Coalification and coal alteration under mild thermal conditions
Pavel Straka
Ivana S(y)korová
摘要：Coalification temperatures are often considered to be approximately 100-170 ℃ for bituminous coal and 170-275 ℃ for anthracite.However,our micropetrographic observations,solid state 27A1 magic-angle spinning nuclear magnetic resonance measurements,interpretation of δ13C values for whewellite in pelosiderite concretions from Carboniferous sediments,and assessment of whewellite thermal stability show that coalification temperatures can be significantly lower.Also the temperatures of coal alteration may be substantially lower than is stated.Ordinarily,hightemperature alteration is reported,but microthermometric measurements of fluids temperatures and micropetrographic observations show that the coal alteration can take place at low temperatures.For this reason,coals from the KladnoRakov(i)k Basin,part of Late Paleozoic continental basins of the Czech Republic,were analyzed.Regarding coalification,micropetrographic characterizations of unaltered coals,the presence of thermally unstable Al complexes in the coal organic mass documented using 27Al MAS NMR method,and proven occurrence of whewellite in pelosiderite concretions suggest a lower coalification temperature,max.～ 70 ℃.Regarding coal alteration,micropetrographic observations revealed (a) the weaker intensity of fluorescence of liptinite,(b) mylonitic structures and microbreccia with carbonate fluid penetration,and (c) high oxygen content in coals (37-38 wt.％).These phenomena are typical for thermal and oxidative alteration of coal.As the temperature of carbonate fluids inferred from fluid inclusion analysis was evaluated as ～ 100-113 ℃,the temperature of coal alteration was suggested as ～ 113 ℃;the alteration was caused by hot hydrothermal fluids.
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资助基金：This work was carried out thanks to the support of the Long-Term Project for the Conceptual Development of the Research Organization (No.RVO 67985891.The authors thank Prof.Ji(r)(i) Pe(s)ek,Faculty of Sciences,Charles University in Prague,for the valuable assistance in selecting the samples and consu)
论文发表日期：2018-01-01
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：16( 358-373 )
英文信息