Minerals

The Tomtor massif is a polychronous ring zonal complex of alkaline ultramafic and carbonatite rocks containing unique Nb and REE deposits. Mineralogical and geochemical studies of minerals from different types of silicate rocks and carbonatites of the Tomtor massif were performed. For excluding traces of the interaction between silicate and carbonatite melts, we limited ourselves to the study of independent small secant bodies located in the immediate vicinity of the massif itself. The presence of through mineral series in various silicate igneous rocks and carbonatite ores of high-titanium chromium spinels, rare-metal, ore and other exotic phases with similar compositional trends was defined. Such studies will help reveal the mineralogical criteria for the genetic relationship between silicate melts and associated carbonatite derivatives, which can form rich rare elements mineralization. Also, such studies help to improve the petrochemical and mineralogical criteria for dividing potentially diamond-bearing magmatites (typical kimberlites) from non-diamond-bearing kimberlites, alpicrites and other non-diamond-bearing rocks convergent to kimberlites, which are formed under different physicochemical conditions. The existence of polychronous complex ore–magmatic ring complexes, such as the Tomtor massif, indicates the existence of large deep intraplate magma-generating chambers in the lithospheric mantle. Full article

An Rb₂CoSi₅O₁₂ leucite analogue has been synthesized. An ambient temperature X-ray powder diffraction study shows that this analogue has the Pbca orthorhombic structure of Cs₂CdSi₅O₁₂. A high temperature X-ray powder diffraction study on this analogue shows a Pbca orthorhombic to cubic phase transition at 457 K. The Rb₂CoSi₅O₁₂ unit cell volume initially decreases with increasing temperature on passing through this phase transition. Full article

Iron is a limiting nutrient in the marine biogeochemical cycle, and hydrothermal processes at mid-ocean ridges are well-known as one of its sources to the water column. However, a major portion of the hydrothermal iron is precipitated near the source and plays an essential role in oceanic elemental cycling. Here, we carried out a detailed study on the geochemical characteristics of Fe, using a sequential chemical extraction protocol, in a short sediment core collected from the eastern Southwest Indian Ridge (SWIR) to understand the iron association in individual mineral phases. Major and trace and rare-earth element concentrations, positive europium anomaly, and rare-earth fractionation show that the source components in the sediment core are composed of biogenic, local mafic, ultramafic, and hydrothermal origin. Solid-phase Fe speciation results indicate that >60% of Fe is associated with the Fe-oxides phase and indicate the hydrothermal plume particulates settled from the water column. A relatively low concentration of Fe associated with the pyrite and silicate (Fe_Res) phase suggests an erosion of sulphide and silicate minerals from the nearby vent field. The down-core variation reflects the transformation of primary ferrihydrite to more stable oxide mineral goethite/hematite and, to some extent, the formation of silicate minerals. Full article

Climate change induced changes in river flow dynamics have the potential to change the composition of suspended sediments in crucial tropical river ecosystems, possibly affecting their resiliency. This study investigates how changes in river discharge and bedrock lithology affected the physiochemical nature of river suspended sediments over a typical year in three Puerto-Rican rivers. Suspended sediment samples were collected on filter membranes in 2006 from three watersheds of differing lithology (quartz-diorite, volcaniclastic, and mixed lithology) in the Luquillo Mountains, Puerto-Rico. By monitoring changes in suspended sediment mineralogical composition (determined by XRD and SEM) as a function of discharge, we determined how sediment loads responded to changes in hydrological input in a typical year. Results showed that bedrock lithology influenced river suspended sediment mineralogy, with the fraction of crystalline versus amorphous material strongly influenced by the dominant lithology of the watershed. Crystalline phases were associated with granodiorite bedrock compared to amorphous material dominating the volcaniclastic watersheds. Thus, the mineralogy of suspended sediments in the river systems was controlled by secondary minerals. Mineralogical results showed that, bearing quantitative changes upon hydrological events, suspended sediments in all three watersheds returned to baseline composition post storm events, suggesting that the three watersheds are resilient to the events recorded that year. While the long-term mineralogical analysis of the evolution of suspended material in the studied rivers provided insights into river response to hydrologic events, it also proved technically challenging as materials in suspension in such pristine rivers are sparse and poorly crystalline. Full article

The in-situ X-ray diffraction (XRD) and Raman spectra of synthetic (Mg, Fe, Mn)CO₃ single crystals for (Mg_0.37Fe_0.31Mn_0.32)CO₃, (Mg_0.49Fe_0.51)CO₃, (Fe_0.47Mn_0.53)CO₃, and (Mg_0.50Mn_0.50)CO₃ were investigated up to 871 K. Lattice parameters and the volumetric thermal expansion coefficients were achieved, demonstrating an inherent anisotropy of c/a near to 3.0. The Raman spectra of our intermediate components all exhibit a negative temperature dependence similar to that of the end members. The temperature dependence of the external modes T, L, anti-symmetric stretching mode ν₃, and out-of-plane bending mode 2ν₂ is generally more prominent than the in-plane bending mode ν₄ and symmetric stretching mode ν₁ except for siderite FeCO₃. Combining thermal expansion coefficients α_V with the relative changes in frequency δνi/δT of Raman spectra, the average thermodynamic Grüneisen parameters (γ_th) for (Mg_0.37Fe_0.31Mn_0.32)CO₃, (Fe_0.47Mn_0.53)CO₃, (Mg_0.50Mn_0.50)CO₃, MgCO₃, and MnCO₃ were obtained as 1.18, 1.36, 1.34, 1.13, and 1.53, respectively. The relationship between Fe²⁺ and Mn²⁺ contents and γ_th illustrates that the concentration of Fe²⁺ causes a negative effect while the concentration of Mn²⁺ causes a positive effect on γ_th. These results could provide a reference for the contribution of Fe²⁺ and Mn²⁺ on the structural and thermodynamic properties of (Mg, Fe, Mn)CO₃ carbonates. Full article

For many decades, wood silicification has been viewed as a relatively simple process of permineralization that occurs when silica dissolved in groundwater precipitates to fill vacant spaces within the porous tissue. The presence of specific silica minerals is commonly ascribed to diagenetic changes. The possibility of rapid silicification is inferred from evidence from modern hot springs. Extensive examination of silicified wood from worldwide localities spanning long geologic time suggests that these generalizations are not dependable. Instead, wood silicification may occur via multiple pathways, permineralization being relatively rare. Mineralization commonly involves silica precipitation in successive episodes, where changes in the geochemical environment cause various polymorphs to coexist in a single specimen. Diagenetic changes may later change the mineral composition, but for many specimens diagenesis is not the dominant process that controls mineral distribution. Rates of silicification are primarily related to dissolved silica levels and permeability of sediment that encloses buried wood. Rapid silica deposition takes place on wood in modern hot springs, but these occurrences have dissimilar physical and chemical conditions compared to those that exist in most geologic environments. The times required for silicification are variable, and cannot be described by any generalization. Full article

Papua New Guinea (PNG) is located at the convergence edge of the Pacific Plate and the Indo-Australian Plate, consisting of three units. There are three chromium mineralization types in PNG. Based on national-scale geochemical mapping in PNG during 2015–2018, 1399 samples of stream sediments were collected from Highland Region, Papua Peninsula, and New Guinea Islands. This paper preliminarily studied chromium’s geochemical background, spatial distribution characteristics, and geochemical anomalies. The chromium concentration ranged from 3 ppm to 74,600 ppm, with a median value of 145 ppm, which was higher than the upper crustal abundance of chromium and the chromium geochemical baseline of Europe, Australia, North America, and China. In terms of stream sediment samples in different tectonic units, as mafic–ultramafic magmatic rocks are widely developed, the median chromium values of the New Guinea Orogen, including the Papuan Fold Belt, the New Guinea Thrust Belt, the Finisterre Terrane, the Aure Fold Belt, the Eastern Fold Belt, and the Eastern Papuan Composite Terrane, were higher than the value of the Melanesian Arc. The ophiolitic complexes, such as the April ophiolite, the Marum ophiolite, and the Papua ultramafic belt, significantly correlated with the higher chromium concentration. Eleven chromium high anomalies with mineralization potential were delineated, including three laterite and podiform prospecting areas and eight placer prospecting areas. Based on the chromium–nickel integrated anomaly map, comprehensive exploration and exploitation of nickel and chromium can be carried out in 1 and 11 high anomaly areas related to lateritic mineralization. Full article

There are still many problems in the stirring dissolution of flocculants: The law of stirring dissolution of flocculants with different molecular weights is not clear, the microstructure of settling floc with different particle sizes of coal slime is still to be explored, and how to apply the law of flocculant dissolution to industrialization? To solve these problems, firstly, mechanical stirring dissolution tests are carried out on anionic polyacrylamide (APAM) with different molecular weights to explore the stirring dissolution law of APAM with 3–25 million molecular weights. Results indicated that the optimal stirring speed of APAM with 3–6 million molecular weight is 800 r/min. The optimal stirring speed of 8–16 million molecular weight APAM is 600 r/min. The optimal stirring speed of 18–25 million molecular weight APAM is 800 r/min. The stirring power formula for APAM dissolution is improved by fitting the experimental data of 3–25 million molecular weight APAM stirring dissolution. Secondly, through APAM performance test, it is verified that the solubility of powdered APAM is the best under optimal solution. Thirdly, through the image measurement and analysis test of settling floc of coal slime, the change law of equivalent diameter of settling floc of different particle sizes of coal slime under the optimal dissolution parameters are explored. Results showed that when the mixing speed is 600 r/min, the equivalent diameter of −0.5 mm slime settling floc is the largest. When the mixing speed is 200 r/min or 400 r/min, the equivalent diameters of 0.5–0.25 mm, 0.25–0.125 mm, 0.125–0.075 mm, 0.075–0.045 mm and −0.045 mm slime settling floc are the largest. The equivalent diameter is positively correlated with the size of slime, and the equivalent diameter of −0.045 mm slime settling floc is the largest. The size of slime is the dominant factor in the change of fractal dimension. The fractal dimension of −0.5 mm slime settling floc is the largest, and the fractal dimension is little affected by mixing speed. Finally, the relationship between the important dissolution parameters of the APAM stirring dissolution test is numerically fitted. In view of the different geometrical parameters of the stirring barrel, a method of deducing the dissolution and stirring time of industrial flocculants is proposed. Full article

The Alta Floresta Gold Province (PAAF) is abundant in gold deposits and, located in the state of Mato Grosso, Brazil, is an ideal place to study the geoelectric signature of gold mineralization. Auriferous mineralization occurs along shear zones in quartz veins and disseminated granites in this region. Ores are associated with oxides and sulfides, mainly with pyrites. To identify primary gold or continuities of the mineralized zones, data were acquired using the geophysical methods of electrical resistivity and induced polarization in three gold mines: Raimunda, Truilio, and Porteira. Dipole–dipole arrays with electrode spacings of 20 and 25 m were used to investigate up to 100 m in depth. Resistivity and chargeability range scales were developed with statistical analyses of all the geophysical and geological data. The geophysical models of the Raimunda and Truilio gold mines showed coherence with the boreholes, but the geophysical models of the Porteira gold mine were not coherent with the boreholes. The resistivity and chargeability parameters indicated that the lithotypes (soils, saprolites, and monzogranites) could be characterized and identified as potential mineralized targets. The soils ranged from 1000 to 8000 ohm.m, the saprolites had values from 150 to 800 ohm.m, and the monzogranite values were from 1100 to 9000 ohm.m. The mineralized targets had values from 18 to 35 mV/V. The results confirm the efficiency of the resistivity and induced polarization methods to find sulfides in shear zones in the Alta Floresta Gold Province. Full article

The aim of this study is to evaluate the thermal maturity of Upper Badenian (Middle Miocene) petroleum source rocks of the Getic Depression, Romania, and to characterize the dispersed organic matter using organic petrography associated with Rock-Eval pyrolysis. A total of 33 core samples of Upper Badenian source rocks from the central–southern part of Getic Depression was studied. The results show that most samples with values of total organic carbon (TOC) < 1% wt.% have a limited potential of hydrocarbons (HC) generation, and 30% of samples with TOC < 1.82 wt. % and kerogen type III, presenting particularly gas generation potential. In three samples from the Bibești, Grădiște and Socu structures the kerogen type III-II was identified, indicating the capability of oil and gas generation. The Badenian source rocks are thermally immature, as few samples are in the pre-oil window, with values of vitrinite reflectance (VR_o%) ranging between 0.41% and 0.55%, and the values of T_max between 409 °C and 443 °C. Optical microscopy with reflected white light and fluorescence blue light was used for identification of terrigenous macerals (vitrinite, liptinite as, resinite, cutinite, sporinite, and inertinite) associated with marine liptinite macerals (telalginite and lamalginite) showing yellow and bright–yellow epifluorescence. Full article

The Chakabeishan (CKBS) deposit is the first pegmatite-type Li-Be deposit discovered in the eastern North Qaidam Tectonic Belt (NQTB) of Tibetan Plateau. The correct understanding of its petrogenesis and the precise determination of its formation age are of great significance for further regional prospecting and the discovery of new economically valuable rare-metal deposits. Therefore, a systematic study of texture, major-element composition, and U-Pb dating of columbite-tantalite group minerals (CGMs) in the spodumene pegmatite dyke from the CKBS deposit was undertaken. Three types of CGMs were identified, including concentric oscillatory ferrocolumbite (CGMs-1), homogeneous ferrocolumbite (CGMs-2), and irregular ferrotantalite (minor manganocolumbite) with abundant early ferrocolumbite replacement remnants (CGMs-3). The zoning patterns and chemical compositions in the CGMs record the complex evolutionary history of their host pegmatite from the magmatic stage (CGMs-1, disequilibrium crystallization) to the magmatic-hydrothermal transition stage (CGMs-2, equilibrium crystallization) and then to the late metasomatic stage (CGMs-3, replacement/re-equilibrium). CGMs U-Pb dating results suggest that the spodumene pegmatite dyke (No.15) emplaced at 230.1 ± 2.6 Ma. Subsequently, it experienced fluid metasomatism at 221 ± 5.3 Ma. Based on the new age data and published geochronological data, it can be concluded that the spodumene pegmatite dykes in the CKBS deposit formed in an oceanic subduction-related setting, representing a new metallogenic event in western China. Except for the CKBS deposit, a large number of rare-metal pegmatite dykes have also been discovered in the eastern NQTB, indicating that the eastern NQTB may be an important potential rare-metal metallogenic belt that should be explored in detail and arouse painstaking attention. Full article

The major problem with Carlin-type gold deposit flotation is that the high dolomite content in the concentrate decreases the quality of gold. Further, the activation mechanisms involved in dolomite flotation are still not fully understood. Herein, the correlation of Fe²⁺ conversion with xanthate adsorption and dolomite flotation was investigated to reveal the effect of dolomite embedded with pyrite. Flotation tests suggested that Fe²⁺ rather than Fe³⁺ improved the floatability of dolomite from 20% to 45%. Contact angles and thermodynamic tests indicated that the hydrophobicity of Fe²⁺-modified dolomite corresponds to the adsorption of xanthate. Importantly, time-of-flight secondary ion mass spectroscopy (Tof-SIMS) and x-ray photoelectron spectroscopy (XPS) attributed the activation of dolomite flotation to the formation of Fe(OH)₂ and FeCO₃. The coordination model of flotation successfully elucidated the selective adsorption of xanthate between Fe(OH)₂, FeCO₃ and FeOOH surfaces. The density function theory (DFT) simulation calculation was performed to identify the reaction rate at the atomic level, and the density of states (DOS) was also conducted to verify the conclusions at the electronic level. This study presents important surface chemistry evidence for understanding and regulating the poor selectivity in the flotation of Carlin-type gold deposits. Full article

The lacustrine shale in the second member of the Kongdian Formation (Ek2) is the most significant target of shale oil exploration in the Cangdong Sag, Bohai Bay Basin, China. To investigate the occurrence mechanisms and to reveal the influencing factors of shale oil mobility in Ek2, a series of analyses (X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), total organic carbon (TOC) analysis, Rock-Eval pyrolysis, low-temperature nitrogen physisorption (LNP), mercury intrusion porosimetry (MIP), and multiple isothermal stage (MIS) pyrolysis) were conducted on samples collected from well cores in the Cangdong Sag. The results show that the lithofacies can be categorized as laminated felsic shales, laminated and massive mixed shales, and laminated and massive carbonate shales. The shales were characterized by a high organic matter abundance and moderate thermal evolution with good to excellent hydrocarbon generation potential and contained a high abundance of Type I and II1 kerogens. Laminated felsic shales and laminated mixed shales, compared with other lithofacies, had clear advantages in the amount of free hydrocarbon that can be volatilized from the rock (S1), the oil saturation index (OSI) value, and the free oil and movable oil content. LNP, MIP, and MIS pyrolysis analyses show that the residual shale oil mainly occurred in pores with diameters smaller than 200 nm, and the pore diameter when residual oil occurred in some laminated shale samples could reach 50 μm. The lower limits of the pore diameter where free oil and movable oil occurred were 7 and 30 nm, respectively. The mobility of shale oil is controlled by the shale oil component, thermal maturity, TOC content, and pore volume. The results herein provide a basis for the evaluation of optimal shale oil intervals. Full article

With the development of high-precision geological observation technology, in situ mineral microanalysis technology, isotope geochemical analysis technology, deep geophysical exploration technology, deep drilling, real-time mining, remote sensing high-resolution hyperspectral image technology, and supercomputer and industrial intelligence, geoscience has entered an era of big data and artificial intelligence in the 21st century [...] Full article

Water cadmium (Cd) pollution has widely aroused concerns due to high Cd toxicity in water bodies and its serious health risks to humans. Adsorption has been identified as an effective and widely utilized technology for water purification with heavy metal pollution. To develop a newly identified adsorbent of modified zeolite that can easily and effectively purify Cd-polluted water, NaOH modification (JZ), high-temperature modification (HZ), humic acid modification (FZ), Na₂S modification (SZ), and ultrasonic modification (CZ) zeolites were developed, and their appearances and adsorption and desorption characteristics were investigated. The results showed that the adsorption capacity of Cd by JZ and SZ were improved by 68.87% and 32.06%, respectively, relative to that by natural zeolite (NZ); however, HZ, FZ, and CZ decreased the adsorption capacity. JZ had a higher adsorption capacity than SZ and could remove 99.90% Cd at an initial concentration of 100 mg/L. The dominant adsorption mechanism of Cd by JZ was the chemisorption of the monolayer. The preferred temperature and pH that enhanced Cd adsorption by JZ were 25–35 °C and 4–8, respectively. With an equilibrium adsorption capacity of 9.37–9.74 mg/g at an initial concentration of 280 mg/L, JZ reached its maximum saturated adsorption capacity; compared with SZ and NZ, the adsorption capacity increase was 27.83%–68.81%. The R² fitted by JZ's Langmuir model and quasi-second-order dynamics model were both above 0.93. In summary, JZ was recognized as a novel absorbent for Cd-polluted water purification. Full article

In this study, a three-dimensional finite difference numerical model of the Jinfeng Gold Mine, including surface topography, ore body, shafts, and main faults, was built to estimate the shaft stability and surface deformation induced by underground mining transferred from open-pit mining. Satellite monitoring data of surface displacement at several points was used to calibrate the numerical model. The sequence of excavation and filling in the simulation was determined according to the mining schemes with appropriate simplification. The distribution of large deformations in simulation is consistent with the cracking areas on the slopes and surface. Besides, shaft deformation in the simulation is small, which is consistent with the reality that there are no large deformations of shafts in the underground mining activities above 30 m level. After the completion of simulated underground mining, the deformations of shafts and surface are generally far less than the critical deformation. Hence, we concluded that the shafts and surface of the Jinfeng Gold Mine can remain stable in the underground mining stage. Overall, the method in the study provides references for the estimation of shaft stability and surface deformation in the underground mining stage of mine transfer from open pit. Full article

The coal-bearing sequences of the Late Permian in southwest China are enriched in critical elements Sc, V, Co, Ni, Cu, Zn, Nb, Ta, Zr and Hf. Ascertaining the conditions and basis for the enrichment of critical elements in this area is very important to support the critical metal demands of China. In this study, we analyzed the concentrations of elemental compositions of coal samples collected from the Late Permian Guishan coalfield in the eastern Yunnan, China. The results show that the C4-Upper coal seam of the Feilongma mine and C5 + 10 coal seam of the Shipeng mine are indeed rich in critical elements. The average concentration coefficients (CC) of transition metal elements Sc, V, Co, Ni, Cu, and Zn are 3.23 and 2.93, respectively, in the two coal seams. The average CCs of high-field-strength elements Nb, Ta, Zr, and Hf and non-variable valence chalcophile elements Ga and In are 2.21 and 2.53, respectively, in the two coal seams. The C4-Upper coal seam of the Feilongma mine can be divided into two sections based on the different ash contents, and the CCs of the critical elements in the two sections are almost equal. The main minerals in the two coal seams are kaolinite, siderite, quartz, gypsum, rozenite and marcasite. Multiple indicators of provenance show that the enrichment of critical elements in the Guishan coalfield is controlled by clastic terrigenous material. The source area of the Guishan coalfield is Kangdian Oldland in the northwest, and the main clastic materials are related with high-Ti basalts from the Emeishan Large Igneous Province. Full article

This study investigates the provenance and tectonic background of the lower Silurian Longmaxi Formation black shale of the Yanyuan Basin in the western Kangdian ancient land and provides guidance for shale gas exploration and development in the area. The mineral petrological and geochemical characteristics of the Longmaxi Formation black shale in this area have been studied in detail. The study area is mainly a passive continental margin environment, but also has the attributes of an active continental margin and island arc environment due to the collision between the western oceanic crust and the Yangtze continental crust. The source rocks are mainly felsic igneous rocks, with a small contribution of intermediate–basic rocks. It is inferred that the Kangdian ancient land in the eastern part of the area could be the main provenance area, but with the contribution of sediments derived from oceanic island arc located in the west. During the whole Longmaxi period, the tectonic movement was intense, the climate was cold, the degree of chemical weathering was low, and it was a highly volatile geological sedimentary basin. Therefore, the highly siliceous organic-rich mudstone, which was different from the Sichuan Basin, was deposited. Full article