Changes of petrographic characteristics and quality of contact-metamorphosed coals in the Datong coalfield

Authors

MA Hongtao, College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China
SONG Xiaoxia, College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China; Shanxi Key Laboratory of Coal and Coal Measure Gas Geology, Taiyuan 030024, China
LI Kaijie, College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China
ZHAO Jingui, College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China;Shanxi Key Laboratory of Coal and Coal Measure Gas Geology, Taiyuan 030024, China
ZHANG Tianguang, Tongmei Datang Tashan Coal Mine Co. Ltd., Datong 037000, China
LIU Jianping, 115 Coal Geological Exploration Institute of Shanxi Province, Datong 037003, China

Abstract

Igneous intrusions in the Datong coalfield caused a considerable amount of contact metamorphosed coal, reducing the industrial value of coal. The effect of a dike in roadway 5222 in Tashan coal mine was determined from analysis of 16 samples collected near the intrusive body. Microscopic and macroscopic observation, proximate and ultimate analysis were used to determine the petrographic characteristics. The results demonstrate that contact-metamorphosed coal experienced significant thermal alteration during intrusive event. Microscopically, various natural coke microstructures, such as mosaic structure, flow structure and pyrolytic carbon were formed under excess heat; instant heating for coals resulted in the elevation of coal ranks, the maximum reflectance of vitrinite increased from 0.67%-0.87% of the normal coal to 0.94%-3.67% of the contact metamorphosed coal; In the contact-metamorphosed coal, the moisture content and the ash yields increased remarkably and volatile yield decreased; In coal samples near dikes, C content increases, H, N and O content decreases. From the comprehensive analysis, it was inferred that the influencing range of the contact metamorphism of the dikes for coal seams is within 4.5 m, 1.25 times of the dike thickness, 1.6 m in a severely metamorphosed zone. The research results provided the basis for assessment of coal mining and utilization.

Keywords

diabase, dike, contact metamorphism, petrography, Tashan coal mine, Datong coalfield

DOI

10.3969/j.issn.1001-1986.2020.02.016

Recommended Citation

MA Hongtao, SONG Xiaoxia, LI Kaijie, et al. (2020) "Changes of petrographic characteristics and quality of contact-metamorphosed coals in the Datong coalfield," Coal Geology & Exploration: Vol. 48: Iss. 2, Article 17.
DOI: 10.3969/j.issn.1001-1986.2020.02.016
Available at: https://cge.researchcommons.org/journal/vol48/iss2/17

Reference

[1]GOODARZI F,GENTZIS T,JACKSON G,et al. Optical characteristics of heat-affected bitumens from the Nanisivik mine,N.W. Baffin Island,Arctic Canada[J]. Energy Sources,1993,15(2):359-376.

[2] 郭国鹏. 接触变质带煤的物理化学结构及瓦斯赋存特征研究[D]. 焦作:河南理工大学,2012. GUO Guopeng. Research on physical and chemical structure of coal and characteristics of gas occurrence in contact metamorphic zone[D]. Jiaozuo:Henan Polytechnic University,2012.

[3] 李久庆. 永安超无烟煤显微组分及其光性演化[D]. 徐州:中国矿业大学,2019. LI Jiuqing. Composition and optical property evolution of macerals in meta-anthracite from Yongan,Fujian,China[D]. Xuzhou:China University of Mining and Technology,2019.

[4] KARAYIGIT A I,WHATELEY M K G. Properties of a lacustrine subbituminous(k1) seam,with special reference to the contact metamorphism,Soma-Turkey[J]. International Journal of Coal Geology,1997,34(1):131-155.

[5] SINGH A K,SINGH M P,SHARMA M,et al. Microstructures and microtextures of natural cokes:A case study of heat-affected coking coals from the Jharia coalfield,India[J]. International Journal of Coal Geology,2007,71(2/3):153-175.

[6] WARD C R,WARBROOKE P R,ROBERTS F I. Geochemical and mineralogical changes in a coal seam due to contact metamorphism,Sydney basin,New South Wales,Australia[J]. International Journal of Coal Geology,1989,11(2):105-125.

[7] 苗琦,权巨涛,秦云虎,等. 天然焦地质勘查研究[J]. 中国煤炭地质,2019,31(6):9-14. MIAO Qi,QUAN Jutao,QIN Yunhu,et al. Study on geological exploration for natural coke[J]. Coal Geology of China,2019,31(6):9-14.

[8] 裴文春. 太原西山杨庄勘查区天然焦与煤的参数特征研究[J]. 中国煤炭地质,2018,30(4):17-21. PEI Wenchun. Natural coke and coal distinction parametric characteristics study in Yangzhuang exploration area,Xishan coalfield,Taiyuan[J]. Coal Geology of China,2018,30(4):17-21.

[9] PADWYSOCKI M H,DUTCHER R R. Coal dikes that intrude lamprophyre sills;Purgatoire River Valley,Colorado[J]. Economic Geology,1971,66(2):267-280.

[10] THORPE A N,SENFTLE F E,FINKELMAN R B,et al. Change in the magnetic properties of bituminous coal intruded by an igneous dike,Dutch Creek mine,Pitkin County,Colorado[J]. International Journal of Coal Geology,1998,36(3):243-258.

[11] GHOSH T. A study of temperature conditions at igneous contacts with certain Permian coals of India[J]. Economic Geology,1967,62(1):109-117.

[12] COOPER J R,CRELLING J C,RIMMER S M,et al. Coal metamorphism by igneous intrusion in the Raton basin,CO and NM:Implications for generation of volatiles[J]. International Journal of Coal Geology,2007,71(1):15-27.

[13] JONES J M,CREANEY S. Optical character of thermally metamorphosed coals of northern England[J]. Journal of Microscopy,1977,109(1):105-118.

[14] JIANG J Y,CHENG Y P,WANG L,et al. Petrographic and geochemical effects of sill intrusions on coal and their implications for gas outbursts in the Wolonghu mine,Huaibei coalfield,China[J]. International Journal of Coal Geology,2011,88(1):55-66.

[15] YAO Yanbin,LIU Dameng. Effects of igneous intrusions on coal petrology,pore-fracture and coalbed methane characteristics in Hongyang,Handan and Huaibei coalfields,North China[J]. International Journal of Coal Geology,2012,96/97:72-81.

[16] YAO Yanbin,LIU Dameng,HUANG Wenhui. Influences of igneous intrusions on coal rank,coal quality and adsorption capacity in Hongyang,Handan and Huaibei coalfields,North China[J]. International Journal of Coal Geology,2011,88(2/3):135-146.

[17] STEWART A K,MASSEY M,PADGETT P L,et al. Influence of a basic intrusion on the vitrinite reflectance and chemistry of the Spring field(No.5) coal,Harrisburg,Illinois[J]. International Journal of Coal Geology,2005,63(1/2):58-67.

[18] RODNOVA E. Change in collector attributes of sediments in contact zone of traps in central part of nosty Tungusskoy sineklize[J]. Tr Vsegei Leningard,1976,308:18-133.

[19] YERMAKOV V I,SKOROBOGATOV V A. Oil and gas geology of west Siberian platform[J]. Petroleum Geology,1984,21(12):537-540.

[20] GOLAB A N,CARR P F. Changes in geochemistry and mineralogy of thermally altered coal,Upper Hunter Valley,Australia[J]. International Journal of Coal Geology,2004,57(3/4):197-210.

[21] GALUSHKIN Y I. Thermal effects of igneous intrusions on maturity of organic matter:A possible mechanism of intrusion[J]. Organic Geochemistry,1997,26(11/12):645-658.

[22] 王泰. 同忻井田煌斑岩侵入特征及对煤层和煤质的影响[J]. 煤田地质与勘探,2002,30(5):11-13. WANG Tai. Intrusive features and its influence of lamprophyre on coal seams and coal quality in Tongxin mine field[J]. Coal Geology & Exploration,2002,30(5):11-13.

[23] 张富强. 大同塔山井田煌斑岩侵入对煤层煤质的影响[J]. 山西煤炭,2007,27(2):17-20. ZHANG Fuqiang. Lamprophyre invasion's effects on coal seam and its qualities in Tashan coal-field of Datong mining district[J]. Shanxi Coal,2007,27(2):17-20.

[24] GURBA L W,WARD C R. Elemental composition of coal macerals in relation to vitrinite reflectance,Gunnedah basin,Australia,as determined by electron microprobe analysis[J]. International Journal of Coal Geology,2000,44(2):127-147.

[25] OTHMAN R,WARD C R. Thermal maturation pattern in the southern Bowen,northern Gunnedah and Surat basins,northern New South Wales,Australia[J]. International Journal of Coal Geology,2002,51(3):145-167.

[26] E. 斯塔赫. 斯塔赫煤岩学教程[M]. 杨起等,译. 北京:煤炭工业出版社,1990:156-164. STACH E. Textbook of coal petrology[M]. YANG Qi et al,Translated. Beijing:China Coal Industry Publishing House,1990:156-164.

[27] TAYLOR G. Development of optical properties of coke during carbonization[J]. Fuel,1961,40(6):465-472.

[28] BROOKS J D,TAYLOR G. The formation of some graphitizing carbons[J]. Chemistry Physics of Carbon,1968,4:243-286.

[29] CRELLING J C,DUTCHER R R. A petrologic study of a thermally altered coal from the Purgatoire River Valley of Colorado[J]. Geological Society of America Bulletin,1968,79(10):1375.

[30] KISCH H J. Carbonization of semi-anthracitic vitrinite by an analcime basanite sill[J]. Economic Geology,1966,61(6):1043-1063.

[31] RIMMER S M,YOKSOULIAN L E,HOWER J C. Anatomy of an intruded coal,I:Effect of contact metamorphism on whole-coal geochemistry,Springfield(No.5)(Pennsylvanian) coal,Illinois basin[J]. International Journal of Coal Geology,2009,79(3):74-82.

[32] SINGH A K,SHARMA M,SINGH M P. Genesis of natural cokes:Some Indian examples[J]. International Journal of Coal Geology,2008,75(1):40-48.

[33] RAYMOND A C,MURCHISON D G. Organic maturation and its timing in a Carboniferous sequence in the central Midland Valley of Scotland:comparisons with northern England[J]. Fuel,1989,68(3):328-334.

[34] BARKER C E,BONE Y,LEWAN M D. Fluid inclusion and vitrinite-reflectance geothermometry compared to heat-flow models of maximum paleotemperature next to dikes,western onshore Gippsland basin,Australia[J]. International Journal of Coal Geology,1998,37(1):73-111.