Triassic palaeosols in the upper narrabeen group of New South Wales

Detailed study of palaeosols in the sea cliffs between Long Reef and Palm Beach, north of Sydney, has given a much clearer idea of the environment and climate of the area during the late Scythian to early Anisian portion of Triassic time.

At the base of the exposed succession, kaolinitic clayey soils with red B horizons were formed on volcanogenic sediments derived from the old Gerringong volcanic ridge to the east. The red Bald Hill Claystone consists largely of soil material, both in place and resorted. These were grey‐brown podzolic soils (ferrods) formed on well‐drained sites under coniferous forest. Humic gleys (fibrists) within the overlying Garie Formation were probably lowland catenary equivalents formed under Dicroidium, Voltziopsis, and equisetalean swamp woodland.

These soils were drowned by the relative rise of the Narrabeen lagoonal complex and the concomitant southward growth of sediments of the Gosford Delta. These sediments formed the lower Newport Formation, of clean quartz‐lithic sandstone and grey kaolinite‐illite shale, derived from an extensive source land to the north and west. The most widespread soils in the delta were gleyed podzolic soils (aquods) under Dicroidium heath. Younger soils of a similar type (alluvial soils or aquents) also supported Dicroidium heath in low‐lying areas and Pleuromeia meadows in interdistributary bays. On slightly more elevated areas a more oxidized gleyed podzolic soil (ochrept) developed. On clayey levees, grey clay soils (fluvents) formed under a Dicroidium flora locally dominated by Taeniopteris lentriculiformis.

Few palaeosols are preserved in the upper Newport Formation and Hawkesbury Sandstone because of the more frequent channel reworking of the floodplain during their deposition.

The dominance of podzols is compatible with a cool temperate climate.     

The Reid's Mistake Formation at Swansea Head,New South Wales

The Reid's Mistake Formation represents the stratigraphic interval that separates the Lower and Upper Pilot Coals within the Boolaroo Sub‐Group of the Newcastle Coal Measures. At Swansea Head it consists mainly of intercalated cherts and claystones with minor amounts of sandstone. The cherts, which frequently have a vitroclastic texture, are composed of chalcedony and analcime with or without feldspars and clay whereas the claystones consist of chalcedony and mixtures of mixed‐layer clay minerals. The intergradation between these rock types indicates that the entire sequence was derived from a common source, either acid volcanics of the New England fold belt or, more likely, contemporaneous ash showers. The detritus apparently accumulated in a flood basin environment where the climate was arid giving rise to saline conditions and the breakdown of the volcanic materials to clay minerals and chalcedony. During protracted periods of desiccation however, sodium ions were concentrated and the pH rose accordingly, sufficient to promote conversion of the clay minerals in the uppermost layers to analcime.     

Kaolinite clayrocks in the Triassic Banks Wall sandstone of the western blue mountains,New South Wales

Fine‐grained and coarsely oolitic kaolinite clayrocks that closely resemble in composition, texture, and structure those of the Garie Formation in the southern part of the Sydney Basin are described from the Western Blue Mountains of New South Wales. The kaolinite clayrocks form part of a fine‐grained unit, here designated the Docker Head Claystone Member. It is concluded that the kaolinite clayrocks are the equivalent of the Garie Formation and represent fluviatile accumulations of detritus derived from the same highly weathered source rocks that gave rise to the Garie Formation.     

The enigma of fine-grained alluvial basin fills: the Permo-Triassic (Cumbrian Coastal and Sherwood Sandstone Groups) of the Solway Basin,NW England and SW Scotland)

The late Permian to Triassic sediments of the Solway Basin consist of a layer-cake succession of mature, predominantly fine-grained red clastics laid down in semi-arid alluvial plain to arid sabkha and saline marginal marine or lacustrine environments. The Cumbrian Coastal Group consists of Basal Clastics and Eden Shales. The Basal Clastics are thin regolith deposits resting unconformably on all-underlying units and are composed of mixtures of angular local gravel and far-transported fine to very fine-grained sands deposited as basal lag. The Eden Shales are predominantly gypsiferous red silty mudstones, with thin very fine-grained sandstone beds, and with thick marine gypsum beds at the base, deposited at a saline lake margin. The overlying Triassic Sherwood Sandstone Group consists of the Annan and Kirklinton Sandstones. The Annan Sandstones are predominantly thick-bedded, multi-storied, fine-grained mature red quartz sandstones in which coarse sand is practically absent despite channels with clay pebbles up to 30 cm in diameter. The overlying, predominantly aeolian, Kirklinton Sandstones consist of festoon cross-bedded and parallel-laminated fine-grained sandstones, almost identical to the Annan Sandstones except that mica and clay are absent. The Stanwix Shales, located above, consist of interbedded red, blue and green mudstones, siltstones, and thin very fine-grained sandstones, with gypsum layers. Although the entire succession can plausibly be interpreted as deposited in a large desert basin opening into a hypersaline marine or lacustrine embayment to the southwest, the uniformly fine-grained nature of the succession is unusual, as is the absence of paleosols, and body and trace fossils. There is almost no coarse sand even in the river channel units, and it seems likely that the basin was not only extremely arid but supplied predominantly by wind rather than water.     

Study on the physical disintegration characteristics of Subang claystone subjected to a modified slaking index test

Some instability problems were found on natural or engineered slopes mostly lying on Subang claystones. The instability problems included excessive erosion, slumps and rock falls. The field performance surveys of the problems suggested that the claystones physically weather rapidly so that the rock properties they exhibit during excavation often change to properties with a more characteristic of soil. Such a phenomenon is generally known as a slaking process. In order to gain better understanding about the slaking of Subang claystones, a series of experimental laboratory studies were carried out involving a modified slaking index test. Claystone samples used in this study were obtained from their exposures along the Northern West Java area of Indonesia. Petrographic analysis was correspondingly performed to identify mineral and texture/fabric, and in turn, to determine the inherent factors of the rocks which might affect the slaking process. The stssudy results indicated that the claystones were characterized by high to very high slaking properties having a maximum slaking index (I_s) of 57.4% and a mean I_s of 43.8%. Major dispersion slaking on sample surfaces and high cracking in response to excessive swelling were recognized as main slaking modes within the claystones. All samples lose progressively less material through the five wet–dry cycles of a slaking index test, indicating a decelerated slaking rate. It was evident that the main inherent factors controlling the slaking process were expandable clay mineral smectite, non-clay mineral pyrite and soluble mineral calcite. Moreover, a quite important of inherent bonding material and stress release energy in the slaking characteristics of the claystones was revealed by a closure phase of an initial hairline crack during unloading.     

Mineralogy and chemical composition of the clay fraction of Neogene shales from the Surma Group in the Bengal basin,Bangladesh

Mineralogical and chemical investigations (<2μm clay separates) of shale samples from the Neogene-age Surma Group obtained from four wells (Habiganj-11, Shahbazpur-1, Titas-11, Titas-15) in the Bengal basin, Bangladesh, were carried out in order to reveal the clay mineral composition as reservoir exploration and exploitation requires a good understanding of the clay minerals. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-Ray fluorescence spectrometry (XRF). Mineralogically, the sub-surface Surma Group shales comprise predominantly quartz, plagioclase, illite, chlorite, kaolinite, with lesser amounts of K-feldspar, dolomite and smectite, and minor to trace amounts of calcite, siderite and pyrite. The chemical composition of the <2 μm clay separates also suggests an illite and chlorite-rich composition. With increasing burial depth, the Surma Group shales are enriched in illite. The gradual decreasing of the smectite clays with depth and ultimate disappearance at greater depths (≥ 3000 m) may have been responsible for the presence of the diagenetic illite. Based on the mineralogical composition it is most likely that the illite-chlorite associations together with quartz and feldspar were predominantly detrital in origin and thus reflect the presence of a rapidly-rising source terrain not subjected to intense weathering.     

Kaolinite Claystones associated with the Wongawilli seam in the southern part of the Sydney basin

Kaolinite claystones that are similar in structure, texture and composition to the kaolin tonsteins of Western Europe, and to some of the flint clays of North America, are associated with the Wongawilli Seam in the southern part of the Sydney Basin, where they form thin persistent bands within the coal and somewhat thicker deposits immediately overlying the seam. The thin bands within the coal are fine grained and consist of brecciated to pelletal clasts composed of well‐ordered kaolinite set in a matrix of similar composition. The thicker deposits overlying the seam are much coarser grained and appear restricted in occurrence to the basin margins. They contain a predominance of oolites with kaolinite clasts bonded by a relatively sparse matrix and in places, remarkable ‘outgrowths’ of vermicular kaolinite. The origin of the deposits is discussed, and it is concluded that most of the unusual features of these claystones can be ascribed to a fluvial environment.     

准噶尔盆地腹部陆梁油田储层特征

陆梁油田油气主要分布于白垩系吐谷鲁群、侏罗系的西山窑组和头屯河组；储层岩性主要为中细砂岩，砂岩分选性好-中等，结构成熟度较低。白垩系吐谷鲁群和侏罗系储集岩的孔隙组合类型主要为粒间孔、粒间孔 高岭石晶间孔，少量粒内溶孔 高岭石晶问孔。影响储层储集性能的主要因素：(1)沉积环境．(2)古气候，(3)成岩作用，(4)构造运动，(5)粘土矿物。     

加积型网纹红土网纹化机制及形成环境

选取九江地区JL剖面网纹层段典型样品,针对红基质与白网纹的物质组成及理化性质展开异同分析,在此基础上探讨网纹红土形成环境。初步得到以下结论:1)红基质与白网纹的粒度组成、元素组成、风化特征基本一致,但铁元素有显著差异,"网纹"并非原生构造,不是岩性差异及差异风化的产物,而是同源物质经历化学风化过程中元素分馏的结果。2)地球化学分析、磁学分析和粘粒级矿物组成分析一致表明,白网纹与红基质在铁含量、铁氧化物形态、铁矿物类型方面存在明显差异。白网纹与红基质相比,全铁含量(4.30%)低于红基质(8.63%);Fe^3+/Fe^2+比值(40.66)低于红基质(90.95);游离铁量及游离度(7.01 g/kg,32.96%)低于红基质(76.21 g/kg,77.52%);铁活化度和晶胶率(25.31%,37.77%)高于红基质(8.77%,9.69%);赤铁矿和针铁矿含量极少,这充分表明白网纹局部存在明显的铁淋失。3)白网纹局部脱色机制主要受控于赤铁矿及其转化,红基质主导矿物为赤铁矿,并含有一定的磁赤铁矿和针铁矿,而白网纹则不含磁赤铁矿,赤铁矿含量也极少。此外高岭石含量也是影响色浅的因素之一,白网纹蛭石、高岭石含量(20.24%和45.08%)均略高于红基质(11.45%和41.82%)。4)赤铁矿的富集、局部铁迁移的特点,整体上指示高温、中强程度化学风化和季节性多水的环境。这在一定程度上暗示网纹红土形成时期气候高温多雨,且季节性反差增强。     

Dryland continental mudstones: Deciphering environmental changes in problematic mudstones from the Upper Triassic (Carnian to Norian) Mercia Mudstone Group,south‐west Britain

The sedimentology, petrography and mineralogy of the seemingly monotonous Late Triassic Mercia Mudstone Group across the Severn Basin and Bristol Channel region reveals a bipartite division of mudrock facies above and below the Arden Sandstone Formation. Frequently cryptic sedimentary and pedogenic features reveal diverse alluvial, aeolian, playa‐lacustrine and pedogenic processes operating at different times, locations and scales probably in response to climate change. The current study found no evidence of significant marine influence in either of the two mudrock facies associations that are described here. Blocky claystones dominate the lower Mercia Mudstone Group (Sidmouth Mudstone Formation), with pedogenic features such as slickensides, mottling, tubules and carbonate/sulphate nodules common and widespread. The claystones are of alluvial/lacustrine origin with subordinate sheet sandstones, themselves overprinted by pedogenic features, reflecting occasional high intensity rainfall events. These facies reflect a seasonal (wet/dry) semi‐arid climate favouring development of transformed/neoformed (smectite‐rich) clay minerals of intrabasinal origin. Massive to weakly stratified silty mudstones dominate the upper Mercia Mudstone Group (Branscombe Mudstone Formation). Commonly conchoidally weathered, locally gypsiferous, but with distinct sedimentary structures scarce, they alternate with subordinate blue‐grey laminated silty mudstones. Together they reflect fluctuating hydrological conditions within extensive saline mudflats and ephemeral playa lakes, with laminated facies deposited under subaqueous conditions during more humid phases whereas massive mudstones reflect modification through interstitial growth/dissolution of sulphates and deflation of surface sediments during drier episodes. These facies reflect increased aridity during deposition of the upper Mercia Mudstone Group compared with the lower Mercia Mudstone Group, favouring development of detrital/transformed (illite–chlorite) clay minerals of extrabasinal origin. The described facies associations and the sedimentary fabrics and structures that characterize them, occur widely in the Mercia Mudstone Group across the United Kingdom and comparable facies associations may be anticipated in other fine‐grained red bed successions. Recognition of these facies may aid palaeoenvironmental interpretation of such sequences on Earth and, potentially, on Mars also.     

Quartz and zircon decoupling in sandstone: Petrography and quartz cathodoluminescence of the Early Triassic continental Buntsandstein Group in Germany

This study illustrates how decoupling of quartz and zircon can be used advantageously in provenance research. Thirty‐eight fine‐grained to coarse‐grained arkose samples of the Early Triassic intracontinental Buntsandstein Group from the Central European Basin in Germany were analysed for their petrography and 1200 grains in 23 of these for their detrital quartz cathodoluminescence characteristics. The samples represent the Hessian and Thuringian sub‐basins and the Eichsfeld–Altmark Swell separating them. The Hessian Sub‐basin includes more metamorphic lithoclasts with a larger content of plutonic grains than are found further east in the Thuringian Sub‐basin. More than 90% of the detrital quartz from the eastern Thuringian Sub‐basin produce medium to bright blue cathodoluminescence colours and corresponding spectra that are typical for igneous or high‐temperature metamorphic origin. Differently, the quartz from the Hessian Sub‐basin mostly luminesces brown and dark to medium blue, typical for a low‐temperature metamorphic origin. Quartz from the Eichsfeld–Altmark Swell and the western Thuringian Sub‐basin is a mixture between these origins. The quartz indicates different catchments for the sub‐basins, possibly the Bohemian Massif and the Massif Central, with converging transport routes on and close to the eastern fringe of the swell. Taking published zircon data from the same samples into account, light mineral‐zircon grain‐size shifts are up to 2 Φ units. That can be explained by mineral decoupling due to different transport modes for quartz and zircon and different zircon‐size availability in the source areas, exaggerated by combined aqueous–aeolian transport, as well as sample preparation‐induced sorting. This study concludes that submerged highs significantly can influence continental sediment transport. Hence, vast, flat continental areas with submerged morphological highs and a seemingly straightforward transportation pattern may be more complex than expected. The results also illustrate that analysis of detritus that has been affected by different dominating transport modes, and further sorting during sampling and preparation can reveal additional source information.     

Clay record of climate change since the mid‐Pleistocene in Jiujiang,south China

To obtain a better understanding of climate change in south China in the Quaternary, a clay mineralogical study was undertaken on the red earth profile at Jiujiang, using X‐ray diffraction (XRD) and particle‐size distribution analysis methods. The XRD results showed that the clay minerals of the Jiujiang red earth were mainly mixed‐layer illite–smectite (I/S), illite, kaolinite and vermiculite, with trace amounts of mixed‐layer kaolinite–smectite (K/S). Changes in clay mineral composition displayed a trend of three‐stage evolution. The higher mixed‐layer I/S clays and kaolinite contents in the lower portion suggest extremely warm and humid climates over the period c. 700 to c. 350 ka ago. A gradual decrease in I/S clays and kaolinite reveals a gradual climate change from warm/humid to cool/dry during the period c. 350 to c. 130 ka ago. The higher illite and vermiculite contents indicate a relatively cool and dry climate during the period since c. 130 ka ago. The particle‐size distribution pattern of the upper section was similar to that of the Xiashu loess, while that of the middle to lower section was similar to those of fluvially reworked red earth. A rapid increase in the abundance of large grain‐size components at 2.6 m depth indicates an intensification of the winter monsoon and a cool and dry climate during the period, in good agreement with results from the clay mineral composition and homogeneous structure. The red earth sequences in south China could probably be used to test the response of tropical to subtropical regions to global climate changes.     

翡翠的白色次生变化产物初步研究

翡翠的白色次生物通常与褐色次生物共存,说明两者形成于相同的表生环境,即氧化环境。白色次生物既可以白沙皮的形式出现,也可以白色絮状物或白斑的形式存在于翡翠的裂隙及其附近颗粒之间。白色次生物在翡翠中以细小粘土矿物等的集合体形式分布于硬玉颗粒的边缘和裂隙中,以交代结构为主,充填结构为辅。结合红外光谱分析和电子探针测试可知,翡翠中的白色次生变化产物以高岭石或高岭石质为主,另外含有不常见的副钡长石和氟硅钙钠石,说明白色次生物的矿物组成较为复杂。     

Clay Minerals in an Active Hydrothermal Field at Iheya‐North‐Knoll,Okinawa Trough

Iheya‐North‐Knoll is one of the small knolls covered with thick sediments in the Okinawa Trough back‐arc basin. At the east slope of Iheya‐North‐Knoll, nine hydrothermal vents with sulfide mounds are present. The Integrated Ocean Drilling Program (IODP) Expedition 331 studied Iheya‐North‐Knoll in September 2010. The expedition provided us with the opportunity to study clay minerals in deep sediments in Iheya‐North‐Knoll. To reveal characteristics of clay minerals in the deep sediments, samples from the drilling cores at three sites close to the most active hydrothermal vent were analyzed by X‐ray diffraction, scanning electron microscope and transmission electron microscope. The sediments are classified into Layer 0 (shallow), Layer 1 (deep), Layer 2 (deeper) and Layer 3 (deepest) on the basis of the assemblage of clay minerals. Layer 0 contains no clay minerals. Layer 1 contains smectite, kaolinite and illite/smectite mixed‐layer mineral. Layer 2 contains chlorite, corrensite and chlorite/smectite mixed‐layer mineral. Layer 3 is grouped into three sub‐layers, 3A, 3B and 3C; Sub‐layer 3A contains chlorite and illite/smectite mixed‐layer mineral, sub‐layer 3B contains chlorite/smectite and illite/smectite mixed‐layer minerals, and sub‐layer 3C contains chlorite and illite. Large amounts of di‐octahedral clay minerals such as smectite, kaolinite, illite and illite/smectite mixed‐layer mineral are found in Iheya‐North‐Knoll, which is rarely observed in hydrothermal fields in mid‐ocean ridges. Tri‐octahedral clay minerals such as chlorite, corrensite and chlorite/smectite mixed‐layer mineral in Iheya‐North‐Knoll have low Fe/(Fe + Mg) ratios compared with those in mid‐ocean ridges. In conclusion, the characteristics of clay minerals in Iheya‐North‐Knoll differ from those in mid‐ocean ridges; di‐octahedral clay minerals and Fe‐poor tri‐octahedral clay minerals occur in Iheya‐North‐Knoll but not in mid‐ocean ridges.     

Diagenetic crystallization and oxidation of siderite in red bed (Buntsandstein) sediments from the Central Iberian Chain,Spain

Compactional deformation facilitated replacement of dolomite and calcite by siderite and its subsequent oxidation in carbonate cemented red beds of the Triassic Buntsandstein in the Iberian Chain. Locally, the sedimentary clasts were cemented by carbonate that was derived from dissolution of locally exposed dolomite in the basement. Microstructures indicate that during sedimentation of the rocks, oxidizing conditions prevailed in the sediments and the basement was reddened by impregnation of hematite. Reducing conditions prevailed during deformation of the sediments. Ferric iron was reduced to Fe²⁺, that reacted with deformed dolomite and calcite cement to produce fine grained siderite. At a later stage, siderite crystallites were (partly) oxidized to form a secondary phase of brown ferric oxide (goethite). Locally, goethite transformed to fine grained hematite that caused secondary reddening of the sediments. The reactions are associated with a combined volume loss of the solid phases of c. 50% per reaction mol; this was accommodated by the formation of pores. Oxidation of siderite was associated with release of CO₂; localized dissolution took place of feldspar and concurrently growth of kaolinite occurred by acidifying condition during release of CO₂. The relation of redox reactions and deformation is comparable to those in red bed conglomerates in the region. Reductive dissolution occurred at sites of stress concentration, particularly at contact points of pebbles. Late stage precipitation of ferric oxides and pyrolusite took place at oxidizing conditions in association with uplift.     

滇西北红粘土的工程地质特性及其灾害效应

在野外地质调查的基础上,结合室内土工试验,系统分析了滇西北红粘土的物质组成、物性特征和工程地质特性,并以此为基础探讨了其地质灾害效应。研究结果表明：滇西北红粘土粒度组成主要以粘粒为主,粘土矿物成分比较复杂,在丽江以南其矿物成分主要以高岭石（K）为主,在丽江以北则以伊利石/蒙脱石（I/S）混层矿物为主。此外,滇西北红粘土具有含水量高、重度低、塑性高、膨胀性弱等物性特征,在天然状态下比较稳定,但是随着含水量的增加其土体强度大大降低,易引发滑坡、水土流失等地质灾害。     

The crystallographic fabric and texture of siderite in concretions: implications for siderite nucleation and growth processes

The crystallographic fabric of siderite in siderite concretions has been determined for upper Carboniferous (Westphalian‐A) non‐marine concretions and lower Jurassic (Pliensbachian) marine concretions. Compositional zoning indicates that individual siderite crystals grew over a period of changing pore water chemistry, consistent with the concretions being initially a diffuse patch of cement, which grew progressively. The siderite crystallographic fabric was analysed using the anisotropy of magnetic susceptibility, which is carried by paramagnetic siderite. The siderite concretions from marine and non‐marine formations exhibit differences in fabric style, although both display increases in the degree of preferred siderite c‐axis orientation towards the concretion margins. The Westphalian non‐marine siderites show a preferred orientation of siderite c‐axes in the bedding plane, whereas the Pliensbachian marine siderites have a preferred orientation of c‐axes perpendicular to the bedding. In addition, a single marine concretion shows evidence of earlier formed, inclined girdle‐type fabrics, which are intergrown with later formed vertical c‐axis siderite fabrics. The marine and non‐marine fabrics are both apparently controlled by substrate processes at the site of nucleation, which was probably clay mineral surfaces. Siderite nucleation processes on the substrate were most probably controlled by the (bio?) chemistry of the pore waters, which altered the morphology and crystallographic orientation of the forming carbonate. The preferred crystallographic orientation of siderite results from the orientation of the nucleation substrate. Fabric changes across the concretions partially mimic the progressive compaction‐induced alignment of the clay substrates, while the concretion grew during burial.     

论晋北石炭二叠系紫色高岭石粘土的成因

晋北地区石炭二叠系煤层中与四号及九号煤伴生的含有机质的软质耐火粘土,即高岭石粘上,俗称紫矸或紫木节。对紫矸的成因过去有两种看法:(1)原生沉积的;(2)后期风化残积“由煤变来的”。笔者认为除这两个因素同时存在外,还与成岩后生作用中有机酸的淋滤和高岭石的重结晶、有序化等有关,尤其是后期风化表生作用使有机质氧化淋滤去SiO_2形成一水软铝石、褪色、溶蚀多孔、质地疏松,形成今日所见紫色高岭石粘土。     

Climatic control on clay mineral formation: Evidence from weathering profiles developed on either side of the Western Ghats

Many physico-chemical variables like rock-type, climate, topography and exposure age affect weathering environments. In the present study, an attempt is made to understand how the nature of clay minerals formed due to weathering differs in tropical regions receiving high and low rainfall. Clay mineralogy of weathering profiles in west coast of India, which receives about 3 m rainfall through two monsoons and those from the inland rain-shadow zones (<200 cm rainfall) are studied using X-ray diffraction technique. In the west coast, 1:1 clays (kaolinite) and Fe—Al oxides (gibbsite/goethite) are dominant clay minerals in the weathering profiles while 2:1 clay minerals are absent or found only in trace amounts. Weathering profiles in the rain shadow region have more complex clay mineralogy and are dominated by 2:1 clays and kaolinite. Fe—Al oxides are either less or absent in clay fraction. The kaolinite—smectite interstratified mineral in Banasandra profiles are formed due to transformation of smectites to kaolinite, which is indicative of a humid paleoclimate. In tropical regions receiving high rainfall the clay mineral assemblage remains the same irrespective of the parent rock type. Rainfall and availability of water apart from temperature, are the most important factors that determine kinetics of chemical weathering. Mineral alteration reactions proceed through different pathways in water rich and water poor environments.     

Enrichment of lithium in the claystone coal gangue from the Malan mine,Xishan Coalfield,Shanxi Province,Northern China

In China, the lack of Li resources is in stark contrast to a large amount of coal gangue produced by coal mining. To determine the distribution patterns and existing status of lithium (Li) elements in the coal gangue, the mineralogical and geochemical analysis were formed on samples of the roof, floor, and parting of No. 02, 2, 8, and 9 coal seams, being mined in Malan mine, Xishan coalfield, Shanxi Province. The results show that the lithium content in this study area is relatively enriched, the highest content is 499 μg/g in sample 02-G, and the average content is 109.8 μg/g, which is two times that of the world average value of claystone (45 μg/g). XRD analysis shows that the mineral composition of parting samples is mainly clay mineral kaolinite, while the coal seam roof and floor samples also include quartz and some iron-bearing minerals, such as pyrite and siderite. Likewise, possible lithium-rich mineral phases and possible lithium-rich factors were investigated in this paper. A comprehensive clay separation experiment and correlation analysis between lithium and major elements indicate that lithium is likely to exist in the clay mineral kaolinite in the study area. It is also found that the content of Li adsorbed by cryptocrystalline kaolinite is generally higher than that of crystalline kaolinite. According to the mechanism of Li⁺ adsorption in clay minerals, the higher lithium content of cryptocrystalline kaolinite is due to its larger specific surface area, which can adsorb more lithium on the surface.