Environmental and Earth Sciences

Abstract: The Cambrian Hetang Formation is widely distributed in the Anhui section of the eastern Jiangnan orogenic belt, a large number of crystalline graphite was found in the hornfels near the contact zone between the stratum and the rock mass, its mineralogical characteristics showed that the crystalline graphite was finely squamose, with a diameter of about 2~60μm and a relatively flat edge; 2H-type graphite characteristic; The thickness of the scale is 30.6~40.7nm, the degree of graphitization is 67~89, the estimated metallogenic metamorphism temperature of graphite is 494.4~564.8°C, and the content of 3R polytype is 10.85%~15.98%. The genetic analysis showed that the δ13C value of graphite in the ore was between -33.218‰ ~ -24.957‰, and the value was obviously negative, indicating that the source of graphite carbonaceous matter was mainly bio-organic carbon deposited in the strata, which was closer to the level of peat, asphalt and modern organic matter. The age of the ore-bearing strata and its surrounding rock mass is 151~132Ma, which is the product of magmatic activity from the Middle-Late Jurassic to Early Cretaceous, and reaches the peak at 140~130Ma; magmatic hydrothermal fluid acts on carbonaceous strata, which is the cause of contact metamorphism.

Abstract: Quartz sand is used throughout oil and gas well engineering, including hydraulic fracturing, wellbore sand control, high-temperature cementing and produced-water treatment, but each use imposes distinct require-ments on particle size, morphology, strength, reactivity and cleanliness. Following the performance chain from mineral source, washing and size classification, storage and transport, slurry injection and fracture placement to long-term service, this review discusses proppant transport and settling, bridging and bed-load migration, breakage and wall embedment under closure stress, fines migration, fracture-fluid residues, mul-tiphase and non-Darcy flow, stress cycling and time-dependent damage. Natural quartz sand, pre-cured and curable resin-coated sands, ceramic proppants and mixed proppants are compared. Material selection should be based on target-well long-term conductivity tests and life-cycle economics. The review also considers gravel packing, where grain-size matching to formation sand, screen compatibility and packing completeness are critical, and high-temperature well cementing, where finely ground silica regulates the calcium-to-silicon ra-tio of hydration products and mitigates strength retrogression. API Std 19C and ISO 13503-2:2024 provide the basic characterization framework, whereas ISO 13503-5:2006 can organize long-term conductivity compari-son but does not provide an absolute in-situ conductivity. A project-level test matrix, minimum reporting set and batch-traceability loop are proposed for resource assessment, product development, procurement and field verification.

Abstract: Lithium (Li) occurrence in natural waters is controlled by interacting hydrogeochemi-cal processes, yet these controls remain poorly constrained in the Mangystau Region of western Kazakhstan outside deep formation and oilfield brines. This study evaluated Li distribution and its principal hydrochemical controls in contrasting surface- and groundwater systems. Two sampling campaigns were conducted in May and August 2026 at 14 sites, including saline lakes, sors, river waters, groundwater wells, and a natural spring; eight sites were resampled in August. Physicochemical parameters and major ions were determined using standardized hydrochemical methods, while Li, Na, and K were quantified by ICP-OES. Relationships were assessed using Spearman rank correlations with Benjamini–Hochberg false-discovery-rate correction. Li concentra-tions ranged from 0.08–0.82 mg L⁻¹ in May and 0.25–2.29 mg L⁻¹ in August, increasing at seven of eight repeatedly sampled sites. Kishi Oymasha had the highest calculated mineralization (274.98 g L⁻¹) but only 0.31 mg L⁻¹ Li. Significant positive associations remained between Li and Cl⁻, Na⁺ + K⁺, SO₄²⁻, TDS, and Mg²⁺. Overall, Li distribution reflects combined effects of source availability, water–rock interaction, hydrological transport and mixing, and evaporation rather than salinity alone.

Abstract: An automatic discrimination of in-situ vitrinite on polished plugs by means of Raman spectroscopy is here proposed on a set of Mesozoic-Cenozoic samples from a well drilled in the Norwegian Sea, offshore mainland Norway. Publish Rock-Eval Pyrolysis predominantly indicates a Type III kerogen, with hydrogen enrichment in specific intervals probably due to organic mud additives used during drilling. In the same publish dataset, organic petrographic analyses show the coexistence of indigenous alongside reworked vitrinite and inertinite macerals. Thermal maturity derived from the reflectance of the indigenous vitrinite show a regular downward increase ranging approximately from 0.35% to 1.4%. Raman spectroscopic analyses have been performed on: 1) specific macerals optically recognized and 2) by high-resolution Raman mapping of small surface where different (i.e. vitrinite and inertinite) macerals have been previously identified. Thermal maturity Raman parameters show downward increase similar to the reflectance ones, when considering indigenous vitrinite fragments. On the other hand, high standard deviation, due to both the presence of different macerals or contaminants, hampers a correct evaluation when a Raman-mapped area is considered. Such a limitation is overcome by applying Mixed Gaussian Model automatic clustering that allows the discrimination of different organic material and the identification of the in-situ vitrinite by looking at the cluster distribution along the section. This work demonstrates how machine learning techniques applied to samples from drill cuttings can effectively reduce uncertainties in thermal maturity assessments.

Abstract: The Tethyan tectonic domain exerted significant impacts on the tectonic evolution of China. However, magmatic‑petrological records of the Neo‑Tethys in southeastern South China are still poorly constrained. To better understand the formation and evolutionary characteristics of the Neo‑Tethyan tectonic domain in South China. Petrography, zircon U‑Pb geochronology, as well as elemental‑isotopic geochemical analyses were carried out on the magmatic rocks from Hainan Island. Geochronological results show that two mafic rock samples yield crystallization ages of 99 ± 1 Ma and 98 ± 1 Ma, respectively, and three granite samples give ages of 97 ± 2 Ma, 98 ± 1 Ma and 102 ± 2 Ma. The mafic samples have SiO₂ contents ranging from 49.98% to 51.26 %, belonging to the calc‑alkaline series. They are enriched in large‑ion lithophile elements, depleted in high‑field‑strength elements, and characterized by enriched light rare‑earth elements. Their εHf(t) values range from −5.26 to −3.19. The granite samples have SiO₂ contents of 73.01 %–76.31 %, and are classified as peraluminous high‑K calc‑alkaline rocks with pronounced negative Nb‑Ta anomalies. Their εHf(t) values vary from −5.47 to −2.84, with two‑stage Hf model ages of 1109–1209 Ma. Synthesis of the above data indicates that the mafic rocks were mainly derived from partial melting of enriched lithospheric mantle metasomatized by subduction‑zone fluids/melts. The granites originated from remelting of Mesoproterozoic crustal materials, with the addition of mantle‑derived materials. Combined with the previously identified Cretaceous EW‑trending subduction zone along the northern margin of the South China Sea, we propose that the subduction of Neo‑Tethyan oceanic crust represents the principal geodynamic mechanism for the extensive Cretaceous magmatism on Hainan Island.

Abstract: Detailed petrography and LA-ICP-MS zircon U-Pb geochronological analyses of metasedimentary rocks in the Jiangbian area are carried out in this study in order to reveal the formation age of Precambrian crystalline basement in the western Hainan Island, South China Block. Field characteristics of the metasedimentary rocks show that they underwent intense deformation and are crystalloblastic texture. They are mainly composed of quartz and muscovite. Zircon U-Pb dating results show that a representative metasedimentary rock sample yields two age peaks of 1736 Ma and 2339 Ma, suggesting that there is Paleoproterozoic crystalline basement on Hainan Island. Integrated with regional geological data, it suggested the protolith of part of the Baoban Group that was previously divided into Mesoproterozoic stratigraphic sequence was likely to be formed in the Paleoproterozoic. All of the Hainan Island, Yangtze and Cathaysia blocks were part of old landmass of China and recorded the assembly of supercontinent Columbia/Nuna.

Abstract: Cobalt-rich ferromanganese (Fe–Mn) crusts from the Magellan Seamount Trail (MST), western Pacific Ocean, record long-lived hydrogenetic mineralization interrupted by dissolution, sedimentation, phosphatization, and renewed crust growth. However, age assignments for phosphatized early crust layers remain uncertain because calcareous nannofossils commonly occur in carbonate fluorapatite (CFA) veinlets, pores, cavities, and fractures rather than in the primary Fe–Mn oxyhydroxide matrix. Here, we combine calcareous nannofossil biostratigraphy with in situ U–Pb LA-ICP-MS dating of CFA to constrain the multistage history of a four-layer Co-rich Fe–Mn crust from the eastern slope of Govorov Guyot. The section comprises, from bottom to top, Layer I-1, sublayer I-2b, Layers II, and III. Calcareous nannofossil assemblages indicate Late Paleocene–Early Eocene fossil-bearing phosphatized carbonate material in Layer I-1, a Late Oligocene–Early Miocene assemblage in sublayer I-2b, Middle Miocene carbonate material in the lower part of Layer II, a Late Miocene–Early Pliocene assemblage in the II–III transition, and Pliocene–Pleistocene assemblages in Layer III. This age sequence in the young part of the crust is consistent with the established MST chronostratigraphic and biostratigraphic scheme. U–Pb dating of CFA reveals additional Late Cretaceous and Miocene phosphatization events. CFA from the phosphatized carbonate substrate beneath Layer I-1 yielded an age of 85.8 ± 4.7 Ma, consistent with the previously documented Turonian–Coniacian phosphatization event involving the oldest known Pacific CFA at Govorov Guyot. CFA veinlets within Layer I-1 yielded ages of 75.3 ± 2.6 Ma and 73.1 ± 4.9 Ma, documenting Late Cretaceous phosphatization of the old Fe-Mn crust section. CFA from the phosphatized sublayer I-2b yielded an age of 15.8 ± 2.3 Ma, recording an additional Early–Middle Miocene phosphatization event. The dated CFA veinlets demonstrate that the Fe–Mn matrix of Layer I-1 predates the 75–73 Ma phosphatization event and is therefore approximately 20 Myr older than the maximum age inferred from calcareous nannofossil biostratigraphy. The chronostratigraphic scheme and generalized section of MST Co-rich Fe–Mn crusts should therefore be complemented by a texturally controlled U–Pb chronology of phosphatization events, particularly for the Late Cretaceous crust succession.

Abstract: Recent years, a series of pegmatite-type rare-metal deposits and occurrences—including Chakabeishan, Shaliuquan, Jinshuikou, Adatan, and Gaduo—have been reported in Qinghai, sparking a wave of rare-metal exploration activity. The Southern Kunlun Convergence Zone is a key tectonic unit of the Eastern Kunlun Orogenic Belt; however, systematic geochronological and geochemical constraints on the granitic-pegmatitic rare-metal mineralization system within this region have long been lacking. This study focuses on the newly discovered beryllium ore body at Wulugou in the Southern Kunlun Mountains. Samples from the ρ10 and ρ38 beryllium-bearing pegmatite veins were selected for petrological analysis, LA-ICP-MS zircon-monazite U-Pb geochronology, and whole-rock major and trace element analyses. Zircon Lu-Hf and monazite Sm-Nd isotope analyses were also conducted on the ρ10 and ρ38 beryllium-bearing pegmatite veins. This study precisely determined the diagenetic and mineralization ages of the pegmatites, systematically clarified the genesis and evolutionary relationships among the ore-bearing pegmatite, the surrounding granite, and the barren pegmatite, and elucidated the characteristics of the magma source region and the mechanisms of beryllium mineralization. LA-ICP-MS dating results for monazite and zircon in the pegmatites indicate that the ore-bearing pegmatite formed during the Early Devonian (404.9–408.3 Ma). Whole-rock geochemical analysis indicates that the albitized granites, barren pegmatite, and beryllium-bearing pegmatites in the study area constitute a continuous, homologous, highly differentiated evolutionary sequence, all of which are highly differentiated granites. As the degree of crystallization increases, the rock undergoes continuous enrichment in SiO₂, Na₂O, MnO, P₂O₅, and Be, while K₂O, Ca, and Sr are progressively depleted. The effects of the four rare-earth groups, along with the Zr/Hf and K/Rb ratios, collectively indicate that saturation and dissolution of volatile fluids in the late stage are the key controlling factors in the precipitation of beryllium ore. Primary magmatic zircon εHf (t) = −2.69 to +1.95 (mean + 0.76); two-stage Hf model age: 1.28 to 1.57 Ga; Isolated εNd (t) = -6.71 to -5.44, Nd two-stage model age 1.57 to 1.68 Ga, The source-area discrimination diagrams all fall within the muddy clastic-melt zone, indicating that the parent magma originated from low-degree partial melting of the Middle Proterozoic Wanbaogou Group metamorphic basement, accompanied by contamination by mantle-derived magma. This study discovered Early Devonian Caledonian-period pegmatite-type beryllium deposits in the Southern Kunlun Mountains, providing a theoretical basis and practical reference for the exploration of granite-pegmatite-type beryllium deposits in the Southern Kunlun Mountains.

Abstract: Sedimentary-basin brines are increasingly evaluated as unconventional lithium (Li) resources, but legacy water-chemistry datasets commonly lack Li measurements. This study develops a geological and geochemical workflow for screening Li prospectivity in the Northern Gondwana Region (NGR). Major-ion, potassium (K), boron (B), bromine (Br) and stable-isotope data from Triassic, Jurassic and Paleogene carbonate aquifers were integrated with basin history and compared with published Li-bearing brines. Na-Cl facies, Cl-Br systematics and isotope compositions indicate residual evaporative components and varying degrees of water-rock interaction, whereas the Paleogene aquifer shows greater meteoric dilution. Triassic and Jurassic samples occupy the region of B-K space populated by published Smackover brines with higher Li concentrations. Comparable associations among Li, K, B and Br occur in Devonian Alberta brines, although Qianjiang data demonstrate that these relationships are basin dependent. The convergence of potential Li sources, evaporative evolution, burial-related water-rock interaction, organic-matter maturation and possible hydrothermal circulation identifies the Triassic and Jurassic aquifers as higher priorities for direct Li analysis. The workflow is an exploration-screening method; it neither predicts Li concentration nor establishes a mineral resource.

Abstract: To investigate how the anatexis of accretionary complexes contributes to crustal differen-tiation in orogenic belts, we present an integrated analysis of whole-rock geochemistry, zircon U-Pb geochronology, and zircon Lu-Hf isotopes for Late Carboniferous granitoids from the Dunhuang orogenic belt. Zircon U-Pb dating indicates that the granitoids were emplaced between 323 and 312 Ma. Their zircon εHf(t) values (−39.3 to 10.7) are largely negative, suggesting derivation primarily from ancient crustal materials. Geochemical correlations and field relationships between the granitoids and their wall rocks suggest that the magmatic sources were dominated by meta-sedimentary rocks with minor me-ta-mafic rocks. The systematic whole-rock Rb-Sr-Ba variations are attributed to wa-ter-fluxed melting of muscovite in a metasedimentary source. Given the continued activity of the Dunhuang subduction zone during the Late Carboniferous, we infer that elevated temperature combined with fluid-rich conditions in the deeper accretionary wedge trig-gered anatexis of the accreted materials. The segregation and upward migration of granit-ic magmas leave a residue within the deeper accretionary wedge that resembles the lower continental crust in composition. This process enhances vertical differentiation within the orogenic belt crust and likely plays an important role in transforming loose accreted ma-terials into more mature continental crust.

Abstract: Permian sedimentary manganese carbonate deposits in the Qiling Basin exhibit substantial resource potential, yet their depositional environments and precipitation pathways remain insufficiently constrained. This study integrates petrographic, mineralogical, whole-rock geochemical, and carbonate C–O isotope data from the Shuibutou Mn deposit in southern Hunan. We compare this deposit with the coeval Dongxiangqiao deposit and other Permian marine sedimentary Mn deposits to constrain its depositional setting, Mn-carbonate precipitation mechanisms, and potential Mn sources. The Shuibutou ores contain 10.88–17.18 wt.% MnO and are characterized by spherulitic–oolitic textures, abundant bioclasts, and framboidal pyrite. Mo–U enrichment indicates anoxic bottom waters, whereas the near-marine δ¹³C_carb values of ore carbonates (−0.24‰ to 1.28‰) are consistent with pre-cipitation within a marine carbonate system and suggest direct precipitation of Mn(II) carbonates from dissolved Mn²⁺ under anoxic conditions. In this setting, dissolved Mn²⁺ accumulated below the chemocline. Partial dissolution of platform-derived calcite grains near the chemocline increased local dissolved inorganic carbon and alkalinity, driving Mn-carbonate supersaturation and the authigenic precipitation of manganoan calcite, ultimately forming manganese carbonate ores. The low Al/(Al + Fe + Mn) ratios, high Fe/Ti ratios, and Co–Ni–Zn and REY geochemical characteristics are consistent with a possible contribution from Mn-rich deep fluids to the dissolved Mn²⁺ inventory of the basin waters. Similarities in mineralogy, geochemistry, and depositional setting between Shuibutou and Dongxiangqiao point to a possible regional role for the direct precipitation of Mn(II) carbonates under anoxic conditions in the Middle Permian Qiling Basin. Relatively deep intraplatform basins may therefore represent favorable targets for manganese carbonate exploration and provide a reference for exploration targeting of Permian sedimentary Mn deposits within the Qiling Basin.

Abstract: The peninsular India is an area of ~16,00,000 sq. km, bound by mountain or hill ranges. It comprises dominantly the Archean-Proterozoic terrain (APT) in the south, Deccan trap Volcanic Terrain (DVT) in the middle and, Mixed-Lithology Terrain (MLT) in the north. Almost all rivers of peninsular India originate in mountain ranges or high plateaus, rain-fed, drain continental rocks and flow westwards into the Arabian Sea or eastwards into the Bay of Bengal (Figure 1). River sediments are formed from weathering and erosion of continental rocks in their drainage basins. Since the drainage basins of the rivers cover the entire landmass of peninsular India, the average geochemical compositions of sediments in the rivers may reflect the average composition of the continental crust. Here, we highlight the differences in the average chemical composition of sediments in rivers along the east and west coast of India that drain dominantly similar geological terrains, update the geochemical composition of the Peninsular India Rivers Average Clay (PIRAC) based on the sediments from 104 rivers and, suggest that the composition of PIRAC serves as reference sediment for the Indian sub-continent. We found that the major elements in river sediments are variably affected by the intensity of weathering, with depleted mobile elements and enriched immobile elements. On an average, the clays from the east coast rivers are enriched with Si, Ti, Fe, Mg and Mn, and Na and depleted with Ca and P relative to those of the west coast rivers. PIRAC showed more depleted Si, Mg, Ca, Na and K and enriched Ti, Fe, Mn and P relative to the Post Archean average Australian Shale (PAAS). Weathering indices suggest that the sediments are extremely weathered in the southern peninsular India and, strong to moderately weathered in the central and northern peninsular India. The average total trace element content (∑TE) of the clays was much higher for the east coast rivers than that of west coast. The ∑TE of PIRAC was lower than in PAAS. The PAAS-normalised trace elements of PIRAC showed high transition trace elements (∑TTE) and low high-field strength elements (∑HFSE) and large-ion lithophile elements (∑LILE). The average rare earth element content (∑REE) of the clays increased from APT to MLT for the east coast rivers but decreased in the west coast rivers. The ∑REE of PIRAC was higher than in upper continental crust (UCC) but lower than in PAAS. The PAAS-normalised REE of PIRAC showed MREE- and HREE- enriched and LREE- depleted pattern, with positive Ce and Eu anomalies. PIRAC is significantly enriched with mafic component dominated material despite Archean-Proterozoic rocks are abundantly wide spread in the peninsular India. The intensity of chemical weathering and, erosion and transportation of easily eroded mafic rocks relative to that of felsic rocks resulted in deposition of mafic component-dominated material at the lower reaches of almost all rivers. Since the composition of PIRAC is significantly different from that of UCC/PAAS and other reference sediments, PIRAC serves as the most suitable reference sediment for the Indian subcontinent.

Abstract: To determine the reprocessing potential of mining liabilities, a comprehensive evaluation of the tailings deposit at the former Halcon mining unit in central Peru was conducted. Direct and indirect methods were employed, including geophysical surveys, sampling through six drill holes up to 9.62 meters deep, textural analysis, mineralogical characterization (optical microscopy, SEM, XRD, and reflectance spectroscopy), and ICP-MS chemical analysis, complemented by geostatistical modeling for resource estimation. Geochemical and mineralogical results reveal highly oxidizing, acidic conditions (pH 1.83–4.91) and significant concentrations of Zn (5.46%), Pb (1.58%), Cu (1.67%), Ag (244 ppm), and Au (3.6 ppm). These economic minerals predominate in fine-grained fractions with high degrees of liberation, favoring metallurgical recovery. Geostatistical modeling estimated a total tailings tonnage of 87,642 tons, highlighting zones of high localized economic potential, particularly for Zn and Ag. Considering specific recovery scenarios, penalties, operational costs, and metal prices, a net financial benefit of approximately US$11.35 million was projected. This pioneering study demonstrates the feasibility of converting environmental liabilities into economic assets through strategic reprocessing initiatives, contributing a robust model for mine tailings valorization within the South American circular economy framework.

Abstract: Located 30 km south–southeast of Kabul in Logar province, Aynak is the largest and best-known copper orebody in Afghanistan. The deposit is hosted by the Loy Khwar Formation, a Neoproterozoic-Cambrian metasedimentary sequence of dolomite marble, carbonaceous quartz schist and quartz–biotite–dolomite schist. The primary ore minerals are chalcopyrite and bornite with less abundant pyrite and minor cobaltite, chalcocite, pyrrhotite, sphalerite and molybdenite. Sulphides occur as bedded laminae and disseminations, in metamorphic segregations, and in syn- to post-metamorphic cross–cutting veins. The geochemistry of sulphide-rich separates from Central and Western Aynak (n=31), analysed by ICP-MS, confirm and quantify previous petrographic observations indicating varying admixtures of sulphide species. Co and As enrichment in chalcopyrite-dominant samples is consistent with cobaltite whereas Co enrichment in the absence of arsenic suggests the presence of carrollite. Fluid inclusion analyses of secondary quartz-hosted inclusions indicate interaction with moderately hot (approximately150- 300⁰C; pressure-uncorrected), highly saline (32.1 to 47.4 equivalent wt% NaCl) chloride-rich brines. It is uncertain whether these fluid parameters relate to primary copper transport and deposition, or to remobilisation during metamorphism. Nevertheless, comparison with analogous sediment-hosted copper deposits suggests that highly saline basinal brines played an important role in the formation and evolution of the deposit. Occurrences of scapolite provide additional evidence for a model of brine-related mineralization. Together with previously published mineralogical, lithogeochemical and sulphur isotope evidence, these findings support a sedimentary–diagenetic origin for the Aynak copper deposit that is broadly comparable with sediment-hosted stratiform copper systems of the Central African Copperbelt.

Abstract: Hydrocarbon reservoirs remain a cornerstone of the global energy landscape; precise reservoir characterization is essential to evaluate the viability of crude oil production. Addressing the challenges inherent in low-permeability, low-porosity formations and near-wellbore environments is critical for maintaining sustainable production. Due to the heterogeneity of deep reservoir cores, non-destructive analytical methods are required for sample reuse. Nuclear Magnetic Resonance (NMR) techniques - specifically low-field (LF) NMR and Magnetic Resonance Imaging (MRI) - have emerged as essential tools for the spatial characterization of pore networks. While these methods are well-established for determining porosity and permeability in sandstones, the characterization of carbonates is more complex due to their intricate chemistry, multi-scale geological features, and geo-mechanical properties. This review article synthesizes the theoretical framework and practical applications of NMR for determining the petrophysical properties of sandstone and carbonate rocks, including porosity, permeability, and fluid saturations. We provide a concise historical overview and a technical evaluation of the primary equations used in LF-NMR data inversion. We examine recent advancements in LF-NMR and MRI applications, identify persistent challenges and future perspectives, and summarize key lessons learned from the recent literature. Hence, this review provides a comprehensive roadmap for applying magnetic resonance to rock core analysis.

Abstract: The fifth member of the Upper Triassic Xujiahe Formation (T₃x⁵) in the southwestern Sichuan Basin contains widely developed organic-rich source rocks, which represent a crucial interval for hydrocarbon exploration in the region. This study systematically evaluates the organic geochemical characteristics, spatial distribution, and hydrocarbon generation potential of these source rocks using total organic carbon (TOC) analysis, organic matter typing, vitrinite reflectance (Ro) measurements, and basin modeling. The results show that the upper and lower submembers have average TOC values of 3.19% and 3.41%, respectively, with organic matter predominantly of mixed sapropelic-humic type (Type II₂). TOC content generally increases from uplift areas to depressions, reflecting the control of depositional environment on organic matter preservation. Thermal maturity exhibits a westward increase and eastward decrease, with the southwestern part reaching high to over-mature stages (Ro generally >1.3%), while the eastern part remains in the condensate-wet gas window. Thickness of the upper submember ranges from 60 to 320 m, with depocenter in the central-southern part of western Sichuan; the lower submember is 60-200 m thick, centered in the Chengdu-Deyang area. Basin modeling, which integrates burial and thermal histories, estimates a cumulative gas generation of approximately 192×10¹² m³ (192 trillion cubic meters), with the highest generation intensity coinciding with the western Sichuan depression. It is concluded that the T₃x⁵ source rocks possess excellent material bases and huge resource potential. Tight sandstone reservoirs adjacent to the gas kitchen should be prioritized in future exploration, with differentiated strategies adapted to various maturity zones.

Abstract: The Siberian Traps has been a reference object for geologists for many years in understanding the origin of Large Igneous Provinces on Earth. Data from high-magnesium rocks in its northern region have traditionally been used to create genetic models. However, the central and southern parts, consisting of the basaltic rocks, remain significantly unexplored, despite their important role in volcanic evolution within the province. This article presents new structural, mineralogical, and geochemical data from the tuff-lava sequence in the central region of the Tunguska syneclise. The studied sections are located along the Lower Tunguska River Valley, near Tura, Babkino, and Vanavara, in the Podkamennaya Tunguska Valley. They consist of pyroclastic rocks belonging to the Korvunchansky Formation, which are overlain by basalts and tuffs of the Nidymsky and Kochechumsky Formations (Early Triassic, 251 Ma). Major and trace element analysis of 64 samples shows that basalts from all formations are relatively similar in composition, belonging to the tholeiite type with MgO concentrations ranging from 4.2% to 7.8%. Trace element patterns exhibit negative Ta-Nb anomalies and positive Pb anomalies, which are typical of the Siberian Platform basalts. Tuffs, on the other hand, differ from the basalts by having higher SiO₂ and K₂O contents and steeper rare earth element (REE) patterns. Isotopic analysis (Sr-Nd) confirms this difference and suggests that basalts and tuffs originated from two distinct magma sources. The Nidymsky basalts have positive εNd values (+2.21 to +3.10), similar to those of the Morongovsky and Mokulaevsky basalts in the Norilsk area. Tuffs, on the other hand, exhibit negative εNd (-1.33 to -4.5) and elevated 87Sr/86Sr (>0.706), in comparison with basalts (0.704-0.706). Geological observations reveal that pyroclastic rocks play a significant role in the initial stages of volcanic activity. The main result of this study is that tuffs from the Korvunchansky and Khakanchansky Formations (in the south and north of the region, respectively) are identical in their geochemical characteristics. This similarity suggests the existence of a single pyroclastic cover over the Siberian Platform. These tholeiitic pyroclastic rocks, which are similar in composition to the lower crust, mark the beginning of trap magmatism, rather than picrites, as suggested by the plume model.

Abstract: Petrology, as one of the fundamental branches of geology, has consistently sought to answer fundamental questions regarding the origin, evolution, and diversity of igneous and metamorphic rocks. This review article, adopting a comprehensive approach without relying on new field data, examines the conceptual and methodological evolution of petrology from its formative years to contemporary research horizons. In the first section, the theoretical framework governing igneous petrology—including concepts of fractional crystallization, partial melting, magmatic series, and the tectonic setting of magmatism—is critically evaluated. In the second section, the principles of phase equilibria, metamorphic facies, pressure-temperature-time paths, and the role of fluids in rock metamorphism are elaborated. Furthermore, the application of geochemical methods, including stable and radiogenic isotopes, alongside novel approaches such as machine learning applications and thermodynamic modeling, are introduced as contemporary research perspectives. The article concludes by emphasizing that the ultimate goal of petrology is the integration of micro-scale observations with macro-scale tectonic theories to construct a unified picture of Earth's evolutionary history.

Abstract: This article describes the mineralogical and geochemical features of the Marsyaty sedimentary deposit of Fe and Mn ores in the Northern Urals (Russia). Oolitic ironstones are localized in coastal sandstones of the Cenomanian age. Сarbonate Mn ores lies within siliciclastic sediments of the Lower Paleocene and are separated from the oolitic ironstone by a layer of gravel. Authigenic iron oxyhydroxides, chamosite/bertierite and superimposed siderite predominate in the ironstones; kaolinite, apatite, perhamite, calcite and dolomite are minor and rare. Rhodochrosite and rencieite are major minerals of the Mn ore; layer Mn-silicates (caryopilite, parsettensite?) are minor and rare. Both ore types contain authigenic glauconite, montmorillonite, sulfides (sphalerite/wurtzite, galena, pyrite), gibbsite/boemite, REE phosphates. The detrital component of both types of ores is represented by clasts of quartz, ilmenite, zircon, monazite, epidote, titanite, muscovite, and feldspars. The δ13Сcarb varies from -18.5 to -23.3 in carbonate ironstone and -10.0 to -41.0 ‰ PDB in manganese ore. The light isotopic composition of carbon and numerous organic relics indicate the participation of microbes in both types carbonate ore formation process. It is concluded that iron and manganese ores belong to a joint transgressive series of sedimentary rocks that arose sequentially during the evolution of the West-Siberian basin. The unique feature of the Marsyaty deposit is that, within a limited area and over a short geological period, favorable conditions were realized first for the accumulation of iron and manganese, and then only for manganese.

Abstract: Accurate prediction of gold enrichment is critical for mineral exploration and resource evaluation, particularly in data-limited environments where only geochemical information is available. This study evaluates machine learning (ML) models against linear baselines for predicting relative gold enrichment defined as ln(Au/G10), where G10 represents the geometric mean of ten predictor elements (S, Fe, Al, Si, Mn, Sr, Ni, Cu, K, Ti). A total of 53,126 samples from a sulphide-hosted orogenic gold system were subjected to compositional data analysis (CoDA) preprocessing, including multiplicative replacement of below-detection values, closure to a constant sum, centred log-ratio (CLR) transformation of predictor variables, and robust outlier filtering using the Minimum Covariance Determinant (MCD) method. After screening, 41,626 samples were retained for modelling. Comparative modelling included linear baselines—Ordinary Least Squares (OLS), Ridge, Lasso, and Huber—and non-linear ML algorithms: Random Forest (RF), Support Vector Regression (SVR), k-Nearest Neighbours (kNN), and Multi-Layer Perceptron (MLP). Under the non-circular formulation, nonlinear models consistently outperformed linear baselines. Random Forest achieved the strongest validation performance (R2 ≈ 0.51), followed closely by MLP and SVR, while linear models remained substantially weaker (R2 ≈ 0.31). SHapley Additive exPlanations (SHAP) applied to the Random Forest model identified sulphur (S) and iron (Fe) as the most influential predictors, consistent with sulphide-controlled gold mineralization processes in orogenic systems. The model predicts relative gold enrichment based solely on multielement geochemistry, providing a robust and interpretable proxy for mineralization intensity in data-constrained environments. This study demonstrates that machine learning models, when combined with CoDA-correct preprocessing and a non-circular target formulation, can provide geologically meaningful and methodologically robust predictions of gold enrichment. The workflow offers a transparent and reproducible framework for early-stage exploration targeting using multielement geochemistry.