煤系高岭石粘土岩的理论与应用研究

我国北方煤系中的高岭石粘土岩是具有很高经济价值的共生矿产,在煤田勘探中应予充分注意,进行详细研究和评价.它有沉积和火山灰蚀变两种成因,不同成因的矿层具有不同的特征.指出渭北太原组5煤的高岭石夹矸属火山灰成因,11煤高岭石夹矸是沉积产物.软质高岭土全属沉积成因,多产于中、新生代煤系中.     

新汶 肥城太原组火山灰蚀变高岭石夹矸化学成分研究

在前人研究成果的基础上,从化学成分特征这一角度,对山东新汶、肥城煤田太原组高岭石粘土岩夹矸进行了主常量元素、微量元素及稀土元素分析。结果不仅进一步证明了,研究区高岭石粘土岩夹矸确由火山灰降落于泥炭沼泽或泥炭坪环境后经蚀变而成,而且通过对微量及稀土元素分析结果的研究,提出该层夹矸的形成可能受到不同期次及不同性质的火山物质影响的新见解,为含煤岩系中火山事件沉积的研究提供了新思路。      

滇东晚二叠世煤田中火山灰蚀变粘土岩夹矸(TONSTEIN)的锆石特征

本文就滇东晚二叠世含煤沉积中同沉积火山灰蚀变粘土岩夹矸和正常沉积粘土岩的锆石进行了统计学和形态学研究.该两种不同成因类型的粘土岩中锆石含量及形态面貌有显著区别.tonsteins中锆石形态参数统计规律因层位而异;同层位tonstein的锆石含量和形态参数在平面上呈有规律地变化.系统研究含煤建造剖面上各类岩石(包括tonsteins)中的锆石特征,能够用以确定物质来源、性质、成因以及以此为基本建立正常地层层序并精确对比层位,因而具有理论和实用意义.     

滇东晚二叠世煤田中火山灰蚀变粘土岩夹矸(TONSTEIN)的锆石特征

本文就滇东晚二叠世含煤沉积中同沉积火山灰蚀变粘土岩夹矸和正常沉积粘土岩的锆石进行了统计学和形态学研究.该两种不同成因类型的粘土岩中锆石含量及形态面貌有显著区别.tonsteins中锆石形态参数统计规律因层位而异;同层位tonstein的锆石含量和形态参数在平面上呈有规律地变化.系统研究含煤建造剖面上各类岩石(包括tonsteins)中的锆石特征,能够用以确定物质来源、性质、成因以及以此为基本建立正常地层层序并精确对比层位,因而具有理论和实用意义.     

用TONSTEIN的锆石形态和微量元素标志厘定层位

本文以滇东、黔西晚二叠世含煤建造中同沉积火山灰蚀变粘土岩夹矸为例,研究了不同层位中锆石晶体含量和形态参数特征以及tonstein的微量元素标志,初步查明了它们在不同层位上和同层位空间上的变化规律,用于精确厘定层位具有独特的效果。在构造复杂、地层正常层序受到严重破坏的地段,应用此一鉴别层位的方法具有重要的实用价值。      

滇东黔西晚二叠世含煤沉积中火山灰蚀变形成的伊利石粘土岩夹矸

本文对广泛分布于滇东-黔西晚二叠世含煤沉积中粘土岩夹矸的岩石学、矿物学、化学组成和微量元素进行了研究。发现粘土岩夹矸的变种伊利石粘土岩夹矸(Illite-tonstein)在沉积盆地空间上成片分布,且与晚期成岩作用有明显的成因联系。粘土岩夹矸中粘土矿物构成与煤阶大体对应的关系,揭示了同沉积火山凝灰蚀变产物的后期变化趋势和规律。     

陕西渭北煤田5#煤层粘土岩夹矸的研究

渭北煤田面积约１０万ｋｍ２。分布于太原组顶部５＃煤层中的粘土岩夹矸，上部层位分为两上分层，上分层夹矸厚度薄，下分层夹矸厚约０２ｍ，俗称“２００矸”；下部层位夹矸厚度变化较大。该文详细论述了粘土岩夹矸的岩矿特征。根据“２００矸”中含有副象β－石英、高透长石、锆石、磁铁矿等高温矿物组合，特有的粒序层理和岩性在全煤田十分稳定等特点，表明其原始物质来源于降落火山灰。根据ＴｉＯ２／Ａｌ２Ｏ３比值的明显变化，探讨了陆源组分的加入对火山灰蚀变粘土岩夹矸化学成分的影响。以“２００矸”为等时标志层，解决了５＃煤层在区域上的对比。     

煤系火山灰蚀变黏土岩:矿物学和地球化学研究进展

含煤地层中广泛分布的火山灰蚀变成因的高岭石黏土岩被称为Tonstein。少数情况下,煤系蚀变火山灰层的黏土矿物以蒙脱石和伊蒙混层矿物为主,则分别称为斑脱岩和钾质斑脱岩。尽管中外学者对煤系火山灰蚀变黏土岩已有大量研究,然而,迄今为止这几个术语在定义和使用上在国内外科学界仍然存在争议。煤中火山灰的淋滤作用会对煤的地球化学组成产生重要影响。含煤地层中这类岩石因为分布广泛可以被用作等时标志层,提供地层对比的依据,其中的原生矿物还可以提供绝对年龄信息。有的碱性火山灰层具有找矿指示意义。煤中火山灰蚀变黏土岩夹矸中化学性质相对稳定的元素可以用来推断原始火山灰的组成,提供原始岩浆的成分以及区域地质历史演化方面的信息。     

华北聚煤区火山灰蚀变粘土岩夹矸的研究

本文论述了火山灰蚀为粘土岩夹矸的层位和分布，对结构构造作了系统分类及命名，首次在我国粘土岩夹矸中发现了较广泛分布的铵云母，还有伊利石和纳云母。成因矿物标型特征的研究为探索原始物质提供了可信的证据。     

中国西南地区晚二叠世含煤岩系中粘土岩夹矸(TONSTEINS)研究的新进展

自1961年首次在云南东部宜威组煤层中发现高岭石粘土岩夹矸(tonsteins)以来(戴恒贵),近20年间,对粘土岩夹矸相继进行了多方面的研究和广泛应用,取得了显著的地质效果。1981年,自滇东粘土岩夹矸中成功地分离、鉴定了组合比较单一的若干高温矿物(主要有β石英、锆英石、独居石、磷灰石等),并用SEM研究了这些矿物的形态学特征。通过与国外同类岩石比较,确认其为中、酸性火山灰同期沉积蚀变的产物。粘土岩夹矸独特的成因及其在大范围内的稳定性、可比性,引起了国内有关方面的关注,促进了其他地区对tonsteins的发现和应用.本文拟就近5年来所获得的新资料作一初步概括和介绍。一、区域地质概况及采样点分布本区包括四川少东南部、云南省东部及贵州省大部地区,总面积10万平方千米以上。区     

Trace element geochemistry of altered volcanic ash layers (tonsteins) in Late Permian coal-bearing formations of eastern Yunnan and western Guizhou Provinces, China

Trace element compositions were determined (by instrumental neutron activation analysis; INAA) in 30 samples of synsedimentary volcanic ash-derived tonsteins and detrital claystones from coal seams within the late Permian coal-bearing formation of eastern Yunnan and western Guizhou Provinces, China. The characteristics of trace-element geochemistry in the tonsteins can be distinguished from those of detrital claystones because of the former's unique volcanic-ash origin. The detrital claystones are characterized by their relatively high content of V, Ti, Sc, Cr, Co and Ni, relatively low content of Th and U, Th/U ratio, and small negative Eu anomaly (Eu/Eu* 0.63–0.93). Overall, these trace element characteristics are consistent with a mafic source similar to the composition of basalt rocks in the erosional region on the western edge of the study area. In contrast, the tonsteins are low in V, Ti, Sc, Cr, Co and Ni contents and have a high Th/U ratio with a distinct negative Eu anomaly (Eu/Eu* normally in the range of 0.2–0.4), consistent with a silicic magmatic source.Within the group of tonsteins, those from the lower section (P_2.1) of the coal-bearing formation are relatively high in Ti, Zr, Hf, Nb, Ta and rare earth elements (REE), as compared to those from the middle and upper sections (P_2.2+3). In trace-element discrimination diagrams (scatter plots) of Hf–Ta, Ti–Ta, Ti–V, Hf–Sc, Lu–Hf and Lu–Th, tonsteins from the P_2.1 horizon always fall in isolated distribution areas, separate from the tonsteins of the P_2.2+3 horizon. These results suggest that the source materials of tonsteins from the two separate horizons were probably derived from volcanic ash falls of two distinctly different natures. Based on a comparison of the concentrations and assemblages of trace elements between various magmatic rocks, the source materials of tonsteins from P_2.1 horizon were mostly composed of calc-alkalic, silica-poor volcanic ash (similar to rhyodacitic magma), whereas those from P_2.2+3 were apparently more siliceous and K-rich (rhyolitic magma). Thus, tonsteins from the two different horizons are characterized by unique geochemical properties, which remain constant over a wide lateral extent. Integration of trace-elemental compositions with mineralogical and textural observations makes possible the establishment of tonstein stratigraphy, thus, facilitating more precise and reliable coal-seam correlations.     

A geochemical and mineralogical investigation of some British and other European tonsteins

The volcanic origin of a number of major tonstein horizons has been established from mineralogical compositions and from trace elements that are quantitatively retained during diagenesis. Discriminant function analysis using the variables Ti/Al, Cr/Al, Zr/Al and Ni/Al allows the tonsteins to be classified according to original composition. Two main groups are recognized amongst the British tonsteins. Those formed from acid volcanic ash are comparable in composition with French and German tonsteins and a common source is postulated, whereas tonsteins formed from basic volcanic ash contain variable amounts of detrital sediment and are thought to originate from local eruptions. Possible lateral equivalents between tonstein horizons in Britain and elsewhere in Europe are suggested.     

滇东南晚二叠世铝土矿地球化学特征及物源分析

滇东南地区晚二叠世铝土矿属典型的喀斯特型铝土矿,矿体赋存于上二叠统吴家坪组(龙潭组),分析其地球化学特征对研究其物质来源具有重要意义。全岩分析显示铝土矿石成分以Al₂O₃、Fe₂O₃、SiO₂和TiO₂为主,其中Al₂O₃与Fe₂O₃ 、SiO₂具有较好的负相关关系。微量元素Cr、Zr、 Hf、Ta、Th、U和稀土元素在铝土矿矿化过程中不断富集,元素Zr-Hf、Nb-Ta之间具有明显的正相关关系。lgCr-lgNi图解、稳定元素比值(Zr/Hf)及稀土元素配分模式等地球化学特征说明峨眉山玄武岩为铝土矿的形成提供了主要的物质来源,同时下伏碳酸盐岩也提供了部分成矿物质。     

华南埃迪卡拉系底部钾质斑脱岩的岩石地球化学特征及其地质意义

我国华南扬子地台不同地区（湖北宜昌、安徽休宁）埃迪卡拉系底部的盖帽碳酸盐岩中均保存有浅色粘土岩层。岩石薄片和扫描电镜观察,以及X射线衍射分析表明,这些粘土岩层以伊利石和伊/蒙混层矿物为主,同时含有港湾状熔蚀石英、高温透长石及岩浆锆石等斑晶矿物。X荧光光谱仪和ICP-MS等离子质谱仪等地球化学元素分析表明,这些粘土岩层具有相似的元素组成和配分模式,以高K₂O、低TiO₂,富含Nb、Ta、Zr、Hf、Th、Y等亲石元素为特征,Al₂O₃/TiO₂、Zr/Hf 和Ti/Th 值均指示了酸性火山灰的性质,同时稀土元素配分模式与花岗岩较为相似。岩石学和地球化学特征表明,这些浅色粘土岩层是火山喷发事件形成的钾质斑脱岩。通过两处剖面的对比,可以将安徽休宁地区的钾质斑脱岩年龄限制在大约635Ma左右。岩浆判别图指示了这些钾质斑脱岩的原始岩浆为高钾亚碱性流纹英安岩;依据微量元素特征和构造环境判别图,初步认为原始岩浆形成于大陆弧环境。这些钾质斑脱岩在区域上的分布,表明我国扬子地台埃迪卡拉纪早期发生了广泛的火山活动,“雪球地球”事件的结束可能是导致这期以钾质斑脱岩为代表的火山喷发事件的诱因。     

Element mobility during alteration of silicic ash to kaolinite—a study of tonstein

A laterally persistent kaolinitic mudstone parting (tonstein) occurring in a Wyoming coal bed of Eocene age was sampled to estimate the compositional contrast with a probable silicic ash precursor, and to determine the compositional influence of leached ash on immediately adjacent coal. With the exception of Al, and possibly Ti, the tonstein is highly to moderately leached of major elements, relative to a range of compositions estimated for silicic ash of the region. In agreement with the behaviour of geochemically similar major elements, alkali trace elements (Rb, Cs) are highly leached, transition-series metals moderately leached, and Ga is residual. Additional immobile trace elements are Zr and Hf but some other trace elements that are considered relatively immobile during low-temperature alteration (Th, Ta, Nb, REE, Y) were apparently leached by the low-Eh, low-pH, organic-rich pore fluids of the coal-forming swamp. The migrational range of many of the leached elements is highly limited by the intimate association of tonstein with enclosing organic matter. Mixtures of coal + minor tonstein that occur within 20 mm of contacts are consistently enriched in some elements relative to either tonstein or nearby coal (U, Cu), or relative to calculated mixtures of tonstein and coal in their measured proportions (Th, Y, REE, Pb, Ba, V, Ti). Direct observations by fission-track radiography and electron microprobe indicate a preference of U and Fe for the organic component of mixtures. Metal fixation is probably by adsorption on insoluble organic matter (humic acids), or by precipitation as minor sulphides in these low-sulphur coals.     

西藏冈底斯带叶巴组火山岩地球化学及成因

叶巴组早侏罗世双峰式火山岩分布在拉萨、达孜至墨竹工卡之间, 岩性为浅变质玄武岩、玄武质熔结凝灰岩、英安岩、酸性凝灰岩及火山角砾岩等.火山岩SiO₂含量集中在41%~50.4%和64%~69%两个区间, 为钙碱性系列的玄武岩和英安岩2类.玄武岩的显著特征是TiO₂含量极低, 仅为0.66%~1.01%, 远低于大陆拉斑玄武岩.玄武岩的稀土总量∑REE=60.3~135μg/g, 英安岩的稀土总量∑REE=126.4~167.9μg/g.玄武岩和英安岩具有相似的稀土和微量元素特征, 两者均为轻稀土富集型, 分布特征相似, 轻、重稀土的分馏较明显, Eu异常均不显著; 均表现为LILE、LREE富集, HFS、HREE亏损的特点.玄武岩亏损Ti、Ta、Nb、Zr, Nb和Ta仅略负亏损, Nb*=0.54~1.17, 平均为0.84;英安岩亏损HFS中P、Ti, Ta、Nb略负异常, Nb*=0.74~1.06, 平均为0.86.玄武岩类的ε_Nd(t) =0.96~10.03、(87Sr/86Sr)_i=0.7043~0.7064, 英安岩的ε_Nd(t) =-1.42~1.08、(87Sr/86Sr)_i=0.7038~0.7049.从微量元素和同位素成分看, 玄武岩和英安岩浆起源于俯冲带之上的地幔楔不同程度的部分熔融, 源岩可能是亏损的尖晶石二辉橄榄岩.源区曾受到具地壳成分特征的流体不均匀交代.后期变质作用对岩石大离子亲石元素含量有影响.叶巴组双峰式火山岩形成于成熟岛弧后期的短暂拉张环境, 是印支期冈底斯岩浆弧演化的结果.      

Origin of the alkali tonsteins from southwest China: Implications for alkaline magmatism associated with the waning stages of the Emeishan Large Igneous Province

A unique type of Nb–Zr–REE–Ga-enriched alkali tonstein of pyroclastic origin occurs exclusively within the late Permian coal measures of southwest China. The alkali tonsteins are located within the lowest Xuanwei or Longtan formations of Wuchiapingian age, indicating that their age is later than the main episode of Emeishan Large Igneous Province (ELIP) magmatism. The alkali tonsteins have intermediate–felsic Al₂O₃/TiO₂ values (12.6–34.2, mean 22.0), light rare earth element-enriched chondrite-normalised patterns, negative δEu and incompatible element ratios similar to those of ELIP alkaline Nb–Ta-enriched syenites. All available evidence shows that the alkali tonsteins from southwest China originated from coeval ELIP alkaline magmatism. The enrichment of Nb–Zr–REE–Ga in alkali tonsteins is derived from the ELIP alkaline Nb–Ta-enriched volcanic ashes and may represent the last stage of mineralisation associated with the Emeishan mantle plume activity.     

内蒙古北山地区哈日阿玛岛弧花岗岩地球化学、年代学特征及其地质意义

哈日阿玛岛弧花岗岩出露于北山造山带公婆泉岛弧带内,与奥陶纪-志留纪公婆泉组弧火山岩伴生,包含闪长岩、石英闪长岩、斜长花岗岩、英云闪长岩等.LA-ICP-MS锆石U-Pb测年表明闪长岩、英云闪长岩分别就位于430.9±4.7 Ma和452.5±3.2 Ma,为晚奥陶世-早志留世.岩石地球化学分析结果显示,这些花岗岩属钙碱性、准铝质-弱过铝质I型花岗岩.岩石样品Mg#值界于44.58~51.85,Rb/Sr比值0.025~0.282,Nb/Ta比值0.068~14.01,Zr/Hf比值13.05~34.00.稀土元素总量（包含Y元素）为59.87×10^-6~118.56×10^-6,球粒陨石标准化稀土配分曲线均呈现明显的右倾型,轻稀土富集,（La/Yb）_N为3.11~23.86,Eu异常不明显.在微量元素原始地幔标准化图中,富集大离子亲石元素Rb、Ba、Th、U、K以及中等不相容元素Ce、La、Hf,亏损高场强元素Nb、Ta、P、Ti,具岛弧花岗岩特征,显示来自地壳的岩浆与来自深部的亏损地幔岩浆混溶.结合其他地质、地球化学证据,认为哈日阿玛花岗岩形成于岛弧环境,为红柳河-牛圈子-洗肠井古洋盆向北俯冲的结果,并最晚在晚奥陶世晚期已经开始俯冲,该洋盆闭合时限应晚于早志留世.     

华北克拉通重力梯度带两侧晚中生代火山岩地球化学特征对比研究及其对岩石圈减薄的时空制约

对华北克拉通重力梯度带东西两侧的河北承德袁家庄和内蒙古四子王旗白脑包出露的晚中生代火山岩进行了地球化
学对比研究。全岩主量元素、微量元素和Sr-Nd-Hf同位素数据表明,袁家庄火山岩和白脑包火山岩具有相似的地球化学特
征。这些火山岩轻、重稀土强烈分异,富集大离子亲石元素(如Rb,Ba,Th,U,K等),亏损高场强元素(如Nb,Ta,Zr,
Hf,Ti等);其同位素具有高(87Sr/86Sr)i,低εNd(t)和低εHf(t)的特征,因此认为袁家庄和白脑包火山岩具有相似的源区,即均来
源于被交代的古老岩石圈地幔的部分熔融。结合文献资料,作者认为,这些晚中生代火山岩是华北克拉通岩石圈减薄的直
接产物,中生代时期华北克拉通岩石圈的减薄不仅仅局限于重力梯度带以东地区,以西的部分地区也有发生。 chengxu       

东南沿海中生代火山岩带地球化学特征

中国东南沿海位于太平洋板块和欧亚板块的结合处,广泛分布着中生代火山岩,并伴随有大规模的成矿作用。酸性火山岩占绝对优势,基性中性火山岩仅零星出露。酸性和中性火山岩为一套富碱、富钾、富铝、低钛的高钾钙碱性系列,基性火山岩为一套富硅贫碱的高钾和中钾钙碱性系列。从基性到酸性火山岩稀土分馏和铕的负异常逐渐加剧。基性火山岩贫Nb、Zr、Y,弱富集Ba、Hf、Th、Ce。中性火山岩和酸性火山岩贫Ba、Ti、P、Nb、Zr、Ta、Sr,强烈富集Pb。通过主量、微量和稀土元素的研究认为,基性火山岩和酸性火山岩为独立的岩浆起源,在中生代,东南沿海广泛存在着玄武岩的底侵作用,给下地壳提供了大量的热源,从而诱发了下地壳重熔,形成了大量的酸性火山岩。中性火山岩由酸性和基性岩浆混合形成,其地球化学特征主要受酸性岩浆的制约。