Deformation metamorphism of bituminous and anthracite coals from China

Cao, Yongzhi; Mitchell, Gareth D.; Davis, A. W.; Wang, Daming

doi:10.1016/s0166-5162(99)00061-0

Cited by 98 publications

(80 citation statements)

References 13 publications

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“…Supercritical water is especially reactive as a catalyst and reactant in high-temperature organic geochemistry (Siskin and Katritzky, 2000). We hypothesize that, in spite of rising temperature with increasing metamorphic grade, the rate of elimination of N org would decrease exponentially, unless tectonic deformation and fracturing of anthracites provide new conduits for circulation and access of fluids (Cao et al, 2000).…”

Section: Proposed Model Of Progressive Metamorphism Of Organic Nitrogenmentioning

confidence: 99%

Organic nitrogen chemistry during low-grade metamorphism

Boudou

Schimmelmann

Ader

et al. 2008

Geochimica et Cosmochimica Acta

136

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-Most of the organic nitrogen (N org ) on Earth is disseminated in crustal sediments and rocks in the form of fossil nitrogen-containing organic matter. The chemical speciation of fossil N org within the overall molecular structure of organic matter changes with time and heating during burial. Progressive thermal evolution of organic matter involves phases of enhanced elimination of N org and ultimately produces graphite containing only traces of nitrogen. Long-term chemical and thermal instability makes the chemical speciation of N org a valuable tracer to constrain the history of sub-surface metamorphism and to shed light on the subsurface biogeochemical nitrogen cycle and its participating organic and inorganic nitrogen pools. This study documents the evolutionary path of N org speciation, transformation and elimination before and during metamorphism and advocates the use of XRay Photoelectron Spectroscopy (XPS) to monitor changes in N org speciation as a diagnostic tool for organic metamorphism. Our multidisciplinary evidence from XPS, stable isotopes, traditional quantitative coal analyses, and other analytical approaches shows that at the metamorphic onset N org is dominantly present as pyrrolic and pyridinic nitrogen. The relative abundance of nitrogen substituting for carbon in condensed, partially aromatic systems (where N is covalently bonded to three C atoms) increases exponentially with increasing metamorphic grade, at the expense of pyridinic and pyrrolic nitrogen. At the same time, much N org is eliminated without significant nitrogen isotope fractionation. The apparent absence of Rayleigh-type nitrogen isotopic fractionation suggests that direct thermal loss of nitrogen from an organic matrix does not serve as a major pathway for N org elimination. Instead, we propose that hot H, O-containing fluids or some of their components gradually penetrate into the carbonaceous matrix and eliminate N org along a progressing reaction front, without causing nitrogen isotope fractionation in the residual N org in the unreacted core of the carbonaceous matrix. Before the reaction front can reach the core, an increasing part of core N org chemically stabilizes in the form of nitrogen atoms substituting for carbon in condensed, partially aromatic systems forming graphite-like structural domains with delocalized π-electron systems (nitrogen atoms substituting for "graphitic" carbon in natural metamorphic organic matter). Thus, this nitrogen species with a conservative isotopic composition is the dominant form of residual nitrogen at higher metamorphic grade.

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Section: Proposed Model Of Progressive Metamorphism Of Organic Nitrogenmentioning

confidence: 99%

Organic nitrogen chemistry during low-grade metamorphism

Boudou

Schimmelmann

Ader

et al. 2008

Geochimica et Cosmochimica Acta

136

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“…Types of structurally altered coal, based on the classification by Rakowski et al (1977) and Jüntgen et al (1969) Cao et al (2000Cao et al ( , 2001Cao et al ( , 2003, analyzing coal samples at high magnifications, provided the following categorization: normal coal, revealing no division into smaller pieces; cataclastic coal, which reveals division into irregular pieces with sharp edges -bits, usually larger than 1mm; granular coal, in which the edges of particular pieces are less sharp and the fragments themselves are smaller; finally, altered mylonitic coal, revealing the highest extent of destruction. Li et al (2003), in turn, divide the coal structures into: undisturbed coal; cataclastic-angular coal; cataclastic-granular coal; foliated coal; and mylonitic coal.…”

Section: Table1mentioning

confidence: 99%

“…The effects of the influence of tectonic phenomena on coal can be the emergence of a dense network of fractures, crushing, or overgrinding -on such a scale that, in extreme cases, the original structure of coal will be totally altered, blurred (Shepherd et al, 1980;Cao et al, 2000). Some specific structural characteristics of hard coal from the so-called shear zone were of interest to -among other researchers - Rakowski et al (1977); Bodziony & Lama (1996); Cao et al (2000Cao et al ( , 2001Cao et al ( , 2003; Li et al (2003); Jiang et al (2004); Ju et al (2005); Gentzis (2006); Liu et al (2009) ;Ming et al (2011). The description and nomenclature regarding the coal structures occurring in the areas of tectonic disturbances, provided by the above-mentioned authors, differ considerably.…”

Section: Introductionmentioning

confidence: 99%

Structurally Altered Hard Coal in the Areas of Tectonic Disturbances – An Initial Attempt at Classification

Godyń¹

2016

Archives of Mining Sciences

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As regards the exploitation of hard coal seams, the near-fault zones and faults themselves are considered to be particularly dangerous areas, which is due to a high probability of the occurrence of gasogeodynamic phenomena. Tectonic dislocations running across a seam have a destructive impact on coal. Degradation of the coal structure, particularly visible in the microscale, is reflected in the coal's strength or gas properties. Such "structurally altered" coal is characterized by the presence of numerous fracturings, crushed areas, or dislocations of some of its fragments, and sometimes even the total destruction of the original structure. The present paper provides a detailed analysis and description of near-fault coal obtained from selected seams of the Upper Silesian Coal Basin, completed due to the application of optical methods. Both the type and the degree of changes in the structure of such coal were identified. On this basis, the author attempted to systematize the nomenclature used in relation to selected Upper Silesian hard coal seams, which, in turn, resulted in a proposed classification of the "altered structures" of the near-fault coal.Keywords: hard coal, faults, coal structures, cataclasis, mylonite Podczas eksploatacji węgla kamiennego, za szczególnie niebezpieczne obszary, ze względu na możliwość wystąpienia zjawisk gazo-geodynamicznych, uważa się strefy przyuskokowe i same uskoki. Przebiegające przez pokład dyslokacje tektoniczne wpływają destrukcyjnie na węgiel. Degradacja struktury węgla dostrzegalna, szczególnie w skali mikro, ma odzwierciedlenie w jego cechach wytrzymałościowych czy też gazowych. Taki, "odmieniony strukturalnie" węgiel, charakteryzuje się występowaniem licznych spękań, skruszeń, czy przemieszczeń poszczególnych fragmentów, a niekiedy i całkowitym zniszczeniem pierwotnej struktury. W pracy, posługując się metodami optycznymi, dokonano szczegółowych obserwacji i opisu węgla przyuskokowego pobranego z wybranych pokładów Górnośląskiego Zagłębia Węglowego. Zidentyfikowano rodzaj i intensywność zmian w strukturze takiego węgla. Na tej podstawie podjęto próbę usystematyzowania stosowanego nazewnictwa w odniesieniu do wybranych górnośląskich pokładów węgla kamiennego, co w konsekwencji zaowocowało zaproponowaniem klasyfikacji "struktur odmienionych" tego przyuskokowego węgla.Słowa kluczowe: węgiel kamienny, uskoki, struktury węgla, kataklaza, mylonit

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“…In extreme cases, the original structure of the coal can be totally blurred (Fig. 2) (Cao et al, 2000;Shepherd et al, 1980;Młynarczuk & Wierzbicki, 2009). In the instructions concerning mining safety in most countries, one can find information on the significance of this parameter in evaluating outburst hazard.…”

Section: Proximity Of the Area Of Geological Distortionsmentioning

confidence: 99%

Estimating Gas and Rock Outburst Risk on the Basis of Knowledge and Experience – The Expert System Based on Fuzzy Logic

Skoczylas¹

2014

Archives of Mining Sciences

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The Author endeavored to consult some of the Polish experts who deal with assessing and preventing outburst hazards as to their knowledge and experience. On the basis of this knowledge, an expert system, based on fuzzy logic, was created. The system allows automatic assessment of outburst hazard. The work was completed in two stages. The first stage involved researching relevant sources and rules concerning outburst hazard, and, subsequently, determining a number of parameters measured or observed in the mining industry that are potentially connected with the outburst phenomenon and can be useful when estimating outburst hazard. Then, the Author contacted selected experts who are actively involved in preventing outburst hazard, both in the industry and science field. The experts were anonymously surveyed, which made it possible to select the parameters which are the most essential in assessing outburst hazard. The second stage involved gaining knowledge from the experts by means of a questionnaire-interview. Subjective opinions on estimating outburst hazard on the basis of the parameters selected during the first stage were then systematized using the structures typical of the expert system based on fuzzy logic.Keywords: coal and methane outburst, fuzzy logic, outburst hazard, experts' knowledge Autor współpracował z polskimi ekspertami związanymi z badaniami i zwalczaniem zagrożenia wyrzutowego. W wyniku współpracy pozyskał ich wiedzę i doświadczenie, na bazie której stworzył system ekspercki, oparty na logice rozmytej. System umożliwia automatyczną ocenę zagrożenia wyrzutowego. Prace przebiegały w dwóch etapach. Pierwszy etap polegał na określeniu istotnych parametrów mierzonych, bądź obserwowanych w górnictwie, które mają silny związek ze stanem zagrożenia wyrzutowego. Następnie wybrana grupa ekspertów dokonała oceny stanu zagrożenia wyrzutowego, bazując na parametrach które w pierwszym etapie uznane zostały za najistotniejsze. Pozwoliło to zbudować system ekspercki na bazie logiki rozmytej, który określa stan zagrożenia wyrzutowego w zależności od bieżącej wartości analizowanych parametrów. Słowa kluczowe: wyrzuty gazu i skał, logika rozmyta , zagrożenie wyrzutowe, wiedza ekspercka

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Deformation metamorphism of bituminous and anthracite coals from China

Cited by 98 publications

References 13 publications

Organic nitrogen chemistry during low-grade metamorphism

Organic nitrogen chemistry during low-grade metamorphism

Structurally Altered Hard Coal in the Areas of Tectonic Disturbances – An Initial Attempt at Classification

Estimating Gas and Rock Outburst Risk on the Basis of Knowledge and Experience – The Expert System Based on Fuzzy Logic

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