Acidic Rocks Research Articles

Multiscale characterisation on the adhesion and selective adsorption at bitumen–mineral interface

The adhesion between bitumen and minerals is essential for the durability of asphalt mixtures, influenced by bitumen composition and mineral structure. The chemical action theory suggests that polar components in bitumen are adsorbed onto the mineral surface, facilitating adhesion. In this study, environmental scanning electron microscopy with energy-dispersive X-ray (ESEM-EDS) is used to analyse bitumen–mineral interfaces at a microscopic level. Elemental analysis reveals selective adsorption of polar substances from bitumen onto the surfaces of four types of minerals. Results show that alkaline rocks (limestone and albite) have a higher adsorption capacity than acidic rocks (granite and quartz). Additionally, treating mineral surfaces with alkaline solutions enhances adsorption. The adhesion properties of bitumen to various minerals are evaluated using the pull-off test. The correlation between ESEM-EDS and pull-off tests demonstrates that the macroscopic adhesion of bitumen to minerals is linked to the microscopic selective adsorption of polar substances.

Characteristics and Risk Assessment of Heavy Metal Contamination in Arable Soils Developed from Different Parent Materials

This study analyzes the heavy metal pollution in cultivated soils developed from different parent materials in Yunnan Province and assesses their risk levels. The results show significant regional differences in soil heavy metal pollution, greatly influenced by the type of parent material. Cadmium (Cd) pollution is most severe in multiple parent material soil regions, particularly in areas with carbonate and purple rocks, exhibiting a high pollution risk. Other heavy metals such as zinc (Zn), copper (Cu), and lead (Pb) also show varying degrees of enrichment in different parent material zones, posing potential pollution risks. The soil pollution levels of heavy metals were classified using the geo-accumulation index method. It was found that soils developed from carbonate rocks and purple rocks have the most severe heavy metal pollution, while soils from quartzitic rocks, acidic crystalline rocks, and basalt exhibit relatively lower pollution levels. By analyzing the characteristics of heavy metal pollution in different parent materials, this study provides a scientific basis for regional soil pollution management and sustainable agricultural development.

Chronostratigraphy and compositional characteristics of miocene volcanism in the Sierra de Pire Mahuida, extra-Andean Patagonia, Argentina

The Pire Mahuida Volcanic Complex (PMVC), located in the extra-Andean region of southern Argentina (68° to 68° 40′W and 41° 51′ to 42° 28′ S), is a bimodal volcanic field that developed during the Miocene (17Ma-14Ma, Langhian-Burdigalian Stages). The complex partially surrounds the southern boundary of the Somún Curá basaltic plateau. The PMVC is mainly composed of acidic pyroclastic and lava facies (rhyolite/dacite flows, lava domes and coulees) and stands out as the one with the largest volume of acid rocks in the Somún Curà province, involving two evolutionary trends (alkaline and subalkaline). Subordinate in volume, basaltic flows overlie this extensive sequence of acidic rocks. Relationships between some units are difficult to establish because they are the result of different eruptive centres. However, stratigraphy, morphology and petrography allow two acid phases to be distinguished, one a mainly lavic phase and the other a mainly pyroclastic phase. U-Pb ages allow precise dating and temporal placement of the acid sequence: 1- lava flows and 2- lava domes and related pyroclastic phases. Two calderas and fissures are responsible for the emission of the felsic rocks. The basaltic facies shows a wide range of characteristics, which also allow two different groups to be distinguished. 1. The basalts of the main plateau are associated with a main fault of NW-SE pattern and 2.The younger basalts are associated with small volcanic edifices. The effusion of the complex was developed in a relatively short time with the basic episode being more prolonged than the acid episode.

Nd-isotope effects through factional crystallisation-assimilation (AFC) processes in the continental crust, heterogeneous in age: the example of ferrobasalts from the Ladoga Graben (Karelia, Russia)

Petrography, geochemistry and isotope geochemistry of the Mesoproterozoic volcanic rocks occurred as lava flows and the Valaam sill in the Ladoga rift, have been studied. The Ladoga rift is located in the area of thrusting of the Palaeoproterozoic Svekofennian orogenic complexes onto the Archean Karelian craton. Ferrobasites of close composition and geological position in lava flows and sill have different Nd isotopic composition, differing by 5 units εNd(t): –4…-5 in ferrobasalts of lava flows and a very low-radiogenic Nd isotopic composition in mafic rocks of the sill (εNd(t) to –11 for ferrogabbro), and identical to the isotopic composition of its acidic rocks (εNd(t) to –11 for granophyres). It is shown that in the crust, heterogeneous in age, the process of fractional crystallisation along the tholeiitic trend combined with assimilation of melt from wall rocks can be an effective mechanism for forming such “paradoxical” features of the Nd isotopic composition. The isotopic composition of sill rocks indicates the probable presence of Mesoarchean blocks in the lower crust of the Ladoga graben region.

Soil hydraulic properties, mineralogical alteration and pore formation in Regosols from southern Brazil

ABSTRACT Regosols (Neossolos) are soils with use limitations mainly related to effective depth, abundant presence of rock and saprolite fragments, and frequently high slope gradients; besides that, they represent a new agricultural frontier for grain production in southern Brazil. This study evaluated soil saturated hydraulic conductivity (K sat ) and water retention and availability in Regosols and saprolites derived from volcanic rocks in southern Brazil and the relationship of these variables with porosity in saprolithic horizons characterized by mineralogical weathering. The study was carried out on eight profiles derived from basic and acidic volcanic rocks of the Serra Geral Formation. We evaluated soil morphology, granulometry, porosity, bulk density (BD), K sat , water retention, electronic/ optical microscopy and chemical composition of parent materials, and soil mineralogy. Soil K sat ranged from 0.0 to 6.40 cm h -1 in the evaluated horizons, without significant difference between the A and Cr horizons. Seven soil profiles showed BD equal to or less than 1.28 Mg m -3 for the Cr samples. Total porosity in the Cr horizons was above 0.5 m 3 m -3 and not significantly different from A horizons. In five of the eight soil profiles, one or more Cr horizons presented greater available water than A horizons. Electronic and optical microscopy evidenced abundant cracks and mineralogical weathering in the rock samples. X-rays diffraction data also indicated advanced degree of weathering of Cr horizons, evidencing abundant formation of pores in the saprolite. and justifying the high-water retention in Regosols profiles in southern Brazil.

Germanium and its isotopes as indicators of hydrogeochemical conditions in a terrestrial geothermal system (Karkonosze granitoid, Sudetes, Poland)

The germanium content and its isotope ratio in thermal waters, aquifer rocks and main silicate minerals in a terrestrial groundwater system located in a granitic pluton (Karkonosze granitoid, Sudetes, Poland) have been investigated. This is the first extensive Ge isotope study carried out in both groundwater and aquifer rocks to better understand previously the identified enrichment of groundwater relative to rocks. This research also provides the first data on δ74/70Ge for hybrid acid rocks formed by mixing magmas from two different sources (mantle- and crustal-derived) and main silicate minerals. The Ge isotopic composition in different facies of granite (porphyritic, equigranular) is comparable (δ74/70Ge of 0.43–1.23‰) to its hybrid rocks (quartz diorite–granodiorite, microgranular magmatic enclaves, composite dykes) – 0.79–1.27‰. However, the range of variability of this feature is quite wide. The minerals have δ74/70Ge values of 1.01–1.04‰ in quartz, 0.84–0.90‰ in alkali feldspars, 0.76–0.88‰ in plagioclase, and 0.36–0.39‰ in biotite. The thermal waters are enriched in heavy Ge isotopes (δ74/70Ge of 1.21–2.78‰) relative to the aquifer rocks (δ74/70Ge of 0.43–1.27‰). Currently, the most likely explanation for this is the influence of secondary mineral phases formed in the geothermal granitic system. This comprises the preferential incorporation and adsorption of light Ge isotopes in/onto iron oxide/hydroxides and clay minerals. The other theoretical explanation, i.e., sulfide formation, is unlikely due to the unfavourable hydrogeochemical conditions in the studied system. The δ74/70Ge values of thermal waters are similar to those of previously studied continental geothermal waters (1.65–3.29‰; Siebert et al., 2011) and fresh groundwater (2.24–4.02‰; Baronas et al., 2020), confirming that groundwater enrichment in heavy Ge isotopes relative to aquifer rocks may be widespread in the upper continental crust. Variation in the isotopic composition of the studied thermal waters is a result of the aquifer rock mineralogy and, in some cases, mixing of the old deep-circulating thermal water with the shallow modern cold groundwater. The general similarities in the chemical composition of the studied waters are due to the influence of porphyritic granite, which is the dominant rock type in this aquifer system. Some differences in chemical composition, including differences in the Ge isotopic composition, are related to the local distribution of hybrid rocks and sulfides. The δ74/70Ge and Ge/Si ratios have been shown to be sensitive indicators of local hydrogeochemical conditions in an alimentation zone and a near-borehole zone of particular water intakes.

REE signatures in quaternary deposits: implication for provenance and economic potentials

The Rare Earth Element (REE) geochemistry of siliciclastic sediment in the Ilaje area, eastern Dahomey basin, southwestern Nigeria was conducted to determine the provenance, geotectonic setting as well the REE economic potential in the sediments. Geochemical analysis results (ppm) revealed the concentration of La varies from 1.87–21.47 while Ce ranges from 1.16–45.98. Others include; Pr (1.07–39.56), Nd (0.71–26.02), Sm (0.42–12.51), Eu (0.20–4.66), Gd (0.27–8.79), Tb (0.29–3.97), Dy (0.28–3.62), Ho (0.22–2.76), Er (0.29–2.64), Tm (0.33–3.83), Yb (0.37–3.75) and Lu (0.29–3.03) respectively while the ∑REE ranges from 2.25 to 6686.75 ppm. The REE normalization plot is characterized by an inclined shape depletion indicating depletion trend. The patterns show an enriched Light Rare Earth Elements (LREE) and Heavy Rare Earth Element (HREE) pattern indicating upper continental crust sourced materials. The plot also revealed a negative Eu anomaly which may be associated with plagioclase fractionation in the acidic source rocks. The high ∑REE in the sediments has uncovered the economic potential of the sediments as a useful raw material resource for technological advancement.

Environmental impact assessement and determination of radiogenic heat production in the North Jabal Maghrabiyah area, Central Eastern Desert, Egypt

The present study deals essentially with the establishment of the environmental natural radiation levels in the surveyed area. These will provide base-line information that can be used as a reference to detect and determine the amount and extent of any possible future variation or contamination in the natural radioactivity levels that might occur in the study area due to any potential incidents involving release of nuclear radiation or fallout of nuclear fission products that could affect both terrestrial and atmospheric radioactivity. A map of radiogenic heat production (RHP) was built from the airborne spectral gamma-ray data of North Jabal Maghrabiyah area, central Eastern Desert, Egypt. The area of study reflects radiogenic heat production varying from 0.03 to 6.44 μWm-3, averaging a value of 0.99 μWm-3, while their standard deviation reaches 0.61 μWm-3. The maximum values are associated with the acidic rocks in the northeastern, central, southeastern, northeastern and eastern parts of the area of study. Results showed several levels of radiation as follows: (less than 0.39 mSv/y), (from 0.39 to 0.59 mSv/y), (higher than 0.59 and reached to 2.01 mSv/y). The dose rate more than 1 mSv/y is considered the radioactivity hazard level which represented mainly with late to post tectonic Potassic calc-alkaline granitoids, calc-alkaline granitoids, Muꞌtiq group, Dukhan volcanic/subvolcanic group, Atallah felsite, Parts of Quaternary deposits, Hammamat sediments, parts of Tarif, Dakhlah and Duwwi Formations. Thus, the North Jabal Maghrabiyah area can be considered as high RHP, because of the relatively high radioactive concentrations. There are good relationships between the derived RHP and the three radioactive elements, equivalent Uranium (eU), equivalent Thorium (eTh) and Potassium (K), as represented by the binary relationship between any of two elements. The importance of radiogenic heat production is the source of ground thermal energy.

Heavy metal spatial distribution, source analysis, and ecological risks in the central hilly area of Hainan Island, China: results from a high-density soil survey.

The presence of heavy metals in soil has gained considerable attention due to their potential risks to ecosystems and human health. In this study, a thorough soil investigation was performed in the hilly region of central Hainan, which was formerly regarded as an area with the highest ecological environmental quality. A total of 7094 soil samples were systematically collected with high density over a large area. Simultaneously, a detailed investigation was conducted on the surrounding environment of each sampling point, including environmental factors such as soil, land use and crop types. The soil samples were analysed for heavy metals, pH, organic matter, and other parameters. The soil heavy metal pollution level, ecological risk and health risk were evaluated using the geo-accumulation index and the potential ecological risk index. The findings showed that the average contents of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were 1.68, 0.042, 24.2, 6.49, 0.0319, 7.06, 29.6 and 49.8mg·kg-1 respectively. Except for Hg, the mean values of the other heavy metals were either lower than or similar to the background values of Hainan. Also, only a few localised areas showed contamination by heavy metals. The primary sources of heavy metals, identified by a positive matrix factorisation model, could be categorised into four types: natural sources related to the soil formation process from acidic intrusive rocks (such as granite); natural sources primarily influenced by atmospheric deposition; anthropogenic sources associated with agricultural activities; and natural sources related to the soil formation process from middle-mafic intrusive rocks and black shales. The correlation analysis and variance analysis findings suggested that the content of heavy metals in the soil was primarily associated with the parent rock. The study area generally had low heavy metal levels and was not significantly polluted. However, agricultural activities still affected the enrichment of heavy metals. Therefore, it is imperative to remain vigilant about the ecological risks linked to soil heavy metals while continuing land development and expanding agricultural activities in the future. These findings indicate that conducting high-density soil surveys can enhance our understanding of regional soil heavy metals and enable reliable recommendations for agricultural planning. Whether in areas with low pollution risk or potential pollution risk, it is recommended that high-density soil surveys be conducted provide scientific guidance for further agricultural development.

Early Ordovician to Early Permian tectonic evolution of the northern Western Kunlun Orogen (NW China): Insights from the Omixia Complex and surrounding rocks

The Palaeozoic tectonic evolution of the Western Kunlun Orogen plays an important role in deciphering the Tethyan tectonic evolution. This study provides new geochronology, geochemistry and Lu–Hf isotopic data of igneous rocks from the Omixia Complex in the eastern section of the northern Western Kunlun, as well as detrital zircon ages from turbidites and meta‐sediments north of it. From the Omixia Complex, the determined ages of five ultramafic–mafic rock samples are approximately 470, 456, 429, 401 and 382 Ma. Two samples of acidic rocks from the same complex yielded ages of approximately 438 and 378 Ma. One pegmatitic plagiogranite sample exhibits feature of accretionary arc granites, while other samples show geochemical characteristics of island arc tholeiite and E‐MORB. Additionally, four turbidite matrix and two limestone samples, with a major peak around ca. 480–500 Ma, have the youngest zircon ages ranging from ca. 481 to 387 Ma, paralleling the age range of igneous rocks in the ophiolitic mélange. The εHf(t) values of these samples reveal a broad spectrum of crustal and mantle processes. The youngest zircon ages of five meta‐sedimentary rock samples north of the Omixia Complex range from ca. 581 to 535 Ma, with peak ages concentrated around ca. 0.9–1.0 Ga. Their provenance characteristics differ from the turbidite matrix in the southern Omixia Complex and from the meta‐sediments in the northern Tiklik terrane with peak ages of ca. 0.8 Ga. A younger limestone sample yielded youngest zircon age of ca. 294 Ma, which is unconformably overlain the Omixia Complex and surrounding older rocks. Based on these new results, combined with previous data, we propose a new tectonic model for the eastern section of the northern Western Kunlun Orogen, suggesting a continuous evolution process of multi‐terrane subduction–accretion collage from the Early Ordovician to the Middle Devonian in the Paleo‐Tethys Ocean, which evolved into an Andean‐type active margin in the Early Permian, contributing to the substantial continental growth of the southern Tarim Craton.

U–Pb zircon, zircon Hf and whole-rock Sm[sbnd]Nd isotopic signatures on the evolution of Late paleozoic bimodal magmatism in Gharebagh area, NW Iran

The Gharebagh area consists of a suite of mafic to acidic rocks located in northwestern Iran, in the Sanandaj-Sirjan zone (SSz), which is part of the Zagros orogenic belt. In this paper, we present a detailed petrological, geochronological, and isotopic study of representative rocks of Late Paleozoic igneous activity in NW Iran. LA-ICP-MS dating of zircons shows that the Gharebagh intrusive body (GIB) was formed in a tight time frame of 300 Ma. Geochemical analyses as well as isotopic studies of LuHf on zircon and SmNd on whole-rock were used to determine the petrogenesis of these rocks and develop a tectonic model. Crustal-model ages (Hf-tNC) of 0.57 to 1.02 Ga indicate the contribution of older Neoproterozoic crust to the formation of these rocks. The partially melted lower crust was one part of the magma together with a mafic melt formed by differentiation of the depleted mantle. The GIB suite was presumably formed by an anorogenic magmatic event (continental rift) that included extensive mantle upwelling and partial melting of the lower crust. So the gabbroid and granitoid rocks are coeval with the 300 Ma but not co-magmatic origin.

Geochemistry of I-type Volcanic Arc Granitoid From Tanggamus Regency, Southern Sumatra

Granitoid intrusion of several provinces on Sumatra is correlated with Southeast Asia tectonics that have occurred since the Permian. Granites from several volcanic arc provinces are located along the western part of Sumatra Island and are found near Bukit Barisan. This study describes the geochemical character of granitoid from the Tanggamus region and its surroundings near the Bukit Barisan cluster. After megascopic description in the field, major oxides, trace elements, and rare earth elements in rock samples were measured using X-ray fluorescence and inductively coupled plasma-mass spectrometry devices. The samples were intermediate to acidic intrusive rocks with SiO2 ranging between 61.35% and 75.29%. The rocks can be described as diorite to granodiorite and were formed as a result of subduction processes. The granitic rock samples showed I-type features of A/CNK value <1.1, volcanic arc granite affinity, K2O/Na2O ratio, and magnesian properties. The total rare earth content was medium with an average of 43.97 ppm. The similarity of the rare earth normalized diagram against the chondrite value indicates that the samples come from an identical origin.

Origin of Grain-Coating Chlorite and Implications for Reservoir Quality in the Triassic Deep-Buried Volcaniclastic Sandstones, Central Junggar Basin, Northwestern China.

The occurrence and genesis of grain-coating chlorite were investigated in order to evaluate the impact of grain-coating chlorite on preserving porosity in the deep-buried Triassic Karamay volcaniclastic sandstones based on thin sections, scanning electron microscopy, and an electron probe. Grain-coating chlorite was formed during the eogenesis, originating from the precursor of smectite through the solid-state transformation (SST) mechanism. The hydration and dissolution of unstable, intermediately basic volcanic rock fragments provided essential Fe2+ and Mg2+ ions for the formation of grain-coating chlorite. Due to relatively high stability and low susceptibility to dissolution, acidic volcanic rock fragments could not promote chlorite formation but resulted in authigenic quartz and clays as pore-filling cements. This process would destroy reservoir properties. Under high hydraulic conditions, medium- to coarse-grained sandstone experienced saltation transport, creating significant velocity differentials and pressure differentials on grain surfaces. Subsequently, clay grains adhere to the surfaces, forming grain-coating chlorite during diagenesis with good continuity. In contrast, pebbly sandstone undergoes rolling transport, resulting in smaller velocity differentials on grain surfaces. This makes relatively ineffective clay adsorption and leads to discontinuous grain-coating chlorite in subsequent stages. Under weak hydraulic conditions, grains and clay particles in fine-grained sandstone undergo suspended transport, lacking mutual movement and velocity differentials. Clay particles cannot effectively cover particles but instead fill the pores between them. Therefore, continuous grain-coating chlorite is more commonly developed in the medium- to coarse-grained sandstones and is crucial for inhibiting quartz cementation with a coverage rate exceeding 80%. Inadequate coatings fail to inhibit quartz cementation effectively, while excessive coatings may block pore throats. Optimal protection of primary porosity could occur only when grain-coating chlorite is moderately developed.

Temporal constraints on magmatic evolution of Acıgöl Bimodal Volcanic Field (Nevşehir, Türkiye)

Neogene to Quaternary post-collisional Central Anatolian volcanism is associated with complex tectonic transition from collisional to extensional regime starting from Miocene. Upper Miocene – Pliocene volcanism is characterized by calc-alkaline effusive products and 10 major ignimbrite sheets. Quaternary represents an evident change in both eruptive styles and the geochemical characteristics of the volcanic products. Pleistocene Acıgöl Bimodal Volcanic Field (ABVF) represents one of the youngest volcanism in Cappadocian Volcanic Province (CPV) and comprises coeval basic and acidic rocks with a Daly Gap between ∼60 % and 72 % SiO2. Pleistocene basaltic volcanism in ABVF is represented by fissural lavas and monogenetic scoria cones, whereas rhyolitic activity is observed as dome/dome flows and pyroclastics including plinian falls and Kumtepe ignimbrite. Basalts of Lower and Middle Pleistocene are silica-undersaturated being nepheline-normative, on the other hand, Upper Pleistocene basic rocks are hypersthene/quartz-normative. Similarly, Lower and Middle Pleistocene rhyolites have higher Sr, Ba, La, than Upper Pleistocene rhyolites which are represented by elevated Y, Th, Nb, Ta and Rb.Petrological data and performed geochemical models show that Lower – Middle Pleistocene primitive basalts can be generated by the partial fusion of an EM-II type spinel peridotite containing amphibole, phlogopite and accessory rutile. Slightly evolved Upper Pleistocene basalts can be formed by crystal fractionation dominated differentiation of earlier basaltic parents. Fractional crystallization of basaltic magmas in high-level segregated chambers with varying amounts of crustal contribution can produce rhyolitic compositions. Furthermore, the amount of crustal contribution diminishes in Upper Pleistocene.

Geochemistry and mineralogy of modern floodplain Nile sediments of Sohag area, Egypt: an environmental perspective

Understanding the characteristics of modern floodplain sediment (MFS) is important for geomorphological, paleoclimatic, sedimentation, and environmental investigations. We collected samples from present floodplain Nile sediments in Egypt’s Sohag area and used mineralogical and geochemical (i.e., major and trace elements) proxies to investigate the characteristics and establish their provenances, climatic conditions during deposition, and weathering influence. The study revealed that the Nile floodplain sediments are composed mainly of silt (26–77%), clay fraction (7–44%), and sand content (3–63%), and their texture is classified as clayey silt. These sediments are classified geochemically as greywacke to shale. The mineralogical studies revealed two main assemblages of heavy minerals: the first assemblage represented by magnetite, goethite, zircon, epidote, and garnet and reflects the basement complex in the Eastern Desert and its surrounding rocks; and the second assemblage of goethite, pyroxene, hornblend, and mica of fooldplain deposits derived from the Ethiopian highlands. The geochemical studies indicate that the Nile sediments are immature and formed due to the moderate degree and nonsteady chemical weathering of the parent rocks. The geochemical studies show different mixed sources of sediments, where fine sediments are mostly mafic igneous with a partial contribution from siliscic sedimentary rocks, while the coarser ones are derived mainly from siliscic sedimentary and acidic igneous rocks. The sediments of the presented modern fooldplain reflected two different tectonic setting source areas (collision and continental rift tectonic setting for high silica and low silica samples, respectively) that were shared in supplying the sediments to the present basin. The study revealed that the investigated area may become desertified as a result of climate change and human activities such as salinity, fertiliser use, sand encroachment, and pollution.

Identification of the Sedimentary Sources and Origin of Uranium for Zhiluo Formation of the Tarangaole U Deposit, Northeastern Ordos Basin

The large-sized Tarangaole uranium deposit and its neighboring Daying and Nalinggou deposits, located in the northeastern margin of the Ordos Basin, constitutes a major uranium resource base in northern China. In order to further clarify the sedimentary material source, uranium source and regional sediment–tectonic setting of the uranium-fed clastic rocks (i.e., Zhiluo Formation(J2z)) in the district, this paper carried out whole-rock geochemistry, heavy minerals composition and in situ U-Pb dating of detrital zircons for sandstones from the lower section of the Zhiluo Formation. The results have shown that the average chemical differentiation index (CIA) for the host rocks is 73.16 and the chemical weathering degree is moderate. Heavy minerals are mainly composed of ilmenite, garnet, chlorpyrite, zircon, pyrite, apatite, hematite, etc. The U-Pb dating of detrital zircon generally indicates three age peaks, i.e., 260~Ma, 1850~Ma and 2450~Ma, respectively. In conclusion, the source rocks may have been formed at active continental margins, e.g., in a continental margin arc environment. The sedimentary materials mainly come from khondalite series, TTGs, granulite, and mafic–ultramafic intrusive rocks distributed among the Daqing–Ula Mountains and adjacent areas, etc. The Late Paleozoic U-rich intermediate and acidic magmatic rocks spreading over the eastern part of the Ula–Daqing and Wolf mountains have provided the main uranium sources for the formation of major U deposits in the northern Ordos Basin.

Hydrothermal alteration of the surface volcanic rocks at the Acoculco geothermal field, Mexico: a multi-parametric approach

AbstractThe studies on hydrothermal alteration-induced effects in surface and subsurface rocks provide useful information in the characterization and exploitation of a geothermal reservoir. Generally, these studies are based on traditional, and reliable methods like petrography (primary and secondary minerals, and grade of alteration), and geochemistry (mobility of elements, changes in mass and concentration of elements, and fluid inclusions). Recently, apart from these established methods, some methods based on the geochemical (Chemical Index of Alteration, CIA; Weathering Index of Parkar, WIP; Loss on Ignition, LOI; and Sulfur, S) and rock magnetic properties (magnetic susceptibility, χlf; and percentage frequency-dependent susceptibility, χfd%) are also being applied in the identification of whether a rock is an altered or a fresh one. The Acoculco Geothermal Field (AGF), Mexico, is characterized by high temperature and very low permeability, and it is considered a promissory Enhanced Geothermal System. The following changes are observed in the rocks as a result of an increase in hydrothermal alteration: (1) an increase in CIA, LOI, and S values, and a decrease in WIP; (2) an increase in quartz and quartz polymorph minerals (silicification), and clay minerals (argillization); and (3) decrease in χlf values. At AGF, the most altered surface acid rocks are characterized by entirely quartz and its polymorphs, and clay minerals. The present study also indicates the applicability of the binary plots of major elements (felsic vs mafic component) and rock magnetic parameters (χlf vs. χfd%). The rock with χfd% value of 2–10 and χlf value < 0.5 × 10–6 m3 kg−1 indicate the presence of single domain and stable single domain grains, which in turn suggests that it is an altered rock. These methods are simple to apply, rapid, reliable, and have the potential to become effective tools for the identification of hydrothermally altered rocks during the initial stage of geothermal exploration.

Taxonomical status of Andreaea clavata var. tenuior Broth. (Bryophyta, Andreaeaceae)

The moss genus Andreaea Hedwig (1801:47) (Andreaeaceae Dumort., Bryophytina Engl.) is found growing on acid and neutral rocks in cool temperate to subpolar environments, as well as in the high altitude mountains of tropical and subtropical regions (Murray 1988). The genus include between 15 and 20 species in the Andean region (Churchill et al. 2020) with many taxa still poorly known. Andreaea clavata Broth. (in Herzog 1916:10) is only know from two collections, one from Bolivia and one from Peru (Hermann 1976; Menzel 1992).

Современное представление о промышленной классификации колчеданно-полиметаллических месторождений Рудного Алтая

There are many classifications of polymetallic deposits. Many researchers, based on the genetic relationship of the deposits, attribute the deposits of the Rudny Altai to the VMS Kuroko type. Other authors classify polymetallic deposits of the Rudny Altai, relying on geodynamic conditions and modes of their formation. Such a variety of classifications makes it difficult to understand and use these classifications for various kinds of research, and questions also arise when comparing with foreign analogues. Therefore, the authors of this article propose to consider the modern unified classification of deposits of the Ore Altai according to J.W. Lydon (1988), based on the division of polymetallic deposits of VMS by volume ratio Zn/(Zn+Pb) into 2 main industrial genetic types (Zn-Pb-Cu and Cu-Zn). The first type (Zn-Pb-Cu) has a mass ratio of Zn/(Zn+Pb) from 0.70 to 0.80; the second type (Cu-Zn) is more than 0.95. Practically all deposits of the Ore Altai can be attributed to the Zn Pb-Cu group, as having mass ratios of Zn/(Zn+Pb) from 0.64 to 0.86 and localized in medium to acidic calcareous-alkaline volcanic rocks mainly of Phanerozoic age

Материалы к флоре печеночников хребта Сетте-Дабан (Восточная Якутия, Россия)

The Sette-Daban Range, about 650 km long, is the southernmost part of theVerkhoyansk Mountains System. The only information on the liverworts of the range so far has been based on the results of field research 2000–2001. The bedrock of the Sette-Daban Range consists mainly of limestone and dolomites, while the rest of the Verkhoyansk Mountains System is composed of acid rocks. Because of this, the flora of the liverworts of the Sette-Daban Range differs significantly in its species. The present research was carried out in 2015–2017 in the basins of the Vostochnaya Handyga and Sakkyryr rivers using the route method in different habitats throughout the vertical profile. The annotated list describes the growth conditions of each species and indicates the structures associated with reproduction. A total of 44 species were identified. Of these, Apopellia alpicola and A. megaspora are new for Yakutia, 22 species are new to the flora of the Sette-Daban Range, seven species are rare in the territory of Yakutia or in the mountains of the northeast of the republic (Arnellia fennica, Eocalypogeia schusteriana, Frullania subarctica, Lejeunea alaskana, Mannia triandra, Sauteria alpina, Scapania sphaerifera). Eocalypogeia schusteriana, Mannia triandra, and Scapania sphaerifera are included in List of Russian Protected Species, Lejeunea alaskana — in the Red Data Book of the Republic of Sakha (Yakutia). At present, 69 species are known for the liverwort flora of the Sette-Daban Range. Sette-Daban is the habitat and conservation area of many basiphilic and calcephilic liverworts, rarely found in the Verkhoyansk and Chersk Mountain systems.