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BACKGROUND: Underground research laboratories (URLs) provide a window on the deep biosphere and enable investigation of potential microbial impacts on nuclear waste, CO2 and H2 stored in the subsurface. We carried out the first multi-year study of groundwater microbiomes sampled from defined intervals between 140 and 400 m below the surface of the Horonobe and Mizunami URLs, Japan. RESULTS: We reconstructed draft genomes for > 90% of all organisms detected over a four year period. The Horonobe and Mizunami microbiomes are dissimilar, likely because the Mizunami URL is hosted in granitic rock and the Horonobe URL in sedimentary rock. Despite this, hydrogen metabolism, rubisco-based CO2 fixation, reduction of nitrogen compounds and sulfate reduction are well represented functions in microbiomes from both URLs, although methane metabolism is more prevalent at the organic- and CO2-rich Horonobe URL. High fluid flow zones and proximity to subsurface tunnels select for candidate phyla radiation bacteria in the Mizunami URL. We detected near-identical genotypes for approximately one third of all genomically defined organisms at multiple depths within the Horonobe URL. This cannot be explained by inactivity, as in situ growth was detected for some bacteria, albeit at slow rates. Given the current low hydraulic conductivity and groundwater compositional heterogeneity, ongoing inter-site strain dispersal seems unlikely. Alternatively, the Horonobe URL microbiome homogeneity may be explained by higher groundwater mobility during the last glacial period. Genotypically-defined species closely related to those detected in the URLs were identified in three other subsurface environments in the USA. Thus, dispersal rates between widely separated underground sites may be fast enough relative to mutation rates to have precluded substantial divergence in species composition. Species overlaps between subsurface locations on different continents constrain expectations regarding the scale of global subsurface biodiversity. CONCLUSIONS: Our analyses reveal microbiome stability in the sedimentary rocks and surprising microbial community compositional and genotypic overlap over sites separated by hundreds of meters of rock, potentially explained by dispersal via slow groundwater flow or during a prior hydrological regime. Overall, microbiome and geochemical stability over the study period has important implications for underground storage applications.

The juvenile Neoproterozoic basement of the Arabian Shield is overlain with angular unconformity by a voluminous Cambro-Ordovician cover sequence known as the Saq Formation and Wajid Group. Provenance studies of this vast siliciclastic cover over the Saudi Arabian part of the Arabian-Nubian Shield (ANS) have to date been based solely on U-Pb zircon data and heavy minerals. We present the first combined in-situ U-Pb, δ18O and Lu-Hf isotopic data for detrital zircon from the Saq and Wajid units exposed along the northeastern margin and southern part of the Arabian Shield. U-Pb age spectra reveal prominent age peaks at ca. 0.8–0.55 Ga and 1.1–0.9 Ga with subordinate peaks at ca. 2.2–1.7 Ga and 2.7–2.5 Ga. The δ18O secular variation mirrors global compilations with Archaean zircon defining a restricted δ18O range of ca. 4.0–8.0 ‰ and younger zircon showing wide variation in δ18O up to ca. 14 ‰. The ca. 0.8–0.55 Ga age peak has the largest variation in εHf(t) with about half of all these Neoproterozoic zircon grains being juvenile (εHf(t) > 5), which are interpreted to be sourced from the juvenile terranes of the ANS. Neoproterozoic zircon with evolved εHf(t) signatures require a more distal source beyond the ANS. As extensive ca. 1.1–0.9 Ga crust is lacking in the vicinity of the ANS, the ca. 1.1–0.9 Ga age peak is interpreted to be derived from either contemporaneous orogenic belts in Central Africa or recycled from older sedimentary rocks containing these age components. Extreme variations in δ18O of post–Archaean zircon, together with the evolved εHf(t), indicate crustal thickening and increased incorporation of supracrustal material associated with collisional orogenesis. The remarkable similarities in age spectra and isotopic compositions of the Saq Formation and Wajid Group sandstones with those from other regions in northern Gondwana indicate a continental–scale homogenization and dispersion process. [ABSTRACT FROM AUTHOR]

This paper presents a thorough investigation into the evolutionary patterns of pore–fissure networks and their anisotropic connectivity characteristics within oil shale. We utilized CT digital core analysis after steam heating at varying temperatures. The study revealed that untreated oil shale has a densely compacted internal structure without distinguishable pore–fissure networks. However, steam exposure at temperatures exceeding 314 °C induced penetrating cracks along the bedding plane. This significantly modifies the mass transfer properties in the parallel bedding direction. Beyond 382 °C, continuous thermal cracking occurred, leading to numerous fissures along sedimentary bedding planes. This was accompanied by clustered pores formed through organic matter pyrolysis. These aggregated pores gradually interconnected adjacent parallel fissures, forming distinctive pore–crack clusters. Notably, as the temperature surpassed 500 °C, these pore–crack clusters continued to expand perpendicular to the lamination plane, profoundly influencing the mass transfer performance in this orientation. This phenomenon underscores the fundamental mechanism altering oil shale's mass transfer behavior perpendicular to the layer plane. From the perspective of percolation theory, the percolation threshold parallel to the lamination orientation was approximately 3%, with the transition around 300 °C. Conversely, the percolation threshold vertical to the sedimentary rock layers was approximately 14%, with the transition at temperatures surpassing 500 °C. [ABSTRACT FROM AUTHOR]

Abstract\nKEY POINTSTwelve hundred whole-rock compositions of the Proterozoic and Paleozoic rocks of Tasmania were compiled from a range of published and unpublished sources. We used these data to establish a chemostratigraphic evolution of the island and to resolve several problems in Tasmanian geology. Six chemostratigraphic mega-sequences were defined for Tasmania. The major events that separate these sequences are the onset of continental rifting (ca 700 Ma), arc–continent collision (ca 515 Ma), post-collisional volcanism (506 Ma) and then the return to continental conditions (500 Ma). Within this large-scale classification, we recognised smaller-scale changes in provenance. Within the Mesoproterozoic, there is a trend to more mafic rocks in the source region, which is interrupted by a short period where granites were prominent in the provenance. The Mesoproterozoic rocks of King Island have a subtly different provenance from the shallow water siliciclastic rocks of the Rocky Cape Group. The distribution of Cr across Tasmania can be attributed to two different events. First, the primitive basalts associated with Cryogenian continental rifting introduced a Cr signature associated with high TiO2. The ophiolite obduction event in the Cambrian produced a second Cr enrichment event dominated by chromite from supra-subduction-zone peridotite. These two events can be differentiated by the composition of the sedimentary rocks but are more clearly defined by the composition of detrital spinels. Within the East Tasmanian terrane, a trend to less weathered sources reflects the influx of young volcanic detritus at the end of the Silurian.The major tectonic events in Tasmania can be recognised from the composition of sedimentary rocks.The West Tasmania terrane can be subdivided into five chemostratigraphic mega-sequences.There are two major events that introduce high Cr anomalies into Tasmanian strata. [ABSTRACT FROM AUTHOR]

NASA's Mars 2020 mission has initiated collection of samples from Mars' Jezero Crater, which has a wide range of ancient rocks and rock types from lavas to lacustrine sedimentary rocks. The Mars Sample Return (MSR) Campaign, a joint effort between NASA and ESA, aims to bring the Perseverance collection back to Earth for intense scientific investigation. As the first return of samples from a habitable world, there are important challenges to overcome for the successful implementation of the MSR Campaign from the point of sample collection on Mars to the long-term curation of the samples on Earth. In particular, the successful execution of planetary protection protocols adds well-warranted complexity to every step of the process from the two MSR Program flight elements to the ground element at the sample receiving facility (SRF). In this contribution, we describe the architecture of the MSR Campaign, with a focus on infrastructure needs for the curation (i.e., the clean storage, processing, and allocation) of pristine Martian samples. Curation is a science-enabling and planetary protection-enabling activity, and the curation practices described in this contribution for the SRF and any long-term curation facility will enable the sample safety assessment, initial scientific investigations of the samples, and establish the MSR collection as a scientific resource that will enable generations of science and discovery through studies of the returned Mars samples. The planetary protection and curation processes established for MSR will provide critical insights into potential future sample return missions from other habitable worlds like Enceladus and Europa. [ABSTRACT FROM AUTHOR]

It is well known that the sedimentary rock record is both incomplete and biased by spatially highly variable rates of sedimentation. Without absolute age constraints of sufficient resolution, the temporal correlation of spatially disjunct records is therefore problematic and uncertain, but these effects have rarely been analysed quantitatively using signal processing methods. Here we use a computational process model to illustrate and analyse how spatial and temporal geochemical records can be biased by the inherent, heterogenous processes of marine sedimentation and preservation. This confirms that sedimentary hiatuses can span a substantial proportion of geological time, caused by inherent geological processes. Moreover, even in marine geochemical records that are essentially spatially continuous and complete, the signal is irreversibly disguised in time as lower frequency signals by an aliasing effect. We demonstrate that Nyquist's theorem correctly predicts these biased signatures, proving that aliasing can be caused by cyclical and multiscale relative sea-level changes - a natural sampling effect. Our combined results show that deeper marine records are significantly more likely to provide unaliased environmental signatures. Also, some proxy residence times will be sufficiently long that they average over aliased frequencies, cancelling these in the geochemical record. And field observations of changes in sedimentation rate (such as hiatuses, condensation, or lateral expansion) can be used to infer possible aliasing. Where aliasing by natural sampling occurs, this cannot be undone simply by increasing sample resolution (density): aliasing is caused by an absence of sedimentary record, which by definition cannot be sampled at all. To overcome these issues, we propose that spatially separated aliased records may still be correctly correlated in age, and true geochemical cycles inferred, if a paired-sampling strategy informed by local stratigraphy is adopted. In this, two (or more) closely-spaced samples are analysed at each sampling point instead of only one, after which aliased cycles are inferred from geochemical gradients. [ABSTRACT FROM AUTHOR]

The Biggenden gold-bearing Fe skarn deposit in southeast Queensland, Australia, is a calcic magnetite skarn that has been mined for Fe and gold (from the upper portion of the deposit). Skarn has replaced volcanic and sedimentary rocks of the Early Permian Gympie Group, which formed in different tectonic settings, including island arc, back arc, and mid-ocean ridge. This group has experienced a hornblende-hornfels grade of contact metamorphism due to the intrusion of the Late Triassic Degilbo Granite. The intrusion is a mildly oxidized I-type monzogranite that has geochemical characteristics intermediate between those of granitoids typically associated with Fe-Cu-Au and Sn-W-Mo skarn deposits. The skarn mineralogy indicates that there was an evolution from prograde to various retrograde assemblages. Prograde garnet (Adr11-99Grs1-78Alm0-8Sps0-11), clinopyroxene (Di30-92Hd7-65Jo0-9), magnetite, and scapolite formed initially. Epidote and Cl-bearing amphibole (mainly ferropargasite) were the early retrograde minerals, followed by chlorite, calcite, actinolite, quartz, and sulfides. Late-stage retrograde reactions are indicated by the development of nontronite, calcite, and quartz. Gold is mainly associated with sulfide minerals in the retrograde sulfide stage. The fluids in equilibrium with the ore-stage calcites had δ13C and δ18O values that indicate deposition from magmatically derived fluids. The calculated δ18O values of the fluids in equilibrium with the skarn magnetite also suggest a magmatic origin. However, the fluids in equilibrium with epidote were a mixture of magmatic and meteoric water, and the fluids that deposited chlorite were at least partly meteoric. δD values for the retrograde amphibole and epidote fall within the common range for magmatic water. Late-stage chlorite was deposited from metasomatic fluids depleted in deuterium (D), implying a meteoric water origin. Sulfur isotopic compositions of the Biggenden sulfides are similar to other skarn deposits worldwide and indicate that sulfur was most probably derived from a magmatic source. Based on the strontium (87Sr/86Sr) and lead (206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb) isotope ratios, the volcanic and sedimentary rocks of the Gympie Group may have contributed part of the metals to the hydrothermal fluids. Lead isotope data are also consistent with a close age relationship between the mineralization at Biggenden and the crystallization of the Degilbo Granite. Microthermometric analysis indicates that there is an overall decrease in fluid temperature and salinity from the prograde skarn to retrograde alterations. Fluid inclusions in prograde skarn calcite and garnet yield homogenization temperatures of 500 to 600 °C and have salinities up to 45 equivalent wt % NaCl. Fluid inclusions in quartz and calcite from the retrograde sulfide-stage homogenized between 280 and 360 °C and have lower salinities (5–15 equivalent wt % NaCl). In a favored genetic model, hydrothermal fluids originated from the Degilbo Granite at depth and migrated through the shear zone, intrusive contact, and permeable Gympie Group rocks and leached extra Fe and Ca and deposited magnetite upon reaction with the adjacent marble and basalt. [ABSTRACT FROM AUTHOR]

The effects of high debris content on pore structure in tight sandstone reservoirs tight sandstone reservoirs are multifaceted. Pore structure is an important factor controlling reservoir quality. Clarifying the effects of different types of rock debris on reservoirs is necessary to study the pore structure and their control factors of tight sandstones. The Western Sichuan Depression with complex rock components, containing multiple types of rock debris, leads to strong heterogeneity of pore throats, so it is necessary to study the factors controlling the development of different types of pore throats in tight reservoirs. In this paper, the Fourth member of Xujiahe Formation (T3x4) is taken as the research object. Based on high-pressure mercury intrusion experiments and the fractal theory, the types of pore throats and their heterogeneity in tight reservoirs were studied, the relationship of fractal dimensions with reservoir physical properties, pore structure, and rock compositions were investigated, and then the controlling factors for the development of different types of pore throats are clarified. The studies show that there are four types of pore throats developed in the T3x4 of the western Sichuan depression, including primary intergranular pore-throats (>350 nm), residual intergranular pore-throats (75–350 nm), dissolution pore-throats (16–75 nm), and intercrystalline pore-throats (<16 nm), among which the homogeneity of dissolution pore-throats are the best, followed by residual intergranular pore-throats and intercrystalline pore-throats, and the primary intergranular pore-throats the most heterogeneous. The permeability has a better relationship with the proportion and fractal dimension of primary intergranular pore-throats and residual intergranular pore-throats of tight reservoir of the Xujiahe Formation. The relation-ship between porosity and the proportion and fractal dimension of primary intergranular pore-throats and dissolution pore-throats is better. Brittle minerals such as quartz and metamorphic debris, as well as early developed films of chlorite and illite mainly control the development of intergranular pore-throats. Potassium feldspar mainly controls the development of dissolution pore-throats, while sedimentary rock debris, volcanic debris, and kaolinite play a destructive role for all types of pore-throats. The high-quality reservoirs in the T3x4 are controlled by the development of primary intergranular pore throats and dissolution pore throats, and they are mainly developed in environments with strong hydrodynamic conditions, large rock grain sizes, high content of brittle minerals such as quartz and metamorphic debris, extensive development of chlorite and illite films, and low content of sedimentary rock debris, matrix, and cemented materials. This study is of guiding significance in clarifying the causes of heterogeneity in different types of pore-throat systems in tight sandstones and the formation mechanism of high-quality reservoirs in tight sandstones with high content of debris. [ABSTRACT FROM AUTHOR]

Dynamic processes of the oceanic crust of seamounts trapped in continental sutures are poorly understood. The discovery and analysis of seamount sequences in the Yarlung Zangbo suture zone allowed us to detect vertical lithospheric movements of the eastern Neo-Tethys Ocean. In this study, we used petrological, geochemical, facies, paleontological, and stratigraphic methods to study composite blocks of mafic and sedimentary rocks in the Zhongba area of Xizang, China. Radiolarian fossils indicate an (early) Early Cretaceous age. Petrofacies and geochemistry show that most basalts occur as pillow lava and are enriched in light rare earth elements and high field strength elements, which suggests an oceanic-island basalt tectonic setting. Sedimentary lithofacies are grouped into breccias, shales, cherts, and limestones (ooid and cortoid grainstone microfacies). Three types of contact between basaltic basements and caps were identified as regular, talus, and erosive. These results demonstrate that two more superposed seamounts exist in the western Yarlung Zangbo suture zone than was known previously, and they comprise at least eight seamount sequences of basalts to sediments. Cap lithofacies and seamount textures illustrate that overall, the Zhongba paleo-seamounts record multiple cycles of abrupt deepening to shallowing, with water depth variations of ~3000 m to ~5 m due to multiple episodes of quick subsidence and uplift of seamounts (lithospheric "ups and downs"). The model of oceanic bypass recurrence and plume rejuvenation is hypothesized to explain the dynamic subsidence and uplift. While plume activities produced the mafic basement and considerable buoyancyrelated lift, oceanic crust bypassed drift, created distance from the plumes, and led to cooling, loss of buoyancy, and rapid subsidence. This model provides a new approach to interpret the evolution of oceanic crusts that have disappeared. [ABSTRACT FROM AUTHOR]

Stable sedimentary basins with complex evolutionary histories generally develop various epigenetic resources, such as sandstone-type uranium deposits. However, the genetic linkage between basin evolution and subsequent uranium mineralization remains unclear. Detrital zircon is a robust mineral, and its U-Pb ages and Lu-Hf isotopes are essential for tracing the evolution of sedimentary basins. The Ordos Basin is the largest intracontinental basin and uranium deposit region in the North China Craton. It consists of Cambrian to Ordovician marine deposits and Carboniferous to Jurassic terrestrial successions, and the origins of the terrigenous clastic sequences are dominantly influenced by the neighboring orogenic belts. This study presents new whole-rock elemental data, detrital zircon U-Pb ages, and Lu-Hf isotopes for the sandstones from the Jurassic Zhiluo Formation of the northern Ordos Basin. With data from the Paleozoic sedimentary rocks of the basin and the southern Central Asian Orogenic Belt, this study aimed to determine sediment provenances, the evolution of the northern Ordos Basin, and the potential implications for uranium mineralization. Detrital zircons from the Zhiluo Formation are generally rounded and preserve magmatic zoning structures. Their ages display four populations, 330-245 Ma, 470-350 Ma, 2100-1650 Ma, and 2750-2200 Ma, which are consistent with the tectono-thermal events of the Central Asian Orogenic Belt and the Yinshan Belt to the north, and the Alxa Block to the northwest. Both their detrital zircon ages and eHf(t) values are similar to those of the underlying sedimentary rocks. In addition, the formation has recycled carbonaceous debris, diverse clastic fragments, and Triassic fossils, and its sandstones show low index of compositional variability values (0.79-0.97) and high SiO2/Al2O3 (5.33-7.25) and Th/Sc (0.71-1.97) ratios. These lines of evidence suggest that the detritus of the Zhiluo Formation was partially derived from the underlying sedimentary strata. It should be noted that the Paleozoic to Mesozoic strata of the northern Ordos Basin also have detrital zircon age patterns and eHf(t) values similar to those of the southern Central Asian Orogenic Belt, and the secular evolution of the Ordos Basin is therefore considered to have been controlled by subduction of the Paleo-Asian Ocean and collision between the Central Asian Orogenic Belt and the North China Craton, as well as the post-collisional crustal extension that ensued. The carbonaceous debris in the Zhiluo Formation provided a reductive environment for the subsequent crystallization of reducing minerals and uranium mineralization. [ABSTRACT FROM AUTHOR]

Eclogite and blueschist are important monitors of subduction zone processes and can record complex polymetamorphic histories during the protracted evolution of subduction systems. However, the rarity of such high-pressure, low-temperature metamorphic rocks in the Indus-Yarlung suture zone of the Himalaya hinders our understanding of the convergence of India and Asia. Here, we examine high-pressure, low-temperature metamorphic rocks from the Milin area of the eastern Indus-Yarlung suture zone. A comprehensive microtextural, mineral chemistry, and phase-equilibrium modeling investigation shows that low-temperature eclogite-facies metapelites with different parageneses (garnet-mica schists) experienced a cold subduction history along a lowthermal gradient, with peak pressures of ~1.6 GPa at ~550 °C. This represents an approximate thermal gradient of ~10 °C km-1. After peak pressure, these rocks underwent a two-step exhumation history with initial exhumation accompanying heating at ~590-600 °C and ~0.8-1.0 Gpa; this was followed by the second stage of exhumation to lower amphibolite-facies conditions. We interpret these low-temperature eclogitefacies metapelites to represent sedimentary rocks that overlaid Neo-Tethyan oceanic crust during subduction. Exhumation paths of high-pressure, low-temperature rocks in the eastern Indus-Yarlung suture zone include an amphibolite-facies overprint, which is absent from high-pressure, low-temperature rocks in the western Indus-Yarlung suture zone. This result is caused by the different timing of exhumation relative to the terminal collision of India and Asia. [ABSTRACT FROM AUTHOR]

Apatite is a widespread U-bearing mineral in igneous, metamorphic, and sedimentary rocks. U-Pb geochronology of apatite can provide significant information for constraining magmatic evolution processes and tracing provenance. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a crucial technique for in situ U-Pb age analysis of apatite. However, the lack of suitable matrix-matched apatite reference materials and the inevitable presence of common lead in reference materials are major obstacles restricting high-precision determination of apatite U-Pb ages. This study investigates the impact of common lead on LA-ICP-MS apatite U-Pb dating results. The significant systematic biases (6%−30%) in both measured lower intercept ages and initial lead compositions are observed when calibrating against MAD apatite without common lead correction. However, accurate apatite U-Pb ages (within 2% systematic bias) can be obtained by correcting for common lead in MAD using the 207Pb method or Tera-Wasserburg plot method prior to Pb/U fractionation calibration. Furthermore, a vapor-assisted laser ablation method is employed in conjunction with NIST612 glass as an external standard to accurately analyze apatite U-Pb ages. This non-matrix matched method eliminates the need to consider the influence of common lead in the reference materials. Novel high-precision LA-ICP-MS apatite U-Pb dating methods are established with both matrix-matched and non-matrix-matched analyses, which greatly promote the application of apatite U-Pb geochronology in Earth science. [ABSTRACT FROM AUTHOR]

The CLose-UP Imager (CLUPI) onboard the ESA ExoMars rover is a camera system that will be used for capturing high-resolution images of Martian rocks and soil. The goal of this study was to define a method based on the Structure-from-Motion (SfM) that allows for generating stereoscopic and three-dimensional data from CLUPI images. Although CLUPI is a mono-optic camera, we were able to identify the ideal CLUPI positioning and calculate the rover movements necessary for acquiring images in a given rover position that we subsequently processed to produce stereoscopic photographs and derive 3D and topographical data with Agisoft. To perform this feasibility test in our laboratory, using the EM+, a CLUPI representative engineering model, the 3D and topographical reconstruction was based on a translation of the rover, on the "close-up outcrop observation" configuration in a fixed drill position. The two acquired images, one before and one after the rover's translation are the stereo pairs needed to perform the digital outcrop model (DOM) reconstruction. By importing the data into Geographic Information System (GIS) software, we generated maps, profiles, and stream maps, which enable a detailed characterization of rock textures and sedimentary structures (e.g., clast and phenocryst shape, size, and distribution, laminations thickness and angular relationships...). This study proposes a method easily reusable for creating 3D and stereo data with CLUPI images. [ABSTRACT FROM AUTHOR]

Recent advances in understanding the induced polarization (IP) method have led to improvements in interpreting hydraulic properties from electrical measurements. Distinguishing the effect of surface conduction from conduction through the electrolyte filling the interconnected pore spaces has been an ongoing challenge in interpreting field-scale electrical resistivity data sets. Previously proposed mechanistic models have suggested that this limitation can be overcome by utilizing the coefficient that describes the ratio between IP measurements and surface conductivity. In this study, we examine this proportionality coefficient (ℓ) through the relationship between IP parameters (imaginary conductivity and normalized chargeability) and surface conductivity for a sample group of 98 sedimentary rocks, composed of sandstones, carbonates and mudstones. A strong linear relationship is observed between the IP parameters and surface conductivity. However, values of ℓ vary significantly across each sample group such that low-salinity estimates of formation factor (F) using the single universal estimate of ℓ are poor. Estimates of F for a single rock type (sandstone, carbonate or mudstone) are improved using ℓ values unique to that rock type, although F estimates for mudstones show high sensitivity to changes in ℓ. Using ℓ coefficients calibrated on a sample group with similar lithological properties to the investigated group moderately improves the estimation of F. Consistent with theory, no relationship is observed between the proportionality coefficient and the measured petrophysical parameters of the porous medium. Our results suggest that, although IP measurements provide a valuable field-scale proxy for surface conductivity, improving petrophysical predictions (i.e. in this case, estimating F) remains a challenge. [ABSTRACT FROM AUTHOR]

In transient electromagnetic surveys, the collected data inevitably contain noise originating from both natural and cultural sources. This noise has the potential to mask transient electromagnetic responses linked to geological features, thereby posing challenges in accurately interpreting subsurface structures. Hence, the implementation of effective noise reduction techniques is crucial in ensuring the accuracy and reliability of inversion outcomes in transient electromagnetic surveys. This study introduces a novel approach that merges k‐means clustering with locally weighted linear regression to denoise transient electromagnetic data. The results from synthetic examples illustrate that the k‐means locally weighted linear regression method can predict transient electromagnetic data closely resembling true values, similar to the long short‐term memory autoencoder. Occam's inversion results derived from denoised data using both the k‐means locally weighted linear regression and long short‐term memory–autoencoder methods can well reflect the true model. Notably, a key advantage of the k‐means locally weighted linear regression method is its independence from labelled data as the sample set. The k‐means locally weighted linear regression method was applied to field data collected at the Narenbaolige coalfield in Inner Mongolia, China. Occam's inversion models generated from the denoised field data delineate the boundary between the basaltic body and sedimentary rocks, aligning with drilling data. The inversion models derived from the noisy field data also can capture this boundary, but deep section views reveal the presence of numerous intricate high‐resistivity anomalous bodies. These observations highlight the effectiveness of the k‐means locally weighted linear regression method in denoising transient electromagnetic data. [ABSTRACT FROM AUTHOR]

A comparison of the copper isotope composition of sedimentary rock strata spanning in age across the Great Oxidation Event (GOE) and that of pyrite, carbon, and native gold from the Mesoarchean Witwatersrand Basin reveal that an oxidative gradient triggered gold precipitation on biologic material, now present in the form of gold-rich carbon seams in the latter. Oxidative redox reactions are known to favor the heavier 65Cu isotope. A sequence of sedimentary rock strata on the Kaapvaal Craton records higher Cu isotope values before the start of the oxidation of the Proterozoic atmosphere in comparison to that of younger transitional-GOE strata. A similar increase in Cu isotope ratios was found in gold within carbon seams in comparison to the Cu isotope ratios in rounded pyrite in auriferous metaconglomerates of the ca. 2.9 Ga basal Central Rand Group. However, the Cu isotope ratios in the post-GOE sedimentary rocks of the Kaapvaal Craton and the pre-GOE native gold in the ca. 2.9 Ga carbon seams record different causes of oxidation. The gold in the carbon seams was not uniformly deposited across the lower Central Rand Basin but in isolated depositional environments. Changes in large-scale atmospheric oxidation, evident by the increase in δ65Cu in the pre and transitional-GOE sedimentary strata in the Kaapvaal Craton, cannot be tied to the elevated Cu isotope values in the carbon seams. Instead, the latter, which are higher than all other measured values (δ65Cu = +2.41 ± 0.24 ‰), mimics Cu isotope fractionation associated with acidophilic bacterial activity. Therefore, the significant difference in Cu isotope values of the carbon seams compared to those of detrital pyrite in the Witwatersrand metaconglomerates could be interpreted as a fingerprint of a microbial redox gradient that might have induced the precipitation of gold, thus having formed the richest known gold province in the world. [ABSTRACT FROM AUTHOR]

The molybdenum (Mo) isotope composition (defined as δ98Mo measured per mil relative to NIST-3134) of many modern arc systems and the upper continental crust is heavier than the mantle and most subducting slab lithologies. This observation has led to a model whereby fluids leaving the slab transfer isotopically heavy Mo preferentially to the mantle wedge, leaving the residual slab isotopically lighter. We explore this model via an Mo isotope study of the metasedimentary and mélange lithologies of the Catalina Schist in California. These rocks record subduction zone metamorphism over a wide range of high-pressure/low-to-medium temperature conditions. Mo isotope compositions of the metasedimentary rocks decrease with increasing metamorphic grade, from a δ98Mo mean of −0.04 ± 0.13 ‰ (1σ, n = 3) for the lawsonite albite facies to −0.38 ± 0.07 ‰ (1σ, n = 5) for the epidote–amphibolite facies. The highest grade [amphibolite facies] samples show a slight uptick in δ98Mo values, with a mean of −0.19± 0.14 ‰ (1σ, n = 4). When coupled with major and trace element variations, the changes in δ98Mo appear to reflect metamorphic effects rather than sedimentary source rock heterogeneity. The positive relationship between δ98Mo and [Mo] and negative relationship with Ce/Mo argue for progressive loss of Mo with isotope fractionation during increasing P-T conditions; the reversal of this trend, seen in the increase in δ98Mo between the epidote amphibolite and amphibolite facies may reflect a subsequent partial re-fertilization by fluids carrying isotopically heavy Mo. δ98Mo values in the mélange across all grades are highly variable, ranging from −1.75 to −0.19‰, consistent with large scale mobilization of Mo with isotope fractionation. A metasomatized amphibolite block and reaction rind show similar light isotope compositions and signs of Mo depletion and transport. Together these three whole-rock data sets demonstrate pervasive open system behavior and mobility of Mo in the Catalina Schist. LA-ICP-MS Mo measurement of minerals in the differing metasedimentary metamorphic grades indicates that Fe oxides and/or hydroxides, titanite, rutile, and epidote are important reservoirs of Mo but when comparing mineral Mo content and modal abundance to whole-rock Mo concentrations, several samples were found to have "missing Mo", something that has been observed in other Mo inventory studies. We attribute this to sample heterogeneity between the thin section and whole-rock powder scales. [ABSTRACT FROM AUTHOR]

Eclogite‐facies rocks provide important constraints on the behaviour of convergent plate boundaries and the geometries of tectonic reconstructions due to the high to ultrahigh pressure conditions at which they form. Many eclogite occurrences are documented near the suture zone of active collisional settings where they are interpreted to mark the approximate location of former ocean basin subduction. Such observations influence tectonic interpretations for older eclogites within more deeply eroded and/or less well‐exposed terranes. The eclogitic Glenelg inlier in northwest Scotland is one such example, with c. 1 Ga eclogites having previously been interpreted as marking the trace of a Grenville‐aged collisional suture zone that defines a third 'arm' to the Grenville orogen alongside well‐defined sutures in North America and Scandinavia. Here we use a combination of geochronology, phase equilibrium modelling and accessory‐phase thermometry to show that the eclogite‐facies assemblages were produced at ∼$$ \sim $$18–19 kbar and 700°C–750°C from c. 1.1 to 1.0 Ga. Accounting for the foreland basin setting of equivalent‐aged sedimentary rocks in the region and demonstrating the thermal viability of this setting, we show that eclogite formation occurred in deforming foreland crust adjacent to the Grenville orogen, in a setting broadly analogous to fault‐bounded basement uplifts in the forelands of active deformation belts, such as the Himalayas and Andes. Our results demonstrate that eclogite‐facies rocks can form in a greater range of tectonic settings than are sometimes considered, with implications for tectonic reconstructions of collisional zones. In this instance, our results remove the need for a third 'arm' of the Grenville orogen by placing Glenelg in a foreland setting, reconciling the absence of plentiful Grenville‐aged metamorphic rocks in northwest Scotland, the sedimentological record and paleomagnetic data in the wider region. [ABSTRACT FROM AUTHOR]

In the lower Kongurblak River, Chinese SW Tianshan, scapolite was first found in a narrow shear zone (the Kongurblak shear zone, KSZ), consisting of variably mylonitized sedimentary rocks, including marble, meta‐sandstone and felsic–marly phyllonite. These rocks show varying scapolite textures and modes (from less than 1% to 15%), as a sporadic fine‐grained matrix phase, porphyroblasts with abundant inclusions, or blocky aggregates. The Cl content of scapolite (0.90–2.79 wt.%) varies between different rock types, which is higher in meta‐sandstone and marble than in felsic–marly phyllonite. Rare patchy lower Cl domains of scapolite and Ba zoning of K‐feldspar in meta‐sandstone and Cl zoning of porphyroblastic scapolite in marly phyllonite suggest pulsed fluid circulation. P–T estimates, thermodynamic modelling and mineral textures indicate scapolite formation through metasomatizing sodic feldspar and/or metamorphic reactions at amphibolite‐facies conditions (470°C°C–600°C and 3–7 kbar). These findings suggest the NaCl–CO2–H2O fluids in the KSZ stem from an external source, not from evaporitic horizons, at ~200 Ma by apatite U–Pb dating. The chlorinity and X (CO2) values of fluids, calculated based on the chemistry of the assemblage scapolite–biotite and T–X (CO2) diagrams, correlate well with specific rock types they traverse, which show different mineral modes and compositions, prograde reactions, structural permeability and host rock cavities. This indicates that the chemistry of medium‐grade infiltrative fluids in shear zones is strongly rock‐buffered, with crucial implications for orogenic metallogenesis in specific rock types. Evidence that the lithologies within the KSZ and their tectonometamorphic histories are distinct from those of the two bounding metamorphic units suggests they represent exotic sedimentary blocks transported over long distances within a large‐scale mélange, also providing new constraints on the tectonic collage of the Chinese SW Tianshan. [ABSTRACT FROM AUTHOR]

Cd (cadmium) has been categorized as a crucial food pollutant by the World Health Organization. Research regarding Cd pollution mainly centers on the source of anthropogenic pollution. Nevertheless, there is scarce knowledge concerning the natural weathering input of Cd, particularly that from sedimentary rocks as bedrocks. Herein, we endeavored to explore the contribution of various sedimentary rocks (Quaternary sediments, mudstone, limestone, sandstone, shale, greywacke, and marl) under similar weathering conditions to the input of Cd in agricultural soils. The concentrations of Cd in soils with different bedrocks are as follows: sandstone: 0.30 ± 0.03 mg/kg (SME) > Quaternary sediments: 0.30 ± 0.04 mg/kg (SME) > shale: 0.25 ± 0.04 mg/kg (SME) > greywacke: 0.24 ± 0.03 mg/kg (SME) > mudstone: 0.24 ± 0.01 mg/kg (SME) > marl: 0.22 ± 0.02 mg/kg (SME) > limestone: 0.21 ± 0.03 mg/kg (SME). The results of major element oxides (K2O, MgO, Na2O, Fe2O3, and CaO) imply that Cd in soil primarily stems from the weathering of bedrocks. However, random forest analysis reveals that the soil formation processes of greywacke, mudstone, and marl lead to the loss of Cd in the soil, while those of shale and limestone result in the input of Cd into the soil. This study emphasizes that the process of Cd import and loss in soil is closely related to the type of bedrock and the weathering process. [ABSTRACT FROM AUTHOR]

The northeastern region of Oman presents exceptional outcrops of carbonatite and ultramafic lamprophyre along the east coast, and they intruded a sequence of marine sedimentary rocks. This study aims to study these outcrops through geological and geophysical methods to assess their dimensions and orientations beneath the recent coastal sediments. Geologically, the area is characterized by sedimentary rocks belongings to the Batain nappes. The Batain Group consists of various formations rich in alkaline volcanic rocks, including the Wahra Formation, which hosts the studied outcrops. Fieldwork revealed folded cherts and shales with fault zones and breccias containing ultramafic lamprophyre and carbonatite. Geophysical surveys utilizing radiomagnetotelluric (RMT) soundings identified the lateral extension of these rock sequences beneath sedimentary cover. Inversion of RMT data provided insights into the resistivity distribution, delineating the ultramafic lamprophyre and carbonatite body beneath the sediments. Structural analysis suggests that these rocks were involved in transpressive deformation during late Neogene tectonic events. Despite challenges posed by conductive beach sediments, the RMT method proved effective in shaping these subsurface features, contributing to understanding the geological complexities of the region. [ABSTRACT FROM AUTHOR]

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AbstractThe sandstone-type uranium deposits located within the Songliao Basin of China, which are noted for their significant reserves and low mining costs, have become a primary focus for uranium exploration in the country. Accurate detection of such anomalies is essential for the exploration and assessment of uranium resources. Traditional logging identification methods face challenges, including low accuracy, slow recognition speeds, and limited generalization capabilities. With advancements in technology, artificial intelligence has introduced a novel research paradigm for identifying uranium deposits.This study, which concentrates on the sandstone-type uranium deposits in northern China’s Songliao Basin, employs two representative ensemble learning algorithm models, extreme gradient boosting (XGBoost) and random forest (RF), to facilitate the automatic identification of stratigraphic lithology and uranium-bearing layers. The performance outcomes of these models are compared with those from the K-nearest neighbor classification algorithm, the gradient boosting decision tree algorithm, the back propagation algorithm, and the support vector machine algorithm, which are recognized as typical machine learning algorithms. The prediction accuracy across all six models exceeded 91%, underscoring the efficacy of machine learning techniques in identifying lithologies associated with uranium deposits.Among them, the XGBoost model demonstrated superior recognition performance with an accuracy rate of 98.54%, followed closely by the RF model at 98.20%. Both the XGBoost and RF models exhibited high accuracy rates in detecting uranium anomaly layers and mineralized zones, achieving accuracies of 98.81% and 98.22%, respectively.To address issues related to imbalanced sample data, this study employed the synthetic minority oversampling technique, thereby enhancing both accuracy and comprehensiveness when identifying thin uranium-bearing layers. The optimization process grounded in ensemble algorithms provides a theoretical foundation as well as technical support for intelligent identification methodologies pertaining to sandstone-type uranium deposits. [ABSTRACT FROM AUTHOR]

Permo-Triassic intrusive rocks and back-arc basins are exposed in the İstanbul-Zonguldak Tectonic Unit in the West Pontides. Their tectono-magmatic history, thus to the evolution of the back-arc basins, is poorly understood. Here, I present on olivine-bearing basalt and andesite dykes and granite dykes and pyroxene-bearing andesite dykes of Permo-Triassic crystallization and their Pb-loss ages from the basement rocks and sedimentary rocks in the İstanbul-Zonguldak Tectonic Unit (NW Turkey). They have holocrystalline and porphyritic to vitrophyric textures. U-Pb dating of igneous zircon grains from olivine-bearing basalt and andesite dykes and granite dykes yielded Middle Permian ages of ca. 270.1 ± 1.1 to 261.4 ± 1.7 Ma (2σ), and pyroxene-bearing andesite dykes obtained Early Triassic ages of ca. 252.1 ± 2.4 to 250.1 ± 2.0 Ma (2σ). Their young ages of the dykes yielded Late Triassic ages of ca. 228 to 220 Ma (2σ). Geochemically, the Middle Permian dykes have a calc-alkaline affinity and are notable for subduction components, as indicated by the presence of distinct negative Nb anomalies. Early Triassic dykes show alkaline signatures and show within-plate character, corresponding to prominent positive Nb anomalies. Combined with data from the literature, the Middle Permian dykes are magmatic products associated with the Tethys Ocean subducting under the Pontides and the Early Triassic dykes are magmatic pulses related to the rifting of the Permo-Triassic back-arc basins. The Late Triassic young ages of the Permo-Triassic dykes in the İstanbul-Zonguldak Tectonic Unit represent a deformation event corresponding to the Cimmerian Orogeny, and this implies that the Permo-Triassic back-arc basins closed during the late Triassic. [ABSTRACT FROM AUTHOR]

Fragments of Proto‐Tethyan oceanic lithosphere are well‐preserved along the southern belt of the North Qilian suture, and the origin and emplacement of these ophiolites have become subjects of intense debate. In this study, we integrate field observations, mineralogical and geochemical analyses, zircon U‐Pb dating, and isotopic data to investigate the Yanglong ophiolite. The Yanglong ophiolitic rocks are found as tectonic slices resting on the Neoproterozoic sedimentary and volcanic rocks. These rocks are composed of Cambrian serpentinized peridotite, gabbro, dolerite, and rodingite. The spinels in the serpentinized peridotites have variable Cr# values (21, 38–46, and 59–61) and display affinity to those in abyssal and forearc peridotites. The dolerites show slight enrichment in Th and have elevated (La/Sm)N ratios (1.19–2.01), indicating a subduction‐related geochemical affinity. The Yanglong ophiolitic rocks have positive zircon ɛHf(t) values (+10.3–+18.4) and whole‐rock ɛND(t) values (+5.3–+6.7) indicating derivation from partial melting of a depleted mantle source. These results, together with the regional geology, collectively suggest that the Yanglong ophiolite was generated in a forearc setting during the Early Cambrian northward intra‐oceanic subduction. It was emplaced onto the Central Qilian Block during the subsequent arc‐continent collision, no later than the Early Ordovician. [ABSTRACT FROM AUTHOR]

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT Aim Location Taxon Methods Results Main Conclusions We aim to refine the definition of peri‐Carpathian forest‐steppe grasslands, provide an updated distribution map, identify consensus indicator species and summarise data on their extreme species richness.East‐Central Europe (Czech Republic, Austria, Slovakia, Hungary, Romania, Ukraine).Vascular plants.A total of 127 vegetation plots from large vegetation databases and field sampling were classified as the Brachypodio‐Molinietum association based on two criteria: (1) the existing formal definition and (2) a threshold of consensus indicator species derived from a literature review. The plots were mapped, and their basic habitat conditions were characterised. Habitat affiliations of consensus indicator species were expressed using the diagnostic species lists in the EuroVegChecklist. Maximum species richness values were extracted from the plot data and summarised.Peri‐Carpathian forest‐steppe grasslands of the Brachypodio–Molinietum association have been recorded across a large area of East‐Central Europe, particularly in the lower to middle altitudes of the Western and Eastern Carpathians and their foothills and adjacent regions. These grasslands typically occur in moderately warm, relatively precipitation‐rich regions with deep soils, primarily on plateaus and gentle slopes of up to 10°, developed predominantly over less consolidated Mesozoic and Tertiary sedimentary rocks. We identified 60 consensus indicator species, mostly species of forest‐steppe habitats, with species of mesic grasslands also well represented. The current maxima of vascular plant species richness exceed 110 species per 10–16 m2. These maxima have been recorded in three regions: the Prut‐Siret Interfluve in western Ukraine, the NW Transylvanian Basin in Romania and the White Carpathian Mts in the Czech Republic.The extremely species‐rich peri‐Carpathian forest‐steppe grasslands are confined to a geographically well‐defined area of East‐Central Europe. The observed fine‐scale species richness of vascular plants is currently the highest known in the world. In addition to similar habitat conditions, the presence of an ancient forest‐steppe species pool appears to be a prerequisite for such extreme species richness. Recent paleoecological evidence supports this hypothesis. [ABSTRACT FROM AUTHOR]

Volcanogenic massive sulphide (VMS) deposits consist of upper stratabound massive-to-semimassive sulphide lenses and discordant stringer sulphides in the footwall, hosting significant base metals like Zn, Cu, and Pb, with some enriched in precious (Ag, Au) and semi-metals (like Se and Te). Selenium occurs at low concentrations (0.05 ppm) in Earth’s crust and is critical for renewable energy technologies. Here, we have combined global Se-bearing VMS deposits to illustrate selenium occurrence, enrichment conditions, sources, and depositional environments. Selenium generally occurs as by-products of Cu-rich ores in VMS Cu–Zn or Cu–Au systems; no independent VMS selenium deposit has been reported worldwide. Selenium mineralization is mainly associated with sulphide minerals formed at high-temperature (~300°C) hydrothermal stages as a function of fluid temperature and can occur as Se minerals under highly oxidizing conditions related to supergene geological processes. Selenium-bearing sulphide minerals (like chalcopyrite) are the result of isomorphic substitutions of S by Se; Se contents generally show a decreasing trend from galena, chalcopyrite, sphalerite, pyrite, to pyrrhotite. Other Se-bearing minerals are dominated by roquesite, tellurium-minerals, and tetrahedrite. Selenium minerals are not common but can precipitate at favourable conditions in VMS systems, including native Se, clausthalite (PbSe), naumannite (Ag2Se), bohdanowiczite (AgBiSe2), eucairite (AgCuSe), and tiemannite (HgSe). Co-existence of galena – clausthalite and chalcopyrite (like at the Xiaorequanzi deposit in China) is due to locally elevated H2Se activities of hydrothermal fluids, and the intergrowth of sulphate and selenide minerals (like in VMS deposits in the Urals in Russia), as well as oxide and selenide mineral assemblages (like at the Apliki deposit in Cyprus) is produced by secondary enrichment processes. Worldwide Se-bearing VMS deposits typically occur in arc settings related to the initial subduction of oceanic plates; the addition of magmatic volatiles into the circulated hydrothermal fluids provide the necessary selenium for anomalous Se enrichment. In some cases, leaching of thick Se-bearing sedimentary rocks by evolved seawater in basins is a critical process accounting for Se mineralization endowment. [ABSTRACT FROM AUTHOR]

In this study, an innovative breakthrough pressure detection system for shale oil is introduced. Experiments were conducted on source rocks from three main rock types in the upper member of the Lower Ganchaigou Formation in the Western Qaidam depression, in Qinghai, China. The results show that the differences between the breakthrough pressures of laminated calcareous mudstone (LCM), siltstone (SS), and massive mixed mudstone (MMM) in the formation are of several orders of magnitude. In particular, the shale oil breakthrough pressure of laminated calcareous mudstone is more than five times greater in the vertical bedding direction than in the horizontal bedding direction. As black medium shale oil turns into yellow light shale oil, the breakthrough pressures in the same lithology and direction are reduced by two-thirds. In laminated mudstone the horizontal breakthrough pressure is lower than the vertical, while in massive mixed mudstone the vertical breakthrough pressure is lower. A composite migration model for shale oil in hybrid strata—horizontal migration along bedding and vertical migration through micro-fractures—is proposed. The results are of great significance for understanding the accumulation of shale oil and for identifying exploration targets. [ABSTRACT FROM AUTHOR]

Two sediment cores from the central part of the Hongsa lignite deposit in northwestern Lao PDR (Lao People's Democratic Republic; Laos) have been analysed in order to understand their sedimentary characteristics using grain-size analysis, petrography, X-ray diffraction and scanning electron microscopy. This analysis has revealed that the deposit is primarily composed of fine-grained sediments, mainly silt and clay, with quartz as the dominant mineral and trace amounts of other minerals such as kaolinite, illite and montmorillonite. Gypsum and chlorite have also been found in some layers. Scanning electron microscope analysis has revealed a card-house structure of clay minerals, suggesting sedimentation from suspension driven by physico-chemical reactions influenced by pH and water chemistry. This arrangement increases porosity and water retention, significantly affecting the permeability and mechanical properties of sediments. Petrographic analysis has documented angular quartz and poorly sorted sediments, indicating minimal sediment reworking or short-distance sources. The palaeoenvironment of the Hongsa Basin, reconstructed from various rock units, suggests low-energy water conditions for the Underburden and moderate sediment supply in a wet forest swamp or bush moor environment for the Lower Lignite Zone Formation. The Middle Lignite Zone Formation indicates a more limited sediment supply in a similar environment, while Interburden Formation 1 suggests overbank deposits or stagnant water deposits. In summary, the Neogene Hongsa lignite deposit is characterised by fine-grained sediments, indicating low-energy water currents in mire environments. Occasional flood events brought coarser grains, although movement of facies should also be taken into account. The mineral composition suggests the presence of components derived from recycled sedimentary rocks along the northern border of the Hongsa Basin. [ABSTRACT FROM AUTHOR]

The Istrian peninsula in western Croatia has surface deposits that consist mostly of Jurassic and Cretaceous carbonate sedimentary rocks, which have been exploited since prehistory. Under Roman rule, this exploitation intensified, as attested by dozens of quarries documented throughout the peninsula. Stone was used for everything from foundations of private houses to funerary monuments and public buildings. Micropetrography can be used to determine the geological age of the stone used in these structures, to then compare the results with a geological database of Roman quarries. As multiple quarries exploited deposits of the same age, however, micropetrography alone is insufficient to determine provenance, so it must be supplemented by transport and profitability analysis. [ABSTRACT FROM AUTHOR]

The newly delineated Xipu Dome, located in the central North Himalayan Gneiss Dome (NHGD), exhibits a significant spatiotemporal relationship with Himalayan polymetallic mineralization. Based on field geological surveys and geochronological analyses, this study provides a comprehensive assessment of the lithological assemblage, tectonic deformation, and metallogenic processes of the Xipu Dome. The findings reveal a three-tiered structure: the core consists of early Paleozoic granitic gneiss (523 Ma) and Miocene leucogranite (13.5 Ma), overlain by a cover of low-grade metamorphic or unmetamorphosed sedimentary rocks, and a detachment zone composed of heavily deformed schists and phyllites. The Xipu Dome underwent three phases of tectonic deformation: a southward thrust caused by continental collision, northward extensional activity driven by the South Tibet Detachment System (STDS), and gravitational collapse and downslope sliding following the emplacement of the dome. Two types of mineralization were identified: structural hydrothermal Au-Cu polymetallic deposits related to detachment and skarn-type Cu-Ag polymetallic deposits associated with leucogranite intrusion. This study enhances the understanding of the spatial distribution and metallogenic potential within the Himalayan Be-Sn rare metal-Pb-Zn-Sb-Au belt, offering a valuable direction for strategic mineral exploration in the Tethyan Himalaya (TH). [ABSTRACT FROM AUTHOR]

The Early Cretaceous gold deposits in the North China Craton are known as Jiaodong-type gold deposits. Here, we summarize a quantity of reported (including this study) pyrite trace element, δ34S, and Pb isotope data from the Jiaodong, Xiaoqinling, and Central Taihangshan gold fields to comprehensively reveal the characteristics of the ore-forming fluids in Jiaodong-type gold deposits. The results show that the Au concentrations in the pyrites from the Jiaodong-type gold deposits are typically less than 8.12 ppm and do not correlate with As but have significant positive correlations with Bi and Te, implying that Bi and Te may govern Au enrichment in pyrite. The overall As concentrations in the pyrites are relatively low, and only the Jiaodong gold field is significantly higher, which may be caused by fluid flowing through As-rich metamorphic sedimentary rocks. In Jiaodong-type gold deposits, Au is dominantly found as visible gold, followed by invisible gold. Invisible gold generally occurs as a solid solution (Au+), and only the proportion of nanoparticles (Au0) in the Xiaoqinling gold field is slightly higher (20%). Sulfidation and fluid immiscibility or boiling were the key mechanisms leading to visible gold precipitation. The Co/Ni ratio, δ34S, and Pb isotopes indicate that the ore-forming fluids in the Jiaodong-type gold deposits exhibit remarkable magmatic features, and the ore-forming materials are primarily derived from a mixture of lower crust and mantle sections. Among them, the ore-forming materials from the lower crust of the Central Taihangshan gold field are slightly higher. [ABSTRACT FROM AUTHOR]

We report here diverse Late Miocene fish assemblages based on otoliths collected from sedimentary rocks deposited in coastal marine settings in northern Borneo (Seria and Miri formations and Tutong beach). Surface-collected, large-sized otoliths, representing > 96% of the whole assemblage, are dominated by the families Sciaenidae and Ariidae, while Haemulidae, Engraulidae, and Lactaridae can be common at certain sites. Additional taxa were revealed by screen-washing of the sediments from selected sites including taxa from the families of Congridae, Bregmacerotidae, Apogonidae, Gobidae, Sillaginidae, and Cepolidae. Among the sciaenids, we describe six new taxa (Advenasciaena bruneiana, Atrobucca borneensis, Bruneisciaena schwarzhansi, Nibea ambugensis, Nibea stintoni, and Protonibea nolfi), and we also report the first fossil occurrence of some other groups (e.g. Lactarius lactarius, Acanthocepola sp.) from the Indo-Australian Archipelago (IAA). All these discoveries add to our understanding of fish palaeobiodiversity in the IAA where today's highest marine biodiversity exists. The compositions of the faunas reflect a shallow marine coastal palaeoenvironment with close connection to estuaries where some of the reported fishes might have migrated seasonally or daily with the tide. Turbid, suspension-loaded water might be also presumed, where ariids, sciaenids, and the haemulid Pomadasys are often observed today. ZooBank LSID for the described genera: Advenasciaena Bruneisciaena ZooBank LSID for the described species: Advenasciaena bruneiana Atrobucca borneensis Bruneisciaena schwarzhansi Nibea ambugensis Nibea stintoni Protonibea nolfi [ABSTRACT FROM AUTHOR]

Paleogeographic reconstructions are of key importance for understanding the history of continental breakups and amalgamations during Earth's history. A special case is the history of the Asian continent, which, compared to other continents, consists of several large cratons and numerous smaller continental blocks. The history of the assembly of South China remains controversial in terms of the timing, Late Neoproterozoic or Early Paleozoic, and the participating continental blocks, e.g. Yangtze, Cathaysia, India and Australia. Detrital rutile U-Pb dating has significant potential with regard to deciphering tectonic settings as rutile frequently crystallizes during orogenic events associated with the processes of collision and subduction. Detrital zircon U-Pb dating is a perfect instrument for identifying the provenance characteristics and age characteristics of sedimentary sources. An integration of these two methods of dating offers better opportunities for reconstructing tectonic settings. This paper presents a first attempt to reconstruct the Neoproterozoic to Early Paleozoic tectonic history and paleogeography of the whole South China based on U-Pb geochronology of rutile and zircon and Hf-in-zircon isotopes from Lower Jurassic Baitianba Formation sedimentary rocks of the western margin of the Yangtze Block, a major part of South China. Our obtained integrated U-Pb rutile and zircon age data show three main age populations of 960–940 Ma, 630–610 Ma and 530–520 Ma. The new U-Pb detrital rutile and zircon ages, compared with former data from Gondwana and Australia, suggest that Yangtze amalgamated with Cathaysia to form South China during the Sibao orogeny at 960–940 Ma. The detrital rutile and zircons of the new 630–610 Ma age group could have been delivered from western Australia during the Late Neoproterozoic to Cambrian Paterson-Petermann orogeny. The abundant 530–520 Ma detrital rutile and zircon ages fit well with the coeval zircon age populations recorded in Gondwana-derived terranes, like India and Indochina. [ABSTRACT FROM AUTHOR]

Sedimentary rock deposits such as siltstone have been attracting interest due to their potential to store and control the movement of sequestered CO2. An understanding of weak caprocks is required to guarantee the safety of CO2 geo-sequestration projects where weak rocks are encountered. The cost and challenge of obtaining intact samples of weak caprocks from depths relevant to potential geo-sequestration targets has resulted in relatively little data on their mechanical behaviour being available. This paper describes the manufacture and characterisation of artificial siltstones, with properties typical of weak rocks, at stress levels relevant to geo-sequestration. It is shown that the artificial siltstones with properties typical of weak rocks can be simply produced from mixtures of sand, feldspar fines, plaster and water. Highlights: Weak siltstones showed evidence of approaching critical states typical of de-structured granular materials when sheared to large deformations after yield. Drained triaxial tests revealed that the stress–strain response and failure mode depend on level of confining pressure and amount of cementation. The artificial siltstone can reproduce the strength, stiffness and mechanical behaviour of weak rock. [ABSTRACT FROM AUTHOR]

The age and properties of detrital zircon grains in a forearc basin provide crucial information on the history of convergent plate margins. These data can be used to constrain provenance dispersal patterns, establish source-tosink relationships, and reveal the tectonic framework and subduction history. The Qilian orogen in the northeastern margin of the Tibetan Plateau records the tectonic history of the Proto-Tethys Ocean from its initial spreading and subduction to final closure. However, the timing of subduction initiation and the subduction polarity of the Proto-Tethys Ocean remain controversial. The Qilian orogen includes the North Qilian, Central Qilian, and South Qilian belts. A succession of sedimentary rocks along the northwestern margin of the Central Qilian belt, previously considered to be Precambrian in age, has been redefined based on detailed field investigation and geochronology. U-Pb analysis of detrital zircon grains from metasedimentary rocks of the Gongcha Group of the northwestern Central Qilian belt yielded Paleozoic ages between 530 and 470 Ma, with prominent Mesoproterozoic and Paleoproterozoic ages between 1800 and 1000 Ma. In contrast, the overlying Duoruonuoer Group yielded predominantly early Paleozoic ages between 465 and 434 Ma, with a few older age populations. This change in source is reflected in a substantial increase in volcanic detritus within the Duoruonuoer Group as compared to the Gongcha Group. The detrital zircon age spectra and lithologic characteristics indicate the Gongcha and Duoruonuoer Groups constitute the lower and upper volcanic-sedimentary strata in the forearc basin. Based on resemblances of statistical ages and eHf(t) values of zircon, we interpret that the early Paleozoic intrusive and volcanic units and Precambrian basement rocks of the Central Qilian belt were the main source of the Gongcha and Duoruonuoer Groups, verifying the southward subduction of the North Qilian Ocean, a portion of the larger Proto-Tethys Ocean, beneath the Central Qilian belt. The detrital zircon ages reveal that the initial subduction of the Proto-Tethys Ocean in the Qilian orogen occurred ca. 530 Ma and closed ca. 435 Ma. These forearc sedimentary units constitute the tectonic boundaries between the Central Qilian belt and North Qilian belt. [ABSTRACT FROM AUTHOR]

The fine-grained sedimentary rocks have numerous bedding-parallel fractures that are essential for the migration, enrichment, and efficient development of oil and gas. However, because of their variety and the complexity of the factors that affect them, their spatial prediction by the industrial community becomes challenging. Based on sample cores, thin sections, and well-logging and seismic data, this study employed a multi-scale data matching approach to quantitatively predict the development of bedding-parallel fractures and investigate their spatial distribution. Bedding-parallel fractures in the Lucaogou Formation in Jimusar Sag frequently occur along preexisting bedding planes and lithological interfaces. Unfilled bedding-parallel fractures inside or near source-rocks exhibit enhanced oil-bearing capacity. They were identified on micro-resistivity scanning images by the presence of regularly continuous black or nearly black sinusoidal curves. Overall, the developmental degree of bedding-parallel fractures was positively related to the brittle mineral and total organic carbon contents and negatively related to single reservoir interval thickness. The maintained porosity of the reservoir matrix contributed to a thorough response to factors affecting the development of bedding-parallel fractures. Here, an effective and objective method was proposed for predicting the development and distribution of bedding-parallel fractures in the fine-grained sedimentary rocks. The method was based on the matched reservoir interval density, reservoir interval density, and matched sweet spot density of bedding-parallel fractures. The prediction method integrated the significant advantages of high vertical resolution from logging curves and strong lateral continuity from seismic data. The average relative prediction error was 8% in the upper sweet spot in the Lucaogou Formation, indicating that the evaluation parameters for bedding-parallel fractures in fine-grained sedimentary rocks were reasonable and reliable and that the proposed prediction method has a stronger adaptability than the previously reported methods. The workflow based on multi-scale matching and stepwise progression can be applied in similar fine-grained sedimentary rocks, providing reliable technological support for the exploration and development of hydrocarbons. [ABSTRACT FROM AUTHOR]

The New Caledonia Trough is a bathymetric depression extending 2,500 km from New Zealand to the Coral Sea. Sedimentary successions up to 10 km thick are contained in three main sedimentary basins, the New Caledonia, Fairway and Deepwater Taranaki basins. Deepwater Taranaki Basin occupies the head of the New Caledonia Trough adjacent to the well-known Taranaki Basin lying almost entirely within New Zealand's marine territory. The inboard part of Deepwater Taranaki Basin is covered by a dense grid of high-quality 2D and some 3D seismic data and one exploration well, Romney-1, which did not drill the syn-rift succession. The oldest sedimentary rocks drilled by Romney-1 are palynologically dated as Teratan (latest Turonian and Coniacian – 91–87 Ma). While the New Caledonia Trough is generally thought to have been initiated by Late Cretaceous (Campbell and Mortimer 2014; Strogen et al. 2017), this paper examines the evidence for the age of the oldest sedimentary rocks in the Deepwater Taranaki Basin and hence its age of inception and by inference, inception of the New Caledonia Trough to suggest a possible Jurassic age. [ABSTRACT FROM AUTHOR]

The saline lacustrine hybrid sedimentary rocks are complex in lithology and unknown for their sedimentary mechanisms. The hybrid sedimentary rocks samples from the Neogene upper Ganchaigou Formation to lower Youshashan Formation (N1-N2¹) in the Fengxi area Qaidam Basin, were investigated through core-log and petrology-geochemistry cross-analysis by using the core, casting thin section, scanning electron microscope, X-ray diffraction, logging, and carbon/oxygen isotopic data. The hybrid sedimentary rocks in the Fengxi area, including terrigenous clastic rock and lacustrine carbonate rock, were deposited in a shallow lake environment far from the source, or occasionally in a semi-deep lake environment, with 5 lithofacies types and 6 microfacies types recognized. Stable carbon and oxygen isotopic compositions reveal that the formation of sedimentary cycles is controlled by a climate-driven compensation-undercompensation cyclic mechanism. A sedimentary cycle model of hybrid sedimentary rocks in an arid and saline setting is proposed. According to this model, in the compensation period, the lake level rises sharply, and microfacies such as mud flat, sand-mud flat and beach are developed, with physical subsidence as the dominant sedimentary mechanism; in the undercompensation period, the lake level falls slowly, and microfacies such as lime-mud flat, lime-dolomite flat and algal mound/mat are developed, with chemical-biological process as the dominant sedimentary mechanism. In the saline lacustrine sedimentary system, lacustrine carbonate rock is mainly formed along with regression, the facies change is not interpreted by the accommodation believed traditionally, but controlled by the temporary fluctuation of lake water chemistry caused by climate change. The research results update the interpreted high-resolution sequence model and genesis of hybrid sedimentary rocks in the saline lacustrine basin and provide a valuable guidance for exploring unconventional hydrocarbons of saline lacustrine facies. [ABSTRACT FROM AUTHOR]

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The steep northern slopes of Giona Mt in central continental Greece are the result of an E-W normal fault dipping 35–45° to the north, extending from the Mornos River in the west to the village of Gravia in the east. This fault creates a significant elevation difference of approximately 1500 m between the northern Giona footwall and the southern Iti hanging wall. The footwall comprises imbricated Mesozoic carbonates of the Parnassos unit, which exhibit large-scale drag folding near and parallel to the fault. The hanging wall comprises deformed sedimentary rocks of the Beotian unit and tectonic klippen of the Eastern Greece unit, forming a southward-tilted neotectonic block with subsidence near the Northern Giona Fault and uplift near the Ypati fault to the north. These two E-W faults represent younger structures disrupting the older NNW-trending tectonic framework. Fault scarps are observed all along the 14 km length of the Northern Giona fault accompanied by cataclastic zones, separating the carbonate formations of the Parnassos Unit from thick scree, slide blocks, boulders and olistholites. Inversion of fault-slip data has shown a mean slip vector of 45°, N004°E, which aligns with the current regional extensional deformation of the area, as confirmed by focal mechanism solutions. Based on the general asymmetry of the alpine units in the hanging wall, we interpret a listric fault geometry at depth using slip-line analysis and we forward modelled a disrupted fault-propagation fold using kinematic trishear algorithms, estimating a total displacement of 6500 m and a throw of approximately 2000 m. Seismic activity in the area of the Northern Giona Fault includes a magnitude 6.1 earthquake in 1852, which caused casualties, rockfalls and extensive damage, as well as a magnitude 5.1 event in 1983. The expected seismic magnitude is deterministically estimated between 6.2 and 6.7, depending on the potential westward continuation of the Northern Giona Fault beyond the Mornos River to the Northern Vardoussia saddle. The seismic hazard zone includes several villages located near the fault, particularly on the hanging wall, where intense landslide activity during seismic events could result in severe damage to regional infrastructure. The neotectonic development of the Northern Giona Fault highlights the importance of extending seismotectonic research into the mountainous regions of central Greece within the alpine formations, beyond the post-orogenic sedimentary basins. [ABSTRACT FROM AUTHOR]

The influence of the parameters of accelerated carbonization in a 99.9% CO2 environment on the hardening kinetics of blended cement with 15 wt% opoka additive, the physical and mechanical properties of the resulting products, the mineralogical composition, and the amount of absorbed CO2 were investigated. Sedimentary rock opoka was found to have opal silica and calcite as its predominant constituent parts. Therefore, these properties determine that it serves as an extremely suitable raw material and a source of both SiO2 and CaO. The strength properties of the mortars (blended cement/standard sand = 1:3) were similar or even better than those of samples based on Ordinary Portland cement (OPC): the compressive strength exceeded 50 MPa under optimal conditions. In blended cement, some of the pores are filled with fine-dispersed opoka, which can lead to an increase in strength. By reducing the amount of OPC in mixtures, the negative impact of its production on the environment is reduced accordingly. Using XRD, DSC, and TG methods, it was determined that replacing 15 wt% of OPC clinker with opoka does not affect the mineralogy of the crystalline phases as the same compounds are obtained. After determining the optimal parameters for sample preparation and hardening, in accordance with the obtained numbers, concrete pavers of industrial dimensions (100 × 100 × 50 mm) were produced. Their strength indicators were even ~10% better. [ABSTRACT FROM AUTHOR]

Limestone has always been widely used in various sectors, thus having significant economic and environmental impacts. The quarrying process is, on the one hand, essential, but on the other, harmful to the environment and people's health, therefore, the challenge is finding a balance. This review explores the multifaceted nature of limestone, a sedimentary rock predominantly composed of calcium carbonate. The formation of limestone, along with its various types and global occurrence, is discussed to provide a basic understanding. The diverse applications of limestone range from historical uses in ancient monuments to contemporary roles in cement production, plasticized polyvinyl chloride (PVC), and soda–lime glass. The discussion extends to post-mining solutions, showcasing successful rehabilitation and innovative repurposing of former quarries into useful infrastructures, wildlife habitats, and cultural spaces. This article draws attention to the importance of sustainable practices and technological developments to balance resource use with environmental conservation. Ultimately, it emphasizes the need for responsible limestone quarrying and proactive rehabilitation strategies to ensure that no permanent ecological problems will occur. [ABSTRACT FROM AUTHOR]

The western coastal area of Alexandria City, Egypt, faces significant environmental challenges due to heavy metal (HM) contamination in beach sediments, driven by intensive urbanization, tourism, commercial harbors, and industrial activities. Therefore, this study focuses on geochemically assessing HM levels in sediment samples from 28 sites and employed various descriptive and multivariate statistical approaches, pollution indices, and sediment quality guidelines (SQGs) to identify pollution hotspots, define contamination grades, and assess the quality of beach sediments. The average concentrations of Cd, Co, Cr, Cu, Pb, and Zn were 25.7, 30, 2.2, 7.5, 2.9, and 8.0 times, respectively, compared to the geochemical background (carbonate sedimentary rocks). et al.-Hanuvil Beach, relatively elevated contents of these metals were recorded. In addition, samples showed Zn levels higher than the corresponding probable effect concentration (PEC) and effect range medium (ERM) values, suggesting adverse impacts on biota. The principal component (PC) analysis revealed the anthropogenic origin of Cd, Co, and Pb in PC1, the mixed origin of Cr, Cu, Mn, and Zn in PC2, and the natural source of Fe in PC3. According to the applied single pollution indices, HM contamination grades were ranked in ascending order of Mn < Fe < Cr < Cd < Cu < Pb < Zn < Co. In conclusion, the HMs (Cu, Zn, Cd, Co, Pb, and Cr) in the study area are anthropogenic, attributed mainly to untreated discharge of municipal and industrial wastewater and solid wastes, atmospheric deposition of air pollutants, and tourism activities. [ABSTRACT FROM AUTHOR]

The Punta Coles Natural Reserve (PCNR), located on the southern coast of the province of Ilo, Moquegua Region, Peru, houses an area rich in marine biodiversity which is composed of natural banks of benthic invertebrates, which constitute the potential and dynamic fishery of commercial interest for artisanal fishermen that impact the area. To mitigate this impact, all stakeholders need to know, understand, value, and balance the dependence of benthic biodiversity with the ecosystem for its preservation and the promotion of sustainable fishing. Along these lines, the components studied are bathymetry, lithology, and the tapestry of bioengineers that make up the reserve's seabed. Mapping of the complexity of the benthic habitat of the seabed was developed on the basis of an integrated analysis of multibeam bathymetric data, geoscientific information associated with the antecedents of benthic biodiversity of the PCNR, sediment maps of the seabed, subtidal sedimentological texture, and photographic records. The characterization and granulometry of the sediments that make up the PCNR were determined according to the Udden–Wentworth classification criterion (Φ). The utility of the GPSMAP 178C multibeam echosounder for the interpretation of seabed sediments stands out. The kriging interpolation method was used to extrapolate the characteristics of the benthic habitat, which is suitable for large areas of the sea. As a result, three habitats were derived and mapped, and three structures (bioengineers), namely, "subtidal kelps" (Lessonia trabeculata), "mussels" (Aulacomya atra), and "red sea squirt" (Pyura chilensis), were associated mainly with sedimentary rock habitats and mixed substrates. In the sand substrate, these algae were found to a lesser extent. The results show that this study is a conceptual model that summarizes the understanding of ecology and prospects for the sustainability of profitable, ecoefficient fishing activities in the Moquegua Region, Peru. [ABSTRACT FROM AUTHOR]

The 1:100,000-scale Porang sheet in South Khorasan province is prone to skarn, massive sulfide, and sedimentary mineralization due to the presence of intermediate to ultrabasic volcanic and plutonic rocks and the variety of sedimentary rocks. This paper introduces the Principal Coordinate Analysis (PCoA) method. The PCoA method, along with the Principal Component Analysis (PCA) and Correspondence Analysis (CA) methods, has been used to identify the possible type of mineralization in the study area. Geological and mineralogical data and the analysis results of 25 elements from 314 stream sediment samples, taken from the study area, have been used for this purpose. The results of the data analysis show that the D1 coordinate, PC1 score, and location in the first cluster maps of the samples are most likely related to the mineralization in ultrabasic, basic, and listivinite rocks. After that, the D2 and D3 dimension maps, the PC2 and PC5 score maps, and the sample location map in the fifth cluster related to sedimentary rocks attribute the most probability to sedimentary mineralization, especially of Mn and Fe mineralization types, in the study area. Finally, there is the possibility of skarn and massive sulfide mineralization, whose locations can be predicted by the D4 dimension maps, the PC3 score map, and the sample location maps in second, third, and fourth clusters. Also, the comparison of data analysis results with two multivariate statistical methods shows that by choosing the number of dimensionality reductions, the principal components method can cover more variability than the principal dimensions method. While connecting the principal coordinate maps to the mineralization is easier and more reliable than the principal component score maps. Therefore, the proposal of this paper is the simultaneous use of PCoA and PCA methods to analyze geochemical data in an exploration region. [ABSTRACT FROM AUTHOR]

This study targeted 15 geological sites in five regions of Japan where landslides occurred due to heavy rainfall between 2014 and 2019. The changes in elevation before and after each disaster were estimated using LiDAR DEMs, and the sediment volume (V) associated with each landslide was calculated. The α and γ coefficients in the landslide volume estimation equation, expressed as V = αAγ (where A is the landslide area), were investigated to clarify their dependency on landslide depth and geological factors, and the results were compared with those of previous studies. The findings showed that there is a negative correlation between the α and γ values, and that the γ value increases as the ratio of the increase in landslide depth to landslide area increases. In terms of geology, igneous rocks tended to have high α values and low γ values. This is hypothesized to be due to a function of the landslide morphology, wherein the landslide depth does not change markedly depending on the area of the landslide. The α and γ values for plutonic rocks and sedimentary rocks were widely distributed, and this was considered to be due to the diverse array of landslide morphologies and their underlying geologies. Metamorphic rocks tend to have a low α values and high γ values, which is suggestive of a landslide morphology in which the ratio of the landslide depth to the landslide area increases. [ABSTRACT FROM AUTHOR]

Provenance analysis of the Qamdo basin reveals convergent tectonic evolution of the southeastern Tibetan plateau region from initiation as a Late Triassic foreland basin to a final phase as a Cretaceous intermontane basin. Sandstone composition and detrital zircon ages consistently reflect recycled sedimentary sources throughout the Mesozoic, with only minor evidence for contributions from magmatic sources. Detrital zircon with Mesozoic ages are rare (≲10% of all ages), with no <160 Ma zircon observed; instead detrital zircon ages form five main age populations (230–330 Ma; 400–500 Ma; 650–1,200 Ma; 1,600–2,100 Ma and 2,400–2,600 Ma). These results indicate that during Late Triassic‐Early Jurassic time, sediment was transported from sources in the Yidun terrane across the Jinsha suture into the Qamdo depocenter as it formed a south‐facing foreland basin. Middle‐Upper Jurassic strata of the central Qamdo basin record local input from volcanic arcs of the Bangong‐Nujiang suture zone as the Meso‐Tethys ocean closed and a north‐facing foreland developed in the Qamdo region. The youngest Cretaceous deposits reflect coarse‐grained alluvial deposition synchronous with development of east‐vergent growth‐strata, reflecting intermontane basin formation resulting from inboard stress transmitted from closure of Neo‐Tethys oceanic lithosphere due to convergence with the Lhasa block. By this time, the Qamdo basin region was a high‐standing depocenter developed within orogenic uplands that preceded formation of the high topography of the "Lhasaplano," and is consistent with models suggesting proto‐plateau formation prior to Himalayan orogenesis. Plain Language Summary: The Qamdo basin represents a rare opportunity to investigate sediment deposition that records Late Triassic‐Cretaceous tectonic development of the southeastern Tibet plateau region. Using ages of zircon sand grains as well as the mineralogical composition of sand grains, we interpret that the Qamdo basin received sediment shed mainly from mountains to the east as the ocean closed during continental collision. Later in the Jurassic, this area received minor and localized sediment input from volcanic arc systems which we interpret to indicate on‐going closure of the Bangong‐Nujiang suture zone. The youngest sediment in the Qamdo basin is Cretaceous and records sediment accumulation in an intermontane basin formed due to tectonism to the south. Together these results indicate the region of southeast Tibet evolved into an elevated region that could represent a plateau that formed prior to the collision of India with Asia. Key Points: Qamdo basin records convergent tectonism along the Jinsha suture during Late Triassic and Bangong‐Nujiang suture zone during CretaceousMost sediment was derived from recycling sedimentary rocks of the Yidun terrane and eastern Qiangtang block, with limited volcanogenic inputBy Cretaceous, Qamdo deposition occurred within an intermontane setting that may represent development of pre‐Himalayan proto‐plateau uplands [ABSTRACT FROM AUTHOR]

New data, including Raman spectroscopy, characterize unusual mineral assemblages from rocks of the Naylga and Khamaryn–Khyral–Khiid combustion metamorphic complexes in Mongolia. Several samples of melilite–nepheline paralava and other thermally altered (metamorphosed) sedimentary rocks contain troilite (FeS), metallic iron Fe0, kamacite α-(Fe,Ni) or Ni-bearing Fe0, taenite γ-(Fe,Ni) or Ni-rich Fe0, barringerite or allabogdanite Fe2P, schreibersite Fe3P, steadite Fe4P = eutectic α-Fe + Fe3P, wüstite FeO, and cohenite Fe3C. The paralava matrix includes a fragment composed of magnesiowüstite–ferropericlase (FeO–MgO solid solution), as well as of spinel (Mg,Fe)Al2O4 and forsterite. The highest-temperature mineral assemblage belongs to a xenolithic remnant, possibly Fe-rich sinter, which is molten ash left after underground combustion of coal seams. The crystallization temperatures of the observed iron phases were estimated using phase diagrams for the respective systems: Fe–S for iron sulfides and Fe–P ± C for iron phosphides. Iron monosulfides (high-temperature pyrrhotite) with inclusions of Fe0 underwent solid-state conversion into troilite at 140 °C. Iron phosphides in inclusions from the early growth zone of anorthite–bytownite in melilite–nepheline paralava crystallized from <1370 to 1165 °C (Fe2P), 1165–1048 °C (Fe3P), and <1048 °C (Fe4P). Phase relations in zoned spherules consisting of troilite +Fe0 (or kamacite + taenite) +Fe3P ± (Fe3C, Fe4P) reveal the potential presence of a homogeneous Fe–S–P–C melt at T~1350 °C, which separated into two immiscible melts in the 1350–1250 °C range; namely, a dense Fe–P–C melt in the core and a less dense Fe–S melt in the rim. The melts evolved in accordance with cooling paths in the Fe–S and Fe–P–C phase diagrams. Cohenite and schreibersite in the spherules crystallized between 988 °C and 959 °C. The crystallization temperatures of minerals were used to reconstruct redox patterns with respect to the CCO, IW, IM, and MW buffer equilibria during melting of marly limestone and subsequent crystallization and cooling of melilite–nepheline paralava melts. The origin of the studied CM rocks was explained in a model implying thermal alteration of low-permeable overburden domains in reducing conditions during wild subsurface coal fires, while heating was transferred conductively from adjacent parts of ignited coal seams. The fluid (gas) regime in the zones of combustion was controlled by the CCO buffer at excess atomic carbon. Paralava melts exposed to high-temperature extremely reducing conditions contained droplets of immiscible Fe–S–P–C, Fe–S, Fe–P, and Fe–P–C melts, which then crystallized into reduced mineral assemblages. [ABSTRACT FROM AUTHOR]