Hasil untuk "Mineralogy"

Clay Minerals, E. Dited, Y. H et al.

C. Fedo, H. Nesbitt, G. M. Young

R. Grim

A. Ebenbichler, P. Moraga Baez, A. Candian et al.

Aims: We characterize the mid-infrared spectrum of the outer regions of the Red Rectangle nebula to probe the carbonaceous dust and molecular content beyond the circumbinary disk. Methods: We present JWST MIRI-MRS observations of the SW whisker, extracted from three distinct environments: the biconical outflow, the whisker itself, and the shadow region outside the outflow. We compare these with an archival ISO-SWS observation of the inner nebula. Results: The JWST spectra display only classical AIB emission on a weak dust continuum, with no signatures of the oxygen-rich circumbinary disk mineralogy nor of the rich molecular emission seen at optical wavelengths. The AIBs are predominantly Class A - in marked contrast to the exclusively Class B profiles previously reported for the inner regions - with systematic differences between the outflow and shadow regions pointing to environmentally driven PAH processing.

Samuel Cody

Diagenetic concretions have been identified at multiple widely separated sites on Mars, including Meridiani Planum (Opportunity), Gale crater (Curiosity), and Jezero crater (Perseverance). Solid concretions at all sites fall within the millimetre size range (typically 1-6 mm diameter), despite differing cement mineralogies. The one substantial outlier -- centimetre-to-decimetre-scale hollow concretions on Bradbury Rise -- formed in coarser basaltic sandstone via a distinct mechanism. I propose that this size convergence reflects a common physical control: the globally uniform fraction of ultra-fine (~3 um), amorphous, equant atmospheric dust incorporated into sediments at all sites. I derive the diagenetic timescale from Mars' ~120 kyr obliquity cycle, which drives periodic subsurface wetting: each high-obliquity pulse (~10^4-10^5 yr) sets the available growth time. Using a diffusion-reaction model with nucleation competition, I show that the low effective diffusivity imposed by the fine dust matrix limits concretion growth to the observed millimetre scale, independent of local fluid chemistry. Formation efficiency in dust-rich sediment exceeds 90%, making concretion formation essentially inevitable wherever liquid water contacts the dust. This mechanism depends on the non-phyllosilicate, equant-grain mineralogy of Martian dust, which maintains connected pore networks unlike terrestrial clays. Growth is self-limiting: the first wetting pulse exhausts reactive phases in the depletion halo, so successive obliquity cycles produce new concretions in fresh sediment rather than enlarging existing ones. Each concretion records a single wetting episode. The narrow size distributions at all sites suggest that Martian concretion populations may constitute a sedimentary archive of the planet's obliquity history.

L. Suttner, P. Dutta

Michael Pekala, Gregory Canal, Samuel Barham et al.

A key factor for lunar mission planning is the ability to assess the local availability of raw materials. However, many potentially relevant measurements are scattered across a variety of scientific publications. In this paper we consider the viability of obtaining lunar composition data by leveraging LLMs to rapidly process a corpus of scientific publications. While leveraging LLMs to obtain knowledge from scientific documents is not new, this particular application presents interesting challenges due to the heterogeneity of lunar samples and the nuances involved in their characterization. Accuracy and uncertainty quantification are particularly crucial since many materials properties can be sensitive to small variations in composition. Our findings indicate that off-the-shelf LLMs are generally effective at extracting data from tables commonly found in these documents. However, there remains opportunity to further refine the data we extract in this initial approach; in particular, to capture fine-grained mineralogy information and to improve performance on more subtle/complex pieces of information.

Xiaolin LI, Pengfei WANG, Yinghui GAO et al.

Objective and Methods This study aims to reduce the economic cost of sulfoaluminate cement-based grouting materials while also achieving excellent grouting reinforcement effects. To this end, it investigated the variation patterns of the compressive strength, setting time, and fluidity of the ultrafine fly ash (UFA)-ultrafine sulfoaluminate cement (USC) system by incorporating different dosages of silica fume (SF) and nano-silica (NS). Furthermore, the mechanisms behind the hydration reactions of the system were explored. Using multiple distinct testing techniques such as X-ray diffraction (XRD) mineralogy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric-differential thermal analysis (TG-DTA), and scanning electron microscopy (SEM), this study analyzed the phase composition and microstructures of the hydration products. Results and Conclusions The incorporation of SF into the UFA-USC system led to decreased compressive strength and setting time of the system across various ages. As NS was added, the compressive strength of the UFA-USC system at all ages showed an upward trend initially and then decreased, with the optimum NS dosage determined at 2%. As only NS was mixed into USC, the compressive strength of USC at various ages also increased initially and then decreased, with the optimum NS dosage proving to be 3%. In contrast, the setting time of the USC at various ages shortened first and then increased when the NS was added. Microscopically, the incorporation of SF or NS did not change the hydration product types of the USC but enhanced its early hydration. Notably, the incorporation of NS resulted in more compact microstructures of the hydration products, thus improving the compressive strength of the USC. The USC-based grouting materials were applied to floor grouting for water blocking at a coal mine in Shanxi Province. The field tests verified that the materials hold high value in engineering. The results of this study provide a theoretical basis for the application of nanomaterials in grouting engineering. Furthermore, they are of significant practical value in improving the grouting reinforcement technology system used for the surrounding rocks of deep roadways.

David A. Brain, Melodie M. Kao, Joseph G. O'Rourke

Planetary magnetic fields are important indicators of planetary processes and evolution, from a planet's outer core to its surface (if it possesses one) to its atmosphere and near-space environment. Magnetic fields are most directly measured in situ, and determining whether distant planetary objects possess magnetic fields can be challenging. At present we have no unambiguous measurements of magnetic fields on exoplanets. Nevertheless, it would be surprising if at least some exoplanets did not generate a magnetic field, like many planetary bodies in the solar system. This chapter provides an overview of the current understanding of exoplanetary magnetic fields and their consequences. In the next section we review the current understanding of planetary dynamo generation as it applies to solar system objects and discuss the implications for exoplanetary magnetic field generation. Following this, we describe seven methods for determining the existence and strength of an exoplanetary magnetic field and discuss the near-term prospects for each method. We close by highlighting four main consequences of exoplanetary magnetic fields for a planet and its evolution.

Bradford J. Foley

Nearly 30 years after the discovery of the first exoplanet around a main sequence star, thousands of planets have now been confirmed. These discoveries have completely revolutionized our understanding of planetary systems, revealing types of planets that do not exist in our solar system but are common in extrasolar systems, and a wide range of system architectures. Our solar system is clearly not the default for planetary systems. The community is now moving beyond basic characterization of exoplanets (mass, radius, and orbits) towards a deeper characterization of their atmospheres and even surfaces. With improved observational capabilities there is potential to now probe the geology of rocky exoplanets; this raises the possibility of an analogous revolution in our understanding of rocky planet evolution. However, characterizing the geology or geological processes occurring on rocky exoplanets is a major challenge, even with next generation telescopes. This chapter reviews what we may be able to accomplish with these efforts in the near-term and long-term. In the near-term, the James Webb Space Telescope (JWST) is revealing which rocky planets lose versus retain their atmospheres. This chapter discusses the implications of such discoveries, including how even planets with no or minimal atmospheres can still provide constraints on surface geology and long-term geological evolution. Longer-term possibilities are then reviewed, including whether the hypothesis of climate stabilization by the carbonate-silicate cycle can be tested by next generation telescopes. New modeling strategies sweeping through ranges of possibly evolutionary scenarios will be needed to use the current and future observations to constrain rocky exoplanet geology and evolution.

Keith D. Putirka

We'll examine plate tectonics on Earth -- its features and forces -- and examine some concepts that may allow astronomers to ask useful questions regarding numeric models that putatively predict tectonic activity. But exo-planetologists should be aware that geologists are still attempting to understand: why does Earth operates as it does, and so much differently than its neighbors? Has it always operated this way and have other planets of the inner Solar System ever mimicked Earth's behavior in their past? These problems are unsolved, though some interesting speculative notions have emerged. Studies by Foley et al. et al. (2012) and Weller and Lenardic (2018), for example, attempt to distill the essential planetary properties that may influence if not dictate possible tectonic states, while Yin et al. (2016) propose a model of planetary tectonic surface features that appears remarkably precise. These studies yield some compelling expedients for analyses of planetary objects both within and outside our Solar System.

Giulia Ceriotti, Alice Bosco-Santos, Sergey M. Borisov et al.

Iron (Fe) reduction is one of Earth's most ancient microbial metabolisms, but after atmosphere-ocean oxygenation, this anaerobic process was relegated to niche anoxic environments below the water and soil surface. However, new technologies to monitor redox processes at the microscale relevant to microbial cells have recently revealed that the oxygen (O2) concentrations controlling the distribution of aerobic and anaerobic metabolisms are more heterogeneous than previously believed. To explore how O2 levels regulate microbial Fe reduction, we cultivated a facultative Fe-reducing bacterium using a cutting-edge microfluidic reactor integrated with transparent planar O2 sensors. Contrary to expectations, microbial growth induced Fe(III)-oxide (ferrihydrite) reduction under fully oxygenated conditions without forming O2-depleted microsites. Batch incubations highlighted the importance of the process at a larger scale, fundamentally changing our understanding of Fe cycling from the conceptualization of metal and nutrient mobility in the subsurface to our interpretation of Fe mineralogy in the rock record.

Natalie R. Hinkel, Edward D. Young

The relationship between stars and planets provides important information for understanding the interior composition, mineralogy, and overall classification of small planets (R $\lesssim$ 3.5R$_{\oplus}$). Since stars and planets are formed at the same time and from the same material, their compositions are inextricably linked to one another, especially with respect refractory elements like Mg, Si, and Fe. As a result, stellar elemental abundances can help break the degeneracy inherent to planetary mass-radius models and determine whether planets may be similar to the Earth in composition or if additional factors, such as formation near the host star or a giant impact, may have influenced the planet's make-up. To this end, we now have observations of the abundances of extrasolar rocks that were pulled onto the surfaces of a white dwarfs, whose compositions act as a direct insight into the interiors of small exoplanets. From measurements of $\sim$30 of these "polluted" white dwarfs, we have found that composition of the extrasolar rocks are similar to Solar System chondritic meteorites.

Natalie R. Hinkel, Allison Youngblood, Melinda Soares-Furtado

It has become a common practice within the exoplanet field to say that "to know the star is to know the planet." The properties of the host star have a strong, direct influence on the interior and surface conditions of the orbiting planet and oftentimes measurements of planetary properties are made relative to the star's properties. Not only are observational measurements of the star necessary to determine even the most basic aspects of the planet (such as mass and radius), but the stellar environment influences how the planet evolves. Therefore, in this chapter, we begin by discussing the basics of stars, providing an overview of stellar formation, structure, photon and particle emissions, and evolution. Next, we go over the possible ways to determine the age of a star. We then outline how different kinds of stars are distributed within the Milky Way galaxy. Afterwards, we explain how to measure the composition of stars and the underlying math inherent to those observations, including caveats that are important when using the data for research applications. Finally, we explain the underlying physics and observations that enable stellar composition to be used as a proxy for planetary composition. In addition, given that this chapter focuses more on astronomy/astrophysics and uses a variety of important terms that may not be familiar to all readers, we have defined many terms either within the text or as a footnote for better interdisciplinary comprehension.

Afsaneh Soltani, Alireza Zarasvandi, Nader Taghipour et al.

The Kuh-e-Esfand copper deposit is located in the southernmost part of the Urmia-Dokhtar magmatic belt. The Oligocene-Miocene intrusive bodies, ranging from diorite to quartz diorite and granodiorite, are emplaced within the Eocene volcanic complex. Based on the classification of veins- veinlets, the main mineralization stage consists of quartz pyrite chalcopyrite associated with potassic alteration. Based on petrographic studies, fluid inclusions in quartz minerals are categorized into three main groups and seven subgroups: 1- Vapor-rich fluid inclusions comprising single-phase vapor inclusions (V), vapor-rich two-phase inclusions (VL), and vapor-rich inclusions with a opaque phase (VLS), 2- Liquid-rich fluid inclusions including liquid-rich two-phase inclusions (LV) and liquid-rich inclusions with a opaque phase (LVS) and 3- Saline fluid inclusions consisting of simple brine three-phase inclusions (LVH), and multi-phase brine inclusions (LVHS) containing solid phases of halite± hematite± anhydrite± sylvite± chalcopyrite. The multi-phase saline inclusions with high temperature and salinity (358-598°C and 42-70 wt.% NaCl equivalent) of magmatic origin are the primary fluid inclusions forming the deposit. The two-phase liquid-rich inclusions with lower temperature and salinity (290-490°C and 11-20 wt.% NaCl equivalent) of magmatic-meteoric origin are related to the final stages of hydrothermal fluid circulation and mixing with lower salinity fluids. The temperature decrease due to secondary boiling and mixing of magmatic and meteoric fluids led to the instability of the chloride complex carrying copper and subsequent mineralization under favorable conditions. Introduction Porphyry deposits are the major global source of Cu, Mo, and Re, along with being noteworthy reservoirs of Au and Ag (Sillitoe, 2010; Arndt and Ganino, 2012; Crespo et al., 2020). Exploration techniques aimed at optimizing the discovering new deposits are evolving towards a deeper understanding of ore genesis. Fluid inclusion studies serve as an enhanced technique to delineate the nature of ore-forming fluids and the processes governing deposit formation (Wilkinson, 2001), alongside other key geological aspects such as tectonic setting, mineral alteration, vein structure, ore-forming zones, and metal transportation and concentration dynamics (Singer et al., 2002; Sillitoe, 2010; Zajacz et al., 2017). Extensive studies have examined the physicochemical conditions, origins, and evolution of hydrothermal fluids in porphyry deposits globally, including in Iran, through fluid inclusion studies. The Kuh-e-Esfand porphyry copper deposit is located in Kerman province, Iran, approximately 90 kilometers southeast of Jiroft. Currently, the deposit is under exploration, and drilling activities are underway to obtain precise information on the type, composition, quantity, and economic potential of mineral reserves for evaluation and extraction purposes. Since fluid inclusion studies contribute to understanding hydrothermal processes as mineralizing agents, in this study focuses on detailed fluid inclusion studies, including petrography and microthermometry, to understand the nature and evolution of ore-forming fluids, as well as the physicochemical processes influencing mineral precipitation in the Kooh-Esfand deposit. Materials and methods In this study, 15 surface samples and 48 drill core samples were utilized for detailed investigations, with BH2, BH3, and BH4 boreholes being drilled at depths of 506 m, 475 m, and 496 m respectively. BH2 and BH3 were drilled into the intrusive mass, while BH4 was drilled into the volcanic unit, encountering a quartz diorite intrusive mass at 340 m depth. Among the selected samples, 42 thin section samples and 11 polished thin sections were prepared and examined. Petrographic studies of fluid inclusions were conducted using optical microscopy, and samples were separated from the veins in mineralogy and fluid laboratories. Temperature and salinity parameters of fluid inclusions in quartz minerals were measured at Pamukkale University in Denizli, Turkey, and part of it was conducted at Tarbiat Modares University in Tehran. In Pamukkale University's laboratory, fine grain size measurements were carried out using a Linkam THMSG 600 freeze-thaw stage equipped with an Olympus microscope. This stage was calibrated using H2O-CO2 fluid inclusions at temperatures of 1.1°C, 0.0°C, and -56.6°C. The upper and lower temperature thresholds for fine grain size measurements were 600°C and -120°C respectively. The heating rate was set at 1°C per minute for determining the homogenization temperature or ice melting temperature. At Tarbiat Modares University, temperature measurements on sections were conducted using a THMCG600 heating-cooling stage equipped with a Leitz microscope, with a temperature range of -196°C to +600°C. Calibration of the stage was performed using C4H3CH3 at 95°C and KNO3 at 335°C. Result The study area encompasses three distinct geological units: volcanic, volcaniclastic, and intrusive units. The intrusive unit range in composition from diorite to quartz-diorite and granodiorite. Various alteration zones, such as potassic alteration, quartz-sericite-feldspar alkaline ± chlorite alteration, phyllic alteration, argillic alteration, and propylitic alteration, have significantly influenced the lithological units in the study area. On the basis of vein classification, the early stage of mineralization predominantly is characterized by quartz ± chalcopyrite ± magnetite ± pyrite veins. The main mineralization stage is characterized by quartz + pyrite + chalcopyrite veins associated with potassic alteration and quartz-sericite-alkali feldspar-chlorite zone. Post mineralization stage is characterized by quartz-pyrite veins. Due to pressure variations from lithostatic to hydrostatic conditions, substantial copper mineralization likely occurred during the main mineralization stage, with comparatively lesser molybdenum mineralization observed in quartz-pyrite-chalcopyrite and quartz-pyrite-chalcopyrite-molybdenite veins. These mineralization stages, often accompanied by abundant vapor-rich and multi-phase fluid inclusions, initiated ore formation through fluid boiling processes. Based on petrographic studies, fluid inclusions in quartz minerals are categorized into three main groups and seven subgroups: 1- Vapor-rich fluid inclusions comprising single-phase vapor inclusions (V), vapor-rich two-phase inclusions (VL), and vapor-rich inclusions with a opaque phase (VLS) (including chalcopyrite, possibly magnetite, and unidentified opaque phases), 2- Liquid-rich fluid inclusions including liquid-rich two-phase inclusions (LV) and liquid-rich inclusions with a opaque phase (VLS) containing opaque minerals (such as chalcopyrite and unidentified opaque phases), and 3- Saline fluid inclusions consisting of simple brine three-phase inclusions (LVH) containing liquid+ vapor+ halite, and multi-phase brine inclusions (LVHS) containing vapor+ liquid+ halite± hematite± anhydrite± sylvite± chalcopyrite. Discussion The relationship between different types of fluid inclusions in the Kuh-Esfand deposit is established through detailed petrographic and micrometerometric investigations. In microthermometric studies, the relationship between different types of fluid inclusions, including liquid-rich, vapor-rich, three-phase, and multiphase inclusions, is investigated to examine the origin and evolution process of the hydrothermal fluid. This investigation is based on variations in homogenization temperature and salinity content. By analyzing variations in homogenization temperature and salinity, these investigations provide valuable insights into the processes governing fluid evolution in the Kuh- e- Esfand copper deposit. On the basis of the microthermometric analyses, the observed changes in homogenization temperature and salinity indicate a systematic decrease from multiphase fluid inclusions to liquid-rich fluid inclusions. Interestingly, vapor-rich fluid inclusions exhibit homogenization temperatures comparable to the upper end of the temperature range observed in multiphase fluid inclusions. Primary fluid inclusions of magmatic origin encompass vapor-rich inclusions characterized by elevated homogenization temperatures (330-600 °C) and diminished salinities (12-22 wt.% NaCl eq.), multisolid fluid inclusions exhibiting extended temperature ranges (385-598 °C) and heightened salinities (42-70 wt.% NaCl eq.), and three-phase fluid inclusions demonstrating significant temperature variations (230-590 °C) alongside elevated salinities (35-65 wt.% NaCl eq.). The presence of multi-phase fluid inclusions is indicative of the initial hydrothermal fluids responsible for the formation of the Kuh-e-Esfand deposit. Conversely, fluid inclusions of magmatic-meteoric source encompass liquid-rich inclusions characterized by homogenization temperatures and reduced salinities (290-490 °C and 11-20 wt.% NaCl eq., respectively). This particular fluid inclusion type signifies the terminal phase of hydrothermal fluid circulation, characterized by interaction and dilution with lower salinity meteoric fluids. The depth of the Kuh-e-Esfand deposit ranges from 0.8 to 1.7 kilometers, with an average depth of 1.4 kilometers (equivalent to 1400 meters). This translates to pressures ranging from 215 to 603 bars on average, with an average hydrostatic pressure of 412 bars and a lithostatic pressure of 1112 bars. In the Kuh-e-Esfand deposit, fluid inclusions exhibit a sequence of influential processes, including secondary boiling phenomena, fluid immiscibility, the interaction of magmatic fluids with meteoric waters, and isothermal mixing, throughout the hydrothermal fluid evolution. Vapor-rich fluid inclusions, characterized by the presence of opaque minerals (e.g., chalcopyrite), are infrequently observed in the Kuh-e-Esfand deposit, suggesting that the brine phase predominantly facilitates the transport of copper metal. Finally, the decrease in temperature due to secondary boiling and mixing of magmatic fluids with meteoric fluids has led to the destabilization of the chloride complex, the primary carrier of copper in the studied deposit, and its deposition under favorable conditions.

A. Donner, P. Töchterle, C. Spötl et al.

<p>The investigation of cryogenic cave minerals (CCMs) has developed in recent decades to be a particularly valuable proxy for palaeo-permafrost reconstruction. Due to difficulties, however, in obtaining reliable chronologies with the so-called “fine” form of these minerals, such studies have thus far utilised the “coarse” form. In this study, we successfully investigate the northernmost-known deposit of fine-grained CCMs, which are situated in Cove Cave (Greenlandic translation: Eqik Qaarusussuaq), a low-elevation permafrost cave in northeastern Greenland (80<span class="inline-formula">^∘</span> N). The Cove Cave CCMs display a complex mineralogy that consists of fine-grained cryogenic cave carbonates and sulfate minerals (gypsum, eugsterite, mirabilite, and löweite). Until now, previous attempts to date fine-grained CCMs have been unsuccessful; however, here we demonstrate that precise dating is possible with both isochron-based <span class="inline-formula">²³⁰</span>Th <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="cp-19-1607-2023-ie00001.svg" width="8pt" height="14pt" src="cp-19-1607-2023-ie00001.png"/></svg:svg></span></span> U dating and <span class="inline-formula">¹⁴</span>C dating if the dead carbon fraction is reliably known.</p> <p>The dating result (<span class="inline-formula">65±17</span> a BP; <span class="inline-formula">1885±17</span> CE) shows that the Cove Cave CCMs formed during the late Little Ice Age, a time interval characterised by cold temperatures and abundant permafrost in northeastern Greenland, making water infiltration into Cove Cave dependent on the water amount and latent heat. We relate the CCM formation to a combination of black carbon deposition and anomalously high temperatures, which led to widespread melting over large areas of the Greenland ice sheet in the course of a few days. We propose that the anomalous weather conditions of 1889 CE also affected northeastern Greenland, where the enhanced melting of a local ice cap resulted in water entering the cave and rapidly freezing. While calcite and gypsum likely precipitated concurrently with freezing, the origin of the other sulfate minerals might not be purely cryogenic but could be linked to the subsequent sublimation of this ice accumulation in a very dry cave environment.</p>

János Szanyi, Ladislaus Rybach, Hawkar A. Abdulhaq

In an era of accelerating energy transition and growing demand for critical metals essential for clean technologies, the innovative integration of geothermal energy with critical metal extraction stands as a paradigm shift in sustainable resource utilization. This comprehensive review unravels the synergistic potential of coupling geothermal energy systems with critical metal extraction, thereby transforming a dual crisis of energy and resource scarcity into an opportunity for circular economy. Through rigorous analysis of existing geothermal technologies, and extraction methodologies, the study establishes a coherent framework that merges energy production with environmental stewardship. It scrutinizes current extraction techniques, and evaluates their compatibility with geothermal brine characteristics, proposing optimized pathways for maximum yield. Through detailed case studies and empirical data, the paper elucidates the economic and environmental advantages of this multifaceted approach, from reduced carbon footprint to enhanced energy efficiency and resource recovery. It concludes that combined heat and mineral production technology can open new, unexplored resources, increasing the supply of previously untapped resources, while the potential of geothermal energy for sustainable mineral extraction and energy production is in line with Sustainable Development Goal 7, which aims to ensure access to affordable, reliable, sustainable and modern energy for all.

C. L. Urueña, C. Möller, A. Plan

<p>The formation of metamorphic zircon after baddeleyite is a well-known reaction that can be used to date the metamorphism of igneous silica-undersaturated rocks. By contrast, metamorphic minerals formed after igneous zirconolite have rarely been reported. In this paper, we document metamorphic titanite <span class="inline-formula">+</span> zircon pseudomorphs formed from the metamorphic breakdown of igneous zirconolite in syenodiorite and syenite, in the southeastern Sveconorwegian Province, Sweden. Water-rich fluid influx during tectonometamorphism in epidote–amphibolite-facies metamorphic conditions caused the release of silica during a metamorphic reaction involving igneous feldspar and pyroxene and the simultaneous breakdown of igneous Zr-bearing phases. Typical titanite <span class="inline-formula">+</span> zircon intergrowths are elongated or platy titanite crystals speckled with tiny inclusions of zircon. Most intergrowths are smaller than 15 <span class="inline-formula">µ</span>m; some are subrounded in shape. Locally, bead-like grains of titanite and zircon are intergrown with silicate minerals. The precursor igneous zirconolite was found preserved only in a sample of near-pristine igneous syenodiorite, as remnant grains of mainly <span class="inline-formula"><i>&lt;</i></span> 2 <span class="inline-formula">µ</span>m in size. Two somewhat larger crystals, 8 and 12 <span class="inline-formula">µ</span>m, allowed semiquantitative confirmation using microprobe analysis. Analogous with zircon pseudomorphs after baddeleyite, titanite <span class="inline-formula">+</span> zircon pseudomorphs after zirconolite potentially offer dating of the metamorphic reaction, although the small size of the crystals makes dating with today's techniques challenging. The scarcity of reports of zirconolite and pseudomorphs reflects that they are either rare or possibly overlooked.</p>

Lucia Mandon, Pierre Beck, Cathy Quantin-Nataf et al.

In the next decade, two rovers will characterize in situ the mineralogy of rocks on Mars, using for the first time near-infrared reflectance spectrometers: SuperCam onboard the Mars 2020 rover and MicrOmega onboard the ExoMars rover, although this technique is predominantly used in orbit for mineralogical investigations. Until successful completion of sample-return missions from Mars, Martian meteorites are currently the only samples of the red planet available for study in terrestrial laboratories and comparison with in situ data. However, the current spectral database available for these samples does not represent their diversity and consists primarily of spectra acquired on finely crushed samples, albeit grain size is known to greatly affect spectral features. We measured the reflected light of a broad Martian meteorite suite as a means to catalogue and characterize their spectra between 0.4 and 3 microns. These measurements are achieved using a point spectrometer acquiring data comparable to SuperCam, and an imaging spectrometer producing hyperspectral cubes similarly to MicrOmega. Our results indicate that point spectrometry is sufficient to discriminate the different Martian meteorites families, to identify their primary petrology based on band parameters, and to detect their low content in alteration minerals. However, significant spectral mixing occurs in the point measurements, even at spot sizes down to a few millimeters, and imaging spectroscopy is needed to correctly identify the various mineral phases in the meteorites. Bidirectional spectral measurements confirm their non-Lambertian behavior, with backward and suspected forward scattering peaks. With changing observation geometry, the main absorption strengths show variations up to 10-15 percents. All the spectra presented are provided in the supplementary data for further comparison with in situ and orbital measurements.

Natalie R. Hinkel, Patrick A. Young, Caleb H. Wheeler

Understanding stellar composition is fundamental not only to our comprehension of the galaxy, especially chemical evolution, but it can also shed light on the interior structure and mineralogy of exoplanets, which are formed from the same material as their host stars. Unfortunately, the underlying mathematics describing stellar mass fractions and stellar elemental abundances is difficult to parse, fragmented across the literature, and contains vexing omissions that makes any calculation far from trivial, especially for non-experts. In this treatise, we present clear mathematical formalism and clarification of inherent assumptions and normalizations within stellar composition measurements, which facilitates the conversion from stellar mass fractions to elemental abundances to molar ratios, including error propagation. We also provide an example case study of HIP 544 to further illustrate the provided equations. Given the important chemical association between stars, as well as the interdisciplinary relationship between stars and their planets, it is vital that stellar mass fractions and abundance data be more transparent and accessible to people within different sub-fields and scientific disciplines.