Minerals Siderite Research Articles

Deciphering the biodegradation of thiamethoxam by Phanerochaete chrysosporium with natural siderite: Synergistic mechanisms, transcriptomics characterization, and molecular simulation

Fungi play vital roles in the fate of organic pollutants, particularly when interacting with minerals in aquatic and soil environments. Mechanisms by which fungi may mitigate pollutions in fungus-mineral interactions are still unclear. Inspired by biogeochemical cycling, we constructed a range of co-culture systems to investigate synergistic effects of the white-rot fungus Phanerochaete chrysosporium and the iron-bearing mineral siderite on thiamethoxam (THX) transformation, a common neonicotinoid pesticide. Co-culturing with siderite significantly enhanced THX transformation during the initial 10 days with a dose effect, achieving 86 % removal within 25 days. Fungi could affect siderite’s dissolution, transformation, and precipitation through their biological activities. These interactions triggered physiological adaptation and resilience in fungi. Siderite could enhance the activity of fungal ligninolytic enzymes and cytochrome P450, facilitating biotransformation. Genes expression related to growth, energy metabolism, and oxidative stress response upregulated, enhancing fungal resilience to THX. The primary THX degradation pathways included nitro-reduction, C-N cleavage, and de-chlorination. Molecular dynamics simulations provided insights into catalytic mechanisms of enzyme-THX interactions. Together, siderite could act as natural enhancers that endowed fungi to resist physical and chemical stresses in environments, providing insights into contaminants attenuation, fungal biomineralization, and the coevolution of the Earth's lithosphere and biosphere.

Analysis of Mineral Types, Density, and Porosity in the Lam Teuba Formation Using Infrared Spectroscopy Method

The Lam Teuba Formation is one of the local fault areas of the Seulimuem segment located in the Grand Mosque sub-district of Aceh Besar regency. The Lam Teuba Formation has several types of rocks such as basaltic andesite lava, pyrolastic flows, pyroclastic falls, and sedimentary rocks, namely claystone, limestone sandstone, agglomerate, limestone. Rocks have physical characteristics, namely density and porosity which have different values in each rock. This difference can be caused by the minerals contained in the rock. The method used to calculate the density and porosity values used the Archimedes method, and the identification of mineral types using the infrared spectroscopy method. The results of data processing obtained the highest original density value at location 1 sample 1 with a value of 3.42 and the lowest value at location 5 sample 2. The highest dry density value was in location 1 of sample 1 with a value of 3.33 and the lowest value was in location 5 of sample 2. The highest saturation density value was in location 1 of sample 1 with a value of 3.43, the lowest value was in location 5 of sample 2 with a value of 2.07. The average porosity value was the highest with a value of 5.41 in the poor quality category in sample 4, while the lowest value was 4.62 in the very bad category in sample 1. The types of minerals found in the Lam Teuba formation are illite, montmorillonite, kaolinite minerals with a mixture of smectite which is a clay mineral group and siderite minerals which are carbonate mineral groups.

Episodic hydrothermal supply and microbial anaerobic Fe(II) oxidation in early Archean ocean: Insights from precursor mineral compositions of the 3.46 Ga Marble Bar Chert, Pilbara Craton, Western Australia

The 3.46 Ga Marble Bar Chert (MBC) from the Pilbara Craton in Western Australia is known as the oldest chert on Earth. The origin of its Fe minerals was investigated to decipher the geochemistry and redox conditions of the early Archean ocean, as well as to explore the possible microbial contribution to the earliest sedimentary processes on Earth. However, the composition of the precursor minerals in the MBC remains poorly understood, giving rise to controversies on its genesis. Here we performed high-resolution petrographic, laser Raman, Mössbauer, X-ray diffraction, and Mn K-edge X-ray absorption near edge structure spectroscopic studies on two typical types of finely laminated MBC, grey-black chert and red chert. The grey-black chert contains considerable amounts of siderite, carbonaceous materials, and minor phyllosilicates and hematite. By contrast, the red chert contains high hematite and silicates, minor siderite and rare carbonaceous materials. Microcrystals in the cores of chert polyhedral are among the earliest mineral phases without signs of alterations, recrystallisation, erosion or replacement histories. Ferrihydrite, greenalite, siderite, and green rust are possible precursors of Fe-bearing minerals in the MBC. Their respective proportion in each lamina was regulated by pH, Fe(II)-oxidation rate, DIC, and Fe(II) content in the seawater. Approximately half Fe in the MBC primary minerals existed as Fe(III), indicating the existence of indigenous Fe(II)-oxidation in the Paleoarchean seawater. The element Mn in the MBC is primarily Mn(II) coordinated with O, suggesting a reduced depositional environment and hence implying the involvement of anaerobic microbial Fe(II)-oxidation in the formation of the MBC. Collectively, the grey-black laminae with abundant carbonaceous materials reflect limited Fe(II)-oxidation and increased dissolved inorganic carbon content likely due to enhanced hydrothermal CO2 supply, while the red laminae with considerable hematite represent substantial Fe(III)-supply due to rapid indigenous anaerobic Fe(II)-oxidation.

Geochemistry of Arsenic and Salinity-Contaminated Groundwater and Mineralogy of Sediments in the Coastal Aquifers of Southwest Bangladesh

This study aimed to develop a geochemical database by thoroughly analyzing groundwater and sediments from coastal aquifers of southwest Bangladesh. Moreover, we investigated the source of sediment deposition and the mechanisms behind the presence of arsenic and salinity in groundwater. The seasonal distribution patterns of arsenic among the shallow and deep coastal aquifers were found to be 45.12 µg/l and 20.65 µg/l during dry and wet seasons, respectively. Moreover, the groundwater salinity distribution ranged from 3262.88 mg/l to 1930.88 mg/l during the dry and wet seasons. Cored sediment samples showed fine to medium sands of 92%, with silt and clay particles. The petrographic study of authigenic and heavy minerals revealed that the mineral grains were subangular to angular, indicating their textural immaturity of coastal sediments. The reactivity of goethite (FeOOH) and siderite (FeCO3) minerals suggests that the aquifers were subjected to slightly oxidized to moderately reducing conditions, with ORP values ranging from +50.40 mv to −149.5 mv. Such redox conditions could potentially result in the enrichment and mobility of arsenic in the groundwater. Although arsenic concentrations in deep aquifers are relatively low, higher salinity values are found in both shallow and intermediate coastal aquifers.

Morphological, Microstructural, and In Situ Chemical Characteristics of Siderite Produced by Iron-Reducing Bacteria.

Dissimilatory iron-reducing bacteria (DIRB) oxidize organic matter or hydrogen and reduce ferric iron to form Fe(II)-bearing minerals, such as magnetite and siderite. However, compared with magnetite, which was extensively studied, the mineralization process and mechanisms of siderite remain unclear. Here, with the combination of advanced electron microscopy and synchrotron-based scanning transmission X-ray microscopy (STXM) approaches, we studied in detail the morphological, structural, and chemical features of biogenic siderite via a growth experiment with Shewanella oneidensis MR-4. Results showed that along with the growth of cells, Fe(II) ions were increasingly released into solution and reacted with CO32- to form micrometer-sized siderite minerals with spindle, rod, peanut, dumbbell, and sphere shapes. They are composed of many single-crystal siderite plates that are fanned out from the center of the particles. Additionally, STXM revealed Fh and organic molecules inside siderite. This suggests that the siderite crystals might assemble around a Fh-organic molecule core and then continue to grow radially. This study illustrates the biomineralization and assembly of siderite by a successive multistep growth process induced by DIRB, also provides evidences that the distinctive shapes and the presence of organic molecules inside might be morphological and chemical features for biogenic siderite.

Understanding siderite mineralization in phyllosilicate-associated cementations in the mid-Carboniferous Anadarko Basin clastic series, U.S.A.

ABSTRACT The present study provides insights into the origin of siderite cementation in closely interbedded bipartite mudstone to sandstone Pennsylvanian strata from the Anadarko Basin. Mineralogical, geochemical, and stable-isotope data were collected from 80 siderite samples and their immediate non-siderite-bearing regions. Geometrically, siderite mineralization occurs in the form of concretions or bands, with the latter being the most common textural type and occurring solely in mudstone, whereas the former is found in both sandstone and mudstone. This microtextural and geochemical investigation posits siderite as a derivate of biological processes at the sediment–water interface. Bacteria cell walls denoted by an omnipresent nanoglobule structure dominate the areas of mineralization. Mineral quantifications indicate higher phyllosilicate content within the mineralization compared to the non-mineralized sediment reflecting the role the clay minerals provide as a source of bio-essential cations, labile FeOx, and organic matter needed for microbial colonies to flourish. Following the formation of biological siderite, the energetically favorable mineralization surfaces served as nuclei for further precipitation of mesogenetic inorganic siderite enriched in 16O. The second mesogenetic cementation features rhombohedral siderite overgrowths with increasing Mg-concentration on the outer rims of nanoglobules. The identified bands and concretions were formed during periods of relative sea-level highs, whereas the siderite-cemented intraclasts were eroded and deposited downstream during times of relative sea-level lows. This is corroborated by relatively low (Ca-Mg)/Fe substitution in eogenetic siderite, typical of mineralization in meteoric-water-dominated realms. Finally, based on enrichment in 12C and textural observations, which suggest suboxic geochemical conditions, we conclude that the ability of siderite to form early on allowed it to maintain net rock porosity by encasing quartz and inhibiting its overgrowth process.

Hydrogen-driven routes to steel from siderite with low CO2 emissions: A modeling study

Efficient use of low-grade siderite minerals can not only potentially mitigate the shortage of iron ores but also enable drastic reduction in CO2 emissions from steel industry in China. In this study, we conducted a systematic thermodynamics analysis toward ferrous carbonate hydrogenation to CH4, which was verified by experimental study over the 5 wt.% Ni/siderite. CO2 hydrogenation reduction was introduced in steelmaking from siderite minerals to further reduce the CO2 emissions. Based on thermodynamic analysis results, we provided four options of hydrogen-driven route to steel from siderite named FTI-CO2HR, FTM-MTI-CO2HR, FTH-HTI-CO2HR and FTW-WTI-CO2HR, respectively. The FTM-MTI-CO2HR process route achieved minimized CO2 emissions (0.56 metric ton CO2/metric ton iron) and was competitive to the steel scrap-EAF route (0.54–0.60 metric CO2/metric ton iron). The proposed process route would be cleaner, more environment friendly assuming successful technology and process development and favorable market conditions in terms of acceptable level of hydrogen production cost.

Genesis of Devonian volcanic-associated Lahn-Dill-type iron ores — part I: iron mobilisation and mineralisation style

Fe-oxide deposits of the Lahn-Dill-type in the eastern Rhenish Massif comprise haematite and quartz with minor siderite, magnetite, and calcite. The deposits are located in the hanging wall of thick volcaniclastic rock sequences and mark the Middle to Late Devonian boundary. Varying ore types with accompanying footwall rocks were sampled from two formerly important ore deposits, the Fortuna mine (Lahn syncline) and the Briloner Eisenberg mine (East Sauerland anticline), in order to elucidate the interplay of processes leading to ore formation. Deposit geology, petrography, and whole-rock geochemistry suggest that the ores formed by iron mobilisation from deeply altered footwall volcaniclastic rocks, subsequent venting of a modified H2O-CO2-Fe-rich and H2S-poor fluid, and precipitation on the seafloor (sedimentary-type), or locally by metasomatic replacement of wall rocks (replacement-type). Petrographic analysis to the sub-micron scale revealed that the sedimentary-type ores most likely formed from a Fe-Si-rich gel and accompanying maturation. Early gel textures include the presence of spherules, aggregates, tubes, and filamentous stalks consisting of nanocrystalline haematite dispersed in a matrix of microcrystalline quartz. Local diagenetic Fe3+ reduction within the gel is indicated by siderite replacement of haematite. Replacement-type ores formed due to a two-step process including coprecipitation of (precursor) haematite and carbonates and subsequent metasomatic replacement by haematite. These ore-forming processes took place during a time when several restricted shallow marine basins in the north-eastern Rheic Ocean were influenced by extensive volcanism and associated hydrothermal fluid flux. Examples of similar volcanic-associated Fe-oxide occurrences of Silurian to Carboniferous age can be categorised as being of Lahn-Dill-type ores as well.

Microbial diversity and authigenic siderite mediation in sediments surrounding the Kedr-1 mud volcano, Lake Baikal.

The gas hydrate-bearing structure-mud volcano Kedr-1 (Lake Baikal, southern basin)-is located near the coal-bearing sediments of the Tankhoy formation of Oligocene-Miocene age and can be an ideal source of gas-saturated fluid. A significant amount of siderite minerals (FeCO3 ) were collected from sediments at depths ranging from 0.5 to 327 cm below the lake floor (cmblf). An important feature of these carbonate minerals is the extremely strong enrichment in the heavy 13 C isotope, reaching values of +33.3‰ VPDB. The δ13 C of the siderite minerals, as well as their morphology and elemental composition, and the δ13 CDIC of the co-existing pore water, differed across layers of the core, which implies at least two generations of siderite formation. Here, we leverage mineralogical and geochemical data with 16S rRNA data from the microbial communities in sediments surrounding layers containing siderite minerals. Statistical data reveal the formation of three clusters of microbial communities based on taxonomical composition, key taxa among bacteria and archaea, and environmental parameters. Diversity and richness estimators decrease with sediment depth, with several similar prevailing clades located at the bottom of the core. Most of the taxa in the deep sediments could be associated with putative metabolisms involving organotrophic fermentation (Bathyarchaeia, Caldatribacteriota, and Chloroflexota). Various groups of methanogens (Methanoregulaceae, Methanosaetaceae, and Methanomassiliicoccales) and methanotrophic (Methanoperedenaceae) archaea are present in the sediment at variable relative abundances throughout the sampled depth. Based on the physicochemical characteristics of the sediment, carbon isotope analysis of carbonate minerals and DIC, and phylogenetic analysis of individual taxa and their metabolic potential, we present several models for subsurface siderite precipitation in Lake Baikal sediments.

Mesoproterozoic biomineralization: Cyanobacterium-like filamentous siderite sheaths ∼1.4 Ga

Biomineralization was a key development in a wide variety of organisms, yet its history prior to the Ediacaran remains poorly understood. In this paper, we describe ∼1420–1330 million year old microscopic tubes preserved as siderite (FeCO3). In size and shape these tubes closely resemble cyanobacterial sheaths forming mineralized mats. We consider two competing explanations for their formation. First, the tubes and associated sediment were originally composed of Ca-carbonate that was subsequently replaced by siderite. In this case, siderite mineralization was early, but post-mortem, as in early silicification, and preferentially preserved the more resilient sheath. However, no relict calcite is observed. Second, the Fe-carbonate mineralogy of the tubes and sediment is synsedimentary. In this case, photosynthetic oxygen may have precipitated Fe-oxyhydroxide that was promptly converted to siderite by dissimilatory iron reduction (DIR). Primary siderite mineralization of cyanobacteria has not been described before. Both explanations link photosynthetic processes to preferential sheath mineralization during the life of the cyanobacteria, as observed in present-day calcified cyanobacteria. This process might include CO2-concentrating mechanisms (CCMs) linked to relatively low levels of atmospheric CO2, consistent with empirical estimates of mid-Proterozoic CO2 levels based on paleosols and weathering rinds. In either case, these cyanobacterium-like fossils preserved in siderite provide an early example of biomineralization and suggest the interactive influences of both metabolic processes and ambient seawater chemistry.

Mineralogical, magnetic and geochemical data constrain the pathways and extent of weathering of mineralized sedimentary rocks

The oxidative weathering of sulfidic rock can profoundly impact watersheds through the resulting export of acidity and metals. Weathering leaves a record of mineral transformation, particularly involving minor redox-sensitive phases, that can inform the development of conceptual and quantitative models. In sulfidic sedimentary rocks, however, variations in depositional history, diagenesis and mineralization can change or overprint the distributions of these trace minerals, complicating the interpretation of weathering signatures. Here we show that a combination of bulk mineralogical and geochemical techniques, micrometer-resolution X-ray fluorescence microprobe analysis and rock magnetic measurements, applied to drill core samples and single weathered fractures, can provide data that enable the development of a geochemically consistent weathering model.This work focused on one watershed in the Upper Colorado River Basin sitting within the Mesaverde Formation, a sedimentary sandstone bedrock with disseminated sulfide minerals, including pyrite and sphalerite, that were introduced during diagenesis and subsequent magmatic-hydrothermal mineralization. Combined analytical methods revealed the pathways of iron (Fe), carbonate and silicate mineral weathering and showed how pH controls element retention or release from the actively weathering fractured sandstone. Drill core logging, whole rock X-ray diffraction, and geochemical measurements document the progression from unweathered rock at depth to weathered rock at the surface. X-ray microprobe analyses of a 1-cm size weathering profile along a fracture surface are consistent with the mobilization of Fe(II) and Fe(III) into acidic pore water from the dissolution of primary pyrite, Fe-sphalerite, chlorite, and minor siderite and pyrrhotite. These reactions are followed by the precipitation of secondary minerals such as of goethite and jarosite, a Fe-(oxyhydr)oxide and hydrous Fe(III) sulfate, respectively. Microscale analyses also helped explain the weathering reactions responsible for the mineralogical transformations observed in the top and most weathered section of the drill core. For example, dissolution of feldspar and chlorite neutralizes the acidity generated by Fe and sulfide mineral oxidation, oversaturating the solution in both Fe-oxides. The combination of X-ray spectromicroscopy and magnetic measurements show that the Fe(III) product is goethite, mainly present either as a coatings on fracture surfaces in the actively weathering region of the core or more homogeneously contained within the unconsolidated regolith at the top of the core. Low-temperature magnetic data reveal the presence of ferromagnetic Fe-sulfide pyrrhotite that, although it occurs at trace concentrations, could provide a qualitative proxy for unweathered sulfide minerals because the loss of pyrrhotite is associated with the onset of oxidative weathering. Pyrrhotite loss and goethite formation are detectable through room-temperature magnetic coercivity changes, suggesting that rock magnetic measurements can determine weathering intensity in rock samples at many scales. This work contributes evidence that the weathering of sulfidic sedimentary rocks follows a geochemical pattern in which the abundance of sulfide minerals controls the generation of acidity and dissolved elements, and the pH-dependent mobility of these elements controls their export to the ground- and surface-water.

Geochemical and organic petrographic analyses on the Late Eocene bentonitic shale bed in Kom Aushim vicinity, Fayum, Egypt; Paleoenvironmental implications

Bentonitic shale bed of the Qasr El Sagha Formation (Late Eocene), located in the Kom Aushim area, Fayum, composes of 5 m thickness of dark massive stratum intercalated with veins of iron bands. In this study, twelve fresh shale samples from this area were investigated concerning their geochemical and organic petrography analyses. A total organic carbon (TOC) of the shale samples is very low (0.07–0.39 wt%). Petrographic analysis of samples shows a dominance of the vitrinite maceral followed by either inertinite and/or liptinite macerals. Theoretically derived vitrinite reflectance (Rocal) reveals that the bentonitic shale bed was subjected to an abnormal increase in maturity toward the invasion of Fe, Zn, Cu rich hydrothermal sulfates and oxides veins. The composition and origin of these veins were investigated by XRD and XRF analyses. The results suggested that the Fe brought from these veins affected the main composition of the shale stratum to exhibit Fe-shale facies. Moreover, rich iron in the depositional medium leads to form siderite minerals (≈10%) and the replacement of lime associated clay to Ferron dolomite (≈25%). The dominant paleoclimate synchronized shale deposition was semi-arid and arid climate, as confirmed by the domination of evaporite (≈44% gypsum). The source area of shale components was found to be sedimentary and mafic igneous (basaltic trend). CIA-ICV and A–CN–K ternary diagrams showed that the shale components were subjected to a variety of intensive to moderate weathering, and they were probably coming from gabbro and tonalite igneous rock. An active sedimentary margin and island arc are the main provinces, as the shale was deposited at the marine anoxic condition of a clay-lime platform of a pro-delta sedimentary setting. The organic matters (OM) are of type III and IIIC that refer to terrestrial OM of marginal aquatic environments. Organic and inorganic studies confirm a prevailing depositional environment of a shallow shelf, shoreline mudflats and evaporitic lagoon that reflects the general trend of sea-level regression in the Fayum area during the Late Eocene.

Synthesis of high-density olivine LiFePO4 from paleozoic siderite FeCO3 and its electrochemical performance in lithium batteries

The lithium-ion cathode material olivine LiFePO4 (LFP) has been synthesized for the first time from natural paleozoic iron carbonate (FeCO3). The ferrous carbonate starting material consists of the mineral siderite at about 92 wt. % purity. Because FeCO3 has divalent iron, the reaction with lithium dihydrogen phosphate (LiH2PO4) provides a unique method to develop iron-(II) containing LFP in an inert atmosphere. Since siderite FeCO3 is a common mineral that can be directly mined, it may, therefore, provide an inexpensive route for the production of LFP. After carbon-coating, the LFP yields a capacity in the range of 80–110 mAh g−1LFP (in one chosen specimen sample), which is lower than commercially available LiFePO4 (150–160 mAh g−1LFP). However, the tap density of LFP derived from siderite is noticeably high at 1.65 g cm−3. The material is likely to be improved with powder purification, nanosized processing, and more complete carbon-coating coverage with increased optimization.

A numerical experiment for geological sequestration of CO[formula omitted] in the pre-Comondú sandstones of Las Tres Virgenes geothermal area, Baja California Sur, Mexico

The most recent studies on geological sequestration of CO2 in Mexico point towards high sequestration potential associated with geologically stable zones and high-emission centres. These studies overlook however, the potencial that high heat flow areas in the country can offer to geological sequestration of CO2 by mineral precipitation. Here we present an assessment of the CO2 sequestration capacity of the Pre-Comondú sandstones, that overlie the productive granitic basement of the Las Tres Virgenes geothermal field (10 MWe). Both, the physical properties and mineralogical description of the sandstone are defined from drilling core analyses reported by the Federal Commission of Electricity. The initial formation water saturating the sandstone is determined by means of a batch simulation of equilibrium between the primary minerals in the rock and a 1 M solution of NaCl in water. Injection of supercritical CO2 is then numerically simulated. Simulations are based on the TOUGHREACT software and the equation of State Module ECO2N. Our results show Pre-Comondú sandstone favour mineralization of CO2 through the precipitation of carbonates in moderate geologic times (100–300 yr). Mineral changes occur within two main zones in the CO2-impacted reservoir, the zone lying close to the injection point is dominated by precipitation of low-albite, kaolinite, calcite, and minor siderite, whereas the distal zone responds with moderate changes in the system illite-smectite. Changes in porosity are moderate and consistent with the two mineralization zones. Furthermore, the decline in porosity occurs in the long term, which suggests moderate risk for injection operations. Although high reservoir temperature is unfavorable to CO2 solubility, high pressure can counteract this effect, so the system can benefit from higher mass diffusivity and reactivity. This manifests in an accelerated sequestration rate.

Core characterisation and predicted CO2 reactivity of sandstones and mudstones from an Australian oil field

CO2 geological storage has been proposed as one method to mitigate climate change. Storage of CO2 in depleted oil or gas fields is one option, potentially following enhanced recovery. Understanding the potential impacts of CO2 water rock reactions is an important aspect of storage feasibility studies. Drill core samples of sandstones and mudstones from the Jurassic Moonie oil field, Australia, were characterised. In the Precipice Sandstone reservoir samples pore throats had broad size distributions, with mercury intrusion porosities 6.2 to 14.6%. Evergreen Formation samples were more variable with 1.2 to 16.1% porosity. Porosities measured by QEMSCAN were in reasonable agreement at 8.6 to 15.3% for Precipice Sandstones, and 0.6 to 21.5 for the Evergreen Formation. Sandstones had larger pore throat sizes and lower threshold pressures indicative of good reservoir rocks. Calcite cemented sandstones had truncated pore throat distributions, and the coal and clay rich mudstones had pore throats <0.1 μm with higher threshold pressures likely to seal or baffle CO2. Quartz grains were naturally fractured, with silica, apatite, rutile, calcite, and siderite cements filling porosity in some samples. Feldspars had been weathered producing secondary porosity but also resulting in kaolinite and illite filling intergranular porosity. Pyrite and barite were mainly associated with coals. Synchrotron X-ray fluorescence mapping showed Sr was mainly hosted in calcite cement, apatite and barite; with Rb in both plagioclase and K-feldspars. Calcite mainly hosted Mn; while Zn and Cu were mainly in sulphides. Sulphide minerals in coal also hosted As in one core. Kinetic geochemical CO2-water-rock modelling using the characterisation data over 30 or 1000 years indicated reaction of carbonate minerals where present, and alteration of mainly plagioclase, K-feldspar and chlorite. Net precipitation of ankerite, calcite or siderite mineral trapped 0.23 to 1.28 kg/m3 of CO2 after 1000 years in the different rock packages and was highest in Evergreen Formation rocks. The predicted pH was in the range 5.0 to 5.4 after 1000 years, or higher at 5.2 to 7.1 in lower CO2 fugacity models. Sandstone reactivity was overall low over 30 years indicating a low likelihood of reservoir scaling which would be favourable, with mineral trapping likely in the overlying Evergreen Formation.

Enhanced Mineral Quantification and Uncertainty Analysis from Downhole Spectroscopy Logs Using Variational Autoencoders

This paper describes an innovative machine-learning application, based on variational autoencoder frameworks, to quantify the concentrations and associated uncertainties of common minerals in sedimentary formations using the measurement of atomic element concentrations from geochemical spectroscopy logs as inputs. The algorithm comprises an input(s), encoder, decoder, output(s), and a novel cost function to optimize the model coefficients during training. The input to the algorithm is a set of dry-weight concentrations of atomic elements with their associated uncertainty. The first output is a set of dry-weight fractions of 14 minerals, and the second output is a set of reconstructed dry-weight concentrations of the original elements. Both sets of outputs include estimates of uncertainty on their predictions. The encoder and decoder are multilayer feed-forward artificial neural networks (ANN), with their coefficients (weights) optimized during calibration (training). The cost function simultaneously minimizes error (accuracy metric) and variance (precision or robustness metric) on the mineral and reconstructed elemental outputs. Training of the weights is done using a set of several-thousand core samples with independent, high-fidelity elemental and mineral (quartz, potassium-feldspar, plagioclase-feldspar, illite, smectite, kaolinite, chlorite, mica, calcite, dolomite, ankerite, siderite, pyrite, and anhydrite) data. The algorithm provides notable advantages over existing methods to estimate formation lithology or mineralogy relying on simple linear, empirical, or nearest-neighbor functions. The ANN numerically capture the multidimensional and nonlinear geochemical relationship (mapping) between elements and minerals that is insufficiently described by prior methods. Training is iterative via backpropagation and samples from Gaussian distributions on each of the elemental inputs, rather than single values, for every sample at each iteration (epoch). These Gaussian distributions are chosen to specifically represent the unique statistical uncertainty of the dry-weight elements in the logging measurements. Sampling from Gaussian distributions during training reduces the potential for overfitting, provides robustness for log interpretations, and further enables a calibrated estimate of uncertainty on the mineral and reconstructed elemental outputs, all of which are lacking in prior methods. The framework of the algorithm is purposefully generalizable so that it can be adapted across geochemical spectroscopy tools. The algorithm reasonably approximates a “global-average” model that requires neither different calibrations nor expert parameterization or intervention for interpreting common oilfield sedimentary formations, although the framework is again purposefully generalizable so it can be optimized for local environments where desirable. The paper showcases a field application of the method for estimating mineral type and abundance in oilfield formations from wellbore-logging measurements.

Characterization of geochemical properties and factors controlling the pore structure development of shale gas reservoirs

The pore structure is an important parameter to understand the transport and storage capacities in shale. There is very limited research reported on the controlling factors of pore development in lacustrine shales to date. This study investigated pore developments and hydrocarbon generation potential of lacustrine Roseneath and Murteree shale formations. Although these shale formations are proven shale gas reservoir in the Cooper Basin, Australia, pore development studies are still rare. The geochemical properties measured on core samples include total organic contents (TOC), thermal maturity, hydrocarbon generation potential, and mineral composition by X-ray diffraction (XRD). Field-emission scanning electron microscopy (FE-SEM), Focused Ion Beam milling scanning electron microscopy (FIB-SEM), and low-pressure nitrogen adsorption-desorption isotherm experiments were used to quantify and qualify pore structure. Furthermore, the factors were analyzed that control pore development through statistical analysis. The results indicate that organic contents for the Roseneath shales (0.9%–1.74% Ro%) and Murteree shales (1%–1.7% Ro%) range between 0.81% and 5.36% and 0.51%–6.69%, respectively. The dominant mineral phases are quartz, clay (Illite, Kaolinite), and siderite, with variable quantities of the studied formations. Rock-Eval pyrolysis suggests Kerogen Type III and implies mostly late oil generation to dry gas generation potential in both shale formations. In Roseneath shale, total surface area (SSA) and total pore volume (TPV) varies from 2.25 cm2/g to 5 cm2/g and 0.005 cm3/g – 0.02 cm3/g, respectively. In Murteree shale, SSA and TPV vary from 3.5 cm2/g to 6.35 cm2/g and 0.005 cm3/g to 0.032 cm3/g, respectively. The pores exhibit unimodal to bimodal distribution with peaks at 2–4 nm, 90–120 nm, and 170–180 nm. The mesopores are dominant in studied formations, followed by macropores and micropores. Mesopores have the largest contribution to specific surface area and pore volume. The desorption hysteresis loop on the N2 adsorption-desorption curve indicates the presence of permeable and impermeable pores, as most of the samples belong to H2 and H3 type hysteresis loop. The pore size of intraparticle and interparticle various greatly; however, the pores with a diameter of 2.5 nm, 18 nm and 49 nm are common in both formations. The organopores contribute to micropores' development, and most organic pores have a pore diameter of 1.5 nm and 1.8 nm. The total pore volume (TPV) and specific surface area (SSA) are positively correlated with organic matter contents, quartz, and thermal maturity in both shale formations. However, clay minerals are positively correlated with SSA and TPV, which indicate that clay minerals have a significant contribution to Roseneath shale's pore development. The siderite mineral contributes to intraparticle pores development and positively correlated with SSA and TPV in Murteree shale. The thermal maturity significantly enhances pore's development by creating organopores and inorganic pores in both shales, as evidenced through statistical analysis and image analysis. The study has significant importance in understanding the pore structure and gas storage mechanism in shale.

Positive Zeta Potential in Sandstones Saturated With Natural Saline Brine

AbstractIt is widely accepted that the zeta potential in natural sandstones is negative in the brine pH and compositions found in the subsurface. The zeta potential is a measure of the electrical potential at a mineral surface. We report new measurements of the zeta potential using a saline natural brine rich in divalent ions. The sandstone samples were quartz dominated but some also contained dolomite, siderite, and clay minerals. The quartz‐dominated sandstones showed behavior consistent with earlier studies, but the dolomite‐ and siderite‐bearing samples returned positive zeta potentials. We suggest that this is caused by a positive zeta potential on dolomite and siderite mineral surfaces, adsorption of divalent ions onto quartz mineral surfaces, and/or ion exchange with clay minerals. The results have broad implications for the zeta potential of natural sandstones, because the magnitude and polarity of the zeta potential impact geophysical monitoring and the transport of the charged contaminants.

Laboratory and field study on changes in water quality and increase in dissolved iron during riverbank filtration.

Changes in the water quality by the riverbank filtration (RBF) process were investigated in the field-scale demonstration sites. The overall water quality was improved by RBF, but Fe2+ concentration significantly increased in the riverbank-filtered water more than in the river water. This result would be caused by the interaction between the iron minerals and the river water in the aquifer and the influx of the hinterland groundwater into RBF wells. Dissolution properties of iron from the aquifer soils cored at the sites were evaluated through incubation experiment considering various values of redox potential (Eh), dissolved oxygen (DO), and hydrogen-ion concentration exponent (pH). These results presented that at the incubator with the final Eh of 470 mV, DO of 3.4, and pH of 4.53, the iron from the aquifer soil was most dissolved, and the pyrite and siderite contents in the aquifer soil decreased significantly from 11.5 to 6.22% and from 50.8 to 24.5%, respectively. Based on changes of ion concentrations (such as Fe2+, Fe3+, SO42- and NO3-) and iron species in the incubators, it was believed that pyrite and siderite minerals in the aquifer soils cause an increase in the Fe2+ concentration with the absence of DO and an increase in the Fe2+ and Fe3+ concentrations with the presence of DO. The dissolution rates of iron minerals into Fe2+ and Fe3+ were dependent on Eh, pH, and DO and were more sensitive to Eh and pH than DO. The results of this study can provide information on RBF site selection and its operation.

Nanoanalytical Identification of Siderite Dissolution-Coupled Pb Removal Mechanisms from Oxic and Anoxic Aqueous Solutions

Lead(II) is a toxic pollutant often found in metal-contaminated soils and wastewaters. In acidic aqueous environments, Pb(II) is highly mobile. Chemical treatment strategies of such systems therefore often include neutralization agents and metal sorbents. Since metal solubility and the retention potential of sorbents depend on the redox state of the aqueous system, we tested the efficiency of the naturally occurring redox-sensitive ferrous iron carbonate mineral siderite to remove Pb(II) from acidic aqueous solutions in batch experiments under oxic and anoxic conditions over a total of 1008 h. Siderite dissolution led to an increase in reactive solution pH from 3 to 5.3 and 6.9, while 90 and 100% of the initial aqueous Pb(II) (0.48 × 10–3 mol kg–1) were removed from the oxic and anoxic systems, respectively. Scanning and transmission electron microscopy, combined with X-ray absorption and photoelectron spectroscopy, indicated that under oxic conditions, Pb(II) was consumed by cerussite precipitation and inner-sphere surface complexation to secondary goethite. Under anoxic conditions, Pb(II) was removed by the rapid precipitation of cerussite. This efficient siderite dissolution-coupled sequestration of Pb(II) into more stable solid phases demonstrates this potential method for contaminated water treatment regardless of the redox environment.