Search Results (16)

The Chacopampean Plain is a major physiographic unit in Argentina, bounded by the Colorado River to the south, the Sierras Pampeanas and Subandinas to the west, and the Paraná River, Río de la Plata Estuary, and the Argentine Sea to the east. Its subsurface preserves sediments from the Miocene marine transgression, while the surface hosts some of the country’s most productive soils. Two main geomorphological domains are recognized: fluvial systems dominated by alluvial megafans in the north, and aeolian systems characterized by loess accumulation and wind erosion in the south. The southern sector exhibits diverse landforms such as deflation basins, ridges, dune corridors, lunettes, and mantiform loess deposits. Despite their regional extent, the origin and chronology of many aeolian features remain poorly constrained, as previous studies have primarily focused on depositional units rather than wind-sculpted erosional features. This study integrates remote sensing data, field observations, and a synthesis of published chronometric and sedimentological information to characterize these aeolian landforms and elucidate their genesis. Our findings confirm wind as the dominant morphogenetic agent during Late Quaternary glacial stadials. These aeolian morphologies significantly influence the region’s hydrology, as many permanent and ephemeral water bodies occupy deflation basins or intermediate low-lying sectors prone to flooding under modern climatic conditions, which are considerably wetter than during their original formation. Full article

The Shabaosi gold field is located in the western Mohe Basin, part of the northern Great Xing’an Range, NE China, and contains multiple gold deposits. However, the sources of the ore-forming materials, the fluid evolution, and the genesis of these gold deposits have been disputed, especially regarding the classification of these deposits as either epithermal or orogenic gold systems. Based on detailed field geological investigations and previous research, we conducted systematic research on the Shabaosi, Sanshierzhan, Laogou, and Balifang gold deposits using fluid inclusion and H-O-S-Pb isotope data, with the aim of constraining the fluid properties, sources, and mineralization processes. Fluid inclusion analyses reveal diverse types, including vapor-rich, vapor–liquid, CO₂-bearing, CO₂-rich, and pure CO₂. Additionally, only a very limited number of daughter mineral-bearing fluid inclusions have been observed exclusively in the Laogou gold deposit. During the early stages, the peak temperature primarily ranged from 240 °C to 280 °C, with salinity concentrations between 6 and 8 wt% NaCl equiv., representing a medium–low temperature, low salinity, and a heterogeneous CO₂-CH₄-H₂O-NaCl system. With the influx of meteoric water, the fluids evolved gradually into a simple NaCl-H₂O system with low temperatures (160–200 °C) and salinities (4–6 wt%). The main mineralization stage exhibited peak temperatures of 220–260 °C and salinities of 5–8 wt% NaCl equiv., corresponding to an estimated formation depth of 1.4–3.3 km. The δD_V-SMOW values (−138.3‰ to −97.0‰) and δ¹⁸O_V-SMOW values (−7.1‰ to 16.2‰) indicate that the magmatic–hydrothermal fluids were progressively diluted by meteoric water during mineralization. The sulfur isotopic compositions (δ³⁴S = −0.9‰ to 1.8‰) and lead isotopic ratios (²⁰⁸Pb/²⁰⁴Pb = 38.398–38.579, ²⁰⁷Pb/²⁰⁴Pb = 15.571–15.636, and ²⁰⁶Pb/²⁰⁴Pb = 18.386–18.477) demonstrate that the gold predominantly originated from deep magmatic systems, with potential crustal contamination. Comparative analyses indicate that the Shabaosi gold field should be classified as a epizonal orogenic gold system, which shows distinct differences from epithermal gold deposits and corresponds to the extensional tectonic setting during the late-stage evolution of the Mongol–Okhotsk orogenic belt. Full article

Geothermal systems play a crucial role in understanding Earth’s heat dynamics. The Yunkai Uplift in southern China exemplifies a geothermally rich region characterized by ancient lithologies and high heat flow. This study investigates the geochemical characteristics of geothermal waters in the Yunkai Uplift. Both geothermal and non-thermal water samples were collected along the Xinyi–Lianjiang (XL) Fault Zone and the Cenxi–Luchuan (CL) Fault Zone flanking the core of the Yunkai Mountains. Analytical techniques were applied to examine major ions, trace elements, and dissolved CO₂ and H₂, as well as isotopic characteristics of O, H, Sr, C, and He in water samples, allowing for an investigation of geothermal reservoir temperatures, circulation depths, and mixing processes. The findings indicate that most geothermal waters are influenced by water–rock interactions primarily dominated by granites. The region’s diverse lithologies, change from ancient Caledonian granites and medium–high-grade metamorphic rocks in the central hinterland (XL Fault Zone) to low-grade metamorphic rocks and sedimentary rocks in the western margin (CL Fault Zone). The chemical compositions of geothermal waters are influenced through mixing contacts between diverse rocks of varying ages, leading to distinct geochemical characteristics. Notably, δ¹³C_CO2 values reveal that while some samples exhibit significant contributions from metamorphic CO₂ sources, others are characterized by organic CO₂ origins. Regional heat flow results from the upwelling of mantle magma, supplemented by radioactive heat generated from crustal granites. Isotopic evidence from δ²H and δ¹⁸O indicates that the geothermal waters originate from atmospheric sources, recharged by precipitation in the northern Yunkai Mountains. After infiltrating to specific depths, meteoric waters are heated to temperatures ranging from about 76.4 °C to 178.5 °C before ascending through the XL and CL Fault Zones under buoyancy forces. During their upward migration, geothermal waters undergo significant mixing with cold groundwater (54–92%) in shallow strata. As part of the western boundary of the Yunkai Uplift, the CL Fault Zone may extend deeper into the crust or even interact with the upper mantle but exhibits weaker hydrothermal activities than the XL Fault Zone. The XL Fault Zone, however, is enriched with highly heat-generating granites, is subjected more to both the thermal and mechanical influences of upwelling mantle magma, resulting in a higher heat flow and tension effect, and is more conducive to the formation of geothermal waters. Our findings underscore the role of geotectonic processes, lithological variation, and fault zone activity in shaping the genesis and evolution of geothermal waters in the Yunkai Uplift. Full article

This investigation focuses on the prevalent continental oil shale within the Triassic Chang 7, a member of the Yanchang Formation in the Ordos Basin and the Permian Lucaogou Formation in the Junggar Basin of western China, and delves into the impacts of hydrocarbon generation and the derived organic acids on the physical attributes of oil shale reservoirs. Water-soluble organic acids (WSOAs) were extracted via Soxhlet extraction and analyzed by a 940 ion chromatograph (Metrohm AG), supplemented with core observations, thin-section analyses, pyrolysis, and trace element assays, as well as the qualitative observation of pore structures via FIB-SEM scanning electron microscopy. The study discloses substantial disparities in the types and abundances of organic acids within the oil shale strata of the two regions, with mono-acids being conspicuously more prevalent than dicarboxylic acids. The spatial distribution of organic acids within the oil shale strata in the two regions is non-uniform, and their generation is inextricably correlated with the type of organic matter, thermal maturity, and depth at which they are buried. During diverse stages of diagenesis, the hydrocarbons and organic acids produced from the pyrolysis of organic matter not only exert an impact on the properties of pore fluids but also interact with diagenetic processes such as compaction, dissolution, and metasomatism to enhance the reservoir quality of oil shale. The synergy between chemical interactions and physical alterations collectively governs the migration and distribution patterns of organic acids as well as the characteristics of oil shale reservoirs. Furthermore, the sources of organic acids within the oil shale series in the two regions demonstrate pronounced dissimilarities, which are intimately associated with the peculiarities of their sedimentary milieu. The oil shale of the Yanchang Formation was formed in a warm and humid freshwater lacustrine basin environment, while the oil shale of the Lucaogou Formation was deposited in a brackish to saline lacustrine setting under an arid to semi-arid climatic regime. These variances not only illuminate the intricacy and multiplicity of the sedimentary attributes of oil shale but also accentuate the impact of the sedimentary environment on the genesis and distribution of organic acids, especially the transformation and optimization of reservoir dissolution by organic acids generated during hydrocarbon generation—a factor of paramount significance for the precise identification and effective development of the “sweet spot” area of shale oil. These areas, characterized by an abundance of organic matter, their maturity, and superior reservoir properties, are the foci of the efficient exploration and development of continental shale oil. Full article

Changes and disturbances to water diversity and quality are complex and multi-scale in space and time. Although in situ methods provide detailed point information on the condition of water bodies, they are of limited use for making area-based monitoring over time, as aquatic ecosystems are extremely dynamic. Remote sensing (RS) provides methods and data for the cost-effective, comprehensive, continuous and standardised monitoring of characteristics and changes in characteristics of water diversity and water quality from local and regional scales to the scale of entire continents. In order to apply and better understand RS techniques and their derived spectral indicators in monitoring water diversity and quality, this study defines five characteristics of water diversity and quality that can be monitored using RS. These are the diversity of water traits, the diversity of water genesis, the structural diversity of water, the taxonomic diversity of water and the functional diversity of water. It is essential to record the diversity of water traits to derive the other four characteristics of water diversity from RS. Furthermore, traits are the only and most important interface between in situ and RS monitoring approaches. The monitoring of these five characteristics of water diversity and water quality using RS technologies is presented in detail and discussed using numerous examples. Finally, current and future developments are presented to advance monitoring using RS and the trait approach in modelling, prediction and assessment as a basis for successful monitoring and management strategies. Full article

To understand why hematite of different genesis behave diversely in flotation systems, this study assesses the flotation response at pH 5 of bulk (morphology, texture, Crystal Preferential Orientation (CPO)) plus interfacial (surface area, zeta potential, immersion enthalpy, contact angle, induction time) characteristics of species formed under distinct metamorphic conditions: low-strain deformation (Hematite-1) versus high-strain deformation (Hematite-2). Hematite-2 (predominantly composed of specular and lamellar morphologies) shows (001) CPO and exhibits fewer Fe sites on its surface that undergo doubly coordinated Fe-OH when exposed to moisture. This results in a less reactive surface associated with a less ordered adsorbed water layer than Hematite-1, which is predominantly composed of granular and sinuous hematite. Those characteristics lead to a naturally hydrophobic behavior characterized by the exothermic energy below the Critical Immersion Enthalpy ($-{∆\mathrm{H}}_{\mathrm{i}\mathrm{m}\mathrm{m}}$ < 200 mJ/m²), lower values of zeta potential due to attenuated dissociation of Fe-OH_(surf), lower induction time (47 ms vs. 128 ms), higher contact angle (39° vs. 13°), and higher flotation recovery (21% vs. 12%) than Hematite-1. Full article

I introduce a Buddhist god named Jiedi, believed to be a personification of the renowned gate mantra in the Heart Sūtra. I argue for a complex genesis story where the transference of the nāga-taming function and aquatic setting from the rainmaking spell in the Great Cloud Sūtra to the Heart Sūtra Mantra, coupled with its exegetical tradition emphasizing the soteriological metaphor of crossing, created an independent cult of the Jiedi Mantra. In battling chthonic snake spirits demanding virgin sacrifice in Sichuan, a regional variation of a cosmopolitan alchemical theme, the mantra was personified into a god associated with water and warfare. The exorcistic function of the mantra was the motor behind its apotheosis in Middle-period China. While he was elevated from a mere spirit to a vidyārāja (“wisdom king”) in tantric Buddhism, his cult was also disseminated in the Song, witnessing him provide broad deliverance in diverse areas such as industry, agriculture, infrastructure, military, and civil service. In late imperial China, he further imprinted himself on sacred geography, became a special class of warrior god, made inroads into Daoism and local religion, and proliferated in vernacular fiction and drama. An exotic Indian god was born on Chinese soil. Full article

Coastal areas have made substantial contributions to global economic development but are plagued by challenges such as groundwater salinization. Groundwater serves as the primary source for drinking, industrial, and domestic purposes in these coastal areas. Therefore, understanding the causes and processes of groundwater salinization holds paramount significance for effective groundwater management. The coastal area of Laizhou Bay in northern China serves as a quintessential example of such a scenario. With substantial groundwater extraction and severe groundwater salinization issues, it exacerbates the disparity between water-resource supply and demand. Currently, our understanding of the processes and influencing factors related to groundwater salinization in this region remains limited. In this study, employing hydrochemical and stable chlorine isotope analyses on 35 groundwater and seawater samples, an in-depth investigation into the complex mechanisms underlying groundwater salinization in the Quaternary aquifers of the eastern coastal plain of Laizhou Bay was conducted. The test results of the samples indicate that brine and saline groundwater are primarily of the Na-Cl type, exhibiting a hydrochemical composition similar to that of seawater. Brackish groundwater exhibits a diverse hydrochemical composition. The hydrogen and oxygen isotope characteristics of brackish and fresh groundwater resemble atmospheric precipitation, while brine, seawater, and saline groundwater show hydrogen and oxygen isotope depletion. Compared to seawater, brine exhibits significant δ³⁷Cl depletion. The analysis of the test results reveals that the formation of brine aquifers results from a complex interplay of climate change, tectonic movements, and sea–land evolution, involving lagoon development during seawater regression, salt concentration through evaporation, and subsequent water–rock interactions. The genesis of saline groundwater involves a complex interplay of brine–seawater mixing, significant evaporation, and potential input of fresh groundwater from atmospheric precipitation and river sources. The formation of brackish groundwater is predominantly influenced by atmospheric precipitation, and agricultural activities, with significant variations in NO₃⁻ concentrations attributed to varying intensities of fertilizer application in the northern plain area. These insights contribute to a deeper understanding of the origins of groundwater and can inform the development of policies for groundwater protection in this area. Full article

The Danjiang River basin is an important water source for the Middle Route of the South-to-North Water Diversion Project. With the shortage of water resources and the increase in pollution pressure, it is of great significance to study the hydrochemical characteristics of surface water in the Danjiang River basin and the risk to human health posed by polluted water bodies for the protection and utilization of water resources. In this paper, 40 surface water samples were collected and analyzed by innovatively adopting the sampling principle of “geological structure unit + landform unit + small watershed unit”. Comprehensive mathematical statistical analysis, Piper trilinear diagrams, Gibbs diagrams, and ion ratio coefficients were used to analyze the hydrochemical composition, spatial distribution characteristics and influencing factors of surface water in the Danjiang River. The entropy weight comprehensive index method (EWQI) and the health risk assessment model recommended by the United States Environmental Protection Agency (HHRA model) were used to evaluate the water quality and potential non-carcinogenic risk of surface water in the Danjiang River source basin. The results showed that the pH of surface water in the study area was 7.02~8.77, with an average value of 8.26; and the TDS was ranged from 134 to 388 mg/L, with an average value of 252.75 mg/L. The main cations in the surface water were Ca²⁺ and Mg²⁺, accounting for 71% and 20% of the total cations, respectively, while the main anions were HCO₃⁻ and SO₄²⁻, accounting for 74% and 19% of the total anions, respectively. The hydrochemical type was HCO₃⁻ Ca·Mg. The hydrochemical genesis was mainly controlled by the weathering of carbonate rocks, while some ions were influenced by the weathering of silicate rocks, and human activities were also an important factor affecting the chemical characteristics of the water. The EWQI of surface water in the whole region was 8.95~25.69, and the health risk index (HI) of nitrate pollution ranged from 0.0122 to 0.2118, in which the HI ranges for children and adults were 0.0217~0.2118 and 0.0122~0.1333, respectively, indicating that the water quality of the entire study area met the Class I water standards, and the potential non-carcinogenic risk of nitrate was low. However, its impact on children was significantly higher than on adults, so it is recommended to monitor the water quality downstream of urban areas in the study area to reduce agricultural non-point source pollution and urban domestic sewage discharge and thereby reduce the potential health risks for young populations. Full article

Lode gold deposits are widespread in orogenic belts of various ages and are a valuable gold source, but their genesis remains debatable. The close relationship between native gold and quartz was considered a reason to search for acid-magmatic sources of heat and fluids (i.e., granite intrusions), while small gabbro bodies were often ignored. Six minor gold deposits associated with NE-strike faults were studied in the Khudolaz area of the South Urals (Tukan, Bilyan-Tau, Fazly-Tau, Muildy-Tamak, Alasiya-II and Isyanbet-I). It was established, for the first time, that all of the studied deposits are similar geologically but differ in mineralogical diversity of ore-bearing quartz veins, which is due to the different composition of host rocks and ore-bearing intrusions of the Khudolaz (325–329 Ma, U-Pb) and the Ulugurtau (321 ± 15 Ma, Sm-Nd) ultramafic-mafic complexes. Results of the geochemical study of quartz veins (ICP MS) and their fluid inclusions (microthermometry, gas chromatography) showed that native gold was mostly precipitated at temperatures of 230–330 °C from a low- to moderate-saline (8–12 wt.% NaCl-eq.) H₂O–CO₂–CH₄-bearing fluid, when weakly oxidized or near-neutral conditions, were replaced by reducing ones. No significant differences between barren milky white and ore-bearing brownish quartz veins were defined, which indicates their common formation settings and an impulse pattern of vein injection. The stable pattern of the fluid salinity, along with low hydrocarbon and N₂ contents, as well as a narrow range of δ¹⁸O values, indicate a prevailing magmatogenic source with a certain influence of host rocks but without the influence of meteoric waters. Based on the presented data, the studied deposits were attributed to the epizonal orogenic type. This study shows the formation of lode gold deposits is possible without the participation of granite massifs. Full article

The pit lakes localized in the eastern part of the Muskau Arch (Western Poland) developed as a result of lignite mining at the turn of the 20th century. The formation of the lakes varied over time and was determined by many hydrogeochemical and biological factors, which resulted in very diverse ecosystems. Thirty of these lakes were studied in the vegetation seasons of 2016 and 2017. The aim of the study was to identify the main factors influencing the diversity of macrophyte vegetation growing under very extreme and diversified habitat conditions. Therefore, in each lake the numbers of macrophyte species and communities were determined, and the water was characterized by 26 physico-chemical parameters and Chl a. Additionally, the genesis, age, area and maximum depth of each lake was determined. The results showed high diversity of habitat conditions. Based on the physical and chemical water properties, four different clusters of lakes were distinguished. The multiple statistical comparisons showed that the main factors responsible for lake differentiation were pH, water mineralization and to a lesser extent, nutrient concentration and water transparency. The physico-chemical differentiation was reflected in the significant differences in the number of species, number of communities, maximum vegetation extent and amount of chlorophyll-a per lake. The correlational analyses confirmed significant relationships between habitat conditions and macrophyte flora diversity in the lakes. Some macrophyte species were found in very extreme environments not previously reported in the literature. Our results showed that in addition to natural processes affecting species diversity in the lakes, the negative impact of anthropogenic pressures (neutralization and fertilization of the water), which leads to the degradation of their unique character, is also an important factor. Full article

Understanding hydrogeological processes at the origin of thermal and mineral groundwater are necessary to ensure their sustainable management. However, many processes are involved in their genesis and often only one or two processes are investigated at the same time. Here, we propose to use an innovative combination of geochemical, isotopic (³⁴S, ¹⁴C, ¹⁸O, ²H) and geothermometry tools to identify, for the first time in a multi-composite geological context, all processes at the origin of diversified thermo-mineral waters. 19 springs covering a wide range of temperature and chemical composition emerging on a restricted area of Corsica Island (France) were selected. Geochemical results highlight five geochemical provinces, suggesting a common origin for some of them. Geothermometry tools show the unexpected involvement of a common deep groundwater reservoir within this non-active zone. Water stable isotopes highlight a contrasted altitude in recharge areas supplying lowland springs. This suggests that different flow patterns have to be involved to explain the wide geochemical diversity observed and to allow the design of a very first conceptual groundwater-flow model. This paper demonstrates the efficiency of the combination of the selected tools as tracers of water–rock interaction, independently of flow depth, intrinsic water properties, geological conditions and interaction time disparities. Full article

Considering the diversity of clay raw materials, we can distinguish their numerous varieties using genesis and retention conditions, as well as specific physical, chemical, and thermal properties as criteria of division. Three samples of fine-grained clay materials, collected randomly from the Turów lignite mine tailing piles, were subjected to testing for their grain and chemical composition and specific surface area. The results show that the tested materials are non-porous adsorbents. Additionally, a thermal analysis was carried out with a simultaneous quadrupole mass spectrometry (QMS). In the tested samples, the weight loss associated with the release of water from the clay was observed in two temperature ranges: from 40 to 240 °C (physically bound water) and from 330 to 620 °C (structured water). The weight loss associated with the decomposition of organic matter was registered in the temperature range of 300 to 560 °C. The results of the conducted tests might provide the basis for further analysis of the potential use of these materials as heat stores, components of insulators, or additives of ceramic products. Full article

Ian Carmichael wrote of an “andesite aqueduct” that conveys vast amounts of water from the magma source region of a subduction zone to the Earth’s surface. Diverse observations indicate that subduction zone magmas contain 5 wt % or more H₂O. Most of the water is released from crystallizing intrusions to play a central role in contact metamorphism and the genesis of ore deposits, but it also has important effects on the plutonic rocks themselves. Many plutons were constructed incrementally from the top down over million-year time scales. Early-formed increments are wall rocks to later increments; heat and water released as each increment crystallizes pass through older increments before exiting the pluton. The water ascends via multiple pathways. Hydrothermal veins record ascent via fracture conduits. Pipe-like conduits in Yosemite National Park, California, are located in or near aplite–pegmatite dikes, which themselves are products of hydrous late-stage magmatic liquids. Pervasive grain-boundary infiltration is recorded by fluid-mediated subsolidus modification of mineral compositions and textures. The flood of magmatic water carries a large fraction of the total thermal energy of the magma and transmits that energy much more rapidly than conduction, thus enhancing the fluctuating postemplacement thermal histories that result from incremental pluton growth. The effects of water released by subduction zone magmas are central not only to metamorphism and mineralization of surrounding rocks, but also to the petrology and the thermal history of the plutons themselves. Full article

Among the most intriguing mysteries in the evolutionary biology of photosynthetic organisms are the genesis and consequences of the dramatic increase in the mitochondrial and nuclear genome sizes, together with the concomitant evolution of the three genetic compartments, particularly during the transition from water to land. To clarify the evolutionary trends in the mitochondrial genome of Archaeplastida, we analyzed the sequences from 37 complete genomes. Therefore, we utilized mitochondrial, plastidial and nuclear ribosomal DNA molecular markers on 100 species of Streptophyta for each subunit. Hierarchical models of sequence evolution were fitted to test the heterogeneity in the base composition. The best resulting phylogenies were used for reconstructing the ancestral Guanine-Cytosine (GC) content and equilibrium GC frequency (GC*) using non-homogeneous and non-stationary models fitted with a maximum likelihood approach. The mitochondrial genome length was strongly related to repetitive sequences across Archaeplastida evolution; however, the length seemed not to be linked to the other studied variables, as different lineages showed diverse evolutionary patterns. In contrast, Streptophyta exhibited a powerful positive relationship between the GC content, non-coding DNA, and repetitive sequences, while the evolution of Chlorophyta reflected a strong positive linear relationship between the genome length and the number of genes. Full article