

Structure of different types of coal metamorphism by HTEM
- 期刊名字:矿业科学技术(英文版)
- 文件大小:293kb
- 论文作者:LI Xiaoming,CAO Daiyong,LIU De
- 作者单位:College of Safety Engineering,College of Geoscience and Surveying Engineering
- 更新时间:2020-06-12
- 下载次数:次
bleonlineatwwwwsciencedirect.comMININGScienceDirectSCIENCE ANDTECHNOLOGYELSEVIERining Science and Technology 20(2010)0835-0838ww.elsevier com/locate/jcumtStructure of different types of coal metamorphism by HTEMLI Xiaoming", CAO Daiyong?, LIU Demin".2a College of Safety Engineering, North China Institute of Science and Technology, Beijing 101601, Chinaollege of Geoscience and Surveying Engineering, China University of Mining Technology, Beijing 100083, chinaAbstract: In order to discuss the effect of tectonic stress on the structural evolution of coal, given the importance attached toHigh-resolution Transmission Electron MicrosHTEM), we investigated several aspects of material structures of high-rankCarboniferous period coal, located in the northern foreland basin of the Dabie orogenic belt in easterm China. High powlattice images of Bright Fields(BF)and Selected Area Diffraction patterns(SAD)of different types of metamorphism inobtained. The results show that the Basic Structural Units(BSU) become increasingly more compact as a function ofUnder pressure, the local orientation of molecules is strengthened, the arrangement of BSU speeds up and thelegree of order is clearly enhancedKeywords: Dabie orogenic belt; high-rank coal; high-resolution transmission electron microscopy; tectonic stress1 Introductionby coarse clastic rocks, where the tectonic deforma-tion is strong and contains many coal beds. However,In recent years, High-resolution Transmission the growth of various coal beds has been extremelyElectron Microscopy (HTEM)is onemethods for studying material structures. It plays anThe thickness and the structure of these coal bedsimportant role in studying the macro-molecular change considerably in both trends and tendency. Thechemical structure of coal. The basic structural unit of level of thermal-evolution of coal is high, reachingcoal can be observed directly from crystal lattice the stage of anthracite to superanthracite. In generalstripe images, when enlarged several hundred thou- the values of the maximum vitrinite reflectancesand times. Observations by transmission electron (Ro. max)are more than 4%microscopy are paid increasingly more attentionGiven the complex tectonic-thermal evolution ofalong with thorough going research. HTEM is ap- Carboniferous coal seams, we collected sets of threeplied in the study of deformed coal, particularly de- types of coal samples for a comparative study. Theformed coal from different types of metamorphism in first set, Bo to Bo, was collected from the Ma'anshanspecial environments, as well as in the investigation area in the west of Shangcheng county in Henanof the essential effects of tectonic stress on the evolu- province, which is located in the N-S trend shearingtion of coalzone. It is intensely affected by tectonic-stress and isreferred to as tectonic-thermal metamorphic coal. The2 Geological background and samples in second set, B63 to B68, came from Pichong towardsthe studyhe east of Shangcheng county, adjacent to the Yang-shanian granitic intrusion. It is affected by high temCoal samples were collected from mine strata of perature as the result of granitic intrusion and is rethe Yangshan Group (Low Carboniferous)in the ferred to as magmatic-thermal metamorphic coal.TheBeihuaiyang area, at the northern edge of the Dabie third set, B26 to Bst, was collected from other smallMountain orogenic belt. The Beihuaiyang area decoal mines, located far from faults and magmaticveloped along with the coal-bearing strata dominatedbodies. This set reflects regional metamorphism; it iscalle中国煤化工 coal-rank. The-acteristics of these*Corresponding author. Tel: 86 10 61596816CNMHGEmail address: Ixm7010( 126. comdoi:10.1016S1674-5264(0960291-Xning Science and Technologyol. 20 No6Table 1 Information of coal samplesNo. Sampling siteGcological MacroscopicDeformationControlling factorB6 Ma'anshan mine C3Mylonitic coal Orientationinear and strip62312997ng deformation extinctioB2 Yangshan mine CiyScaly coal1577Regional heat4.9B6 Pichong mine CGranulated coal Anomalous high heatBrittle-ductile Sheet-like5.197B6 Pichong mine ClyCataclasticorientational pressuredeformation3 Experimentalthat displayed in Fig. Ic as flexible crape graphite3.2 Sample separation processing and experi3.1 Basic principlestIonsThe Transmission Electron Microscope(TEM)isVitrain or bright coal strips were hand-picked fromnot only a type of high resolution(0.3-1.0 nm)opti- raw coal samples and ground to a 200 mesh size aftercal microscope, but also a kind of effective mi- crushing. Then a mineral-free treatment was carriedcro-area diffraction installment. It can supply massiveout. At first, the coal samples were heated with hyamounts of information on micro-structures while the drochloric acid and hydrofluoric acid in a water-bathappearance of the material can be observed directly (60-80C), removing carbonate, silicon dioxide,With a TEM. the transmission electron beam or the silicates and other impurities from the coal. Secondly,diffraction electron beam can be used separately to iron pyrites needed to be removed with nitric acidform images. The former beam can form images of from samples with a sulfur content 21%. Finally,theight fields and the second images of dark fields. In coal samples were scrubbed with water, dried andimages of bright fields, the streaking cluster of the ground to 0. 432 mm(325 mesh)BSU can be observed and in images of dark fields, aThe experiments were performed on JEM-2010,abright spot or a group of bright spots can be displayed High-Resolution Transmission Electron Microscopewhose dimensions and shapes are different because (UHRTEM)manufactured by the JEOL Company, inthe BSU of coal is a type of amorphous state material an electron microscope room for analysis and meas-of short range order. During the process of coal evo- urements at the Beijing University Center forlution, the images of bright fields and the Selected Chemical Technology. The LaB, filament was illuArea Diffraction(SAD) patterns of dark fields show minated, I magnification was in the order of 100000-different characteristics when moving from superan- 400000, the accelerating voltage was 200 kv, thethracite to graphite(Fig. 1). This suggests that the corresponding wave length 0.00251 nm, the lengthsaromatic structure of coal changed from small to of the camera lens were 100 cm and 120 cm respec-large, the directing property from week to strong and tively. After a mineral-free treatment, the coal sam-crystalline state. Oberlin referred to the phenomena which caused them to subside on the micro reseau forshown in Fig. Ib as micro-column graphite and to electron microscopic observation(a) Streaking cluster structure(d) Structure of straight graphiteFig. 1 TEM images of structural evolution from superanthracite to graphite4 Results and discussiondraw中国煤化工ences among theFrom the observation with the tem, we conclude variCNMHGm in the crystalthat the high rank coal (Ro.max>4.0%)from the north- latticeDngnt nelas, observed by highern foreland basin of the Dabie orogenic belt, we resolution transmission electron microscopy. TheLI Xiaoming et alStructure of different types of coal metamorphism by HTEMbright spots of the basic structural units, in the coal of The brightness of the door diffraction ring of SAD, inbackground coal-rank, show dispersed and isolated the magmatic-thermal metamorphic coal, is generallyshapes, the phenomenon of streaking clusters barely big, the du diffraction ring becomes gradually moreappears and there is no directing property in the distinct, but the dio diffraction ring is again barelyBSUs(Figs. 2a and 2b). The clusters of magmatic- visible(Fig. 3b). The brightness of the doo2 diffractionthermal metamorphic coal are loosely arranged, but ring of SAD, in the tectonic-thermal coal, is mostmore closely than the coal of background coal-rank; pronounced with each scattering link largely disinte-the directing property is not obvious(Figs. 2c and 2d): grated(Fig 3c). within the local area of the graphiThe clusters of tectonic-thermal metamorphic coal toid fabric in the tectonic-thermal coal, the scatteringshow a thin and long vermiform structure; an obvi- ring of the Sad is composed of spots which cannotously streaking cluster appeared, arranged more connect mutually. The scattering becomes thin andclosely, suggesting that the tectonic-thermal meta- narrow, with brightness clearly increasing(Fig 3c)morphic coal is locally highly ordered(Figs. 2e and3)From our study of the three kinds of differermetamorphic coal, we conclude that, no matter which2)The SAD also shows obvious variation among series of coals in the Bsu cluster of crystal latticedifferent types of coal metamorphism. The brightness images is augmented, the degree of order is enhancedof the dooz diffraction ring of the SAD pattern, in the the degree of disintegration of its SAD diffractioncoal of background coal-rank, is generally dim and disk also increased, along with the increase in coalthe du diffraction ring is only faintly visible(Fig. 3a). deformation(Fig. 3c)b)B×30000(c)Bax40000(d)B6x30000(e)B6x40000(Bx30000Fig 2 THEM Bright-Field images(BF)of different type of metamorphic coal(c)B6 camera length, 120 cmFig 3 SAD patterns(THEM dark-field images) of different types of metamorphic co5 Conclusions中国煤化工 erature and stress(reflal anisotropy alsoThe information indicated by the high power crys-CNMH G, especially undertal lattice images of the bright fields and the SAD in orientatorure, the local orientation of molethe study area show that the BSu gradually increases cules is strengthened, the BSU arrangement closesMining Science and TechnologyVol 20 No 6quickly and the degree of order is clearly enhanced5-7.(In ChineseThese conclusions are basically consistent with the [7 Zheng Z, Zhang SS L Study on Microstruc-results, such as non-isotropic extinction enhancementture and Reflectivitysphere geologicalof coal under the microscope, caused by the effect ofBeijing: Earthquake Press1996.(In Chinese)stress, X-ray diffraction analysis, micro-FTIR analy-.[8 Oberlin A, Oberlin M. Graphitazability of carbonacencssis, Electron Paramagnetic Resonance (EPR)analysismaterial as studied by TEM and x-ray diffraction. J Microscopy, 1983, 132(3): 135-143. (In Chinese)[9] Cao Y, Li M. Zhang SR. Influence of tectonic stressAcknowledgementson coalification: stress degradation mechanism and stresspolycondensation mechanism. Sci China Ser DEarthSci,2007,501):43-54. (n Chinese)Financial support for this work, provided by the [10] Li X M, Cao D Y, Zhang S R. Contrast study on mi-National Natural Science Foundation of chinacro-FTIR characters between deformed and undeformed(No. 40872105)and the Scientific Research Foundacoals. Coal Geology of China, 2005, 17(3): 9-11.(Intion of the north China Institute of Science Technology(No. A08002), is gratefully acknowledged[11] Cui G W, Zhu S Q, Zou L Z, Xie Ww. Effects of high-the slurry ability of coals.Journal of China Universiry of Mining TechnologyReferences2007,17(4):562-565.( In chinese)[12] Zheng L Q, Li X Q, Lu X, Zhong NN, Huang XY, Zhou[1] Qin Y. Micropetrology and Structural Evolution ofQ. Thermal evolution of organic matter and secondaryHigh-Rank Coals in P R China. Xuzhou: China Univer-hydrocarbon generation from upper Paleozoic coal deity of Mining& Technology Press, 1994. (In Chinese)osits in northern China. Joumal of China University of[2] Ju Y w. Tectonic Coals: Structures and Physical Proper-Mining Technology, 2007, 17(4): 526-533 (In Chi-nese)ties of Reservoirs. Xuzhou: China University of Mining [13] Zhang X P, Ren Y J, Sun Z. Study on grain refining andTechnology Press, 2005. (In Chinese)[3] Jiang B Qin Y, Jin FL demetamorphism of ZLlll aluminum alloys Joumal ofsuper micre tnd tuesinif co al esner se onet si o.China University of Mining Technology, 2006, 16(4)47547933(1):17-23.( In Chinese)[14] Wang B, Jiang B, Liu L, Zheng GQ, Qin Y, Wang HY,4] Zhao F H, Ren D Y. Study on microstructure and theLiuh l, li g Z.simulation of hydrodynamicfabric of coal by applying high-resolution transmissiononditions in higalbed methane reservoir for-electron microscopy. Geological Review, 1995, 4(6)mation, Miningd Technology, 2009, 19(4):564-569.(In Chinese)43540[5] Li X M. Study on the Deformation and metamorph[15] Lu Y, Tu S H. Rules of distribution in a plastic zone ofHigh-Rank Coal the response to the Clrocks surrounding a roadway affected by tectonic stress.Geologic Environments [Ph D. dissertationMining Science and Technology, 2010, 20(1): 47-52.hina University of Mining Technology, 2[6] Li X M, Cao D Y, Zhang SR, Xing X Y. 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Fractal study of crack中国煤化工ms吗 ics. Transactionsscale distribution in coal mass. Journal of China CoalCNMHG
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