International Journal of Coal Geology最新文献

{"title":"A critical review of experimental and theoretical studies on shale geomechanical and deformation properties, fluid flow behavior, and coupled flow and geomechanics effects during production","authors":"Ifeanyi Valerian Nwankwo ,&nbsp;Morteza Dejam ,&nbsp;Scott Austin Quillinan","doi":"10.1016/j.coal.2025.104777","DOIUrl":"10.1016/j.coal.2025.104777","url":null,"abstract":"<div><div>Flow in shale differs substantially from that in conventional reservoirs due to unfavorable reservoir features such as ultra-low permeability and very poor porosity. Shale also exhibits considerable anisotropy and heterogeneity, with clay laminae and bedding angle being the primary variables influencing anisotropy. As a result, shale is subjected to high stress sensitivity and deformation during depressurization, which affects fluid flow. Furthermore, non-Darcy flow mechanisms exist thereby making flow in shale a complex phenomenon. Nonetheless, many studies have recently focused on the geophysical and geomechanical characterization of shale. Various works have equally examined the complexity of fluid flow. Numerous studies were particularly interested in the influence of non-linear flow parameters and stress sensitivity on apparent permeability, intrinsic permeability, and porosity during pressure depletion. However, relatively few works, mostly theoretical, have been carried out on coupled flow and geomechanical reactions. This review thus includes a report on fluid flow and geomechanical characterization of shale formation, as well as an identification of the factors that influence rock deformation and fluid flow during production. The review showed that flow regimes are predominantly dependent on pore pressure and pore size, whereas flow regimes regulate apparent permeability. For example, at low pressures and pore radius less than 10 nm, flow regims were found to significantly increase the apparent permeability. However, at higher bulk modulus (&gt;10 GPa), pore radius has essentially no impact, hence, pore pressure becomes the dominant factor influencing flow. In addition, the review shows that during depressurization, geophysical metrics are more sensitive to pressure changes than geomechanical properties. Finally, some results in literature revealed that the impact of geomechanical characteristics on cumulative production can be ignored in competent formations with high Young's modulus (about 6 × 10⁶-10 × 10⁶ psi). In conclusion, recovery from shale could be optimized by integrating experimental studies with hydromechanical models during initial reservoir studies.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104777"},"PeriodicalIF":5.6,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modes of occurrence of rare earth elements and yttrium in the subbituminous coal of the Jungar Coalfield, Ordos Basin, North China","authors":"Bo Jiu ,&nbsp;Zhijun Jin ,&nbsp;Huidi Hao ,&nbsp;Zhaoguo Wang ,&nbsp;Wenhui Huang ,&nbsp;Zhenguang Shang ,&nbsp;Runchao Liu ,&nbsp;Yang Li ,&nbsp;Linhao Huang ,&nbsp;Binchao Qin ,&nbsp;Zixuan Huang ,&nbsp;Li Long ,&nbsp;Wenzhong Zhang ,&nbsp;Yian Wang","doi":"10.1016/j.coal.2025.104785","DOIUrl":"10.1016/j.coal.2025.104785","url":null,"abstract":"<div><div>Modes of occurrence of rare earth elements (REE; if including Y, REY) in coal have attracted much attention owing to the extraction potential of REY from coal fly ash. Although previous studies have explored the associations of REY in coals with different ranks and the affinities of light, medium, and heavy REY associated with organic matter, challenges remain due to the limitations of indirect or in-situ analytical techniques. This study focused on the in-situ distribution of REY in the selected subbituminous coals from the Jungar Coalfield as well as in their associated mudstone and tonstein partings and the widely distributed calcite veins inside the coal seam, using LA-ICP-MS spot and mapping analysis. The results showed that in the subbituminous coal, La and Ce as well as other light REY (LREY) are concentrated in the minerals such as bastnasite and monazite. Small amounts of Pr, Nd, and Sm can be associated with organic matter including vitrinite and liptinite. Medium REY (MREY) and heavy REY (HREY) are highly enriched in vitrinite in the subbituminous coal. In terrigenous mudstone of the subbituminous coal, La and Ce are concentrated in monazite. Other LREY are present in Ti-oxides, while HREY tend to occur in zircon. MREY can be associated with both Ti-oxides and zircon. The calcite veins in the coal seam are classified into three types based on their morphology and occurrence features: bedding calcite veins in the upper part of the coal, vertical calcite veins in the middle, and vertical calcite veins with a high Sr value in the lower part of the coal. Polarization and crystal size of calcite crystals in these veins exhibit multistage growth. LA-ICP-MS spot analysis shows that the bedding and vertical calcite veins are characterized by positive Y and Gd anomalies, suggesting their formation under meteoric water leaching. The vertical calcite vein in the lower part of the coal seam displays a positive Gd anomaly and high Sr concentrations, indicating formation under seawater injection. The concentration of REY in all epigenetic calcite veins increases with depth. For calcite veins with multi-stage growth, the REY content in the late-stage calcite is consistently higher than in the early stages. It is proposed that leaching of meteoric water and seawater on the coal seams is the key factor for the association of REY with organic matter, influenced by the chemical composition and pH value of the leaching fluids. In particular, MREY and HREY are preferentially associated with organic matter, mainly vitrinite, and the over-leached MREY and HREY in coal were concentrated in epigenetic minerals, with calcite being the primary phase in this study.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104785"},"PeriodicalIF":5.6,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143855308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Middle Jurassic black shale deposits from the Pieniny Klippen Belt, Western Carpathians: Insights into organic matter composition, thermal maturity, depositional, and palaeoenvironmental variations","authors":"M. Zielińska ,&nbsp;J. Kus ,&nbsp;J.G. Mendonça Filho ,&nbsp;E. Szram ,&nbsp;M. Blumenberg ,&nbsp;M. Fabiańska","doi":"10.1016/j.coal.2025.104772","DOIUrl":"10.1016/j.coal.2025.104772","url":null,"abstract":"<div><div>An integrated multi-method research study, employing maceral identification and analysis, microphotometry, fluorescence microspectrometry, palynofacies analysis, Rock-Eval pyrolysis and biomarker geochemistry, and was applied to determine sources of variation of organic matter (OM) type, its provenance, thermal maturity, as well as hydrocarbon potential of the Middle Jurassic Szlachtowa Formation in the Pieniny Klippen Belt of the Western Carpathians in Poland and Slovakia. In addition, a reconstruction of paleoenvironmental conditions and dinoflagellate cyst biochronology were performed. The presence of first-cycle vitrinite was well-discerned from phyllovitrinite and a reworked vitrinite population. It allowed for determination of thermal maturity at 0.74 % VR_o (0.04–0.10 % SD). Although a comparison between measured and calculated λ_max and Q_650/500 for sporinite and alginite yielded a marked discrepancy, both spectral fluorescence parameters illustrate a clear similarity between lamalginite and dinoflagellate cysts. The samples contain predominantly thermally mature organic-lean Type III kerogen of terrigenous-derived macerals of first-cycle vitrinite, phyllovitrinite, reworked vitrinite, and liptinite (sporinite) with admixture of Type II kerogen associated with lamalginite. This is in line with Rock-Eval and biomarker data as well as the palynofacies composition, the latter indicating predominance of phytoclasts kerogen groups over palynomorphs and amorphous components. The occurrence of reworked, oxidized, and fragmented terrigenous OM is attributed to weathered and eroded sedimentary rocks from the Upper Carboniferous to Triassic and Lower Jurassic periods as well as from the lowermost Middle Jurassic cover. Together with predominant primarily indigenous terrigenous OM, the reworked sedimentary strata served as a source for siliciclastic sedimentation and formation of turbiditic deposits in marine slope to abyssal plain settings. In the extensional active tectonic setting, sediment flux and runout in turbidity currents were derived from overstepped margin slopes, fault-bounded tilt blocks, and the Czorsztyn Ridge. In addition, organic contributions to pelagic deposits included planktonic microorganisms such as dinoflagellate cysts, foraminiferal test linings, and, to a lesser extent, prasinophytes and acritarchs. It is likely that the deposition of Middle Jurassic black shales occurred in a predominantly heterolithic-oxic shelf and dysoxic-suboxic shelf to basin transition. The Szlachtowa Formation yielded dinoflagellate cysts indicative of the Middle Jurassic Aalenian to Bajocian stages, with a few species also appearing in the Toarcian and Bathonian stages. Significant changes in OM preservation influenced hydrocarbon generative potential of studied black shales, accounting for its low to fair source rock generative potential (avg. ∼0.6 wt% TOC; Hydrogen Index avg. ∼100).</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104772"},"PeriodicalIF":5.6,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143842696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization and upgrading of a new Mozambican graphite ore for the production of graphene materials","authors":"Salvador Mondlane Jr. ,&nbsp;Yuliesker Yaque ,&nbsp;Adrián Vigil ,&nbsp;Isabel Suárez-Ruiz ,&nbsp;Uriel Sierra ,&nbsp;Marcos Granda ,&nbsp;Amadeu Carlos Dos Muchangos ,&nbsp;Alfonso Mercado ,&nbsp;Patricia Álvarez","doi":"10.1016/j.coal.2025.104773","DOIUrl":"10.1016/j.coal.2025.104773","url":null,"abstract":"<div><div>This study investigates the mineralogical characteristics of Mozambique graphite, with a particular focus on the Ancuabe deposit, located in the Cabo Delgado Province of northern Mozambique. Analysis of the mineralogy of the ore shows the presence of large flakes of graphite in parallel veinlets that follow the strike of the main foliation and in a disseminated form with structures that feature massive, highly foliated schists. The ore's mineral composition, as determined by XRF is dominated by SiO₂ (∼75 %), containing &lt;0.5 wt% of critical raw materials as Ti, V_, Ni, and Cr. Approximately 30 % of the ore is carbon, which is attributed to graphite as determined by XRD, Raman spectroscopy and optical microscopy.</div><div>The potential of these graphite deposits to serve as a raw material in the production of graphene was examined. For that, the graphite ore was purified through size fractionation, employing standard graphite purification methods. The total graphite, along with the graphite fractions, were utilised as raw material for the preparation of graphene oxide (GO) via standard chemical oxidation and exfoliation methods. The monolayers of GO obtained from the whole graphite fraction exhibited the typical oxidation of basal planes and edges but were obtained at a low yield. However, this yield was enhanced by subjecting the three graphite fractions to an optimized procedure, which involved employing longer reaction times with the larger-sized graphite fractions. Consequently, the overall process yield was significantly increased, and it was also possible to obtain GO sheets of controlled lateral size, ranging from very large to small.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"304 ","pages":"Article 104773"},"PeriodicalIF":5.6,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry and mineralogy of Permo-Carboniferous coals from the Fugu mining district, Shaanxi Province, China: Implications for the evolution of the northeastern Ordos Block","authors":"Guohong Qin ,&nbsp;Daiyong Cao ,&nbsp;Huan Wang ,&nbsp;Yadong Liu ,&nbsp;Shahab Varkouhi ,&nbsp;Ran Wang ,&nbsp;Yingchun Wei ,&nbsp;Zixiao Guo","doi":"10.1016/j.coal.2025.104775","DOIUrl":"10.1016/j.coal.2025.104775","url":null,"abstract":"<div><div>The northeastern Ordos Block, a pivotal transition zone between the stable North China Craton and the reactivated Yinshan Orogenic Belt, preserves critical records of intra-cratonic responses to the closure of the Paleo-Asian Ocean. However, the Permo-Carboniferous tectonic evolution of the northeastern Ordos Block is debated due to the conflicting sediment source interpretations. This study reports the systematic geochemical and mineral characteristics of three coal seams (Nos. 9, 4, and 2 upward) of the Permo-Carboniferous period collected from the Fugu mining district, northeastern Ordos Block, China, and focuses on the evolution therein. The studied coal samples exhibited slight enrichments in Th, Zr, Hf, Ta, Li, and Ga compared with the word hard coals. The Al₂O₃/TiO₂ ratio, Zr/Sc and Th/Sc plots, REY patterns, and Sr-Nd isotope analyses suggested that the elevated trace elements in three coals originated from the Benxi Formation bauxite in the northeastern Ordos Block. In the No. 9 coal (lower section of the Taiyuan Formation), the alteration in the provenance supply, as traced by variations of the high field strength elements (HFSEs), Al₂O₃ contents, Al₂O₃/TiO₂ ratios, and presence of Al-hydroxides, indicated that the northeastern Ordos Block underwent a rapid and brief uplift during the early depositional period of the No. 9 coal, followed by a sharp subsidence, and finally a gradual uplift throughout the middle to late depositional periods. The medium–high sulfur content, high Sr/Ba ratio, and negative correlation between Sr/Ba and ash yields in the No. 9 coal reflected a mixed intrusion of freshwater and seawater to the Ordos Block during this period. In the No. 4 coal (lower section of the Shanxi Formation), relatively low contents of the HFSEs and Al₂O₃ suggested the minimal terrigenous input from the Benxi Formation bauxite, indicating inconspicuous uplift occurring in the northeastern Ordos Block during the initial stage of peat accumulation. Subsequently, a gradual increase in these elements, accompanied by occurrence of minerals like Al-hydroxides, rutile, and zircon, indicated an enhanced supply from Benxi Formation bauxite, suggesting a gradual uplift. After peat accumulation, a decrease in these elements implied a diminishing influence of Benxi Formation bauxite and subsequent subsidence of the northeastern Ordos Block. In the No. 2 coal (upper section of the Shanxi Formation), variations in the supply of elements (the HFSEs and Al₂O₃) and anatase from the Benxi Formation bauxite indicated vigorous tectonic activity in the northeastern Ordos Block, with a short-lived subsidence during the initial stage, then a slow uplift, and finally sharp uplift and subsidence during the middle to late stages.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104775"},"PeriodicalIF":5.6,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143842695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrological, mineralogical, and geochemical study of pyrometamorphic rocks in the northeast margin of Ordos Basin, China: Insight into high-temperature coal combustion events","authors":"Xiaoying Ding ,&nbsp;Qiang Sun ,&nbsp;Xin Hu ,&nbsp;Chenxi Dong ,&nbsp;Shaofei Wang ,&nbsp;Shihao Yuan ,&nbsp;Xianliang Chen","doi":"10.1016/j.coal.2025.104774","DOIUrl":"10.1016/j.coal.2025.104774","url":null,"abstract":"<div><div>Coal combustion and coal fires occur globally, and pyrometamorphic rocks produced by coal combustion and coal fires are widely distributed in the northeastern Ordos Basin, China. Studies on the characteristics and genetic environment of pyrometamorphic rocks within the study area remain limited. In this light, the paper explored the petrological, mineralogical, and geochemical properties of pyrometamorphic rocks in the northeast margin of Ordos Basin, China. Macroscopic features and petrology were examined through fieldwork and optical microscopy. SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectrometer) and XRD (X-ray diffraction) analysis provided detailed mineralogical information. Major and trace elements, including rare earth elements (REE), were quantified using ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry) and ICP-MS (Inductively Coupled Plasma Mass Spectrometry), respectively. The results indicate two types of pyrometamorphic rocks consisting of clinkers and paralavas. Typical high-temperature minerals such as tridymite, cristobalite, mullite, cordierite, sekaninaite, hematite, and magnetite were detected in clinkers and paralavas. Large ion lithophile elements such as Rb, Sr, Cs and Ba vary greatly in pyrometamorphic rocks, which may be caused by heating. Both the clinkers and paralavas show Se, As, Mo, Sn, and Tl anomalies, indicative of hydrothermal activities following the pyrometamorphic event. The clinkers appear enriched in LREE, while the paralavas exhibit enrichment in HREE. REE distribution patterns normalized to UCC (upper continental crust) display no apparent δCe and δEu anomalies in clinkers and paralavas. This study contributes to the understanding of pyrometamorphic rocks by providing new insights into their genesis and high-temperature formation conditions.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104774"},"PeriodicalIF":5.6,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering the Douro Carboniferous Basin (Pejão Coalfield, Portugal): Geochemical, petrological, and mineralogical evidence of depositional, diagenetic, and hydrothermal processes","authors":"Mariana Costa ,&nbsp;Ary Pinto de Jesus ,&nbsp;Eduardo Ferreira da Silva ,&nbsp;Isabel SuárezRuiz ,&nbsp;Fernando Rocha ,&nbsp;Deolinda Flores","doi":"10.1016/j.coal.2025.104771","DOIUrl":"10.1016/j.coal.2025.104771","url":null,"abstract":"<div><div>The Douro Carboniferous Basin (DCB) in Portugal hosts significant coal deposits, with the Pejão Coalfield being among the most important. This study integrates petrographic, geochemical, and mineralogical analyses to investigate the sedimentation, hydrothermal influences, and paleoclimatic conditions of the DCB. Petrographic analysis classifies these coals as high-rank anthracite A, with vitrinite as the dominant maceral (&gt;90 %). Geochemical analyses reveal trace element enrichments (Ag, As, Pb, Sb, and V), suggesting a combination of primary sedimentary input and later hydrothermal overprinting, as indicated by the presence of REE-bearing phosphates (florencite, monazite, xenotime) and sulfosalts (tetrahedrite, bournonite).</div><div>Paleoweathering indices (CIA, PIA, WIP, MIA) suggest intense weathering and subtle sediment recycling, while paleosalinity proxies indicate periodic evaporation events linked to ephemeral lacustrine zones, possibly playa-type systems. The REE distribution patterns and provenance indicators suggest a limited zircon enrichment, supporting minimal sedimentary recycling, especially intracarboniferous breccia and sandstone lithologies. These findings provide new insights into the basin's depositional environment, diagenetic history, and hydrothermal alteration, contributing to a broader understanding of Carboniferous intermontane basins.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"304 ","pages":"Article 104771"},"PeriodicalIF":5.6,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The K isotopic signatures of coals: A reconnaissance study","authors":"Zhihan Ji ,&nbsp;Jun Mu ,&nbsp;Suping Yao ,&nbsp;Weiqiang Li","doi":"10.1016/j.coal.2025.104770","DOIUrl":"10.1016/j.coal.2025.104770","url":null,"abstract":"<div><div>Potassium (K) isotopes are significantly fractionated in sediments, with biological samples exhibiting even greater K isotopic variability than geological samples. Coal is a unique type of sedimentary rock composed of organic matter and minerals, both of which are K-rich. Therefore, K isotopes hold the potential for tracing the origin of coal and understanding coal-forming processes. However, our knowledge of K isotopes in coals is limited due to the scarcity of K isotopic studies on coals. In this study, we conducted the first detailed investigation of K isotopes in 12 coal samples of varying ranks by analyzing the abundance and isotopic compositions of K in different phases. We ashed the coals and sequentially leached K from the ashes with deionized water (DW), ammonium acetate (AA), HCl, and HF, followed by elemental and isotopic analyses. The majority of K occurs in DW-leached and HF-leached fractions of these coal samples, representing the K associated with organic matter and the K that exists in the silicate phase, respectively. The bulk K content of the twelve studied coals ranges from 0.004 to 1.308 wt%, with the HF-leached K holding the dominant K budget. The δ⁴¹K values vary from −1.19 ‰ to 0.52 ‰ in the DW-leached phase, and from −1.27 ‰ to −0.22 ‰ in the HF-leached phase of the low temperature coal ashes. The large variations in δ⁴¹K values of DW leachate are attributed to the plants decay and diffusion in pore fluids in the early stage of diagenesis. The K isotope compositions of the HF-leached K in coals are variable and lighter than average igneous rocks (δ⁴¹K_BSE = −0.43 ‰). Pore fluid exchanges likely caused the preference for ³⁹K in the silicate phase of coal. The K isotope compositions of coals overall reflect ³⁹K enrichment during diagenesis or organic matter inheritance.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"304 ","pages":"Article 104770"},"PeriodicalIF":5.6,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143791166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"micro-Raman indicates biochar has similar stability and structural features as natural fusinite and semifusinite","authors":"H.I. Petersen ,&nbsp;M.R. Stokes ,&nbsp;P.C. Hackley ,&nbsp;A. Rudra ,&nbsp;Z. Zhou ,&nbsp;H. Sanei","doi":"10.1016/j.coal.2025.104769","DOIUrl":"10.1016/j.coal.2025.104769","url":null,"abstract":"<div><div>Semifusinite and fusinite macerals are formed through carbonization of plant material in naturally occurring wildfires. Both macerals, belonging to the inertinite maceral group, are carbon-rich and oxygen-poor, and are typical constituents of charcoal. The charring of plant material into charcoal is a naturally occurring process that effectively stores carbon over geological timescales. The stability of carbon in biochar formed by pyrolysis of biomass are determined by its degree of carbonization, and long-term storage in soil assumes that the biomass has been completely transformed into inertinite biochar. Inertinite biochar is thought to have a structural composition comparable to highly stable natural fusinite, whereas less carbonized biochar is similar to less stable semifusinite. In this study, micro-Raman spectroscopy was employed to examine the structural composition of 16 biochar samples produced at different temperatures from various lignocellulosic feedstocks, as well as one natural semifusinite isolated from a coal deposit. The estimated carbonization temperatures, representing the actual internal heating temperatures experienced by the biomass, ranged from 326 to 825 °C. The micro-Raman results of the biochar samples were compared with previously published micro-Raman data on naturally formed semifusinite and fusinite. The findings show that biochar, semifusinite, and fusinite likely undergo similar structural evolution with increasing temperatures, suggesting that the process of pyrolyzing biomass into biochar may mimic the natural charring process that occurs during wildfires. Though additional work could help to validate benchmarks, these results support the idea that biochar stability is similar to that of fusinite and semifusinite and indicate its potential as a long-term storage solution in the context of the geological carbon cycle. Furthermore, the results indicate that in addition to the established inertinite benchmark (IBR_o2%; R_o = 2 %) for determining biochar stability, up to four new micro-Raman benchmarks can be used to define inertinite biochar: (1) D3-band position: 1460 cm^‐1 or higher, (2) D1/G amplitude ratio: 0.80 or higher, (3) Raman band separation (RBS): 250 cm^‐1 or higher, and possibly (4) G-FWHM (full width at half maximum): 72 cm^‐1 or lower. The availability of multiple benchmarks that can indicate biochar stability could provide tools for evaluating biochar long-term storage potential, thus reinforcing carbon dioxide removal (CDR) via biomass waste pyrolysis as a viable technique to mitigate climate change.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"304 ","pages":"Article 104769"},"PeriodicalIF":5.6,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143791167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A lithofacies-coupled palynofacies model for meandering river floodplains in the Late Cretaceous: Insights from the Dinosaur Park Formation, Alberta, Canada","authors":"Muditha Goonetilleke ,&nbsp;Ricardo L. Silva ,&nbsp;João G. Mendonça-Filho ,&nbsp;Paul R. Durkin","doi":"10.1016/j.coal.2025.104768","DOIUrl":"10.1016/j.coal.2025.104768","url":null,"abstract":"<div><div>Alluvial floodplains accommodate various sub-environments that preserve evidence of fluvial dynamics, aiding in the reconstruction of terrestrial paleoenvironments. While floodplains serve as major sources and sinks for organic matter, characterizing sub-environments within ancient floodplains using fossil organic matter (kerogen) is sparsely applied due to its unclear relationship with organic matter dynamics in modern fluvial settings. This study develops a lithofacies-coupled palynofacies model for fluvial environments to address this gap and reveal organic matter dynamics in paleo-floodplains. The sedimentary successions of the Upper Cretaceous Dinosaur Park Formation in Dinosaur Provincial Park, Alberta, Canada, offer an ideal fluvial setting to develop this model, compare it across geological time intervals, and refine paleoenvironmental reconstructions of the Dinosaur Park Formation.</div><div>A floodplain-dominated stratigraphic section of the Dinosaur Park Formation comprises six recurring lithofacies and two facies associations representing channel-belt and floodplain deposits. All observed kerogen assemblages originated from terrestrial environments. Channel-belt deposits are characterized by sandstones containing opaque and amorphous non-biostructured phytoclasts, as well as amorphous organic matter. Levee deposits are characterized by sandy mudstones, while proximal floodplains are characterized by gray mudstones. Despite these distinctions, kerogen assemblages are relatively similar and heterogeneous, with opaque phytoclasts remaining prevalent. Backswamps (carbonaceous mudstones and shales) and distal floodplain environments (brown mudstones) exhibit a high abundance of cuticles, membranes, sporomorphs and amorphous non-biostructured phytoclasts. Total organic carbon content discriminates between different sub-environments, with higher organic carbon content found in backswamp and distal floodplain environments. The results show that lithofacies and kerogen assemblages (i.e. palynofacies) in the Dinosaur Park Formation's floodplains were mainly influenced by channel proximity and floodplain topography. When compared with modern and deep-time fluvial examples, the model supports palynofacies analysis as a robust proxy for distinguishing floodplain sub-environments and demonstrating its applicability in understanding fluvial dynamics over geological timescales.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"304 ","pages":"Article 104768"},"PeriodicalIF":5.6,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143824314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}