Abundance Of Carbonate Minerals Research Articles

Magnesite everywhere: Formation of carbonates in the alkaline lakes and playas of the Cariboo Plateau, British Columbia, Canada

The Cariboo Plateau in central British Columbia, Canada, hosts the largest aerial extent of low temperature lacustrine magnesite in the world. Magnesite was the most abundant carbonate mineral in 21 of 33 sampled alkaline lakes and 20 of 22 sampled playas. Calcite, hydromagnesite and very high magnesium calcite (VHMC, also called disordered dolomite) were also found in closed basin alkaline lakes on the plateau. Carbonate mineralogy was strongly associated with lake water geochemistry, particularly total alkalinity. VHMC was the dominant carbonate mineral in lakes with the highest alkalinities (>1000 mEq/kg), magnesite was the dominant carbonate mineral in lakes in the middle range of alkalinities (generally 70 to 800 mEq/kg) and hydromagnesite with minor amounts of magnesite was the phase assemblage in lakes with lower relative alkalinities (<110 mEq/kg). The geochemical trends for the activity of CO32−, Ca2+ and Mg2+ suggest that these constituents in all Cariboo water bodies are controlled by the precipitation of Ca- and/or Mg‑carbonate minerals. The waters are near equilibrium with metastable crystalline Ca‑carbonate and Mg‑carbonate minerals. We hypothesize that carbonates present in the lakes likely formed via non-classical crystallization pathways based on the relationship between aqueous geochemistry and mineralogy and the chemical composition of the Ca-bearing magnesites. Non-classical crystallization offers new models for thinking about magnesite formation in lacustrine environments.

Comparison of Pb2+ Adsorption Properties of Biochars Modified Through CO2 Atmosphere Pyrolysis and Nitric Acid

Acid modification has been widely used to modify the structural properties of biochars. However, acid modification led to the large consumption of acid, increased difficulty of waste effluent disposal, and a high application cost. To evaluate the advantages and application potential of biochars prepared under CO2, utilizing pyrolysis to directly modify biochars to improve heavy metal removal efficiency and reduce production cost, would be an important prerequisite for the broad application of biochars. The sorption performance of Pb2+ with CO2-modified biochars was compared with that of HNO3-modified biochar. The elemental compositions and structural properties of biochars were characterized through elemental analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results revealed that for biochars produced at 500℃, HNO3 modification produced abundant carboxylic groups and -NO2 (asy) and -NO2 (sym) groups, promoting the surface activities and complexing abilities of biochars. The CO2-modified biochars contained abundant carbonate minerals, which could remove Pb2+ by electrostatic ion exchange and coprecipitation or complex. In addition, compared to that of HNO3-modified biochars, CO2-modified biochars had the larger specific surface area and better microporous structures, which were beneficial to the diffusion of Pb2+ and further promoted surface sorption. CO2 modification increased the maximum Pb2+ sorption capacity of W500CO2 and W700CO2, which were 60.14 mg·g-1 and 71.69 mg·g-1. By contrast, HNO3-modified biochars W500N2-A and W700N2-A showed the lower Pb2+ sorption capacities, which were 42.26 mg·g-1 and 68.3 mg·g-1, respectively. The increasing of the specific surface area and functional groups simultaneously promoted the sorption capacity of CO2-modified biochars. Consequently, the CO2-modified biochar had the advantages of low cost, environmental friendliness, and high heavy metal removal efficiency, which is a modification method worthy of promotion and application.

New analytical method for the evaluation of heterogeneity in cation compositions of dolomites by micro-XRF and Raman spectroscopies.

Dolomite (CaMg(CO3)2) is an abundant carbonate mineral contained in sedimentary rocks and plays significant roles in water and carbon cycle in geo/cosmochemical environments. Since the cation compositions of carbonates are sensitive to the aqueous environment where they were precipitated and persisted, quantitative analysis of their cation compositions provides valuable information on the aqueous environments and their changes. The difficulty for the analysis of natural dolomite is that Mg2+ is continuously substituted by Fe2+ or Mn2+, and hence they sometimes possess micrometer-scale heterogeneity. Such heterogeneity carries quite important information on the gradual changes in aqueous environments due to changes in thermodynamic conditions and/or aqueous chemical compositions. In the present study, we explored a new quantitative scale to assess such heterogeneity of cation composition in natural dolomite and ferroan dolomite by combining X-ray fluorescence (XRF) and Raman spectroscopy. While the Fe + Mn content differed spot-by-spot, it was found that the Raman wavenumber and Fe + Mn content linearly correlated with each other. Since the spatial resolution of micro-Raman spectroscopy is as high as 1μm, it does not require vacuum conditions, and is free from so-called matrix effect faced in other methods utilizing X-Rays and electron beams, the proposed qualitative analytical scale can provide a useful tool to assess the cation compositions in dolomites found in nature.

Factors controlling tungsten mobility in W[sbnd]Cu skarn tailings

Few studies have addressed the mobility of tungsten in mine waste, which could act as a point source for metal leaching of this potentially toxic metal. This study examines the behavior of tungsten in acidic floodplain tailings and circumneutral impoundment tailings at the Cantung Mine in the Northwest Territories, Canada. In the Cantung deposit, tungsten is present as scheelite (CaWO4), copper is hosted in chalcopyrite (CuFeS2), and gangue mineralogy consists of abundant pyrrhotite (Fe1-xS), silicate minerals, and carbonate minerals. Samples of surface waters, tailings porewaters, and solid tailings samples were collected from Cantung Mine. For surface waters, both filtered (0.45 μm) and unfiltered aliquots were collected to compare dissolved and particulate element concentrations.Tungsten concentrations range from 5.8 to 30.0 μg/L in water samples with pH values between 7.1 and 8.1, whereas samples below pH 7.1 have concentrations below the detection limit of 0.1 μg/L. Tungsten and iron concentrations are both on average 1.7 times higher in unfiltered aliquots compared to filtered aliquots, suggesting that tungsten is transported as dissolved species but is also adsorbed to suspended Fe-oxyhydroxide minerals at neutral pH. Tailings were analyzed by scanning electron microscopy (SEM) paired with automated mineralogy software (MLA), synchrotron-based μX-ray diffraction and fluorescence (μXRD-XRF), and partial leach digestions with inductively coupled plasma mass spectrometry (cold and hot hydroxylamine hydrochloride, aqua regia, Li-metaborate fusion, and 4-acid digestion with HNO3-HClO4-HF-HCl). Samples from the impounded tailings and the highly oxidized Flat River Tailings distributed on the floodplain (FRT) have similar scheelite content (0.15 wt% and 0.21 wt%, respectively), and scheelite shows no evidence of alteration. Synchrotron-based μXRD of Fe-oxyhydroxide minerals in the FRT identified goethite (FeOOH) and lepidocrocite (γ-FeOOH) as products of pyrrhotite oxidation. Rare rims on pyrrhotite from the tailings impoundment have μXRD spectra consistent with hematite (Fe2O3) and maghemite (γ-Fe2O3). The μXRF maps of the hematite-maghemite rims have prominent tungsten peaks, which represent included scheelite grains and possibly structurally incorporated tungsten. The hydroxylamine leaches yield higher tungsten concentrations in tailings samples from the circumneutral impoundments than samples from the acidic FRT, suggesting the tailings impoundments have more tungsten that is associated with poorly crystalline and amorphous Fe-oxyhydroxide phases than the FRT. Over time, labile-hosted tungsten in the FRT may have been washed down the Flat River during Fe-oxyhydroxide recrystallization and high energy flooding events. These results indicate that scheelite has limited solubility in neutral or acid mine waters, and the mobility of the small amount of tungsten released is governed by the present of iron oxyhydroxide minerals, the transport of colloidal material in surface water, and the stability of the depositional environment.

Enhancing the thermoplastic behavior and mechanical performance of recycledHDPE/CaCO3composites using oxidized polyethylene

AbstractThere is a growing interest in sustainable materials based on recycled or natural feedstocks for the circular economy. Ideally, thermoplastic materials are anticipated to show appropriate melt‐flow behavior for thermo‐mechanical recycling, good melt stability, and mechanical performance. Thermoplastic polyolefins such as polyethylenes are used as single‐use packaging materials and generate environmental concerns. This article reports the melt‐processing and characterization of composite materials based on recycled high‐density polyethylene (rHDPE) and naturally abundant calcium carbonate (CaCO3) mineral at various mass ratios such as 70/30, 50/50, and 30/70. Oxidized polyethylene (OPE) is used as an additive, with 20 wt% replacement of rHDPE, to improve the materials' mechanical performance and thermoplastic behavior. Various characteristics such as tensile, viscoelastic, melt‐flow, phase morphology, and thermomechanical recyclability of the materials are analyzed. It reveals that composites with high CaCO3content compatibilized with OPE show improved tensile strength and modulus. For example, the composite based on 10/70/20 (wt%) of rHDPE/CaCO3/OPE shows an average tensile strength of 27.4 MPa and Young's modulus of 4.5 GPa, in contrast to the rHDPE sample, which shows an average tensile strength of 12.4 MPa and Young's modulus of 967 MPa. Notably, adding OPE decreases the melt‐viscosity of the rHDPE/CaCO3materials, thus improving the composites' melt‐flow and thermoplastic behavior. This study indicates the possibility of developing natural CaCO3‐rich polymer composites with thermoplastic behavior for real‐life applications with superior mechanical and melt‐flow properties suitable for thermomechanical recycling.

How water desorbs from calcite.

Calcite is the most abundant carbonate mineral in Earth's crust. Upon cleavage, the (10.4) plane with a rectangular unit cell is exposed. Interestingly, several experiments suggest a (2 × 1) surface reconstruction. However, clear experimental evidence and a theoretical confirmation were long missing. Recently, convincing indication for a (2 × 1) reconstruction has been given by atomic force microscopies taken at 5 K. Here, we show temperature-programmed desorption (TPD) experiments of water and ethanol desorbing from calcite (10.4) around room temperature. The TPD curves fit excellently to a kinetic model considering two different adsorption sites, as expected in case of a (2 × 1) reconstruction. This finding applies to the desorption of water and ethanol, illustrating that the effect is characteristic for the calcite cleavage plane. Our results thus show that the (2 × 1) reconstruction not only exists at room temperature but has significant impact on the interfacial properties of calcite.

Incorporation of 16O-rich anhydrous silicates in the protolith of highly hydrated asteroid Ryugu

The abundant phyllosilicate and carbonate minerals characterizing most of the returned particles from asteroid Ryugu suggest a history of extensive aqueous alteration on its parent body, similar to the rare mineralogically altered, but chemically primitive, CI (Ivuna-type) chondrite meteorites. Particle C0009 differs mineralogically from other Ryugu particles examined so far by containing anhydrous silicates at a level of ~0.5 vol%, and thus can help shed light on the unaltered original materials that constituted Ryugu’s protolith. In situ oxygen isotope measurements of the most Mg-rich olivine and pyroxene in C0009 reveal two populations of Δ17O: −25‰ to −15‰ and −8‰ to −3‰. The former and the latter populations correlate well with silicate morphologies similar to those seen in amoeboid olivine aggregates and chondrule phenocrysts, respectively, both of which are abundant in less aqueously altered carbonaceous chondrites. This result also highlights the presence of olivine with Δ17O close to the solar value in either a CI chondrite or an asteroid with CI-chondrite characteristics, and provides strong evidence that amoeboid olivine aggregates and Mg-rich chondrules accreted into Ryugu’s protolith. Our data also raise the possibility that the protoliths of CI and other carbonaceous chondrites incorporated similar anhydrous silicates.

Polymineralic Inclusions in Megacrysts as Proxies for Kimberlite Melt Evolution—A Review

Polymineralic inclusions in megacrysts have been reported to occur in kimberlites worldwide. The inclusions are likely the products of early kimberlite melt(s) which invaded the pre‐existing megacryst minerals at mantle depths (i.e., at pressures ranging from 4 to 6 GPa) and crystallized or quenched upon emplacement of the host kimberlite. The abundance of carbonate minerals (e.g., calcite, dolomite) and hydrous silicate minerals (e.g., phlogopite, serpentine, chlorite) within polymineralic inclusions suggests that the trapped melt was more volatile‐rich than the host kimberlite now emplaced in the crust. However, the exact composition of this presumed early kimberlite melt, including the inventory of trace elements and volatiles, remains to be more narrowly constrained. For instance, one major question concerns the role of accessory alkali‐halogen‐phases in polymineralic inclusions, i.e., whether such phases constitute a common primary feature of kimberlite melt(s), or whether they become enriched in late‐stage differentiation processes. Recent studies have shown that polymineralic inclusions react with their host minerals during ascent of the kimberlite, while being largely shielded from processes that affect the host kimberlite, e.g., the assimilation of xenoliths (mantle and crustal), degassing of volatiles, and secondary alteration. Importantly, some polymineralic inclusions within different megacryst minerals were shown to preserve fresh glass. A major conclusion of this review is that the abundance and mineralogy of polymineralic inclusions are directly influenced by the physical and chemical properties of their host minerals. When taking the different interactions with their host minerals into account, polymineralic inclusions in megacrysts can serve as useful proxies for the multi‐stage origin and evolution of kimberlite melt/magma, because they can (i) reveal information about primary characteristics of the kimberlite melt, and (ii) trace the evolution of kimberlite magma on its way from the upper mantle to the crust.

Geochemical characteristics of Early Cretaceous marine oil shale from the Changshe Mountain area in the northern Qiangtang Basin, Tibet: Implications for palaeoweathering, provenance, tectonic setting, and organic matter accumulation

The Early Cretaceous Shengli River–Changshe Mountain marine oil shale belt, located in the northern Qiangtang Basin, Tibet, is estimated to be the largest marine oil shale resource in China. However, its palaeoweathering, provenance, and tectonic setting during the depositional history have received little interest. In this paper, 19 outcrop marine oil shale samples from the ChangsheMountain (CSM) area were studied to investigate the provenance, palaeoclimate, palaeoweathering, and tectonic setting during the marine oil shale deposition. The total organic carbon and organic sulphur contents of the CSM oil shales range from 2.2% to 13.44% and 0.19% to 1.08%, respectively. The CSM oil shale samples contain abundant carbonate (e.g., calcite and dolomite), quartz, and clay minerals. The clay minerals of the CSM oil shale samples is dominated by illite and then by smectite. Other minerals, including haematite, apatite, pyrite, baryte, and celestite, were also identified by scanning electron microscope–energy‐dispersive X‐ray spectrometer. The total rare earth element (∑REE) contents of the oil shales range from 9.01 to 105.96 ppm (average 57.56 ppm), close to the average REE contents of U.S. coals. The REE contents in oil shale samples are mainly controlled by terrigenous input. The CSM oil shales show LREE‐enriched, HREE‐depleted, with the LREE/HREE ratios ranging from 5.12 to 10.18, negative Eu anomalies (0.56–0.84) and slightly negative Ce anomalies (0.87–1.05). The chemical index of alteration values of the CSM oil shales range from 67 to 76 (average 73), indicating a moderate chemical weathering condition. Sr/Cu and Rb/Sr ratios suggest the CSM oil shales were mainly deposited under a warm and humid climate regime. Sr/Ba ratios, ranging from 0.54 to 7.84, suggest a palaeoenvironment with fluctuant salinity. Major element, trace element, and REE relationships indicate that the CSM oil shales are mainly from the felsic and intermediate igneous rocks. The REE distribution patterns of the CSM oil shales are similar to the Late Triassic Nadi Kangri felsic volcanic rocks in the Qiangtang Basin, indicating that the CSM oil shale may be derived from the Late Triassic volcanic rocks and the oil shales were mainly formed in rift tectonic setting. Favourable preservation condition (e.g., warmer palaeoclimate, higher palaeosalinity, and dysoxic to anoxic water column environment) could be the main controlling factor for organic matter accumulation.

Sulfur-siderite autotrophic denitrification system for simultaneous nitrate and phosphate removal: From feasibility to pilot experiments

Siderite (FeCO3) is one kind of abundant and cheap carbonate minerals, but it has never been used as inorganic carbon sources and pH buffer in the sulfur autotrophic denitrification before. In this study, sulfur-siderite autotrophic denitrification (SSAD) system was formed. Batch, column and pilot experiments of the SSAD system showed that siderite could provide inorganic sources and pH buffer for sulfur autotrophic denitrification. The optimal volume ratio of sulfur and siderite was 1:3 for the SSAD system. Siderite could not be used as an electron donor by the sulfur autotrophic denitrifiers. The SSAD column removed 28 mg/L NO3−-N and 3.1 mg/L PO43--P completely at 12 h HRT. The SSAD pilot biofilter during treating secondary effluent obtained stable NO3− and PO43− removal, and controlled effluent NO3−-N and PO43--P around 4 and 0.2 mg/L, respectively, at 4 h HRT, and no blocking occurred in operation of 401 days. In the SSAD system, the main bacteria were Thiobacillus (67.8%), Sulfurimonas (20.0%), and Simplicispira (3.5%); and Sulfurimonas (29.4%), Ferritrophicum (15.2%), and Thiobacillus (10.3%) during treating synthetic wastewater and secondary effluent, respectively. PO43− was removed through iron phosphate precipitate. The SSAD system was a promising way to remove NO3− and PO43− simultaneously from wastewater lack of organic carbon sources.

The influence of the thermal aureole asymmetry on hydrocarbon generative potential of coal beds: Insights from Raniganj Basin, West Bengal, India

The aim of the present study is to uncover hydrocarbon generation potential of an area intruded by lamprophyre dyke. Lamprophyre dyke induced a short-distance asymmetric thermal aureole in coal beds with more intense impact along the dip direction. Large ash yield, carbon content, lower volatile matter content, hydrogen indices, presence of natural coke, disordered kaolinite peaks, less pronounced aliphatic peaks, higher aromaticity under Fourier Transform Infra-Red spectroscopy (FTIR); highly rugged surface and large pores with the aid of Atomic force microscopy (AFM); abundant calcium carbonate mineral phases (calcite, dolomite, ankerite) and high-temperature silica phases (tridymite, sanidine) under X-ray diffraction (XRD) are the consequences of pronounced thermal effect and expulsion of hydrocarbons. Furthermore, the estimated vitrinite reflectance (EVRo) calculated through maximum pyrolysis temperature (Tmax) and measured mean random vitrinite reflectance (VRo) show the maximum difference in the heat-affected coal samples. In addition, parameters for source rock reconstruction and indices for quantification of FTIR spectra i.e. index of aliphaticity (IAL), index of aromaticity (IAR) and index for hydrocarbon generation (IHG) are introduced for coals. The distant (i.e. least-heat-affected) coals collected opposite to the dip direction of the coal bed have a higher potential for hydrocarbon generation. The igneous intrusion thus played a significant role in enhancing the maturity of the organic material, in turn, augmenting the hydrocarbon generation potential for targeting hydrocarbon plays of the area although at the expense of proximal samples.

A novel mineralogical approach for provenance analysis of late Quaternary marine sediments: The case of Myrtoon Basin and Cretan Sea, Aegean, Greece

Sediments from two deep-sea bottom cores from the Myrtoon basin in the SW Aegean Sea and Eastern Cretan Sea were examined by quantitative mineralogical and geochemical analysis to infer sediment provenance and climatic conditions and palaeo-environmental control on sediment deposition. Both cores contain calcareous muds and silts with dark olive-grey organic rich intervals corresponding to the regional sapropel S1 horizon. The presence of a few tephra layers documents volcanic activity in the southern part of the Aegean Sea. The bulk sediments contain abundant carbonate minerals (mainly calcite and Mg-calcite) and clay minerals (mainly illite and smectite) and accessory serpentine, talc and hornblende, which attest to contributions from ultrabasic sources. There is a sharp decrease of the Mg-calcite content and the Mg/Ca ratio of the carbonate fraction in sapropelic sediments followed by an increase of the average grain size. A well expressed negative relationship between illite and smectite was observed in the clay fraction in full accordance with previous studies. However, this trend is absent from the bulk sediments, because smectite is significantly overestimated in the oriented clay fractions. Clay mineral distribution is controlled mainly by sediment sorting, with deposition in the sapropelic sediments being also affected by climatic changes. The different types of smectite in the cores and the presence of smectite with high dehydroxylation temperature in the SE Aegean, suggests that the sediment supply from SE Mediterranean sources should be limited.

English

Coral reef area in northwest of the Arabian Gulf was investigated for mineralogy and geochemistry to throw lights on such unique Iraqi Marine Environment; six specimens of two main species of coral reefs, Platygyra pini Chevalier, 1975 and Octocoral Menella were collected at two sites. While eight samples of the surrounding sediments are chosen from other two sites. The mineralogy is determined by XRD, and reveals that calcite, low magnesium-calcite, and aragonite are the main minerals that comprise the Octocoral Menella in site 1, whilst aragonite and calcite are dominate in the P. pini coral reef at site 4. The non–carbonate fractions indicate that these coral reefs contain quartz, anorthite feldspare , halite, and gypsum; the highest content of aragonite was observed in the P. pini compared to calcite. The abundance of carbonate minerals (92.1%) in the P. pini is in contrast to (73.1%) in the Menella. The main minerals in the sediments of site 2 are represented by chlorite and talc, whereas quartz and phengite are the most prominent minerals that diagnose in sediments of site 3; phengite mineral is a first discovery in the sediments of Arabian Gulf, whilst talc is a first detection in Iraqi marine sediments. The concentration of CaO is the most abundant oxide in all the analyzed specimens of the coral reef followed by SiO2. There are high proportions of calcium oxide in P. pini Chevalier coral (56.65 %) than the Menella (48.81%). There are some special pattern of distribution for major and trace elements in coral reef area based on calcium content. Most of the silica came from quartz, phengite and clay minerals; the highest concentrations of Al2O3, Fe2O3, K2O, Na2O, MgO, SiO2, TiO2, V2O5, Cr, Ni, Cu, Rb and Zr are found in the sediments of site 2 as opposed to the other sites. These results could affect the association of these elements with clay minerals through adsorption or absorption, the highest content of P2O5, Ga, W and As in the sediments of site 3 may reflect the adsorption of these elements on surface of the quartz and phengite; from the other hand, the highest concentrations of Sr, Zn, Br, Sn, Ta, and Pb in the P. pini may indicate the relative effects of the environmental variation within the studied area.

Subducted Mg-rich carbonates into the deep mantle wedge

Recent studies have concluded that subducted calcium (Ca-) rich carbonates could be dissolved in slab-derived aqueous fluids and transported upwards into the shallow mantle wedge (75–120 km), while magnesium (Mg-) rich carbonates could be delivered to a greater depth (i.e., the mantle transition zone, ∼410 km), melted, and recycled into the convective upper mantle. However, it remains unknown whether or not Mg-rich carbonates can be transferred to the deep mantle wedge (>∼120 km) by subduction-zone fluids, which, if true, is important for tracing deep carbon. In this paper, we report a comprehensive mineralogical, geochemical, stable (Mg and O) and radiogenic isotopic (zircon U–Pb) study of garnet clinopyroxenites from the Maowu ultra-mafic massif (a slice of the mantle wedge) in the Dabie orogeny, Central China. Whole-rock and mineral trace elemental features and zircon U–Pb ages reveal evidence of mantle wedge metasomatism by a slab-derived melt or supercritical fluid from the subducted rutile-bearing eclogitic Paleo-Tethys oceanic crust, in addition to subsequent metamorphism occurring during the Triassic collision between the South and North China blocks. Combined with the results of previous works, the high Th/U ratios of both whole rocks and metasomatized zircons with no oscillatory zoning lead us to infer that a supercritical liquid rather than a melt was the metasomatic agent during oceanic subduction at peak conditions (5.3–6.3 GPa and ∼800 °C, 160–190 km). Abundant carbonate mineral inclusions (including calcite, dolomite and magnesite) and the high δ18OVSMOW values of the metasomatized zircons (up to 12.2‰) indicate that sedimentary carbonates were leached by the supercritical fluid. Furthermore, whole-rock δ26Mg values (−0.99‰ to −0.65‰) that are lower than normal mantle values (−0.25±0.07‰) imply that the incorporated carbonates contain not only calcites but also a certain amount of dolomites (approximately 1–10 wt.% of the metasomatic supercritical liquid). The dissolved Mg-rich carbonates in the slab-derived supercritical liquid could effectively modify the Mg isotope composition of the deep mantle wedge. Our study represents a critical step towards achieving a broad understanding of the behaviours of recycled carbonate during slab subduction.

Organic matter, mineral composition, pore size, and gas sorption capacity of lacustrine mudstones: Implications for the shale oil and gas exploration in the Dongying depression, eastern China

Because clay minerals and pore-size distribution are important for oil and gas accumulation in lacustrine mudstone reservoirs, this study aimed to characterize the pore-size distribution in lacustrine mudstone, reveal the importance of clay minerals in gas sorption capacity (GSC), provide insights into the primary GSC controls for lacustrine mudstones, and discuss the shale oil and gas resource potential and possible risks in their future production. A total of 256 core samples from the lower Paleogene sequence of the Dongying depression in the Bohai Bay Basin in China were analyzed to determine organic richness and hydrocarbon generation potential. A series of analyses was conducted on a suite of 28 mudstone samples from the S121 well to investigate the mineral composition, pore-size distribution, and primary controls on GSC. Scanning electron microscopy and x-ray diffraction were used to observe the microscopic characteristics and identify various minerals. Nitrogen adsorption experiments at low temperatures and a methane isothermal adsorption test were conducted to study the pore sizes and gas adsorption capacities. Experimental results show that the majority of the samples were rich in type II and I kerogen with moderate to high hydrocarbon generation potential and are thermally mature in the main oil window. The contents of illite and mixed layer illite–smectite (I–S) are high (>40%) in these lacustrine mudstones. The pores were mainly thin, long, and bottleneck shaped and dominated by type IV and H2 hysteresis loop characteristics. The abundance of quartz, feldspar, illite, and mixed layer I–S all presented a positive correlation with their Brunauer–Emmett–Teller surface area and total pore volume, whereas the abundance of carbonate minerals (dominated by calcite) showed a negative correlation. The volume of micropores and clay minerals were the main factors controlling GSCs. The results highlight the importance of clay minerals, including the illite and mixed layer I–S, in the lacustrine mudstones because of their considerable GSC. High content of illite and mixed layer I–S in lacustrine mudstone is in favor of gas storage, whereas at the same time, it is not conducive to shale gas development because of its reducing the brittleness of shale. The Paleogene of Dongying depression has shale oil and gas resources; however, several key geological factors, including pore-size distributions, pore diameters, oil density, and low brittleness, may pose risks in shale oil and gas development.

Pressure Effect on the Multicycle Activity of Natural Carbonates and a Ca/Zr Composite for Energy Storage of Concentrated Solar Power

This work is focused on the use of the Calcium-Looping process (CaL) in Concentrated Solar Power (CSP) plants for Thermochemical Energy Storage (TCES). Cheap, abundant and nontoxic natural carbonate minerals, such as limestone and dolomite, can be employed in this application to store energy through the cyclic calcination/carbonation of CaCO3. In a recent work, a closed CO2 cycle has been proposed for an efficient CaL-CSP integration in which the CO2 in excess effluent from the carbonator is used to generate electricity by means of a gas turbine. Process simulations show that the thermoelectric efficiency is enhanced as the carbonator pressure and temperature are increased provided that the multicycle CaO conversion is not affected. On the other hand, the use of just one reactor for both calcination and carbonation has been suggested to reduce capital cost. However, the experimental results shown in the present work indicate that sintering is notably enhanced as the pressure in the reactor is increased. S...

Application of micro-FTIR mapping and SEM to study compositional heterogeneity of siltstones: Example from the Late Devonian-Early Mississippian Middle Bakken Member.

This paper explores the applicability of micro-FTIR mapping to study heterogeneity of organic matter-lean siltstones. Closely spaced samples of Late Devonian dolomitic siltstones of the Middle Bakken Member were analysed with micro-FTIR, powder X-ray diffraction, and scanning electron microscopy (SEM) to explore the distribution and chemical properties of organic matter (OM), muscovite/feldspar/clay group, carbonates, and quartz, and their influence on porosity and permeability of these rocks. Our results show that quartz is the dominant component of the samples, and the main mineralogical differences between the samples are reflected in the abundance of carbonate minerals. Organic matter content is usually far below 1 wt. % and dominantly represented by terrestrially derived vitrinite and inertinite. Micro-FTIR mapping demonstrates that the more spatially connected quartz and muscovite/feldspar/clays become, the larger permeability in the rock develops, and these correlations are especially strong for planes parallel to bedding. In contrast, carbonate connectivity shows a strong negative correlation with permeability. No correlations between connectivity of components and porosity have been detected. These observations suggest that micro-FTIR not only can document compositional heterogeneity of siltstones, but also has potential to help understanding their permeability systems.

Large-scale high-temperature solar energy storage using natural minerals

Abstract––– The present work is focused on thermochemical energy storage (TCES) in Concentrated Solar Power (CSP) plants by means of the Calcium-Looping (CaL) process using cheap, abundant and non-toxic natural carbonate minerals. CaL conditions for CSP storage involve calcination of CaCO3 in the solar receiver at relatively low temperature whereas carbonation of CaO is carried out at high temperature and high CO2 concentration to use the heat of reaction for power production by means of a CO2 closed power cycle. Under these conditions, large CaO particles derived from limestone to be used in industrial processes are rapidly deactivated due to pore-plugging, which limits the extent of the reaction. This is favored by the relatively small pores of the CaO skeleton generated by low temperature calcination, the large thickness of the CaCO3 layer built upon the CaO surface and the very fast carbonation kinetics. On the other hand, at CaL conditions for CSP storage does not limit carbonation of CaO derived from dolomite (dolime). Dolime is shown to exhibit a high multicycle conversion regardless of particle size, which is explained by the presence of inert MgO grains that allow the reacting gas to percolate inside the porous particles.

Mineral carbon MinC(%) from Rock-Eval analysis as a reliable and cost-effective measurement of carbonate contents in shale source and reservoir rocks

The abundance of carbonate minerals in rocks is an important element for petroleum geochemists, geologists and engineers to consider during hydrocarbon exploration and production. Carbonate minerals can be related to the depositional environments of the source rocks and hence the type of organic matter that can be subsequently modified through diagenetic processes. The total carbonate content in shales can also be used to deduce their fracability as reservoir rock for shale gas/oil extraction. At present, mineralogical analysis by X-ray diffraction (XRD) is the most widely used technique in the oil and gas-related petrophysical and geochemical laboratories for identifying and quantifying carbonate minerals in rock samples. In contrast, the use of the total mineral carbon content parameter MinC (%) from Rock-Eval analysis has been limited despite (1) the parameter's effectiveness as demonstrated through instrument and methodology development; and (2) the presence of a large volume of Rock-Eval results due to its widespread use in the oil and gas industry.In this study, we acquired XRD and Rock-Eval analytical results on over nine hundred rock samples ranging from Ordovician to Cretaceous age from four petroleum sedimentary basins in Canada. Least-squares regression analyses produce empirical equations with R2 values greater than 0.92 for the correlations between XRD total carbonate contents and the Rock-Eval MinC (%) values of six different suites of samples. This indicates that the MinC (%) values generated by Rock-Eval 6 and other instruments of similar capability can be used with confidence for estimating the amounts of total carbonates in sedimentary rock samples. While the correlation between the two types of carbonate content measurements is geology-specific, a global linear regression model (R2 of 0.97) based on the large combined data set has been proposed for approximating the total carbonate abundances based on Rock-Eval MinC (%) values.

Consumption of atmospheric CO2 via chemical weathering in the Yellow River basin: The Qinghai–Tibet Plateau is the main contributor to the high dissolved inorganic carbon in the Yellow River

The high HCO3− concentrations in the Yellow River (China) are generally believed to originate primarily from the carbonate-rich Loess Plateau as a result of carbonate weathering reactions that consume atmospheric CO2. We studied chemical weathering across the entire Yellow River basin in 2007 and 2009 and found that the amounts of CO2 consumption by carbonate and silicate weathering were 87.61×109mol/a and 10.70×109mol/a, respectively. As the source of water for the Yellow River, although the Qinghai–Tibet Plateau accounts for only 30% of the area of the basin, it has a strong leaching effect and contributes a majority (61%) of the atmospheric CO2 consumption of the entire basin and a majority of the riverine DIC flux (66%) to the ocean. As a result, the dissolved inorganic carbon (DIC) concentrations in this river are among the highest of the world's major rivers. In contrast, despite the abundant carbonate mineral content in the Loess Plateau, the high ratio of evaporation to precipitation (4.2) limits the weathering processes, and the low amount of runoff restricts the transport of weathering products, which results in a relatively low contribution (38%) to the basin-wide atmospheric CO2 consumption, which is much lower than was previously thought. The Qinghai–Tibet Plateau is the origin of the high levels of HCO3− in and acts as the main DIC contributor to the Yellow River.