接触变质作用对煤基石墨烯量子点的影响研究

为研究煤的接触变质作用对煤基石墨烯量子点性质的影响,以形成于深成变质、区域岩浆变质的煤为对比,采用氧化剥离法进行煤基石墨烯量子点的制备,并利用X射线衍射（XRD）、拉曼光谱（Raman）、透射电镜（TEM）、X射线光电子能谱（XPS）、荧光光谱（PL）对原煤及制备产物的结构进行分析。实验结果表明,随煤级升高,脱灰煤的结构缺陷减少,芳香片层逐渐增大,晶体结构向有序化方向进行。以煤为碳源制备而成的量子点,粒度均一性良好,并随煤级升高粒径有更大的趋势。碳元素以 C—C/C—H 形式为主,氧主要存在于碳氧官能团中,C∶O≤7∶3,且氧含量随煤级升高而升高。在紫外光（λ=297 nm）的照射下,样品散发蓝色荧光,且在煤级较低时荧光强度较大,并随煤级升高逐渐降低。相较于深成变质、区域岩浆变质形成的煤,接触变质作用形成的煤,产物具有更多的 COO— 结构,而 C==O 键含量降低;荧光强度在煤级较低时的上升趋势更为明显,并在高阶烟煤达到最大;受接触变质作用影响的煤,具有更加规则的石墨化结构。     

煤变质作用研究

本文从4个方面扼要地讨论了煤变质作用的近期进展。在煤级参数方面对镜质体反射率及其缺点和弥补的方法做了介绍,简述了近来提出的新的煤级参数。在煤化作用机理与特点方面概述了涉及煤化作用的煤结构研究新进展及其在煤化过程的演变中与镜质体反射率、挥发份的内在联系;煤化作用跃变与沥青化作用;“惰性组的煤化径迹”——煤化作用的一个新的方面。新的煤变质作用类型探讨。煤变质因素和煤化作用平衡,煤变质作用研究应用于其它地质学科。最后提出了应进一步研究的煤变质问题。     

中国煤的叠加变质作用

中国煤变质具有多阶段演化与多热源叠加变质的特点;部分中国煤经历过3个变质演化阶段：以深成变质作用为主的第1演化阶段。以多热源叠加变质作用为特征的第2演化阶段和以奠定煤变质格局为主的第3演化阶段。除煤的深成变质普遍存在外,区域岩浆热变质为另一种中国煤的主要变质模型;多热源叠加变质是中国大多数中、高煤级煤产生的主要原因,其中区域岩浆热变质作用的影响最显著;中国煤的叠加变质作用主要发生在第2演化阶段;文中归纳出5种叠加变质作用类型。     

华北地区南部晚古生代煤的变质成因：地下水热液对煤变质作用影响的…

在分析造成华北地区南部晚古生代煤变质分带性的地质因素基础上，阐述了煤变质成因与区域构造格局演化的密切联系；从古地热异常形成机制出发，着重讨论了地下水热液对煤变质作用的影响，建立了煤的地下水热液变质作用地质模式；用古地热－煤变质系统的概念，根据热源、载热体和通道、聚热体３个要素的配置，分析了煤变质成因。     

新疆煤类分布、变质规律及变质作用分析

以新疆多年来煤炭资源远景调查评价和众多煤矿勘查成果为基础,在全面总结全疆各主要含煤盆地煤类分布特点的基础上,对煤的变质规律和变质作用进行了初步分析,以期对目前疆内大规模开展的煤田地质勘查工作有所借鉴.     

新疆艾维尔沟煤变质作用研究

新疆艾维尔沟矿区是侏罗纪天山褶皱带中的一个小型山间含煤盆地。多项煤变质指标的分析结果表明:该区煤级在横向上分带明显,垂向上煤级突变,煤岩组份中出现热变显微组份,煤晶核指标(La/Lc)大于1,矿区广泛发育热液石英脉和方解石脉,煤层围岩也具有中低温热液蚀变现象。所有这些特征都充分表明,艾维尔沟的煤变质属区域热变质类型。推测其附加热源位于该煤盆地西部,地下水热液的对流为主要热传导方式。矿区及其外围的构造、地层结构、地势、水文等条件均有利于地下水热液循环。     

构造煤的动力变质作用及其演化规律

采用Ｘ射线衍射分析，电子顺磁共振等方法研究了构造煤的动力变质作用特征和演化规律。构造煤与煤层的变形变质历史有关，动力变质作用形成的构造煤，其结构特征与其它变质类型煤不同，演化途径也不同，但它们的演化规律一致。     

焦作煤田二1煤层煤变质作用特征及其影响因素

燕山期深成岩浆热变质作用，使二1煤层由低煤级的烟煤阶段上升到D段无烟煤三号高变质阶段，同时叠加的浅成岩浆热变质作用，使二2煤层变质程度达到E无烟煤一号或E段无烟煤二号变质阶段，形成煤田中部煤变质程度低于东西两端的变化格局。     

浅谈区域岩浆热液对广西煤变质的影响

列举了岩浆作用在广西一些煤田的表现, 认为成煤期的区域岩浆絷液活动, 与广西煤的变质有着密切的联系。     

Effects of Coal Rank and High Organic Sulfur on the Structure and Optical Properties of Coal-based Graphene Quantum Dots

Coal‐based graphene quantum dots (GQDs) were successfully produced via a one‐step chemical synthesis from six different coal ranks, from which two superhigh organic sulfur (SHOS) coals were selected as natural S‐doped carbon sources for the preparation of S‐doped GQDs. The effects of coal properties on coal‐based GQDs were analyzed by means of high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), ultraviolet‐visible (UV‐Vis) absorption spectroscopy, and fluorescence emission spectra. It was shown that all coal samples can be used to prepare GQDs, which emit blue‐green and blue fluorescence under ultraviolet light. Anthracite‐based GQDs have a hexagonal crystal structure without defects, the largest size, and densely arranged carbon rings in their lamellae; the high‐rank bituminous coal‐based GQDs are relatively reduced in size, with their hexagonal crystal structure being only faintly visible; the low‐rank bituminous coal‐based GQDs are the smallest, with sparse lattice fringes and visible internal defects. As the metamorphism of raw coals increases, the yield decreases and the fluorescence quantum yield (QY) initially increases and then decreases. Additionally, the surface of GQDs that were prepared using high‐rank SHOS coal (high‐rank bituminous coal) preserves rich sulfur content even after strong oxidation, which effectively adjusts the bandgap and improves the fluorescence QY. Thus, high‐rank bituminous coal with SHOS content can be used as a natural S‐doped carbon source to prepare S‐doped GQDs, extending the clean utilization of low‐grade coal.     

Deformation metamorphism of bituminous and anthracite coals from China

Tectonic displacement of coal seams in China has resulted in faulting parallel to coal bedding. Displacement along these faults caused significant comminution of the coal on the footwall contributing to various mining problems, the worst of which is catastrophic failure, or “outbursting” of the working face during mining. The granular texture and mostly unconsolidated nature of the coal suggests that faulting occurred relatively late in the coalification sequence, at a time of maximum tectonic stress. Coal samples taken on either side of the fault plane (normal and deformed coal layers) were obtained in an effort to establish what influence these tectonic stresses might have had on coal properties as well as what they might reveal about the influence of tectonic pressure on organic maturity. Sample sets were collected within coal beds from undisturbed and adjacent deformed layers, including 21 bituminous samples from the Pingdingshan coal field and nine anthracite samples from the Jiaozuo coal field, the Tieshenggou coal mine of the Yuxi coal field in Henan province, the Beijing Xishan coal field, the Baijiao mine of the Furong coal field in Sichuang province and the Baisha coal field in Hunan province, China. Results from vitrinite reflectance, proximate and ultimate analyses show some differences in reflectance, hydrogen content and nitrogen content of anthracite coal. No significant difference was found between volatile matter yields of normal and deformed coal specimens. GC measurements of the saturated hydrocarbon fraction of chloroform extracts from bituminous coals showed that lower molecular weight carbon fragments were concentrated in the deformed samples. Therefore, although changes in the gross chemical properties of the deformed coal were insignificant, some modification of the chemical structure is seen to have occurred as a result of exposure to tectonic pressure.     

煤岩构造变形与动力变质作用

煤岩是一种对温度、压力等地质环境因素十分敏感的有机岩,地质演化过程中的各种构造-热事件必然导致煤岩发生一系列物理与化学结构的变化,并形成不同类型的构造煤。在构造应力作用下,煤岩不仅发生脆性和韧性变形,而且还产生不同程度的动力变质作用。因而,关于煤岩构造变形与动力变质作用的研究不仅具有重要的科学意义,而且在煤层气资源评价以及煤与瓦斯突出危险性预测方面也具有重要的实际意义。文中在已有研究成果基础上,通过对构造煤系列Ro,max、XRD和NMR(CP/MAS+TOSS)等测试和实验方法的对比研究,深入分析了煤岩不同构造变形和动力变质特征,进一步探讨了构造应力下煤岩动力变质作用的机理。研究成果表明,在构造应力作用下,煤岩脆性变形主要是通过破裂面上快速机械摩擦转化为热能而引起煤岩化学结构与其成分的改变;而韧性变形煤主要是通过局部区域应变能的积累而引起煤岩化学结构的破坏,从而发生不同机制的动力变质作用。     

Effects of fluid production on fluid flow during regional and contact metamorphism

Numerical and analytical models of fluid flow that account for fluid production during prograde regional and contact metamorphism show that expulsion of metamorphic fluids dominates the convective flux when crustal permeabilities are less than 0.1–100 μD, depending primarily on the rate of fluid production. When this is the case, fluid circulation is limited or prevented, fluid pressures are elevated above hydrostatic values, and flow throughout most of the model is up and away from the region of maximum fluid production. Fluid circulation is predicted to occur where permeability is high, in dry rocks, or after rates of fluid production decrease as peak temperatures are reached. Large changes in the pattern of flow and influx of externally derived fluids may thus occur in metamorphic terranes when dehydration wanes or ceases and cooling begins. Inclusion of an impermeable horizon in the models further inhibits fluid circulation. Earlier, shallow hydrothermal models and interpretations based on the Rayleigh number may be inappropriate for characterizing fluid flow during prograde metamorphism at depth because they do not account for fluid production.     

Evolution of fluid pressure and fracture propagation during contact metamorphism

Abstract Rock fracture enhances permeability and provides pathways through which fluids migrate. During contact metamorphism, fluids contained in isolated pores and fractures expand in response to temperature increases caused by the dissipation of heat from magmas. Heat transport calculations and thermomechanical properties of water-rich fluids demonstrate (1) that thermal energy is a viable mechanism to produce and maintain pore fluid pressure (P_f) in a contact metamorphic aureole; (2) that the magnitude of P_f generated is sufficient to propagate fractures during the prograde thermal history (cause hydrofracture) and enhance permeability; and (3) that P_f-driven fracture propagation is episodic with time-scales ranging from years to thousands of years. Because P_f dissipation is orders of magnitude faster than P, _f buildup, P_f oscillations and cyclical behaviour are generated as thermal heating continues. The P_f cycle amplitude depends on the initial fracture length, geometry and the rock's resistance to failure whereas the frequency of fracture depends on the rate of heating. Consequently, oscillation frequency also varies spatially with distance from the heat source. Time series of fluid pressures caused by this process suggest that cyclical fracture events are restricted to an early time period of the prograde thermal event near the intrusive contact. In the far field, however, individual fracture events have a lower frequency but continue to occur over a longer time interval. Numerous fracture cycles are possible within a single thermal event. This provides a provisional explanation for multiple generations of veins observed in outcrop. P _f cycling and oscillations may explain several petrological features. If pore fluids are trapped at various positions along a pressure cycle, the large amplitude of P_f variations for small fractures may account for different pressures recorded by fluid inclusions analysed from a single sample. P_f oscillations, during a single thermal episode, also drive chemical reactions which can produce complex mineral textures and assemblages for discontinuous reactions and/or zoning patterns for continuous reactions. These can mimic polymetamorphic or disequilibrium features. Temporal aspects of fracture propagation and permeability enhancement also constrain the likely timing of fluid flow and fluid-mineral interactions. These data suggest that fluid flow and fluid-mineral reactions are likely to be restricted to an early period in the prograde thermal history, characterized by high P_f coincident with relatively high temperatures, fracture propagation and consequent increases in permeability. This early prograde hydration event is followed by diffusional peak metamorphic reactions. This relationship is evident in the complex mineralogical textures common in some metamorphosed rocks.     

Characteristics of telemagmatic metamorphism of the Ceshui Formation coal in Lianyuan coal basin

The Ceshui Formation coal is mostly anthracite and its metamorphism has been less documented.By analyzing systematically the reflectance of vitrinite and the results of X-ray diffraction of the Ceshui Formation cola in the Lianyuan coal basin,the spatial variation characteristics of coal ranks,coal metamorphic regions,the extension of coal metamorphic belts.coal metamorphic gradients,coal chemical structure and the effect on the degree of metamorphism of heat-production and -storge conditions,buried depth of the Indosinian-Yenshanian granites at the margins of the Lianyuan coal basin are discussed.The research results in conjunction of the features of regional hydrothermal alterations,endogenetic deposits with the Ceshui Formation coal measures,and the development of secondary vesicles indicate that the telemagmatic metamorphism is the main factor leading to the metamorphism of the Ceshui Formation coal in the region studied.     

构造物理化学条件对煤变质作用的控制

煤是对温度和压力等地质因素十分敏感的有机岩,各种构造-热事件控制下的物理化学条件,是促进煤岩演化的根本动力。本文对煤变质作用过程的研究现状进行了综述,着重讨论了煤岩在高煤阶-石墨演化阶段的控制因素、演化过程和演化机制。煤变质作用包括煤化作用阶段和石墨化作用阶段,共同构成一个连续的有机质演化过程,总体趋势是分子结构有序化、化学成分单一化,最终演变为以碳元素为主、三维有序结构的石墨。温度和压力(应力)是控制煤变质作用两大因素,在不同的演化阶段,这两大因素所起的作用和演变机理都有所差异。在低、中煤阶演化阶段,温度是煤化学结构演化的主要控制因素,为化学键断裂提供活化能,应力缩聚和应力降解则对煤化学结构演化具有催化作用。高煤阶-石墨化阶段的主要机制是导致基本结构单元BSUs之间相互联结使短程有序化范围增大的拼叠作用,构造应力在其中起到关键作用,BSUs定向和面网间距不断减小,促进大分子物理结构演化。加强煤变质作用的高级阶段-石墨演化过程的研究,将丰富和深化对煤-石墨物理化学结构完整演化序列的认识。煤系石墨成矿机制的高温高压模拟实验,则为煤变质作用构造物理化学条件研究提供了可行的技术手段。     

煤基石墨烯原料与制备技术研究进展

作为21世纪的新兴碳纳米材料,石墨烯具有十分优异的性能,在众多领域中都展现出巨大的应用潜力。煤是储量最丰富、价格最低廉的碳源,且具有独特的结构和物质组成。将煤用于石墨烯等新型碳质材料及其复合材料的开发应用,是一项值得深入探索的工作。煤基石墨烯的发展既能促进煤的洁净利用也能提升煤炭资源的附加值。通过综述分析煤结构研究、煤石墨化机理以及煤基石墨烯研究与制备等方面的发展概况,并提出煤基石墨烯研究的现存问题和未来展望。认为,目前以煤为碳源制备石墨烯及其衍生物的研究尚属于起步阶段,研究的重点是在优化产品制备和性能的方面上,有关煤岩特性对产品质量影响的研究较少。原料煤的结构和物质组成的差异最终会影响煤基石墨烯产品的结构和性能,而煤的结构演变受地质因素影响显著。因此,未来煤基石墨烯的发展应该加强地质作用下的煤原始结构和物质组成对煤基石墨烯产品的影响研究,进而为加快煤基石墨烯研究和提高煤的清洁高效利用提供理论支撑。     

内蒙古中部地区晚古生代地层接触变质作用研究初探

内蒙古中部晚古生代地层由于中生代岩浆的侵入,部分发生接触变质,变质程度多处于沸石相或葡萄石绿纤石相。通过对典型剖面的泥质岩石中的粘土矿物、伊利石结晶度以及镜质体反射率的分析,得出以下结论：（1）粘土矿物以伊利石和绿泥石为主,只在极少数样品中有伊蒙混层和蒙脱石,多数缺乏伊绿混层;（2）伊利石结晶度为022~040;（3）镜质体反射率Ro值为15~40。其结果表明：在岩浆侵入地区有小规模的接触变质,为极低级变质带,并未发生大规模的低绿片岩相的区域变质,而且这种变质只影响到晚二叠世以前沉积的地层和油气,分布范围有限。