Clay Components Research Articles

Study on the Improvement Performance of Different Clay Components with Desulfurization Gypsum-Containing Cementitious Material

Study on the Improvement Performance of Different Clay Components with Desulfurization Gypsum-Containing Cementitious Material

Clay Minerals/TiO2 Composites—Characterization and Application in Photocatalytic Degradation of Water Pollutants

TiO2 used for photocatalytic water purification is most active in the form of nanoparticles (NP), but their use is fraught with difficulties in separation from solution or/and a tendency to agglomerate. The novel materials designed in this work circumvent these problems by immobilizing TiO2 NPs on the surface of exfoliated clay minerals. A series of TiO2/clay mineral composites were obtained using five different clay components: the Na-, CTA-, or H-form of montmorillonite (Mt) and Na- or CTA-form of laponite (Lap). The TiO2 component was prepared using the inverse microemulsion method. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, FTIR spectroscopy, thermal analysis, and N2 adsorption–desorption isotherms. It was shown that upon composite synthesis, the Mt interlayer became filled by a mixture of CTA+ and hydronium ions, regardless of the nature of the parent clay, while the structure of Lap underwent partial destruction. The composites displayed high specific surface area and uniform mesoporosity determined by the size of the TiO2 nanoparticles. The best textural parameters were shown by composites containing clay components whose structure was partially destroyed; for instance, Ti/CTA-Lap had a specific surface area of 420 m2g−1 and a pore volume of 0.653 cm3g−1. The materials were tested in the photodegradation of methyl orange and humic acid upon UV irradiation. The photocatalytic activity could be correlated with the development of textural properties. In both reactions, the performance of the most photoactive composites surpassed that of the reference commercial P25 titania.

Spatial variations and vertical migration potentials of petroleum hydrocarbons with varying chain lengths in soils of different depths: Roles of solid and dissolved organic matters and soil texture

Petroleum hydrocarbons (PHs) in contaminated sites may threaten human health and ecological safety, while the environmental behaviors of PHs with varying carbon chains and critical influencing factors need to be elucidated, thus facilitating efficient risk management. This study explored the occurrence characteristics and spatial variations of different PHs at the depths of 0–10 m in an abandoned industrial site, as well as evaluated the effects of solid organic matter (SOM), dissolved organic matter (DOM), and soil texture on the migration potentials of PHs with varying carbon chains. Furthermore, the leaching potentials of different PHs were integrated into their risk assessment. The total concentrations of PHs in contaminated soils ranged from 22.7 to 397 mg/kg in contaminated soils, and the long-chained PHs (C22-C40) represented the major components with an average contribution of 46.9 %, followed by short-chained PHs (C10-C12, 32.0 % average) and medium-chained PHs (C13-C21, 21.1 % average). As soil depth increased, a declining trend was observed in the proportions of long-chain PHs, with an augmentation in the relative abundance of short-chain PHs. The random forest model coupling redundancy analysis showed that SOM was the major contributor to the occurrence and vertical attenuation of PHs with longer carbon chains in underground soils, with clay component exerting a greater additional effect than silt and sand components. While DOM in soils exhibited a relatively high contribution to the retention of PHs with short carbon chains. These results demonstrated the significant influence of SOM and clay on the behavior of long-chained PHs and DOM on that of short-chained ones. Besides direct human exposure, the leaching potentials of PHs, particularly short-chained ones, in soils should be considered for a more comprehensive risk assessment. The findings of this study may assist with the behavior modelling and prediction of different PHs as well as the corresponding risk control.

Characterization and ceramic properties evaluation of Lombok clay

Purpose. This research aims to assess the characteristics of ceramics made from Lombok clay to optimize the quality of ceramic products in the Lombok region and surrounding areas. Methods. Methods used to characterize Lombok clay include measuring its chemical composition, loss on ignition, plasticity level and conducting mineral analysis. Additionally, the influence of sintering temperature on clay properties and shrinkage is studied. Findings. The main mineral component of Lombok clay is kaolin, which has a high level of plasticity and a water absorption rate of 7 ± 0.6%. The ceramic body produced from this clay is classified as semi-porcelain, making it suitable for medium-sized tableware manufactured using the rotating technique. Originality. This research highlights the effect of sintering temperature on the mineral transformation of Lombok clay and provides valuable information on its optimal applications. It fills a gap in the literature by providing comprehensive data on clay properties and optimal processing conditions that have previously been underexplored. Practical implications. Lombok clay is used predominantly by small-scale ceramic craftsmen in Lombok and Bali due to its relatively low market price. With the findings of this study, these craftsmen can enhance the quality of their products to semi-porcelain standards by adjusting the sintering temperature.

Effects of clay type and component fineness on the hydration and properties of limestone calcined clay cement

Effects of clay type and component fineness on the hydration and properties of limestone calcined clay cement

Efficient technology for manufacturing electrical ceramics from low-iron diopside rocks

Relevance. The use of natural diopside CaMgSi2O6 in the production of ceramic dielectrics was implemented at two enterprises in the Chelyabinsk region in 1985 on the basis of comprehensive studies of diopside rocks of the Southern Baikal region by the team of the Department of Silicate Technology of Tomsk Polytechnic University. Natural diopside was used as an additive to the charge of electrical porcelain. In addition, ceramic dielectrics with a diopside crystalline phase were manufactured for exploitation at the frequencies of 106 Hz. Currently, the need for ceramic dielectrics in Russia is covered by imports. Though, the development of new technologies for ceramic dielectrics from domestic raw materials is relevant. Aim. To develop an efficient technology for ceramic dielectrics with a diopside crystalline phase from natural low-iron diopside rocks. This technology includes the production of compacts of unfired products by moulding aqueous suspensions of compositions of nonplastic components. Object. The technology of ceramic dielectrics with a diopside crystalline phase, including the firing of compacts formed from aqueous suspensions of diopside concentrate compositions with perlite as flux. Methods. The suspension was obtained by grinding the components in an aqueous environment in a ball mill with uralite balls at humidity of 20±2%. Compressive and bending strength, electrical strength, dielectric constant of the samples were determined according to the SS 24409-80, water absorption was measured according to the SS 26093-84. X-ray phase analysis was carried out on a DRON-3M diffractometer (Burevestnik, Russia), structure analysis was implemented on a JSM 6000 electron microscope (Jeol, Japan). Results. A distinctive feature of the proposed technology is the use of nonplastic components only to prepare the suspension and the exclusion of clay components. This makes it possible to reduce the humidity of the castings and stabilize the formation of the ceramic structure during firing. The authors have obtained ceramic dielectric with a diopside content of 70±2 wt % by firing products molded at 1130–1150°C. The bending strength reached 85–90 MPa with an electrical strength of 35–38 k V/mm2.

Firing the wall: A novel way to protect earth buildings

It is widely recognized that external earthen renders are susceptible to accelerated degradation caused by environmental factors. Therefore, chemical stabilization has become a common approach to address this issue. This study focuses on the stabilization of earth renders by heat treatment, considering criteria such as energy efficiency and the judicious use of resources. Different earth rendering mortars with additives such as wheat paste and horse dung were investigated. These were subjected to surface heat treatment at 400 °C for one minute. Changes in mechanical properties, including shear strength, adhesion and water erosion resistance were examined. The results showed that surface heat treatment at 400 °C improved water erosion resistance but negatively affected shear strength and adhesion to the adobe substrate. Interestingly, the mortar containing wheat paste showed the least reduction in shear strength and adhesion, with a 16 % decrease, while it experienced a water erosion resistance. The phenomenon was observed in all specimens and is attributed to the microstructural changes induced by the irreversible processes of dehydration and dehydroxylation, which alter the clay components on the surface of the earthen render. Overall, heat treatment shows promise for improving the durability of earthen renders against environmental degradation.

Effect of sintering temperature on ceramic membrane fabricated using coal flyash and natural clay for lignin recovery

This study explores the utilization of coal fly ash combined with natural clay as a precursor for creating ceramic membranes through the uniaxial compaction method, aiming at lignin separation. These membranes were sintered at varying temperatures from 600 to 1000 °C. Thermal Gravimetric Analysis (TGA) revealed the robust thermal stability of the membranes. Fourier Transform Infrared (FTIR) analysis affirmed the presence of silica and alumina within the membranes. X-ray Diffraction (XRD) peaks indicated the crystalline structure and the presence of metal oxides originating from the fly ash and clay components. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images illustrated the porous nature and rough surface of the ceramic membranes. The average pore radius of the fabricated membrane expanded from 43.12 to 7.91 nm with increasing temperature. Concurrently, membrane flux decreased from 4.13 to 0.96 ×10−6 m3/m2 s with higher temperatures. Lower contact angles indicated the hydrophilic properties of membranes. All membranes exhibited superior corrosion resistance and negative zeta potential, owing to the significant silica content in the fly ash. Lignin separation efficiency increased from 65 % to 81 % with increasing temperatures. The optimal sintering temperature was determined to be 800 °C, achieving a lignin recovery greater than 76 % and a membrane permeability of about 7×10−9 m3/m2 s kPa. Thus, the fly ash-clay-based ultrafiltration membranes synthesized in this study offer the potential for lignin biomass recovery from biorefinery effluent.

Petrographic and geochemical study of Precambrian and Paleozoic rocks in the western Anti-Atlas belt, Morocco: Facies, weathering, provenance and economic exploitation

Detrital and volcanic-detrital rocks from the Ifni Buttonhole and Lakhssas Plateau were analyzed to determine their provenance, compositional maturity, and alteration source. Geochemically, the sediments were classified as arkoses, lithic arenites, grauwackes, sandstones, lithic arenites, and Fe-rich sands, indicating low compositional and mineralogical maturity. A high average SiO2 concentration and low Al2O3 were consistent with a low abundance of shale and clay components. The geochemical signatures of the detrital and volcano-detrital (RDVD) rocks indicate that they have undergone a moderate to low degree of chemical alteration. The CIA study also suggests that the granitic, granodioritic rocks represent the source provenance which, during weathering and transport, supplied the detritus to the supra-crustal units. The major trace element data suggest that these rocks are largely derived from felsic igneous rocks, namely granitoids, with a minor contribution from intermediate sources. The carbonate rocks do not represent a wide variety of facies: dolomitic limestone, calcareous limestone, and calcaro-dolomitic chert. Calcitic and dolomitic samples show a linear increase in SiO2, regardless of their CaO/LOI ratio values, which remain relatively constant. The highest SiO2 contents are observed in the calc-dolomitic chert. Geochemical analysis of RDVD from the Ifni buttonhole determined their origin, maturity, and alteration. Major oxides decreased with higher silica content, indicating quartz control. Samples, formed under semi-arid conditions, show maturity under stable deposition. They suggest a felsic, recycled source, with moderate alteration and zircon enrichment during recycling. In the study area, limestones and dolomites serve as materials applicable in the building sector, suitable for all types of concrete. The Taliwine Formation harbors Lower Cambrian dolomites and limestones, ideal for mosaic aggregates. Described as variable in color, compact, homogeneous, very hard, and resistant to alteration, the plutonic rocks form prominent peaks. They exhibit both subalkaline characteristics in granitoids and an alkaline trend in dolerite dykes. Most samples display minimal alteration, indicating the reliability of their major element compositions for geochemical analyses. These granitoids constitute valuable deposits for ornamental and building rock purposes.

Insight on molecular interactions in shrinkage of Na-montmorillonite clay by molecular dynamics simulation

Expansive soils are known to be hazardous materials for infrastructure due to their high shrinking or swelling potential. Understanding the shrinking factors of expansive soils such as montmorillonite (MMT) is essential for predicting their mechanical properties. The interactions between the components of Na-MMT clays, e.g., MMT layer–layer (LL), layer–cation (LC), layer–water (LW) and water–cation (WC), are responsible for its shrinking behavior. In this study, molecular dynamics simulation and grand canonical Monte Carlo simulations are used to investigate the interaction energy evolution in the layered structure of Na-MMT for the shrinkage mechanisms analysis of clay. The results of simulation indicate that the magnitude of the interaction energy contributed by the interlayer cations dehydration is the driving force of the interlayer shrinkage. Furthermore, in the hydrated state, with one water layer, two water layers and three water layers, the attractive interactions between WC and LW, maintain the stability of the clay layers. However, at the dry state, the interaction energy between layers and cations appears to be the most essential component in holding the stacked layers together, which provides structural stability to the clay sheets. Finally, the study reveals that intermolecular interactions contribute to the mechanical properties of clays such as cohesive and elastic properties.

Effect of pore-bearing fluids on the mechanical behavior of siliceous cemented sandstones containing different clay contents and types

The clay minerals contained in the reservoir rock of CO2 geological storage formations can adsorb fluids and swell, which weakens the rock and promotes deformation. This phenomenon has not been widely investigated due to the complexity of the mineral components of the rock. To study the relationship between fluids in rock pores and the mechanical behavior of clay-bearing reservoir rocks, three types of siliceous cemented sandstones mainly composed of clay minerals and quartz, both dry and saturated with various fluids (i.e. N2, scCO2, H2O), were subjected to conventional triaxial compression tests. The results show that the fluids weakened the mechanical strength of the sandstones, and the degree of weakening depended on the clay composition and the type of fluid, with no significant relationship to the clay content. For the sandstone containing montmorillonite, compared to the dry condition, scCO2 and H2O reduced the peak strength by up to 7.16% and 15.33%, respectively, while for the sandstone containing only kaolinite as clay component, scCO2 and H2O reduced the peak strength by 3.34% and 3.18%, respectively. As a control, N2 weakened the strength of the three types of sandstones between 1.46% and 4.04%. By considering the failure characteristics of sandstone at the macro- and microscales, the failure mechanism of the sandstones was explained from two perspectives: the intercrack surface energy reduction and the swelling of clay. This study offers new perspectives for assessing the mechanical stability of fluid-bearing reservoirs and clarifies the role of clay in the connection between fluids in rock pores and the mechanical behavior of rocks.

Processes occurring during the synthesis of wollastonite‑containing refractory used in non‑ferrous metallurgy

This article presents the results of research on the processes occurring during the synthesis of wollastonite‑containing ceramics obtained from various clay components. The peculiarities of crystalline phase formation in the material are described. The obtained information lays the foundation for the organization of ceramic production that is in demand in the metallurgical industry.

ASSESSMENT OF THE POSSIBILITY OF USING RECYCLED COARSE AGGREGATE IN A WOOD-SOIL CONCRETE SLAB

Problem statement. During the process of post-war reconstruction in Ukraine, there will be a need for a large number of affordable and ecological building materials, especially in the part of restoration and construction of low-rise buildings. Such building materials can be soil-concrete and aggregates from crushed concrete waste. The proposed constructive solution of the ribbed floor, in which the ribs are made of pine beams and OSB sheets, and the slab part is made of soil concrete on fixed formwork. The purpose of the article is to determine the optimal composition of the soil-concrete mixture using crushed stone obtained after crushing concrete scrap, taking into account the configuration of the wood-soil concrete slab, to determine the strength of soil-concrete of this composition, to determine the possibility of using recycled coarse aggregates. Conclusions. Based on the results of determining the optimal composition of soil-concrete, it was established that the maximum compressive strength is achieved when the mass content of the binder in the cement-soil mixture is at the level of 20 %. Taking into account the configuration of the slab part of the floor, a fraction of 5...7.5 mm is accepted for coarse aggregate. During the test of soil-concrete samples with recycled aggregate with a mass content of 10 %, 20 % and 30 %, the compressive strength of soil concrete decreased. Obviously, the presence of a clay component (loam) in the mixture reduces the adhesion in the contact zone between the aggregate and the soil-concrete, which increases the heterogeneity of the entire structure of the soil-concrete. Thus, the use of natural or recycled coarse aggregates in soil-concrete is impractical. Taking into account the determined strength of soil-concrete without aggregate, a scheme of combined concreting of the soil-concrete slab is proposed – heavy concrete above the rib and soil-concrete in the overhangs. In this case, there is a need for research on the possibility of using recycled coarse aggregate of the required size in heavy concrete.

Microstructural Observations on the Durability of Stabilized Rammed Earth

This study provides a qualitative microstructural investigation of fly ash geopolymers' role in rammed earth's durability against water ingress and contact erosion. A series of SEM (scanning electron microscopy) images were captured on geopolymer-stabilized as well as unstabilized rammed earth samples. These samples were fabricated from predefined amounts of sand and fine materials together with fly ash geopolymers in the laboratory by static compaction to 25 MPa inside rigid molds. Two standardized durability tests were performed, namely, the dip test and the spray (also known as erosion) test. The results of these tests reflected excellent durability properties (practically zero erosion) of the stabilized material. The microscopic investigation provided an insight into the reason behind this improvement, where geopolymer networks inhabited the macro and micro pores and served as a cementing agent interconnecting the earthen materials’ grains. On the contrary, grains of the unstabilized material were weakly bonded by the clay component of the mixture, as observed with the SEM images; therefore, they were more susceptible to erosion by water.

3D-printed clay components with high surface area for passive indoor moisture buffering

This study focuses on implementing a novel approach in which clay 3D-printed matrices were designed as a passive comfort solution to enhance indoor moisture buffering and air quality. Liquid Deposition Modeling additive manufacturing and parametric design were implemented to develop the components, which were characterized for having an increased specific surface exposed to air and moisture per volume unit, which showed to significantly enhance moisture buffering. This revealed a clear linear relationship between the two parameters. Additionally, the components showed a significant increase in the practical Moisture Buffering Value (MBV) and mass reduction compared to a solid clay reference. Furthermore, this research analyzed the influence of two stabilization techniques on the moisture uptake capacity of the samples, i.e. thermal treatment at different temperatures between 600 and 1000 °C and mixing with calcium hydroxide paste within the 10–40 % range. Finally, the morphological (scanning electron microscopy) and crystallographic (X-ray diffraction) analyses of the samples show a correlation between microstructural modifications and the variations of moisture uptake capacity and MBV. In addition, nitrogen adsorption-desorption measurements revealed that sample porosity decreased as the temperature of the thermal treatment increased, showing a correlation with the decrease of practical MBV.

Rheo-SAXS study of a shear-thinning hydrogel containing clay nanoplatelets

Shear-induced orientation of clay nanoplatelets within a physically cross-linked hydrogel based on ionenes, positively charged polyelectrolytes, is studied here. Small angle X-ray scattering measurements (SAXS) are performed under shear within a Couette cell cylinder (rheo-SAXS). As the SAXS signal is dominated by that of the clay component, we follow the evolution of the orientational distribution of the clay nanoplatelets within the hydrogel as a function of shear. We investigate the effect of the clay volume fraction, polyelectrolyte concentration, clay charge location and clay charge density by screening three different types of clay: Wyoming and Arizona montmorillonites and Idaho beidellite. The orientational field of clay nanoplatelets in the gel is shown to strongly depend on the clay charge location and shear rate, whereas it is independent of the clay volume fraction. Approaching the critical gelation concentration of the polyelectrolyte system, these features change drastically.

Measurements of Thermodynamic Data of Water in Ca-Bentonite by Relative Humidity Method

Buffer material (compacted bentonite), one of the engineered barrier elements in the geological disposal of a high-level radioactive waste, develops swelling stress due to groundwater penetration from the surrounding rock mass. Montmorillonite is the major clay mineral component of bentonite. Even previous studies provide few mechanical and thermodynamic data on Ca-montmorillonite. In this study, thermodynamic data on Ca-montmorillonite were obtained as a function of water content by measuring relative humidity (RH) and temperature. The activities of water and the relative partial molar Gibbs free energies of water were determined from the experimental results, and the swelling stress of Ca-bentonite was calculated using the thermodynamic model and compared with measured data. The activities of water and the relative partial molar Gibbs free energies obtained in the experiments decreased with decreasing water content in water contents lower than about 25%. This trend was similar to that of Na-montmorillonite. The swelling stress calculated based on the thermodynamic model was approximately 200 MPa at a montmorillonite partial density of 2.0 Mg/m3 and approximately 10 MPa at a montmorillonite partial density of 1.4 Mg/m3. The swelling stresses in the high-density region (around 2.0 Mg/m3) were higher than that of Na-montmorillonite and were similar levels in the low-density region (around 1.5 Mg/m3). Comparison with measured data showed the practicality of the thermodynamic model.

Creation of Organic/Inorganic Hybrids in Two‐Dimensional Organized Films Using Natural Materials and Control of Their Morphology

AbstractStarch, an insoluble natural polymer, can be spread into a Langmuir monolayer on the surface of water as amylodextrin by solubilization, where it forms a spherical single‐particle layer at the air–water interface. In this study, we fabricated a two‐dimensional mixed monolayer from soluble starch and organo‐modified montmorillonite and attempted to control its morphology by varying the mixing ratio. The behavior of the organo‐modified montmorillonite was dependent on the spreading solvent and miniaturization was possible using a suitable solvent for spreading insoluble starch. Although both materials formed phase‐separated systems, nearly homogeneous particle layers were formed in some cases because of clay miniaturization. However, X‐ray photoelectron spectroscopy showed that the clay components remained intact and a rectangular morphology derived from aluminosilicate was observed in the mixed film with a high clay ratio. Functionalization as a mixed film clearly demonstrated the hydrophilic properties imparted by the starch particles and the selective adsorption of biomolecules on the clay surface.

Study on failure characteristics and evaluation index of aquifer shale based on energy evolution

AbstractThe presence of abundant clay components and microporous structure in shale results in its high hydrophilicity, making a water-rich environment inevitable in petroleum exploration projects. Therefore, it is crucial to consider the influence of bedding structure, moisture content, confining pressure, and their combined effects on the geomechanical properties of shale. This article aims to investigate the mechanical properties of deep shale under varying water content conditions, elucidate the failure mode and failure mechanism of shale in actual engineering scenarios, and explores the interplay between stress, structure, moisture content, and other factors on its mechanical properties. The evaluation of wellbore stability and fracture propagation effects is proposed based on laboratory experiments using triaxial stress and strain data, along with the application of energy evolution theory. The experimental procedures encompass an analysis of shale's microscopic components and structure, as well as anisotropic shale triaxial compression tests conducted under different moisture contents and confining pressures. The results demonstrate that shale exhibits dense pores in its microstructure and displays pronounced anisotropic characteristics in its macrostructure. The presence of water within these pores, combined with the in situ stress within the formation, significantly influences the mechanical properties of shale. This anisotropy decreases with increasing moisture content, but the mechanical performance still decreases. Under triaxial compression conditions, the increase in confining pressure to some extent enhances the anisotropy of shale's deformation characteristics, which is related to the failure modes of shale. However, the detrimental effect of moisture content on shale's mechanical properties still persists. In order to quantify the impact of these factors, this study utilizes the elastic modulus as an indicator of the coupling effect. It combines the triaxial strain curve obtained from laboratory tests and proposes an evaluation index for shale mechanical properties based on the energy evolution theory. This index is suitable for assessing wellbore stability (the stability index called SIr) and crack expansion (the brittleness index called BIr). The calculation results reveal that, during the wellbore drilling process, excavating parallel to the direction of shale bedding while maintaining low moisture content and high confining pressure yields a higher SIr value, indicating better wellbore stability. On the other hand, during reservoir fracturing, fracturing perpendicular to the shale bedding direction and maintaining low confining pressure and moisture content result in a smaller BIr value. This approach is more beneficial for the expansion of shale fracture network in engineering.

Origin and microbial degradation of thermogenic hydrocarbons within the sandy gas hydrate reservoirs in the Qiongdongnan Basin, northern South China Sea

Large-scale natural gas hydrate accumulations (generally over one billion cubic meters of natural gas) in coarse-grained marine sediments are the most valuable types for commercial exploration and exploitation. The formation of such a gas hydrate deposit generally requires a sufficient natural gas supply such as deeply buried thermogenic gas source. However, the worldwide discovered thermogenic gas hydrate deposits are rare, leaving relatively a poor understanding of their formation and evolution. Based on the geochemical and microbial analyses of eleven hydrate-related gas and five sediment samples from the thermogenic gas hydrate deposits in the Qiongdongnan Basin in northern South China Sea, we systematically investigated the origin and evolution of thermogenic hydrocarbons within sandy gas hydrate reservoirs. Results show that natural gas within high saturated gas hydrate-filled sandy sediments is predominately of thermogenic (the proportion is 57.1–70.5%), characterized by “dry gas” (99.38–99.7% C1, 0.26–0.47% C2 and <0.5% C3+), relatively lower C1/(C2+C3) ratio (187–376), and heavier δ13C–C1 values (−55.0 to −31.3‰). In addition, typical biomarkers (including the alkanes, tricyclic terpanes, hopanes and steranes) generated from mature source rocks were detected in the hydrate-filled fine sand reservoir, as well as the biomarker indicators (including the unresolved complex mixtures (UCMs) hump and the 25-norhopane homologous series) for severe hydrocarbon biodegradation. Furthermore, large amounts of hydrocarbon degrading bacteria (50.5% of bacteria) and methanogenic archaea (34.3% of archaea) were detected within hydrate-filled sandy sediment. Our results indicated that the deeply buried thermogenic source can indeed provide sufficient gas supply for the formation of a large-scale gas hydrate deposit, but thermogenic liquid hydrocarbons within gas hydrate reservoirs are very susceptible to be degraded and consumed by hydrocarbon degrading bacteria. In addition, we also found that the clay components of argillaceous gas hydrate reservoirs can adsorb and store large amounts of in situ immature organic matter, which can significantly obscure or cover up the original geochemical signatures of thermogenic hydrocarbons therein. These findings suggest that the relative contribution of deeply buried thermogenic source for gas hydrate accumulation worldwide may be underestimated, because we have previously ignored the fact that thermogenic hydrocarbons within gas hydrate reservoirs would be significantly consumed by hydrocarbon degrading microbes or diluted by in situ immature sedimentary organic matter. Our findings are highly significant for the evaluation and exploration of thermogenic gas hydrate accumulations worldwide.