Basalt Samples Research Articles

Mare Volcanism in Apollo Basin Evaluating the Mare Basalt Genesis Models on the Moon

The Apollo basin is a well-preserved double-ringed impact basin located on the northeastern edge of the South Pole–Aitken (SPA) basin. The Apollo basin has been flooded and filled with large volumes of mare lavas, indicating an active volcanism history. Based on orbital data, we reveal that the Apollo basin exhibits an overall asymmetric configuration in the distribution of mare basalts as well as its topography, chemical compositions, and crustal thickness. The Apollo basin is an excellent example for assessing the influences of the above factors on mare basalts petrogenesis and evaluating mare basalt genesis models. It was found that the generation of mare basalt magmas and their emplacement in the Apollo basin seems to be strongly related to local thin crust (<30 km), but the formation of basaltic magmas should be independent of the decompression melting because the mare units (3.34–1.79 Ga) are much younger than the pre-Nectarian Apollo basin. The mare basalts filled in the Apollo basin exhibits a large variation of TiO2 abundances, indicating the heterogeneity of mantle sources, which is possible due to the lunar mantle overturn after the LMO solidification or the impact-induced mantle convection and migration. However, the prolonged mare volcanic history of the Apollo basin is not well explained, especially considering the low Th abundance (<2 ppm) of this region. In addition, the central mare erupted earlier than other mare units within the Apollo basin, which seems to contradict the predictions of the postbasin loading-induced stresses model. Laboratory investigations of the Chang’E-6 mare basalt samples could possibly answer the above questions and provide new insight into the mare volcanic history of the lunar farside and the connections between mare volcanism and impact basin formation/evolution.

Correlative X-ray micro-nanotomography with scanning electron microscopy at the Advanced Light Source.

Geological samples are inherently multi-scale. Understanding their bulk physical and chemical properties requires characterization down to the nano-scale. A powerful technique to study the three-dimensional microstructure is X-ray tomography, but it lacks information about the chemistry of samples. To develop a methodology for measuring the multi-scale 3D microstructure of geological samples, correlative X-ray micro- and nanotomography were performed on two rocks followed by scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) analysis. The study was performed in five steps: (i) micro X-ray tomography was performed on rock sample cores, (ii) samples for nanotomography were prepared using laser milling, (iii) nanotomography was performed on the milled sub-samples, (iv) samples were mounted and polished for SEM analysis and (v) SEM imaging and compositional mapping was performed on micro and nanotomography samples for complimentary information. Correlative study performed on samples of serpentine and basalt revealed multiscale 3D structures involving both solid mineral phases and pore networks. Significant differences in the volume fraction of pores and mineral phases were also observed dependent on the imaging spatial resolution employed. This highlights the necessity for the application of such a multiscale approach for the characterization of complex aggregates such as rocks. Information acquired from the chemical mapping of different phases was also helpful in segmentation of phases that did not exhibit significant contrast in X-ray imaging. Adoption of the protocol used in this study can be broadly applied to 3D imaging studies being performed at the Advanced Light Source and other user facilities.

Unusual mineralization in basaltic andesite of submarine volcano Esmeralda (Mariana Island Arc)

The results of studies of a basaltic andesite sample complicated by a mineralized crack and voids, with a crack and gas voids filled with secondary mineralization dredged on the Esmeralda underwater volcano, are presented. A detailed comparative study of the mineral composition of the substance lining the crack, the space around the crack, and the part of basaltic andesite unaffected by secondary changes made it possible for the first time for the underwater Esmeralda volcano to establish the presence of an association of minerals that is not characteristic of unaltered volcanic rocks. In the intracrack space and adjacent zones of basaltic andesite, wide ranges of plagioclase composition were determined, isomorphism in the Fe-Ca-pyroxene series was studied, REE oxides, hydroxides and fluorohydroxides were studied, and variability in the composition of minerals in the magnetite-hematite series was shown. It is assumed that tectonic movements led to the emergence of permeable zones in the previously formed basaltic andesites through which new portions of the melt leaked. In a limited space, high fluid gas saturation, temperature and pressure made it possible to extract metal compounds from the melt and host rocks.

Basalt Alteration in a CO2–SO2 Atmosphere: Implications for Surface Processes on Venus

AbstractVenus' surface and interior dynamics remain largely unconstrained, due in great part to the major obstacles to exploration imposed by its 470°C, 90 bar surface conditions and its thick, opaque atmosphere. Flyby and orbiter‐based thermal emission data provide opportunities to characterize the surface composition of Venus. However, robust interpretations of such data depend on understanding interactions between the planet's surface basaltic rocks and its caustic carbon dioxide (CO2)‐dominant atmosphere, containing trace amounts of sulfur dioxide (SO2). Several studies, using remote sensing, thermodynamic modeling, and laboratory experiments, have placed constraints on basaltic alteration mineralogy and rates. However, constraints on the effects of SO2‐bearing reactions on basalts with diverse compositions remain incomplete. Here, we present new data from a series of gas‐solid reaction experiments, in which samples of two basalt compositions were reacted in an SO2‐bearing CO2 atmosphere, at relevant Venus temperatures, pressure, and oxygen fugacity. Reacted specimens were analyzed by scanning electron microscopy and scanning transmission electron microscopy using sample cross‐sections produced with focused ion beam milling. Surface alteration products were characterized, and their abundances estimated; subsurface cation concentrations were mapped to show the depth of alteration. We demonstrate that the initial development of reaction products progresses rapidly over the course of 30‐day runs. Alkaline basalt samples are coated by Na‐sulfate (likely thenardite, Na2SO4) and amorphous calcium carbonate (CaCO3) alteration products, and tholeiitic basalt samples are primarily covered by anhydrite (CaSO4), Fe‐oxide (FexOy: likely magnetite, Fe3O4), and other minor phases. These mineralogies differ from previous experiments in CO2‐only atmospheres.

Recording of ultra-low frequency electromagnetic emission during loading of a rock sample

The review of publications devoted to the study and features of the registration of electromagnetic emission observed during the loading of samples of rocks, metals, composite materials in laboratory conditions, as well as in areas of disintegration of rock massifs at mining sites is given. Electromagnetic emission observed during the destruction of rock samples in laboratory experiments and field conditions can appear itself not only in the high and low frequency ranges (1000–3·106 Hz and 500–1000 Hz, respectively), but also in the very low and ultra-low frequency (200–500 Hz and 0.01–200.00 Hz, respectively) ranges. However, the overwhelming majority of experimental studies of rock samples under the influence of a destructive load in laboratory conditions are aimed at measuring electromagnetic emission of the high frequency range. An instrumentation and measurement complex is described that allows recording electromagnetic emission in the ultra-low frequency range. The composition of the instrumentation and measurement complex includes magnetic modulation transducers of magnetic induction as magnetic field sensors. The methodology of laboratory experiments on recording electromagnetic signals arising from the influence of an external load on rock samples using an instrumentation and measuring complex is presented. An example of uniaxial loading of a basalt sample is given. When loading the sample under consideration, the amplitude of the electromagnetic emission pulses exceeds the background values of technogenic magnetic noise by two orders of magnitude. The high sensitivity of the magnetic modulation transducer of magnetic induction allows it to be used to register the components of magnetic induction in the process of destruction of rock samples in conditions of interference from technogenic magnetic noise. The results obtained are important for monitoring and forecasting the process of cracking before mining impacts, as well as for studying the geological environment and processes that generate low-frequency electromagnetic emission in the mining areas.

Intrasample osmium isotope disequilibrium in young volcanic rocks: Insights from a new progressive digestion procedure

Some young volcanic rocks have been found to possess intrasample Os-isotope heterogeneity. This has important implications for source tracing and dating. Here, we use a new procedure through which it is possible to sequentially extract, from a single aliquot, the 187Os/188Os ratio of: i) the surface contaminant(s) (hydrobromic acid leachate); ii) the residual bulk rock powder (Step I) and iii) the Os-bearing phases entrapped within silicates (Step II). We applied this technique to two young basaltic reference materials (RMs), USGS BHVO-2 and EN026 10D-3. The former samples the 1919 lava from the Kīlauea summit crater (Hawaii) and the latter is a basalt sample dredged from Mohns Ridge (Greenland Sea). Both rock standards have previously been shown to display large intrasample Os isotope heterogeneity. In addition to analyzing these RMs, we also analyzed the RM USGS BHVO-1 for comparison, as well as another sample from the Kīlauea 1919 summit eruption (Kil 1919-6) along with a picritic tholeiite from the Kīlauea Iki 1959 eruption.Our leaching results show that BHVO-2 is contaminated with a highly radiogenic and labile contaminant with 187Os/188Os ratio of 0.525 ± 0.021. Without leaching, the Step I 187Os/188Os ratios varied from 0.1399 ± 0.0013 to 0.1568 ± 0.0014 while those for Step II were uniform (average = 0.1286 ± 0.0006, N = 5). A comparison of Re, Mo concentrations and 187Os/188Os ratio of the leachates of BHVO-2 and its predecessor (BHVO-1) indicates that BHVO-2 was contaminated during preparation. After leaching, the Step I and Step II 187Os/188Os ratios of BHVO-1 and another sample (Kīlauea 1919-6) from the same lava flow are identical within error to that of the Step II ratio of BHVO-2. A picrite from the 1959 Kīlauea Iki eruption also analyzed using the new technique gives homogenous results for both the steps with an average 187Os/188Os ratio of 0.1302 ± 0.0005. The 187Os/188Os ratio of recent Kīlauea lavas is identical within error to that of the primitive upper mantle (=0.1296). The Kīlauea Os-isotope composition could represent a “common component” that occurs globally in many plumes. The Step I 187Os/188Os ratio of EN026 10D-3 is 0.136 with Step II ratio being 0.131 (N = 2). The Step II 187Os/188Os ratios are more radiogenic than the nearby Jan Mayen lavas (187Os/188Os = 0.124–0.129) that have been argued to influence the chemistry of the Western section of the Mohns Ridge basalt but fall within the range of the Primitive Upper Mantle. We also discovered that BHVO-1, KIL 1919-6, 1959 Kīlauea Iki picrite, and EN026 10D-3 show Os-isotope disequilibrium between the leachate and Step I, suggesting wall rock assimilation during magma ascent. The data set presented here indicates a need for re-evaluating the extent to which mantle heterogeneities influence the Os isotope composition of ocean basalts.

Platinum-Group Elements and Nb-Ta geochemistry of the Deccan basalts from Kumbharli and other Ghat sections and the Koyna Seismic Zone, Maharashtra (India): Crustal contamination and implication for sulfide saturation of the magma

The Deccan basalts from Kumbharli, Nadlapur, Bijaynagar, Hazarmacchi, and Surli Ghat sections (surface samples) and the Koyna borehole-7 (KBH-7, sub-surface samples) from Maharashtra (western India) demonstrate a two-stage crystallization process. Olivine and chromite were crystallized earlier in a shallow crustal magma chamber while clinopyroxene and plagioclase phenocrysts were crystallized in the sub-volcanic conduits forming the crystal mush, and carried to the surface by the evolved Fe-Ti-rich ascending basaltic magma. The high modal abundance of plagioclase at the top and clinopyroxene at the bottom part of the Kumbharli Ghat section is responsible for an increase in Sr and a decrease in Sc content towards the upper flows. The surface and sub-surface basalt samples contain Pd = 5–31 ppb, Pt = 4–15 ppb, Ir = 1–4 ppb, Ru = 1–3 ppb, and Rh = 3–5 ppb. Negative relations of Pd/Ir, Pd/Ru, and Pd/Rh with MgO from both sets of samples indicate partitioning of Ir, Ru, and Rh to early fractionated cumulus chromite (or olivine). Magnetite is a late crystallizing phase from the evolved Fe-Ti-rich basaltic magma. With an increasing modal abundance of magnetite, there is an increase of FeO total , TiO 2 , and V with Pd indicating fractionation of Pd by magnetite. Geochemical characters show that the surface basalt samples are less contaminated compared to the sub-surface KBH-7 basalts. High Nb (6.8–13.6 ppm) and low Ta (0.2–0.37 ppm) content and elevated Nb/Ta ratios of the surface samples from the ghat sections indicate the possible interaction of the basaltic magma with the carbonate metasomatized subcontinental lithospheric mantle (SCLM). On the other hand, a high degree of partial melting with limited crustal contamination can also elevate the Nb/Ta ratios of the basalts from the ghat sections. Deccan basalts from the study areas do not bear the signature of sulfide supersaturation and subsequent immiscible sulfide segregation. This is evidenced by their high chalcophile element concentrations (Ni = 79–103 ppm, Cu = 121–259 ppm) and ratios like Cu/Zr (≥ 1), Ni/MgO (13.7–21.8) with low Cu/Pd (2140–29938) compared to other Ni-Cu (PGE) sulfide mineralized continental flood basalts. The lack of crustal sulfur in the various contaminants is perhaps the main reason for this sulfide-undersaturated character of the Deccan basalts of the current study.

Assessment of mineral compositions on geo-mechanical time dependent plastic creep deformation

Understanding rock mechanical time-dependent plastic deformation enables the researchers to accurately predict rock responses during loading and unloading. This research focuses on the geomechanical aspects of hydrogen storage, particularly rock resistance to creep deformation under varying stresses and pressures. Modelling creep deformation in underground storage mediums has been overlooked and requires further consideration, as it is a critical, cyclical, time-dependent phenomenon essential for hydrogen containment. The study's novelty is demonstrated in its focus on geomechanical properties of rock minerals, providing insights that aid in site-selection criteria for hydrogen storage A creep deformation model with varying mineral compositions is used to assess creep deformation strain. In homogenous cases, calcite showed the highest resistance to creep deformation after three loading cycles, primarily due to its high Young's Modulus. As for the heterogenous cases, the results indicated that the mixture of calcite and quartz was the most creep-resistant rock composition. In terms of rock types, basalt samples demonstrated the highest resistance to creep deformation, while siltstone exhibited the highest susceptibility to deformation. It was observed that as the number of cycles increase, the rock mechanical stability decreases, hence optimizing the number of cycles is a must to ensure hydrogen geo-containment.

Geochronology and Petrogenesis of Late Carboniferous to Early Permian Basalts in the Central Lhasa Subterrane, Southern Tibet: Implications for the Evolution of the Sumdo Paleo‐Tethys Ocean

AbstractBasalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane, southern Tibet. Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo‐Tethys Ocean and its dynamic mechanism. Basalt samples from the Luobadui Formation in the Leqingla area, NW of Linzhou City in the central Lhasa subterrane, southern Tibet exhibit arc‐like geochemical signatures in a subduction‐zone tectonic setting characterized by high Al2O3 and low TiO2 contents, fractionated REE patterns with low Nb/La ratios and high LREE concentrations, and negative HFSE anomalies. Based on their higher Th/Ce, Nb/Zr, and lower Ba/Th, Pb/Nd ratios, slightly negative to positive εNd(t) values, and the relatively high Sr‐Pb isotopic compositions, these samples were probably derived from partial melting of a depleted mantle source of garnet + spinel lherzolite, metasomatized by subducted sediments around 297 Ma. Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine, clinopyroxene and minor plagioclase during magma ascent and eruption. It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo‐Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.

Radioactive Attenuation Using Different Types of Natural Rocks.

Humans benefit from nuclear technology, but it also generates nuclear radiation that is bad for both the environment and human health. The serious issue of radiation leakage affects many technological applications. Shielding is required to protect both users and the environment from negative side effects. This work describes the radioactive attenuation properties of some natural rocks, such as claystone, bentonitic claystone, bentonitic shale, sandstone, and basalt using a NaI(Tl) detector. The mass attenuation coefficients μm of these rocks at various photon energies, half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP) were determined. The validation of obtained values of μm was carried out against the theoretical calculations from the XCOM program, and the correlation factor and relative deviation between the two methods were evaluated. It was noted that basalt samples exhibit superior shielding parameters when compared to other rock samples. Also, the concentrations of naturally occurring radioactive elements (238U, 226Ra, 232Th, and 40K) were measured, allowing for the calculation of environmental hazard indices and assessment of attenuation (%) efficiency for certain natural rocks, such as bentonite, sandstone, and basalt. The results revealed that increasing the thickness of Basalt-AZ from 1.5 cm to 2 cm results in an approximate 11% rise in attenuation percentage, with values reaching 77.12%, 67.2%, 67.65%, and 59.8% for NMA-U, IAEA-Th, IAEA-Ra, and IAEA-K, respectively.

The Underwater Esmeralda Volcano (Mariana Island Arch) and some Features of the Composition of its Composition Rocks

A generalization of the available original data and literature data on the geological and geophysical knowledge of the underwater volcano Esmeralda, located in the Mariana Island Arc, has been carried out. As a result of studying the rocks dredged during the 4th and 5th cruises of the R/V Vulkanolog at the present level, new data were obtained on the silicate and rare-element composition of the rock samples that make up this underwater volcano. It has been established that the studied volcanic edifice is composed of five types of rocks: basalts, basaltic andesites, dacites, gabbro, and basanites. For the first time, samples of dacite and basanite have been discovered, indicating that the petrochemical diversity of the underwater volcano Esmeralda is wider than previously thought. All dredged rocks are characterized by a slightly increased content of incoherent elements LILE and HFSE. The studies carried out made it possible to attribute the main part of the dredged rocks to the association of island-arc ferruginous tholeiites (IAB, IAT) and only the composition of a single sample of alkaline basalt (basanite) falls into the field of alkaline basalts of oceanic islands (OIB, OIA). The increased content of iron in plagioclase phenocrysts confirms that the rocks belong to the high-iron tholeiite association.

Effects of Olivine Alteration on Micro-Internal Structure and Geomechanical Properties of Basalts and Strength Prediction in These Rocks

Understanding the variations of the geomechanical properties of rocks in geotechnical projects from the perspective of their micro-structures and alteration conditions is crucial for ensuring the safety and long-term sustainability of rock engineering (e.g., tunnels, slopes, mining). This study was carried out on basaltic rocks from the Akcakale and Mersin vicinities in Trabzon City to investigate the geomechanical and mineralogical properties in comparison with the uniaxial compressive strength (UCS). This study was conducted in three different locations (A1, M2, and M3) where the basaltic rocks outcrop belongs to the same lithological formation. During this study, quite different results were obtained from the basalt samples taken from different sites and the reasons for these differences were examined by petrographic, SEM (Scanning Electron Microscopy), and EDS (Energy Dispersive Spectroscopy) analyses. Since the number of comprehensive studies on basalts is very limited, this study aims to investigate practical and useful equations in the estimation of the UCS for various alteration conditions. Statistically, significant relationships were observed between geomechanical properties with the UCS and serpentinization rate (SR). This study revealed that the serpentinization of the olivine mineral is the most important factor causing the differences in the experimental results. The proposed equations for estimating the UCS are particularly significant for geotechnical applications where direct sampling is challenging, such as in weak-rock environments.

Geological context of the Chang’e-6 landing area and implications for sample analysis

Research on returned samples can provide ground truth for the study of the geological evolution history of the Moon. However, previous missions all collected samples from the near side of the Moon, which is significantly different from the far side of the Moon in terms of the thickness of the lunar crust, magma activity, and composition. Therefore, the samples from the far side of the Moon are of great significance for a comprehensive understanding of the history of the Moon. China's Chang'e-6 (CE-6) probe has successfully landed on the lunar far side and will return samples in the coming days. With the precise location of the CE-6 landing site, a detailed analysis of the geological background is conducted in this research. The landing site of CE-6 is within the Apollo crater, which is inside the largest impact basin on the Moon, i.e., the South Pole-Aitken (SPA) basin. According to the numerical simulation of the formation process of the SPA basin, CE-6 landed at the edge of the SPA impact melting zone, which is presumably composed of impact melt of the lunar mantle. The Apollo crater subsequently excavated deep material again, which constitutes the basement of the CE-6 landing area. Later, erupted basalt covered these basement rocks, and they also constitute the main source of the CE-6 samples. Based on the dating method of crater size-frequency distribution, we find that the basalt is ∼2.50 Ga. The CE-6 samples also possibly contain basement rocks as excavated and ejected by craters, and they can provide crucial information for our understanding of lunar geological history along with the basalt samples.

Continental flood basalts sample oxidized mantle sources

Large igneous provinces (LIP) are vast (0.2 to >1 Mkm3) outpourings of basaltic lava and voluminous intrusions of magmas that have had important environmental consequences, in many cases leading to immense greenhouse gas release and mass extinctions. Magmatic oxygen fugacity (fO2) influences the chemistry of volcanic gases and is an important parameter for examining the links between LIP eruptions and environmental change. To constrain the fO2 of LIP magmas, we report olivine elemental chemistry of 399 crystals from a set of fifteen olivine-rich LIP samples, spanning in age from the Proterozoic (∼1270 Ma) to the Miocene (∼17 Ma). Concentrations of V in olivine are used to show that mafic LIP lavas erupted at +1.20 ± 0.95 ΔFMQ, on average more oxidized than mid ocean ridge basalts (MORB) at −0.28 ± 0.28 ΔFMQ. Mafic LIP magmas show a much larger range than MORB, however. Additionally, fO2 shows a negative correlation with parental magma MgO content, with high MgO lavas approaching the MORB range. This correlation is likely due to sampling of a heterogeneous mixture of oxidized and reduced lithologies, as also sampled by ocean island basalts (OIB). Correlation between fO2 and isotopic ratios such as 143Nd/144Nd demonstrates that the oxidized endmember is geochemically enriched, and may result from subduction recycling of oxidized surficial materials. The high fO2 of primitive LIP magmas demonstrate that they largely emitted oxidized gases during eruption, and furthermore, that LIP magmas associated with mass extinctions have similar magmatic fO2 to those that are not. Global plate tectonic position, magnitude and duration of LIP volcanic eruptions and magmatic degassing, as well as interaction with sedimentary basins in the crust - but not mantle source fO2 - are likely to be the critical factors for whether a LIP was associated with a mass extinction.

Assessing lunar paleointensity variability during the 3.9 - 3.5 Ga high field epoch

Numerous paleomagnetic studies suggest that a lunar dynamo, with surface field intensities potentially as high as 40-100 µT, existed between ∼3.9 Ga and ∼3.5 Ga. This period is referred to as the High Field Epoch (HFE). However, the debate over the origin of magnetization recorded in lunar rocks still persists. In addition, whether the Moon could have sustained a continuously strong dynamo during the HFE remains unclear. To unravel the origin of magnetization preserved in lunar rocks and to better characterize the evolution of the ancient lunar dynamo, we conducted a comprehensive set of experiments including rock magnetic tests, electron microscopy, and paleomagnetic investigations on four HFE-aged Apollo 11 mare basalt samples: 10003, 10044, 10069, and 10071. Rock magnetic experiments and electron microscopy indicate that the remanence carriers are kamacite grains of varying sizes and domain states. Sample 10003 recorded a paleointensity of 54.10 ± 4.66 µT. Sample 10044, which was shocked (peak pressure >5 GPa), did not preserve a stable high coercivity remanent magnetization. Samples 10069 and 10071 recorded paleointensities of 61.46 ± 26.09 µT and 10.69 ± 2.87 µT, respectively. A series of hydrostatic pressure experiments, isothermal remanent magnetization (IRM) acquisition experiments, and viscous remanent magnetization (VRM) tests preclude the possibility of our samples containing shock remanent magnetization from transient impact-generated fields, IRM acquisition from exposure to spacecraft fields, and VRM acquisition from exposure to the Earth magnetic field. Overall, our study suggests that the source of these magnetizations was likely the lunar dynamo and may indicate nearly order-of-magnitude magnetic field fluctuations during the HFE.

Thermo‐physical characterisation of natural rocks and impact analysis of variations in their thermo‐physical properties on thermal storage performance

AbstractIn this study, the thermal characterisation of natural rock samples from Zimbabwe for low‐temperature industrial thermal energy storage (TES) applications was carried out. Thermal stability, specific heat capacity, thermal diffusivity, thermal conductivity and density were determined. Variations in these parameters were evaluated and their impact on thermal storage performance was analysed. Basalt and dolerite samples from different locations were found to have average specific heat capacities of 826 and 853 J/kg K, respectively, at room temperature. Insignificant variations were observed with differences of 3.4% for basalt and 1.7% for dolerite samples. Also, negligible differences of 0.3% and 0.7% in densities for rocks of the same type but of different origins were obtained for basalt and dolerite samples, respectively. However, significant variations in thermal diffusivity of all the igneous and metamorphic samples were observed with quartzite rock exhibiting the highest value of 2.1 × 10−6 m2/s, while the values for the other samples range from 0.9 × 10−6 to 1.6 × 10−6 m2/s. This implies that the thermal efficiency of sensible TES systems that use different or the same rock types from different locations can be significantly high to be overlooked. Thermo‐gravimetric analysis results revealed that the rock samples studied have good thermal stability for low‐temperature heat storage applications.

A new look at the geodynamic development of the Ediacaran–early Cambrian forearc basalts of the Tannuola-Khamsara Island Arc (Central Asia, Russia): Conclusions from geological, geochemical, and Nd-isotope data

Abstract Oceanic igneous rocks throughout the Altai-Sayan Fold Belt (ASFB) in central-southern Siberia are often considered to be late Precambrian–early Paleozoic accreted elements of oceanic crust – often of uncertain paleogeographic or geodynamic origin. We explore the role of suprasubduction zone settings in the formation of different ASFB terranes. Our study offers a non-accretionary perspective on the tectonomagmatic development of basalt-bearing units in the ASFB on the example of the forearc terrane of the Ediacaran–early Cambrian Tannuola-Khamsara island arc (herein termed Sayan-Tuvan forearc zone). We describe the geochemistry, structural geology, and stratigraphic relations of basalts of the Aldynbulak, Uttug-Khaia, and Chingin formations, which are integral parts of the Sayan-Tuvan forearc zone. The Aldynbulak basalt samples mainly fall in the compositional fields of ocean island basalts and enriched mid-ocean ridge basalts (E-MORB) and likely derived from a deep mantle source. The Uttug-Khaia and Chingin basalts are N- and E + T-MORB-like basalts, carrying forearc geochemical signatures. Specifically, the Chingin Formation contains boninite dikes and is associated with a boninite-bearing ophiolite. Boninites are commonly associated with forearc magmatism and thus a forearc formation setting is likely. Tectonic and stratigraphic considerations imply that the Aldynbulak basalts formed first, followed by the Uttug-Khaia and later the Chingin basalts and boninites. A schematic model, involving decompression melting of the mantle, is proposed for the development of the studied forearc basalt suites that are linked with the growth of the Tannuola-Khamsara island arc system 580–540 million years ago.

Mantle Sources and Geochemical Evolution of the Picture Gorge Basalt, Columbia River Basalt Group

The Columbia River Basalt Group (CRBG) is the youngest continental flood basalt province, proposed to be sourced from the deep-seated plume that currently resides underneath Yellowstone National Park. If so, the earliest erupted basalts from this province, such as those in the Picture Gorge Basalt (PGB), aid in understanding and modeling plume impingement and the subsequent evolution of basaltic volcanism. Using geochemical and isotopic data, this study explores potential mantle sources and magma evolution of the PGB. Long known geochemical signatures of the PGB include overall large ion lithophile element (LILE) enrichment and relative depletion of high field strength elements (HFSE) typical of other CRBG main-phase units. Basaltic samples of the PGB have 87Sr/86Sr ratios on the low end of the range displayed by other CRBG lavas and mantle-like δ18O values. The relatively strong enrichment of LILE and depletion of HFSE coupled with depleted isotopic signatures suggest a metasomatized upper mantle as the most likely magmatic source for the PGB. Previous geochemical modeling of the PGB utilized the composition of two high-MgO primitive dikes exposed in the northern portion of the Monument Dike swarm as parental melt. However, fractionation of these dike compositions cannot generate the compositional variability illustrated by basaltic lavas and dikes of the PGB. This study identifies a second potential parental PGB composition best represented by basaltic flows in the extended spatial distribution of the PGB. This composition also better reflects the lowest stratigraphic flows identified in the previously mapped extent of the PGB. Age data reveal that PGB lavas erupted first and throughout eruptions of main-phase CRBG units (Steens, Imnaha, Grande Ronde Basalt). Combining geochemical signals with these age data indicates cyclical patterns in the amounts of contributing mantle components. Eruption of PGB material occurred in two pulses, demonstrated by a ~0.4 Ma temporal gap in reported ages, 16.62 to 16.23 Ma. Coupling ages with observed geochemical signals, including relative elemental abundances of LILE, indicates increased influence of a more primitive, potentially plume-like source with time.

Origins of titanite in the Emeishan basalts: Implications for niobium enrichment in the upper Permian Xuanwei Formation, eastern Yunnan–western Guizhou region, Southwest China

The occurrence of the polymetallic Nb layer in the upper Permian Xuanwei Formation in southwest China has been documented extensively. The origin of Nb, as well as other metals like Zr and rare earth elements (REEs), has received much research attention; however, the source of these elements remains enigmatic. In recent studies, an uncommon Nb-rich titanite (CaTiSiO5) has been discovered in the Emeishan basalts beneath the Xuanwei Formation in the eastern Yunnan–western Guizhou region. However, its origins and genetic relationship to the polymetallic Nb layer remain unclear. In this study, we used in situ microanalytical and UPb dating techniques to investigate the titanite in these Emeishan basalts. Our objectives were to determine the origins of the titanite and its relationship to the polymetallic Nb layer in the lowermost Xuanwei Formation. The basalts consist of approximately 70%–90% phenocrysts and 10%–30% matrix. The phenocrysts are mainly coarse-grained (>30 μm) plagioclase, clinopyroxene, and Fe-Ti oxides (ilmenite and magnetite), whereas the matrix comprises mainly fine-grained (<30 μm) titanite and glass. The titanite is hypautomorphic or xenomorphic and occurs as small, disseminated grains within the matrix. The titanite U-Pb dating of basalt sample reveals a Tera–Wasserburg lower intercept age of ca. 259.6 ± 4.3 Ma, which corresponds to the age of the eruption timing of Emeishan large igneous province (ELIP; 260.9–257.4 Ma). This implies that the formation of titanite within the matrix can be attributed to rapid cooling of residual melt subsequent to fractional crystallization of a substantial quantity of phenocrysts. The LA-ICP-MS analysis reveals that the trace element composition of titanites in the Emeishan basalts exhibits similarities to weathering-type titanite, as evidenced by elevated LaN/YbN ratios and low concentrations of Y, ΣREE, Th, and U, as well as reduced Lu/Hf and Th/U ratios. Thus we propose that these titanites crystallised during the late-stage magmatic evolution, resulting from magmatic fractional crystallization and subsequent weathering alteration. The materials required for titanite crystallization in the basalt matrix primarily sourced from the residual melt, while weathering dissolution of plagioclase and clinopyroxene in the phenocrysts may have provided additional Ca and Eu for titanite formation. As weathering progressed, the Nb-rich titanite underwent a transformation into Nb-rich anatase and gradually became enriched in the regolith. This material was subsequently transported to nearby basins and deposited in terrestrial environments, resulting in formation of the polymetallic Nb layer in the lowermost Xuanwei Formation. Our findings provide insights into the origins and evolution of titanite in the Emeishan basalts, as well as formation of the polymetallic Nb layer in the lowermost Xuanwei Formation in the eastern Yunnan–western Guizhou region, southwest China.

Emplacement of shergottites in the Martian crust inferred from three‐dimensional petrofabric and crystal size distribution analyses

AbstractShergottites are mafic to ultramafic igneous rocks that represent the majority of known Martian meteorites. They are subdivided into gabbroic, poikilitic, basaltic, and olivine–phyric categories based on differences in mineralogy and textures. Their geologic contexts are unknown, so analyses of crystal sizes and preferred orientations have commonly been used to infer where shergottites solidified. Such environments range from subsurface cumulates to shallow intrusives to extrusive lava flows, which all have contrasting implications for interactions with crustal material, cooling histories, and potential in situ exposure at the surface. In this study, we present a novel three‐dimensional (3‐D) approach to better understand the solidification environments of these samples and improve our knowledge of shergottites' geologic contexts. Shape preferred orientations of most phases and crystal size distributions of late‐forming minerals were measured in 3‐D using X‐ray computed tomography (CT) on eight shergottites representing the gabbroic, poikilitic, basaltic, and olivine–phyric categories. Our analyses show that highly anisotropic, rod‐like pyroxene crystals are strongly foliated in the gabbroic samples but have a weaker foliation and a mild lineation in the basaltic sample, indicating a directional flow component in the latter. Star volume distribution analyses revealed that most phases (maskelynite, pyroxene, olivine, and oxides/sulfides) preserve a foliated texture with variable strengths, and that the phases within individual samples are strongly to moderately aligned with respect to one another. In combination with relative cooling rates during the final stages of crystallization determined from interstitial oxide/sulfide crystal size distribution analyses, these results indicate that the olivine–phyric samples were emplaced as shallow intrusives (e.g., dikes/sills) and that the gabbroic, poikilitic, and basaltic samples were emplaced in deeper subsurface environments.