-Hadaithy

The current study including geochemical and mineralogical aspects of 12 rock samples from Anah and Euphrates formations in two outcrops, The first outcrop is at Haditha city, with 12.5 meters thickness, and the second location is at Al-Baghdadi city, with 21 meters thickness. The mineralogical study by X-ray diffraction indicated that calcite is the main mineral in the rocks of Anah Formation, while calcite and dolomite exist in Euphrates Formation, where calcite is concentrated in the lower part of Euphrates Formation, while dolomite is common in the middle and upper parts of this formation, in addition to other minor minerals such as quartz and feldspar. Geochemical study was carried out by XRF to determine the major oxides(CaO, MgO, Fe2O3, Al2O3, SiO2, SO3, K2O, Na2O, MnO) and the suitability of Anah and Euphrates rocks as raw material for Portland cement and Al-Noura (lime) cement industries. According to the results it is found that Euphrates Formation in the Al-Baghdadi and Haditha outcrops is not suitable for the Portland cement, because of high percentage of MgO as a result of the high percentage of dolomitic limestone. The chemical analysis of the samples of the Anah Formation in Haditha outcrop are suitable for the Noura cement (lime) industry according to the Iraqi standard. The high content of magnesium in the Euphrates Formation at Al-Baghdadi area used as indicator that the rocks deposited in shallow marine and warm condition, and the environment was mostly isolated with warm condition. Low Sr content indicates shallow carbonate rocks. Thus, the sedimentary environment of the Anah Formation at Haditha outcrop was relatively shallower than that of the Euphrates Formation.

Dayana María Beyra-Fernández, Juan Ruiz-Quintana, María Caridad Ramírez- Pérez et al.

La producción de asfaltos en las refinerías cubanas no satisface la demanda nacional de los proyectos viales.  El propósito de este estudio fue delinear los posibles escenarios que pudieran tener lugar en la producción de asfaltos a partir de la refinación de crudos pesados en Cuba. Para ello se empleó una metodología que combinó el trabajo con expertos y la Prospectiva Estratégica de Godet. De la aplicación del método Matriz de Impactos Cruzados Multiplicación Aplicada a una Clasificación se obtuvieron tres variables (factores) claves que permitieron formular igual número de hipótesis y definir ocho posibles escenarios. Utilizando el método Sistema de Matrices de impactos Cruzados Probabilizados (Smic Prob-Expert) se precisaron los tres escenarios más probables: el más favorable, en el cual se cumplen las tres hipótesis; el menos favorable, en el que no se cumple ninguna de las tres, y un escenario en que se cumple solamente la primera hipótesis. Según estos resultados, el escenario más favorable sería aquel en el que se garanticen la materia prima para las refinerías, un procedimiento tecnológico que permita obtener más asfalto con menos costo y la disponibilidad técnica del equipamiento tecnológico.

Hassan Kamaleldin M., Brunarska Irena

This report presents the results of a petrographical and mineralogical (optical microscopy, BSE-EDS image analysis) study of zircon in samples from the Lower Nubian monzogranite. The mineral occurs as smaller grains (< 80 μm) in a fine-grained quartz-feldspar-matrix, coexisting with other accessory minerals including biotite, clinochlore, titanite, and britholite-(Ce). Zircon is also present within biotite and britholite-(Ce), suggesting that it started crystallization at about the same time as these two minerals. Two types of thorite inclusions within zircon are reported in this study. Type 1 is widely distributed throughout the zircon grain, forming crystallites of which each is typically < 1 μm in size. Type 2 is relatively larger (5-15 μm) and occurs only in one part of the grain. For the thorite inclusions, three possible origins are briefly discussed: (1) exsolution of thorite from zircon; (2) dissolution/reprecipitation of zircon; and (3) growth syngenetically with zircon. Of these potential hypotheses, the syngenetic growth model seems more favorable for zircon-thorite intergrowths than the other two hypotheses. Thorite inclusions and their host zircons seem to have grown from magma rather than hydrothermal or supercritical solutions. Here, they have primary textures and consistent chemical compositions that are consistent with whole-rock geochemistry.

G. Franz, P. Lyckberg, V. Khomenko et al.

<p>We report on Precambrian microfossils from igneous rocks of the Volyn pegmatite district, associated with the Paleoproterozoic Korosten pluton, northwestern Ukraine. The fossils were recovered from meter-sized miarolitic cavities and show a well-preserved 3D morphology, mostly filamentous but with a large variety of types and also in irregular, flaky shapes reminiscent of former biofilms, as well as rare spherical objects. Based on literature data, pyrolysis experiments, and reflected light microscopy results, the organic matter (OM) is characterized as (oxy-)kerite. Further investigations with microscopic techniques, including scanning and transmission electron microscopy, and electron microprobe analysis show that fossilization likely occurred during a hydrothermal, post-pegmatitic event by silicification dominantly in the outermost 1–2 <span class="inline-formula">µm</span> of the microfossils. The hydrothermal fluid, derived from the pegmatitic environment, was enriched in <span class="inline-formula">SiF₄</span>, Al, Ca, Na, K, Cl, and S. The OM shows O enrichment in which N and S content is low, indicating simultaneous N and S loss during anaerobic oxidation. Mineralization with Al silicates starts at the rim of the microfossils, continuing in its outer parts into identifiable encrustations and intergrowths of clay minerals, feldspar, Ca sulfate, Ca phosphate, Fe sulfide, and fluorite.</p> <p>Breccias, formed during collapse of some the miarolitic cavities, contain decaying OM, which released high concentrations of dissolved <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><msub><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn></msub><mo>+</mo></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="47abf32743cd28df9573e01430c76658"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1795-2022-ie00001.svg" width="29pt" height="14pt" src="bg-19-1795-2022-ie00001.png"/></svg:svg></span></span>, responsible for the late-stage formation of tobelite-rich muscovite and buddingtonite. The age of the fossils can be restricted to the time between the pegmatite formation, at <span class="inline-formula">∼1.760</span> Ga, and the breccia formation at <span class="inline-formula">∼1.49</span> Ga. As the geological environment for the growth of the microorganisms and fossilization, we assume a geyser system in which the essential biological components C, N, S, and P for growth of the organisms in the miarolitic cavities were derived from microorganisms at the surface. Fossilization was induced by magmatic <span class="inline-formula">SiF₄</span>-rich fluids. The Volyn occurrence is a distinct and uncommon example of Precambrian fossils, and the results underline the importance of cavities in granitic rocks as a possible habitat for microorganisms preserved in the deep biosphere.</p>

Lucas Iwahara, Cláudio Pereira, Maria Angélica Wasserman et al.

The soil-plant transfer factor (Fv) is used methods in the computational models for radiological risk assessment by ingestion of radiocobalt-contaminated food. Different soil types, plants types and agricultural practices contribute to a wide dispersion of Fv values, indicating the need to study the criteria that influence root uptake in a regional view. In this scenario, Artificial Neural Networks (ANN) have become a possibility to predict Fv values based on critical pedological parameters. This work aims to apply ANN to evaluate the possibility of predicting Fv for 60Co in reference plants as a function of soil properties considered relevant for transfer processes in the soil-plant system. Through the systematic literature review, mineralogy, organic matter, texture, pH, CEC and nutrients were identified as soil properties that affect Fv values for 60Co. However, although these attributes were not always reported, still it was possible to create databases of Fv for 60Co in radish root and leaf, with pH, organic matter, and CTC as potential edaphic indicators. Learning sets were structured and due to the complexity of the search space and the small amount of available data, deep ANN with regularization (dropout) layers were required to achieve good prediction and avoid overfitting. The best model obtained showed good correlation in the validation and training set, considering the chosen parameters.

Violeta Gamez Rosas, Jacob W. Isbell, Walter Jaffe et al.

In the widely accepted 'Unified Model' solution of the classification puzzle of Active Galactic Nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects and added dusty clumps and polar winds but left the basic picture intact. However, recent high-resolution images of the archetypal type-2 galaxy NGC 1068 suggested a more radical revision. They displayed a ring-like emission feature which the authors advocated to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the type 1-2 dichotomy. Here we present new multi-band mid-infrared images of NGC1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data, our maps locate the central engine below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the Unified Model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre.

Paul Horton, Hannah R. Kerner, Samantha Jacob et al.

While innovations in scientific instrumentation have pushed the boundaries of Mars rover mission capabilities, the increase in data complexity has pressured Mars Science Laboratory (MSL) and future Mars rover operations staff to quickly analyze complex data sets to meet progressively shorter tactical and strategic planning timelines. MSLWEB is an internal data tracking tool used by operations staff to perform first pass analysis on MSL image sequences, a series of products taken by the Mast camera, Mastcam. Mastcam's multiband multispectral image sequences require more complex analysis compared to standard 3-band RGB images. Typically, these are analyzed using traditional methods to identify unique features within the sequence. Given the short time frame of tactical planning in which downlinked images might need to be analyzed (within 5-10 hours before the next uplink), there exists a need to triage analysis time to focus on the most important sequences and parts of a sequence. We address this need by creating products for MSLWEB that use novelty detection to help operations staff identify unusual data that might be diagnostic of new or atypical compositions or mineralogies detected within an imaging scene. This was achieved in two ways: 1) by creating products for each sequence to identify novel regions in the image, and 2) by assigning multispectral sequences a sortable novelty score. These new products provide colorized heat maps of inferred novelty that operations staff can use to rapidly review downlinked data and focus their efforts on analyzing potentially new kinds of diagnostic multispectral signatures. This approach has the potential to guide scientists to new discoveries by quickly drawing their attention to often subtle variations not detectable with simple color composites.

YiRen Chang, ZhiYong Xiao, YiChen Wang et al.

The Chang’E-4 mission has been exploring the lunar farside. Two scientific targets of the rover onboard are (1) resolving the possible mineralogy related to the South Pole-Aitken basin and (2) understanding the subsurface processes at the lunar farside. Publications to date that are based on the reflectance spectra and radar data obtained by the rover have shown a persistent inconsistency about the local stratigraphy. To explain both the abnormal surface topography at the landing site and the unexpected radargram observed by the rover, the Alder crater has been frequently reported to be older than the mare basalts at that landing site. However, this argument is not supported by earlier geological mapping nor recent crater statistics. Resolving this controversy is critical for a full understanding of the geological history of the landing area and for correct interpretations of the scientific data returned. Employing detailed crater statistics, rigorous statistical analyses, and an updated crater chronology function, this study is determined to resolve the relative ages of the Alder crater, Finsen crater, and the mare basalts on the floor of Von Kármán. Our results reveal that while background secondaries and local resurfacing have widely occurred in the study area, affecting age determinations, the statistics are significant enough to conclude that the Alder crater is the oldest among the three targets. This independent constraint is consistent with both the crosscutting relationships of different terrains in this area and global stratigraphic mapping. Our results exclude Alder as a possible contributor of the post-mare deposits at the landing site, appealing for a more systematic stratigraphy study to resolve the provenances of these deposits.

Kenny Vilella, Thomas Bodin, Charles-Edouard Boukaré et al.

Here, we provide a reappraisal of potential LLSVPs compositions based on an improved mineralogical model including, for instance, the effects of alumina. We also systematically investigate the effects of six parameters: FeO and Al$_{2}$O$_{3}$ content, proportion of CaSiO$_{3}$ and bridgmanite (so that the proportion of ferropericlase is implicitly investigated), Fe$^{3+}$/$\sum$Fe and temperature contrast between far-field mantle and LLSVPs. From the 81 millions cases studied, only 79000 cases explain the seismic observations. Nevertheless, these successful cases involve a large range of parameters with, for instance, FeO content between 12--25~wt\% and Al$_{2}$O$_{3}$ content between 3--17~wt\%. We then apply a principal component analysis (PCA) to these cases and find two robust results: (i) the proportion of ferropericlase should be low ($<$6vol\%); (ii) the formation of Fe$^{3+}$-bearing bridgmanite is much more favored than other iron-bearing phases. Following these results, we identify two end-member compositions, Bm-rich and CaPv-rich, and discuss their characteristics. Finally, we discuss different scenarios for the formation of LLSVPs and propose that investigating the mineral proportion produced by each scenario is the best way to evaluate their relevance. For instance, the solidification of a primitive magma ocean may produce FeO and Al$_{2}$O$_{3}$ content similar to those suggested by our analysis. However, the mineral proportion of such reservoirs is not well-constrained and may contain a larger proportion of ferropericlase than what is allowed by our results.

Hui-Jie Han, Xiao-Ping Lu, Ya-Zhou Yang et al.

The absorption features of olivine in visible and near-infrared (VNIR) reflectance spectra are the key spectral parameters in its mineralogical studies. Generally, these spectral parameters can be obtained by exploiting the Modified Gaussian Model (MGM) with a proper continuum removal. However, different continua may change the deconvolution results of these parameters. This paper investigates the diagnostic spectral features of olivine with diverse chemical compositions. Four different continuum removal methods with MGM for getting the deconvolution results are presented and the regression equations for predicting the Mg-number (Fo#) are introduced. The results show that different continua superimposed on the mineral absorption features will make the absorption center shift, as well as the obvious alterations in shape, width, and strength of the absorption band. Additionally, it is also found that the logarithm of a second-order polynomial continuum can match the overall shape of the spectrum in logarithmic space, and the improved regression equations applied to estimate the chemical composition of olivine-dominated spectra also have a better performance. As an application example, the improved approach is applied to pulse laser irradiated olivine grains to simulate and study the space weathering effects on olivine diagnostic spectral features. The experiments confirm that space weathering can make the absorption band center shift toward longer wavelength. Therefore, the Fo# estimated from remote sensing spectra may be less than its actual chemical composition. These results may provide valuable information for revealing the difference between the spectra of olivine grains and olivine-dominated asteroids.