内蒙古西乌珠穆沁旗阿木山组海绿石的特征及其沉积环境

在内蒙古西乌珠穆沁旗晚石炭世—早二叠世阿木山组第三段泥晶灰岩中发现有海绿石。对海绿石的微观特征分析表明,阿木山组海绿石呈团粒状结构,同时呈胶体产出于方解石周边,显示了原生海绿石的基本特点。电子探针的组分分析表明,阿木山组中的海绿石为高成熟度的海绿石。通过对不同地区和不同环境下海绿石的组分特征分析,建立了一种海绿石沉积的理想模式,同时揭示了阿木山组第三段海绿石化作用是在含氧量不够充分的弱还原状态下的正常浅海中进行的。本区阿木山组的下碎屑岩段和上灰岩段是在海水两进两退环境下的沉积,阿木山组灰岩中发现的海绿石则有可能代表了一个海进的开始。本区海绿石的发现及研究,对于进一步研究该区层序地层特征、地层格架及区域地层对比具有重要意义。     

滇西南澜沧地区南段组砂岩粒度特征与意义

近期完成的1∶50000区域地质调查中,在澜沧地区南段组(DCn)三个岩性段不同类型砂岩中采集了27件粒度分析样品,结果表明：沉积环境分属三角洲、海岸带、大陆斜坡浊流环境,主要为海进层序。三角洲环境砂岩具三角洲上前滨、河流中之边滩、支流河口砂坝特征。海岸带砂岩具三角洲支流河道中之主河道、邻近天然堤浅水支流河道特征。大陆斜坡浊流环境砂岩与浊流沉积中之哈德孙海下扇相似,更好地反映了古特提斯昌宁-孟连盆地形成与演化历史。     

藏西南札达白垩纪海绿石的形成机制及控制因素

西藏札达地区夏拉剖面海绿石砂岩之下的地层中含有少量处于不同演化阶段的海绿石质物质。为了更好的理解海绿石化过程、查明海绿石的形成机制和控制因素,本文利用岩相学和扫描电镜(SEM)以及电子探针微分析(EPMA)等技术,对其中处于不同演化阶段的海绿石进行了系统的矿物学研究。分析表明,海绿石呈微晶片状集合体形态,具明显的交代特征。海绿石化过程主要表现为交代碱性长石或岩屑中的富钾组分,这种交代反应为溶解-沉淀-重结晶机制控制的界面迁移反应。交代形成的海绿石继承了原矿物或岩屑颗粒的外形,表明其形成于很弱的水动力学条件。交代过程受沉积物供应速率、母源物质的溶解速率和反应界面附近的氧化还原条件控制。铁铝蛇纹石的大量存在表明当时的环境主要为一种还原环境,而海绿石则形成于局部的亚氧化(sub-oxic)环境中。砂岩中不同演化程度的海绿石都表现出富钾贫铁的特征,表明交代碱性长石(或钾长石)或岩屑中的富钾组分的海绿石化过程不同于前人提出的新生理论和两阶段模式。元素的富集是通过与交代作用同时进行的重结晶作用完成的,该过程不需要前人提及的后期单独的钾富集的过程,并区别于交代贫钾矿物的过程。     

新疆哈拉奇地区古生代沉积相及沉积环境

为进一步研究哈拉奇地区古生代沉积地质,根据研究区的岩性、岩相建造、古生物化石、沉积演化、沉积构造等基本数据,采用野外观察与室内研究相结合的方法,对古生代的沉积环境进行了分析。结果表明,该区古生代岩性组合依次为灰岩-砂岩-灰岩-白云质灰岩,反映了海退-海进-海退的沉积序列。     

云南乌蒙山区中下三叠统层序地层与沉积相研究——以彝良地区为例

通过对云南乌蒙山区彝良地区中下三叠统6条野外地质剖面测量及500余片岩石薄片镜下观察,结合区域构造特征,将该地区中下三叠统划分为6个三级层序。岩石类型主要为泥铁质粉砂岩、细粒长石岩屑砂岩、含钙质泥质粉砂岩、细粒岩屑砂岩、钙质胶结细粒岩屑砂岩、含生物屑泥晶灰岩、泥灰岩、泥灰岩-含海绿石铁质生物屑亮晶砂屑灰岩、微晶灰岩-泥晶灰岩-含海绿石泥晶砂屑灰岩、亮晶鲕粒灰岩、含粉砂质泥质微晶灰岩、微晶灰岩等。结合沉积物的结构特征、组分及其组合特征,认为彝良地区中下三叠统的沉积相主要为海岸和碳酸盐岩开阔台地相。     

藏西南札达地区白垩系海绿石的成因及意义探讨

<正>海绿石是含水、富铁的云母类矿物,钾含量一般高于6%。通常认为,海绿石形成于海底沉积物与水的接触界面附近,与低的沉积物供应速率有关(Odinetal.,1981;Amorosi,1997;Huggettetal.,2010)。含海绿石地层以形成层序地层学中的凝缩层为特征,被认为与海进序列有关(Van     

华北中南部地区石盒子群沉积环境研究新进展

华北地区石盒子群的沉积环境长期以来一致存在较大的争议,大多数研究者认为该时期完全为陆相沉积,也有一些学者在该地层中发现了海相沉积物。本文着重对鲁西、河南等地区石盒子群的奎山砂岩进行岩石学、沉积学、地球化学等指标研究,在该砂岩中发现了冲洗交错层理,并在该砂岩中上部发现了海绿石的存在。通过详细分析奎山砂岩中海绿石的显微特征、元素地球化学特征,并进行比较研究发现,华北地区奎山砂岩中海绿石的化学成分、含量与国内外古代的海相、过渡相海绿石基本一致,推断其为滨浅海富氧环境的产物。华北地区奎山砂岩中发育的沉积构造和所含海绿石的元素地球化学特征,揭示了该时期曾发生过海侵,反映了石盒子群沉积期沉积环境的复杂性。华北地区石盒子群奎山砂岩中上部海相沉积环境的确定,可能改变华北盆地二叠纪以来单纯为陆相沉积的认识,这为精细研究华北地区中晚二叠世的盆地格局、充填演化及恢复古地理景观,提供了新的思路和重要依据。     

河北秦皇岛柳江盆地新元古界海绿石矿物特征与形成环境研究——以鸡冠山长龙山组为例

在河北秦皇岛柳江盆地鸡冠山新元古界青白口系长龙山组石英砂岩中发现有海绿石.对海绿石宏观特征分析表明,砂岩中海绿石的含量随着颗粒直径的减小而增大,含量大多为5％～20％.综合野外露头勘验、岩石薄片显微镜下观察和样品扫描电镜观察,对海绿石微观特征分析表明,长龙山组大多为晕边状和颗粒状,也可见其他形态,分析认为该区海绿石属于...     

中元古代晚期浅海高能沉积环境中的海绿石:以天津蓟县剖面铁岭组为例

海绿石是一种富钾、富铁的含水层状铝硅酸盐矿物,在沉积学领域常被作为一种普遍的指相矿物。多年研究的结果表明,现代海绿石主要形成在慢速、弱还原的较深水环境中,而且还可以作为"凝缩段"的识别标志之一。天津蓟县剖面中元古界铁岭组第二段灰岩中的海绿石,产在高能叠层石岩礁之中,主要以胶体形式富集在叠层石和均一石的边界上,代表较为典型的原地海绿石;较高的氧化钾含量(大于8%)而显示出高成熟海绿石的特点。很明显,铁岭组二段灰岩中的原地高成熟海绿石,不但不能作为"凝缩段"的识别标志,而且也不是长时间地层间断的产物。由于形成在正常高能浅海环境,而且处于中元古代末期,与现代沉积中的海绿石存在较大的差异,可能代表了中元古代末期的正常浅海还处于含氧量不够充分的弱还原状态,最终使铁岭组灰岩中的海绿石成为前寒武纪海绿石产出的一个典型代表,也间接的表明了在漫长的地质历史演变过程中海绿石产出的多样性特点。     

奥连特盆地白垩系海绿石成因类型及沉积地质意义

厄瓜多尔奥连特盆地白垩系Napo组UT段发育一套分布广泛的富含海绿石的硅质碎屑岩,针对海绿石的岩相、矿物学、地球化学及时空属性进行分析,可以揭示海绿石的组分、成熟度、形成及成因类型,结合地质约束有助于理解其形成的沉积地质意义.利用偏光显微镜、X射线衍射、电子探针及Qemscan对海绿石矿物的岩相、矿物组成和主量元素进行系统地分析.暗绿色、呈弯曲玫瑰花状的海绿石具有高的K₂O含量(平均值为8%,质量百分比),是形成于海相低沉积速率环境的高演化成熟型海绿石云母矿物或狭义范畴的海绿石.化学组分和时空属性揭示研究层段的海绿石经历了一定程度风暴流和/或潮汐流作用的搬运改造,属于层内准原地海绿石.UT段海绿石含量向上的增大趋势和成熟度的变化,以及横向上从盆地东部斜坡区埋深2~3 km到西部盆缘露头区相距约120 km的海绿石在形态和化学成分上具有相似性,指示其主要是层内准原地海绿石的特点.UT段垂向上海绿石含量增大的趋势同时反映外陆棚物源区原地海绿石向岸方向的短距离迁移,反映了相对海平面持续上升的海进过程;而且同时期海绿石平面上的广泛分布指示沉积时期的环境属于构造稳定的陆表海.      

A COMPARATIVE STUDY OF GLAUCONITE AND THE ASSOCIATED CLAY FRACTION IN MODERN MARINE SEDIMENTS

The crystallinity and mineralogy of both the glauconite and the clay fraction of samples from six contemporary marine environments were investigated by X-ray diffraction. In those areas where glauconite is now forming, the mineralogy and the degree of crystallinity of both the glauconite pellets and the associated clay fraction are similar. In contrast, detrital and relic glauconites are observed to have mineralogies that are different from their clay fractions. No consistent relationship was observed between degree of crystallinity and color of the pellets. Further, only two classes of glauconite as defined by BURST (1958) were common: expandable, interlayered clays and two or more clay minerals in a mixed assemblage. Based on the clay fraction-glauconite similarities and other supporting evidence, glauconite on the Scotia Ridge is concluded to be authigenic. Glauconite from Santa Monica Bay, California and from the continental shelf off Morocco appear to be detrital. Glauconite pellets in the shelf sediments off Guinea and the southeastern Atlantic Shelf of the United States are both detrital and authigenic. The poor crystallinity exhibited by the Chatham Rise glauconite is in contrast to the well-crystallized associated clay fraction and indicates that they are not genetically related. However, the origin of this glauconite remains in doubt.     

The origin and maturation of lagoonal glauconites: a case study from the Oligocene Maniyara Fort Formation,western Kutch,India

An integrated study of the sedimentology, micropalaeontology, mineralogy and geochemistry of glauconites in the Oligocene Maniyara Fort Formation (western Kutch, India), has been undertaken. Authigenic glauconites, mostly of evolved type, formed within a back‐barrier lagoonal environment. Foraminifera help constrain the biostratigraphy and along with sedimentological evidence, provide information on the depositional conditions. Glauconite in the Maniyara Fort Formation occurs either as infillings within intra‐particle pores of larger foraminifers, or as an altered form of faecal pellets. X‐ray diffraction studies reveal the less mature nature of glauconite infillings compared to the glauconite pellets. Electron microprobe investigation confirms a relative enrichment of K₂O and total Fe₂O₃ in the latter. Both varieties of glauconite formed by initial authigenic precipitation of K‐poor glauconite and subsequently matured by addition of potassium in the interlayer sites and fixation of total iron in the octahedral sites; calcium, magnesium and aluminum were released from the glauconite structure concomitantly. Alkaline conditions during the entire process of glauconite formation did not allow dissolution of foraminiferal tests. Mineralogical and chemical characteristics of the Maniyara Fort Formation glauconites are more similar to deep marine glauconites than those reported from other shallow or marginal marine settings. A low negative cerium anomaly, as well as abundant pyrite, suggests formation of glauconite in sub‐oxic micro‐environments, created by decay of organic matter associated with foraminiferal chambers and faecal pellets. Sub‐oxic condition apparently prevailed relatively longer within the Maniyara Fort Formation lagoons. Copyright © 2011 John Wiley & Sons, Ltd.     

Glauconitic bryozoan shells in shelf sediments of Western Kamchatka

Glauconite segregations in Oligocene–Miocene shelf sediments of Western Kamchatka (Kakert and Gakkha horizons) are studied. Glauconite occurs in the studied samples as morphologically different grains, finely dispersed cement, and pseudomorphoses after organogenic structures (siliceous sponge spicules, diatom algae frustules, and others). In addition, samples of the clasts of bryozoans, volcanic glass, and terrigenous grains revealed for the first time traces of the boring algae similar to recent species of genus Hyella and, possibly, Dalmatella, whose tubules are sometimes filled with the finely dispersed glauconite. Our data based on the detailed petrographic studies and SEM investigations confirm and supplement the opinion of several researchers about an important role of microbiota on the glauconite formation. The paper discusses different stages of the glauconite formation in sediments of the Kakert and Gakkha horizons and the possible setting of glauconite infilling in the algal borer trails and holes.     

Glauconitization of detrital silica substrates in the Barton Formation (upper Eocene) of the Hampshire Basin, southern England

Upper Eocene detrital silica grains (chert and quartz) of the Hampshire Basin display alteration and replacement fabrics by glauconite. Silica grains have etched surfaces due to glauconitization which appear green in reflected light and thin section. Quartz grains were glauconitized by surface nucleation and replacement, which spreads from the margin with progressive glauconitization, replacing the quartz grain interior. Chert grains were glauconitized by surface replacement and nucleation internally along cracks and in pores. Different forms of glauconite are associated with the two minerals; glauconite associated with quartz is generally highly-evolved whereas glauconite associated with chert is of the evolved variety. This is interpreted as being due to different surface-reaction control mechanisms associated with the two forms of silica. There is no evidence to suggest that glauconite evolved in stages from a nascent form. Two crystalline morphological forms of glauconite are found associated with both quartz and chert. Glauconite growing within a confined space has a laminated morphology whilst glauconite occurring on the surface has a rosette morphology.     

佳木斯地块金矿石英的热释发光与含金性

乌拉嘎、平顶山、老柞山金矿是佳木斯地块三个重要的金矿。研究表明，石英是金矿中重要的脉石矿物，也是金的主要载体。ＳｉＯ２含量低于９８％，而∑（Ａｌ２Ｏ３＋Ｋ２Ｏ＋Ｎａ２Ｏ）含量高于１．３％的石英为含金石英；含金或富含金石英的热释发光谱以双峰或多峰为其主要特征。因此，上述石英的标型特征可作为金矿床重要的找矿标志，对佳木斯地块的矿点评价和扩大找矿远景有着重要的意义     

DETERMINATION OF NINE RARE EARTH ELEMENTS IN EIGHT USGS REFERENCE SAMPLES AND IN THE ANRT GLAUCONITE, GL-O, BY SEQUENTIAL INDUCTIVELY COUPLED ARGON PLASMA SPECTROMETRY

Nine rare earth elements have been determined by inductively coupled plasma spectrometry (ICP) in eight USGS reference samples, MAG-1, SCo-1, SDC-1, BIR-1, DNC-1, W-2, BCR-1 and BHVO-1 and in the ANRT Glauconite, GL-O. Along with these new data, updated compilations are presented for these samples. Good agreement is observed between the present work and the compiled values.     

Glauconite

The term glauconite has been employed in two senses. It has been used most commonly as a morphological term for sand-sized greenish grains found in sedimentary rocks, but also as a name for a specific mineral species, a hydrated iron-rich micaceous clay mineral. The two uses are not synonymous, since not all morphological glauconite consists exclusively of mineral glauconite, nor is the latter restricted in its occurrence to such pellets. Mineral glauconite in sensu lato is a random interstratification of nonexpanding 10A?layers and expanding montmorillonitic layers. The amount of expandable layers may be over 50 % but it is customary to restrict the name mineral glauconite in sensu stricto to varieties with less than 10 % expandable layers. The variation in amount of expandable layers explains many of the observed variations in the properties of glauconite including chemical composition (especially potassium content), thermal characteristics, cation exchange capacity, colour, refractive index and specific gravity. Mineral glauconite is believed to form by the progressive absorption of potassium and iron by a degraded layer silicate lattice of low lattice charge and elimination of other silicate-lattice types under suitable environmental conditions, of which the most critical seems to be the redox potential. The catalytic activity of marine organisms is no longer thought to be essential, although decaying organic matter and empty foraminiferal tests supply the ideal environment for glauconite genesis. The process of glauconitization is arrested by rapid sedimentation, so that there is a relationship between the variety of mineral glauconite formed and the nature of the host rock. Glauconite is found associated particularly with marine transgressions. Morphological glauconite grains are believed to form as casts, faecal pellets or by accretionary growth, but may have their morphology modified by subsequent re-working. A number of characteristic internal and external morphologies have been recognised. The wide range of environmental conditions suitable for its formation and its common detrital occurrence debars the use of glauconite in palaeo-environmental studies. Its major use in geology is for the absolute age dating of sedimentary rocks by the K-Ar method. Glauconitic deposits have no present day commercial value, but soils formed on glauconitic parent materials are notable for their fertility. Glauconite weathers by loss of potassium to produce a montmorillonitic or vermiculitic product with the release of, or oxidation of, structural iron, so that the grain has the appearance of having weathered to limonite.     

对“指相矿物”海绿石的重新认识

长期以来，海绿石一直被认为是在特定海洋条件下形成的自生矿物，被作为海相标志，随着陆相海绿石的不断发现，有必要对这一观点进行重新认识。本文通过对不同地区、不同环境中的海绿石的统计研究认为：海绿石既可以形成于海洋环境，也可以形成于陆相湖泊环境，海绿石不能作为海洋环境的指相矿物；一般来说，形成于陆相湖泊环境的海绿石与形成于海洋环境的海绿石相比，在化学成分上具有Ａｌ２Ｏ３、Ｋ２Ｏ含量高而ＦｅＯ含量低的特点     

Pyritized mudstone and associated facies in the Permian–Triassic boundary of the Çürük Dağ section,Southern Turkey

This paper is the first study of pyritized mudstones (PM) in the Permian–Triassic (P–T) boundary section of the Çürük Da? (Taurus, Antalya Nappes, Turkey). The mudstones were generally formed as lensoidal-shaped layers or infill materials within nodular platform limestones (hardground). Normal marine fauna is diminished in the pyritized limestones, whereas tube-like microorganisms are apparently increased with the association of pyrite crystals consisting of both framboidal and cubic crystals. The total rock volumes are up to 50–60% clay minerals and are mainly made up of in situ kaolinite and subordinate mixed layer clays (illite–vermiculite). Kaolinite preferentially developed on feldspar crystals, sometimes covering ostracoda bivalves together with gypsum micronodules composed of fan-shaped gypsum crystals. The origin of the kaolinite is, in situ, directly related to feldspar dissolution via heterotrophic bacteria. Thus, kaolinite is found along with bacterial structures. Other mineralogical compositions include established quartz (mostly β-quartz), gypsum crystals (100–200 μm) glauconite and magnetite. Magnetite grains comprise a minor amount (1–2%) and show some bacterial-induced crystal orientations. Glauconite is formed as an accessory mineral that occurs as infill material in biogenic grains. On the other hand, some microspheres represented by a silica-dominated composition are only observed in scanning electron microscopes (SEM) studies under high magnification. Isotope values (d34S) obtained from the pyritized mudstones show an isotopic heterogeneity that suggests that the pyritized mudstone consists of at least two components, with different sulphur-concentrations and d34S values.     

海绿石 K-Ar、40Ar/39Ar 年代学研究

海绿石是与沉积岩同时形成的高钾层状硅酸盐自生矿物，其 K-Ar、40Ar/39Ar 年龄存在失真现象。笔者认为，引起年龄失真的主要原因是由于该矿物结构中含有可膨胀层。通过测量可膨胀层含量及中子活化过程中39Ar的丢失率，使可对海绿石常规 K-Ar、40Ar/39Ar 年龄进行校正，得到其年龄校正公式。