区域岩浆热变质作用及其对我国煤质的影响

本文根据中国煤变质的特点分析了促使煤变质演化的地质条件,阐述了接触变质作用和动力变质作用的局限性,主要是深成变质作用使中国煤演化到低变质阶段,燕山期岩浆活动导致的区域岩浆热变质作用弥补了这一缺点,使很大一部分中国煤增高了煤级,形成了储量丰富,多用途的中、高变质煤。并根据岩浆性质、侵入规模、侵入层位和深度以及沉积盖层的封闭程度对区域岩浆热变质作用进行分类,划分出三个亚型:深成岩浆热变质作用、中深成岩浆热变质作用和浅成岩浆热变质作用,总结了区域岩浆热变质作用的鉴定特征及其对中国煤质的影响。     

阿拉善台隆同位素年龄数据及其地质意义

阿拉善台隆是连接塔里木地台与华北地台的咽喉构造带,属华北地台的次级构造单元,它的南、北两侧毗邻古生代地槽活动带,直接影响阿拉善台隆的构造发展并使其复杂化。据187个变质岩和侵入岩同位素年龄数据及有关地质资料的综合分析说明:阿拉善地台基底形成是华北地台最晚的地区之一,完成于中条旋回(17亿年左右)并伴生同构造旋回的花岗岩和花岗伟晶岩侵入。中晚元古代为地台发展阶段,蓟县墩子系沟群以角度不整合覆于基底变质岩系之上,其与震旦系韩母山群为平行不整合关系,武陵旋回及晋宁期基性、超基性岩、花岗伟晶岩脉沿断裂侵入基底变质岩系中。阿拉善台隆脱离海浸最早,早元古代为陆隆区分割塔里木地台及华北地台两大海域。古生代及中、新生代为阿拉善地台的“活化”阶段,块断作用和各类岩浆侵入活动异常发育,以晚古生代最为强烈,形成隆、坳相间的构造格局,北部较南部裂陷深,是构造岩浆活动的鼎盛对期。阿拉善台隆南缘主要发育加里东旋回、华力西旋回早、中期的岩浆侵入及局部变质作用和混合岩化作用,北部主要为华力西晚期和印支旋回、燕山旋回的侵入活动及局部变质作用和混合岩化作用。侵入岩包括超基性、基性、中酸性、酸性及碱性岩,以花岗岩为主,占岩体出露总面积90％以上。多旋回的构造岩浆作用,导致具多旋回的成矿特点。     

华北煤变质作用对煤含气量和渗透率的影响

通过华北和美国煤层气地质条件的对比, 基于华北煤变质特点, 指出了区域岩浆热变质有利于提高煤层含气量和渗透率, 并对其作用机理进行了初步探讨.在中国, 经受燕山期岩浆侵入影响之前的煤级较低, 因此在快速增温的高温作用下, 煤层气再次发生即“叠加生烃”或“叠加成气”的潜力大, 孔、裂隙系统发育更趋完善, 区域岩浆热变质的生气时间晚而利于煤层气保存.叠加有区域岩浆热变质形成的煤级分带, 包括高煤级煤和中煤级煤在内都将明显提高煤的含气量和渗透率, 因此, 华北地区应重视在区域岩浆热变质煤中寻找煤层气勘探目标.      

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。     

宁夏煤变质规律初探

宁夏煤炭资源丰富,煤类多,在区域和垂向上呈现出明显的规律性。晚古生代煤层以中、高变质的烟煤、无烟煤为主,中生代煤层以低变质的烟煤为主,从各含煤区分布看,贺兰山、香山含煤区多为高变质的烟煤和无烟煤,灵盐、固原含煤区以低变质烟煤为主,青铜峡-固原深断裂西部的煤变质程度明显高于东部。分析认为深成变质作用对各时代煤变质具有普遍意义,在此基础上,岩浆热力变质作用和动力变质作用也是导致局部地区煤变质增高的因素,如贺兰山含煤区的汝箕沟矿区,受隐伏岩浆热力影响,以岭大井田为中心,呈现北东向展布的半环带状煤级分带;香山含煤区各时代煤类分布方向与区域构造线方向一致,推测可能在深成变质作用下叠加了岩浆热力变质和动力变质作用。     

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进一步探讨

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,建立了煤的地下水效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。     

河南省石炭-二叠纪煤类分布及煤变质特征

为系统研究河南省石炭-二叠纪煤的变质作用类型及变质演化规律,采用野外钻探、测试分析、统计、计算机模拟等方法,对石炭-二叠纪煤类、煤的变质程度、变质作用类型等进行研究。结果表明,石炭-二叠纪煤变质程度总体较高,以焦煤-无烟煤为主,可采煤层的变质程度以及煤类在平面上近似呈环带状分布。煤的变质作用主要为深成变质作用、动力变质作用、接触变质作用和区域岩浆热变质作用。深成变质作用对石炭-二叠纪煤的变质具有普遍控制作用。煤的变质演化历程表明,经历了印支期三叠纪深成变质作用;燕山期侏罗纪,煤系处于高温低压带环境,岩浆活动强烈,区域岩浆变质作用使煤级剧增,叠加动力变质作用、接触变质作用后,局部煤级进一步增加,形成了现今石炭-二叠纪煤变质分带,其后不同时期各类变质作用对煤级的影响已经非常微弱。     

华北晚古生代煤层变质成因的探讨

华北晚古生代煤的变质样式，通常表现为中心变质程度高，向外围变质程度逐渐减的环带状结构。区域性环带结构是二次区域地温场作用的综合效应，局部环带结构则是在早期区域地温场作用基础上。主要是后期异常地温场作用的叠加结果。沿断理解带岩浆上涌或地下水气化热液作用通常形成异常地温场，但地壳活化期在密集的基底断裂网络条件下，其它地质因素配合，也可以形成区域地温场。     

河南省中北部地区煤变质作用地质因素探讨

河南省中北部地区煤的变质是在区域变质作用基础上受到区域岩浆热变质作用影响的结果。褶皱前时期(C_2-T-3)煤经历区域变质作用,形成气煤—肥煤;褶皱时期(J_1-K_2)煤遭受岩浆热变质作用形成焦煤以上各煤级;褶皱后时期(E_1-Q_4)煤以区域变质作用为主,但由于煤曾遭受过褶皱时期岩浆热的高温作用,此时期的区域变质作用仅对煤的变质产生微弱影响。     

湖南中生代岩浆活动与晚二叠世煤变质特征

岩体同位素年龄和空间展布分析表明，中生代岩浆活动受多期活动的深大断裂控制且具有多阶段和多期次演化特征。根据Ｘ 射线衍射分析、包体测温、热液矿点的分布以及煤质参数等特征可以证明，除了深成变质作用外，岩浆热变质作用是该区主要的煤变质作用类型。岩浆热变质作用可进一步划分为区域岩浆热变质作用和接触变质作用。通过对湖南的煤类、岩浆活动、构造特征及地球物理特征的比较，可划分出４个煤变质区，其变质程度自北西向南东逐渐增高，这是中、新生代太平洋板块与欧亚板块长期相互作用的结果     

中国煤变质作用

通过煤变质热源及作用方式的研究，总结了中国煤变质作用主要类型，动态地史－热史模拟表明，煤盆地的地热状态以非均－地温场影响深成变质格局，如鄂尔多斯盆地三叠纪的地温高于前后时代，大地热流同盆地了中心增高，四川盆地中心莫霍面较浅，与高变质煤分布基本一致，区域岩浆热变质是形成中国大多数中高煤级煤的主因，模拟分析了湘赣中南部印支－燕山期花岗岩体与煤变质，煤热水变质作用以载热的深循环流体构成派生热绿岩侵入的增     

东秦岭北缘煤的变质作用与板块构造的关系

以河南省东秦岭造山带北缘山西组二１煤层的煤岩、煤质、煤有机地球化学和“晶核”结构的综合研究为前提，结合板块构造和地球物理场的研究分析，认为该区二１煤的变质热源主要与长期复杂的板块俯冲、Ａ型碰撞所引起的地壳结构调整而使前陆盆地区岩石圈结构变化，大地热流急增的结果有关。二１煤的变质主要经历了早期（印支期前）的区域深成变质（达肥－气煤）和后期（印支－燕山期）的典型异常热变质作用（达无烟煤－高阶无烟煤）。     

铁法盆地煤变质作用及煤层气生成特征

对铁法盆地的地质背景、煤系上覆地层和埋藏史、岩浆活动、煤体结构、煤阶分布、煤变质特征等进行了综合分析,认为铁法盆地的煤变质以浅成岩浆热变质作用为主;煤层热解气生成的时间、条件和方式受煤变质过程控制;煤变质与煤层气是同一地质环境下一个事物的两个方面。      

Preliminary investigation on the metamorphism of Chinese coals

The fact that most Chinese coals are of a relatively high degree of coalification indicates that the metamorphism of Chinese coals has its own characteristics. As contact metamorphism and dynamic metamorphism have influenced the coals only to a restricted extent, they are not the causes of this distinguishing feature. Though geothermal metamorphism of coal occurs universally in China, the maximum subsidence as reflected by the thickness of coal measures and their overlying rock series is so small that the palaeo-temperature to which most Chinese coals were subjected was low and only low-ranking coals were formed. Hence, geothermal metamorphism is also not the principal cause of the higher ranking Chinese coals. Next to temperature, time is an important factor in geothermal metamorphism; the degree of coalification is dependent on the temperature and duration of heating that the coal has undergone.It is inferred that palaeogeothermal anomalies ought to be held responsible for most of the higher ranking Chinese coals. They are principally caused by magmatic intrusions, or by deep-seated faults, or by the uplift of the Moho with the corresponding uplift of the asthenosphere, and these three causes are interrelated. Telemagmatic metamorphism has so widely influenced Chinese coals that it accounts mainly for the majority of higher-rank Chinese coals. Consequently Chinese coals have first and universally been coalified by geothermal alteration to lower rank and then partially promoted by telemagmatic metamorphism to medium and high ranks. Based upon the patterns of magmatic intrusions and associated hydrothermal processes, the telemagmatic metamorphism of Chinese coals can be tentatively divided into the following types: (1) type a, produced mainly by hypabyssal or meso-epimagmatic intrusions; (2) type b, produced mainly by hydrothermalism from blind intrusive bodies; (3) type c, produced mainly by mesoepimagmatic and epimagmatic intrusions; and (4) type d, produced mainly by hydrothermalism and epimagmatic intrusions. Characteristics of coalification zones, wall rocks and coal itself may be used as criteria to differentiate the telemagmatic metamorphism from other kinds of metamorphism. Magmatic activities which caused the telemagmatic metamorphism and its extent are controlled by structural systems, especially by the latitudinal structural systems and other structural systems associated with the former.     

Iodine in Chinese coals and its geochemistry during coalification

To determine the I distribution in Chinese coals, a nationwide survey was undertaken based on the distribution, periods of formation, rank and production yields of various coal deposits. A total of 305 coal samples were collected and their I contents were determined by catalytic spectrophotometry with pyrohydrolysis. The geochemistry of I during coalification (including both peat diagenesis and coal metamorphism) was assessed. It was found that the I contents of Chinese coals range from 0.04 mg kg^–1 to 39.5 mg kg^–1 and exhibit a lognormal distribution, with a geometric mean of 1.27 mg kg^–1. Statistical correlation analysis and the observation that I contents increase with coal rank indicate that coal I is chalcophile in nature, and not generally organically bound. When peat developed into lignite through diagenesis, 95–99.9% of the original I was lost. The composition and structure of clay minerals present in the coal were controlled by the original depositional environment. The higher the I content of coals, the more likely the original sediments were affected by a marine environment. Iodine contents increased from lignite through sub-bituminous and bituminous coals to anthracite. This indicates that coal absorbed excess I from hydrothermal fluids during metamorphism (including geothermal metamorphism and telemagmatic metamorphism). The telemagmatic metamorphism was caused by magmatic activities that depended on the specific geological structure of the region. In China, most high-rank coals were formed by telemagmatic metamorphism.     

桐柏－大别造山带随县群变质变形作用研究

中新元古代随县群分布于秦岭—大别造山带南部，是一套形成于大陆裂谷环境中的砂页岩—流纹英安质火山碎屑岩建造，并在拉张环境中受到了辉长辉绿岩墙侵入．从新元古代末开始经历了多期变质和变形作用改造，记录了华北与扬子两大陆块及其造山作用的复杂演化历史．以现代变质地质学理论为指导，结合岩石学与构造学，宏观与微观研究，确立了随县群的地质事件序列．其主要有３个变形和变质演化阶段：晋宁期伸展滑脱固态流变，低绿片岩相变质；印支期韧性剪切，绿帘—蓝片岩相变质；早燕山期逆冲推覆，低绿片岩相变质     

重庆地区二叠系上统龙潭组/吴家坪组煤变质规律及其对煤层含气量的影响

通过对重庆地区煤炭资源勘查资料总结,分析了二叠系煤类分布特征,并探讨了煤变质对煤层含气量的影响。分析认为,重庆地区二叠系煤层主要以高、中变质煤的无烟煤、贫煤和瘦煤为主,煤类分布具有明显的分带性,煤变质作用以区域深成变质类型为主;煤的变质程度R0为1.39%~2.51%,处于吸附能力较强的阶段,因此煤层含气量较高,其中松藻矿区无烟煤R0为2.43%~2.51%,煤层含气量达27.1m3/t。