Organic petrographic and mineralogical composition of the No.6 coal seam of the Soutpansberg Coalfield,South Africa:Insights into paleovegetation and depositional environment
Sanki Biswas
Nicola J.Wagner
Ofentse M.Moroeng
DSI-NRF CIMERA/PPM Research Group,Department of Geology,University of Johannesburg,Johannesburg,South Africa
摘要：This study investigates the paleodepositional conditions of the No.6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic petrography and inorganic geochemical proxies.The coals are predominantly high-volatile bituminous B-A rank with high ash yields(avg.36.1 wt％),characterized by high-vitrinite(～41.5 vol％),moderate-to-high inertinite(9.8 vol％-33.7 vol％)and low liptinite(～2.3 vol％).The distribution of inertinite varies among different coal horizons(from bottom-lower to middle-upper),sug-gesting differential oxidation conditions and/or paleofire occurrence.Vitrinite-to-inertinite(V/I)ratio,tissue preservation-gelification index(TPI-GI),and groundwater-vegetation index(GWI-VI)plots,indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions.The presence of structured macerals(i.e.,telinite,collotelinite,fusinite,and semifusinite)suggests well-preserved plant tissues,whereas framboidal pyrite and sulphur content(0.24 wt％-2.16 wt％)point to brackish-water influence at the peat stage.The coals contain quartz,kaolinite,siderite,muscovite,dolomite,calcite,and pyrite minerals,most of which were likely sourced from felsic igneous rocks.The Al/(Al+Fe+Mn)and(Fe+Mn)/Ti ratios for the studied samples range between 0.24-0.97 and 0.57-70.10,respectively.The ratios,Al-Fe-Mn plot,and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or flu-ids from hydrothermal activity post-deposition.Moreover,the chemical index of alteration(CIA:98.25-99.67),chemical index of weathering(CIW:92.04-97.66),and A-CN-K ternary diagram suggest inorganic matter suffered strong chemical weathering,indicating warm paleoclimatic conditions during the coal formation.
机标关键词：insightsenvironmentorganicseamafricacoalfieldcompositiondepositional
论文发表日期：2024-06-28
在线出版日期：2025-08-15（本平台首次上网日期，不代表文献的发表时间）
页数：18( 190-207 )
英文信息