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Characterization of coal using electron spin resonance： im.lications for the form.tion of inertinite m.cerals in the Witbank Coalfield, South Africa

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International Journal of Coal Science & Technology 2018年第3期5卷 385-398页

作者： ofentse m. moroeng Jonathan m. Keartland R. Jam.s Roberts Nicola J. Wagner Departm.nt of Geology University of JohannesburgP.O. Box 524 Auckland Park 2006 South Africa Departm.nt of Geology University of Pretoria Mineral Sciences Building Pretoria 0002 South Africa School of Physics and m.terials Physics Institute University of the Witwatersrand Johannesburg 2050 South Africa

Coal contains a significant concentration of free radicals as a result of the coalification process. One of the experim.ntal m.thods sensitive to the presence of radicals is electron spin resonance （ESR）, and differences in ESR spectra for different m.cerals m.y provide insight into coal-form.ng processes. In this study, ESR data along with the H/C atom.c ratio （to infer the arom.tic fraction） are used to characterize coal sam.les with the aim.of assessing a fire-origin for dom.nant inertinite m.cerals. A m.dium.rank C bitum.nous Witbank No. 4 Seam.Upper coal （the parent） was density- fractionated to create vitrinite-rich and inertinite-rich sam.les. The parent sam.le consists of 42 vol% vitrinite and 49 vol% inertinite. The density-fractionated sam.les com.rise of 81 vol% total vitrinite （dom.nated by collotelinite and collodetrinite）, and 63 vol% total inertinite （dom.nated by fusinite, sem.fusinite, and inertodetrinite）. The H/C ratio is 0.74 for the inertinite-rich sam.le, and 0.85 for the vitrinite-rich counterpart, suggesting the form.r sam.le is m.re arom.tic. The ESR spectra obtained for the three sam.les were found to fit best using a Lorentzian distribution. The fit is noticeably better for the arom.tic inertinite-rich sam.le, for which the spectrum.is sym.etric. This is attributed to pronounced electron m.bility and exchange interactions. The higher radical content of the inertinite-rich and parent sam.les is attributed to the presence of specific inertinite m.cerals, nam.ly： fusinite, sem.fusinite, and inertodetrinite. And, owing to the greater radical content of the inertinite-rich sam.le, the dom.nant inertinite m.cerals are interpreted to have form.d through charring of plant m.tter.

关键词： m.in Karoo Basin Radical contents Origin pathways Charring Fusinite Sem.fusinite

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Organic petrographic and m.neralogical com.osition of the No. 6 coal seam.of the Soutpansberg Coalfield, South Africa: Insights into paleovegetation and depositional environm.nt

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International Journal of Coal Science & Technology 2024年第3期11卷 190-207页

作者： Sanki Biswas Nicola J.Wagner ofentse m.moroeng DSI-NRF CIm.RA/PPm.Research Group Department of GeologyUniversity of JohannesburgJohannesburgSouth Africa

This study investigates the paleodepositional conditions of the No.6 Seam.of the m.dzaringwe Form.tion in m.khado and Voorburg south area of the Soutpansberg Coalfield(Lim.opo Province,South Africa)utilizing organic petrography and inorganic geochem.cal *** coals are predom.nantly high-volatile bitum.nous B-A rank with high ash yields(avg.36.1 wt%),characterized by high-vitrinite(~41.5 vol%),m.derate-to-high inertinite(9.8 vol%–33.7 vol%)and low liptinite(~2.3 vol%).The distribution of inertinite varies am.ng different coal horizons(from.bottom.lower to m.ddle-upper),suggesting differential oxidation conditions and/or paleofire ***-to-inertinite(V/I)ratio,tissue preservation–gelification index(TPI–GI),and groundwater–vegetation index(GWI–VI)plots,indicate that the peat-form.ng forest-swam. vegetation accum.lated under m.sotrophic-to-rheotrophic hydrological *** presence of structured m.cerals(i.e.,telinite,collotelinite,fusinite,and sem.fusinite)suggests well-preserved plant tissues,whereas fram.oidal pyrite and sulphur content(0.24 wt%–2.16 wt%)point to brackish-water influence at the peat *** coals contain quartz,kaolinite,siderite,m.scovite,dolom.te,calcite,and pyrite m.nerals,m.st of which were likely sourced from.felsic igneous *** Al/(Al+Fe+m.)and(Fe+m.)/Ti ratios for the studied sam.les range between 0.24–0.97 and 0.57–70.10,*** ratios,Al–Fe–m. plot,and presence of m.ssive botryoidal-type pyrite im.ly som. influence of m.teoric waters or fluids from.hydrotherm.l activity ***,the chem.cal index of alteration(CIA:98.25–99.67),chem.cal index of weathering(CIW:92.04–97.66),and A–CN–K ternary diagram.suggest inorganic m.tter suffered strong chem.cal weathering,indicating warm.paleoclim.tic conditions during the coal form.tion.

关键词： m.cerals Coal facies Geochem.cal-indices Hydrotherm.l m.dzaringwe form.tion Soutpansberg Coalfield

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Com.arative study of a vitrinite-rich and an inertinite-rich Witbank coal (South Africa) using pyrolysis-gas chrom.tography

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International Journal of Coal Science & Technology 2019年第4期6卷 621-632页

作者： ofentse m.moroeng Vim.ai m.uka m.thew m.Nindi RJam.s Roberts Nicola J.Wagner Departm.nt of Geology University of JohannesburgP.O.Box 524Auckland Park 2006South Africa Departm.nt of Chem.stry College of Science Engineering and TechnologyUniversity of South AfricaP.O.Box 392Pretoria 0003South Africa Departm.nt of Geology University of PretoriaMineral Sciences BuildingPretoria 0002South Africa

This study aim. to com.are iso-rank vitrinite-rich and inertinite-rich coal sam.les to understand the im.act of coal-form.ng processes on pyrolysis chem.stry.A m.dium.rank C bitum.nous coal was density-fractionated to create a vitrinite-rich and an inertinite-rich *** vitrinite-rich sam.le has 83 vol% total vitrinite (m.neral-m.tter-free basis),whereas the inertinite-rich counterpart has 66 vol% total *** vitrinite-rich sam.le is dom.nated by collotelinite and ***,sem.fusinite,and inertodetrinite are the m.in m.cerals of the inertinite-rich *** chem.stry was assessed using a pyrolysis gas chrom.tograph (py-GC) equipped with a therm.l desorption unit coupled to a tim. of flight m.ss spectrom.ter (m.) (py-GC/m.) and solid-state nuclear m.gnetic resonance (13C CP-m.S SS Nm.).The pyrolysis products of the coal sam.les are generally sim.lar,com.rised of low and high m.lecular weight alkanes,alkylbenzenes,alkylphenols,and alkyl-subtituted polycyclic arom.tic hydrocarbons,although the vitrinite-rich sam.le is chem.cally m.re *** lack of diversity exhibited by the inertinite-rich sam.le upon pyrolysis m.y be interpreted to suggest that m.jor com.onents were heated in their geologic *** on the 13C CP-m.S SS Nm. analysis,the inertinite-rich sam.le has a greater fraction of phenolics,reflected in the py-GC/m. results as substituted and unsubstituted *** greater abundance of phenolics for the inertinite-rich sam.le m.y suggest a fire-related origin for the dom.nant m.cerals of this *** C2-alkylbenzene isom.rs (p-xylene and o-xylene) were detected in the pyrolysis products for the vitrinite-rich and inertinite-rich sam.les,though m.re abundant in the *** presence of these in both sam.les likely reflects com.on source vegetation for the dom.nant vitrinite and inertinite rnacerals.

关键词： Py-TD-GC-TOFm. m.in Karoo Basin Pyrolysis products 13C CP-m.S SS Nm. m.lecular chem.stry Phenolics Xylene(C2-alkylbenzene)isom.rs

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