一种深水沉积标志-“瘤状结核”及其成因

“瘤状结核”是由富灰硅质结核和富粘土质“外壳”组成.从结构和成因可划分瘤状结核(不连续)、连续,瘤状结核和压扁瘤状结核(或压扁构造).据研究“瘤状结核”是在海水较深的外陆棚至盆地环境中形成的.“瘤状结核”有三种不同的成因,即(1)瘤状结核是在底流和洋流作用下,促使沉积作用中断,于沉积物-水界面附近,由海底早期成岩胶结作用形成;(2)连续瘤状结核是在较长的沉积作用中断和成岩作用相结合,致使结核体发育和生长以及互相连结,由岩化作用形成和(3)压扁瘤状结核是一种次生沉淀成因,它是由晚期埋藏和溶解、压实联合作用下形成的.     

浙江江山砚瓦山组瘤状灰岩的成因

浙江江山地区砚瓦山组瘤状灰岩的结构构造及其形成机理复杂多样,一般可划分出五种岩石类型,即压扁瘤状泥灰岩、揉皱角砾状泥灰岩、压溶瘤状灰岩、干裂角砾状灰岩和粗砾屑灰岩。瘤状灰岩形成于碳酸盐台地浅水部位,水体为半浑浊。其发育程度及其层位的区域变化规律表明,泥质浑水系来自海盆东侧的华夏古陆。     

新疆柯坪中奥陶统结核状灰岩的沉积环境及成因

对新疆柯坪地区中奥陶统灰岩和泥岩交互沉积地层中的结核状灰岩的沉积环境和形成机制进行了研究。根据野外观察并结合室内偏光显微镜下阴极发光和染色等方法分析其结构和构造特征，发现有团块状、网纹状、透镜状3种结核状灰岩。运用X光衍射仪和质谱仪等化学分析手段对其常量元素、微量元素、碳氧同位素、酸不溶物等进行了测定。综合分析矿物、岩石、生物和地球化学特征，认为它们形成于陆棚中水体较深的沉积环境，灰岩和泥岩交互韵律层是在表层洋流、大洋底流和物源供给的周期变化作用下形成的。结核状灰岩形成于沉积-成岩早期阶段，它们的形成机制分别是：团块状灰岩是在洋流活动后的平静期因水体中碳酸钙沿凝结核凝结、增大、胶结而形成；网纹状灰岩是在盐度不饱和的深海底流的周期作用下冲刷同生期沉积的碳酸盐灰泥而形成；透镜状灰岩是通过上覆水体与沉积物的差异压实作用而形成的。     

川北早寒武世碳酸盐岩台缘斜坡沉积特征及变形构造形成机制探讨

基于对川北米仓山西部旺苍县鼓城乡唐家河下寒武统仙女洞组露头剖面的观察与镜下分析发现,仙女洞组下段由生物碎屑泥晶灰岩(L)、粉砂质泥岩(M)、似瘤状砾屑灰岩(L')、角砾灰岩(R)、藻凝块灰岩(A)和含生屑钙质砂岩(S)组合而成,其以角砾灰岩、似瘤状砾屑灰岩和藻凝块灰岩为特征,且发育异地岩块和滑塌变形构造。进一步分析认为:L-M岩石组合为正常的斜坡环境低能沉积;L'-R岩石组合中的角砾灰岩为上斜坡生物灰泥丘崩坍滑动至下部而形成的,似瘤状砾屑灰岩可能是由于L-M岩石组合快速沉积导致沉积物失稳滑动变形、上斜坡生物灰泥丘崩落角砾致使的差异压实和滑动、以及后期物质成分差异引起的压溶作用等共同作用的结果,从而使灰质层发生破碎并被泥质包围形成断续的砾屑状,甚至轻微的位移,进而形成条带特征不明显的杂乱变形构造;微生物岩(Mb)组合为上斜坡的灰泥丘沉积;S-M岩石组合为斜坡上部的浊流沉积。根据上述分析结果建立米仓山西部仙女洞组碳酸盐岩台缘斜坡沉积模式,表明仙女洞组沉积早期米仓山西部存在台缘斜坡相沉积。     

重庆南川地区中二叠统茅口组眼球状灰岩成因

中二叠世茅口组中-下部发育一种特殊的眼球状灰岩, 眼球部分通常为颜色较浅, 富含生屑颗粒的灰岩; 而眼皮部分通常为颜色较暗的泥灰岩。其成因一直存在分歧。本文通过对重庆南川大铺子剖面茅口组底部眼球状灰岩的野外观察和室内研究, 认为陆源输入的改变导致眼球和眼皮部分泥质含量的差异; 在成岩过程中, 碳酸盐沉积物为主的眼球部分因为胶结作用而没有被机械和压实作用破坏, 泥质含量较多的眼皮部分则受到强烈的压实。因此, 该地区眼球状灰岩的形成是沉积和成岩过程相互作用的结果, 为浅海陆棚沉积环境。     

碳酸盐岩白垩状结构成岩环境及白垩状结构化成因

白垩状结构碳酸盐岩是一种白色或淡色疏松、酥脆、多微孔的灰岩。狭义白垩状结构灰岩是指深 水盆地、陆棚斜坡及内台地局限海相(如湖)中形成的白垩状微孔隙灰泥岩及粒泥岩基质。广义白垩状结构 灰岩指盆地相和陆棚相中包括生物礁、滩的各种沉积体内各种沉积组构产生的白垩状灰岩,也包括白垩状去白 云化灰岩及 (真)白垩。综合各国学者的有关研究资料,建议将白垩状结构化定义为：“ 碳酸盐沉积物和碳酸盐 岩中的镁方解石和文石在不同成岩阶段通过新生变形而转变成低镁方解石微晶和微亮晶格架,并在其中产生和 保存晶间孔喉网络的作用;强化白垩状结构化是指微晶和微亮晶格架受到进一步溶蚀和淋滤,从而形成次生溶 蚀孔隙网络的作用” 。论述了世界各地的地史中不同成岩阶段白垩状结构碳酸盐岩成岩环境的例证和白垩状结构 化成因。     

Differential Diagenesis of Limestone-Marl Alternations

灰岩-泥灰岩韵律层包括结核状灰岩到灰岩和泥灰岩互层,广泛分布在陆棚及深海环境中,出现于各地质时期,是研究高分辨率地层学和环境恢复的理想工具.但是成岩作用在灰岩-泥灰岩韵律层形成过程中的作用一直存在分歧,有的学者认为差异化学压实成岩作用加强了原始沉积的差异,有的学者认为成岩作用不仅能够强烈歪曲原始环境特征,还可以通过自身成岩作用形成与原始沉积特征类似的现象.灰岩-泥灰岩韵律层中的差异成岩作用是指泥灰岩中的不稳定碳酸盐矿物在海底成岩环境中经过溶解、迁移和在灰岩中再沉淀,导致灰岩层没有明显被压实,而泥灰岩层受到明显压实.本文重点评述了差异成岩作用发生的环境和过程,并对与之相关的胶结物来源问题和有机质在早期成岩过程中的作用进行了讨论.并以华南中二叠统栖霞组韵律层为例,探讨了差异成岩作用在其形成过程中的作用,最后对以后的研究方向进行了展望.     

蠕虫状灰岩特征和成因新探

下扬子地区下三叠统中广泛分布着一种外貌独特的灰岩——蠕虫状灰岩,这种灰岩出现在该区深水和浅水的多种环境中,具有灰泥结构和粒泥(或泥粒)结构;斜层理、生物扰动构造和压扁透镜状构造。蠕虫状灰岩是多成因的,各成因之间有着一定的联系,其中,先期形成的可被后期形成的叠加和改造。沉积作用、沉积分异作用是形成蠕虫状灰岩的一个重要前提,而生物扰动作用、水流作用和压实、压溶作用则是形成各种蠕虫状灰岩的关键。     

华北地台早古生代竹叶状灰岩岩石特征及成因研究进展

砾屑灰岩在华北地台寒武系-奥陶系广泛发育,竹叶状灰岩只是其中一种,且所指范围界限模糊,常与其他类型的砾屑灰岩伴生在一起。古代陆表海提供了砾屑灰岩广泛发育的环境基础。潮坪和潮下开阔海是陆表海广泛发育的基本地貌单元,也是砾屑灰岩形成的重要场所。古板块运动表明,寒武纪华北地台处于低纬度地区,符合古风暴频发的要求。风暴及潮汐流是砾屑灰岩形成的主要动力。另外,成岩过程中的压实和固结脱水也是板条状砾屑的重要成因。条带状薄层灰泥石灰岩与泥岩及泥质灰岩的频繁互层是发生破碎并形成砾屑的物质基础。华北地台砾屑灰岩具有多种成因,可以按照砾屑的颜色特征、形态及磨圆程度、砾屑灰岩的支撑结构、充填物的类型等进行区分并进行成因分析。     

灰岩-泥灰岩韵律层的差异成岩作用

灰岩-泥灰岩韵律层包括结核状灰岩到灰岩和泥灰岩互层,广泛分布在陆棚及深海环境中,出现于各地质时期,是研究高分辨率地层学和环境恢复的理想工具.但是成岩作用在灰岩-泥灰岩韵律层形成过程中的作用一直存在分歧,有的学者认为差异化学压实成岩作用加强了原始沉积的差异,有的学者认为成岩作用不仅能够强烈歪曲原始环境特征,还可以通过自身...     

Near-surface shrinkage and carbonate replacement processes, Arran Cornstone Formation, Scotland

A 47 m thick succession of conglomerates, sandstones and mudstones, of Late Devonian or Early Carboniferous age, outcrops at Fallen Rocks in northeast Arran (western Scotland). It is defined here as the type section of the Arran Cornstone Formation. At numerous levels in the succession, varieties of fissures and carbonate concretions formed during the accumulation of the Formation. The fissures opened as a result of drying-shrinkage, and were closed again either by filling with different sediment, or by wetting and expansion of the fissure wall sediment. Carbonate concretions form complete beds, discontinuous, bedding-concordant sheets, or bedding-discordant nodules or rods (the rod cornstones). These concretions formed close enough to the surface to be incorporated, after erosion and redeposition, as clasts into overlying beds. The concretions were formed by growth of micrite, mainly by replacement, but shrinkage displacement played an important role in subsequently fracturing and reworking the micrite. The micrite was also locally replaced by microspar and spar, and this involved dissolution and precipitation. No independent evidence of biological influence in any of these processes has been found.     

Early marine lithification of the nodular limestones in the Silurian of New Brunswick

A sequence of irregular nodular limestones in the Silurian of northern New Brunswick appear to have undergone early marine lithification. Nodules and crusts formed soon after deposition in the argillaceous lime sediments by sporadic diagenetic precipitation of calcium carbonate and were subsequently modified by differential compaction and minor flowage. While lack of both borings and encrusting organisms on the nodules indicates they were not ‘hard grounds’, computed porosities at the time of lithification based on the ratio of carbonate to insoluble residues suggest lithification depths within a few tens of feet of the sediment-water interface. Consideration of the availability of calcium carbonate suggests lithification very close to the sediment surface.     

攀西会理群的碳酸盐滑积岩等深积岩及其构造条件浅析

本文通过对岩石的原生沉积构造和结构成分的研究,确定了浅变质岩系中碳酸盐复理石——野复理石建造的主要岩石成囡类型,有滑积岩、崩塌跌积岩和等深积岩所组成,由重力崩落、碎屑流、液化沉积物流和浊流所形成。它们的岩相特征表明当时沉积盆地中存在水下缓坡和陡崖以及与之并存的深水槽盆,是同沉积构造活动的产物。 上列岩石的物质组成特点是内外源混积,构成砂质(或含砂)碳酸盐浊积岩系列。将统计之石英、长石(少量),砾屑含量投影于Schwab的三端元图上,表明是台地断陷或断块复活的产物。因此滑积岩、崩塌跌积岩等可作为指示盆地同沉积断裂活动历史的地质参数。     

STRUCTURAL AND TEXTURAL EVIDENCE OF EARLY LITHIFICATION IN FINE-GRAINED CARBONATE ROCKS

SUMMARY
Absence of compaction, intraformational breccias, resedimention, internal sediments and synsedimentary hardgrounds indicate early lithification of finegrained carbonate rocks. One of the factors controlling early lithification is the purity of lime mud. Less than 2% of insoluble residue (especially clay minerals) favours cementation and recrystallisation before further sediment accumulation causes compaction. Thus, early lithification is terminated in or near the environment of sedimentation. "Electrodiagenesis" is considered to be a possible mechanism for cementation.     

中国南方泥盆系瘤状灰岩的成因

本文从碳、氧同位素、化学成分、矿物组成及岩石的结构、构造等特点出发,探讨了广东凡口和广西大厂两类不同类型的瘤状灰岩的成因。广西大厂地区的瘤状灰岩是在较深的水体中沉积,并在周期性的海底底流的溶解作用下形成的。而凡口地区的瘤状灰岩则可能是在比较浅的水体中快速堆积,在重力作用的挤压流动以及成岩作用期间的溶解作用下形成的。     

Barite concretions as evidence of pauses in sedimentation in the Marnes Bleues Formation of the Vocontian Basin (SE France)

Several intervals rich in barite nodules occur in the mid-Cretaceous marls of the Vocontian Trough (SE France). These concretions, which grew on heterogeneities in the sediment, are arranged as horizons parallel to the bedding, and are often associated with carbonate and phosphate nodules. Detailed sedimentological and stratigraphical observations suggest that they represent the consequence of short-term pauses in sedimentation during early diagenesis, but the most important occurrences of barite are below prominent discontinuities. This may be explained by the frequency of pauses in sedimentation caused by a progressive starvation, or an increase in the energy of bottom-water currents. The high number of barite occurrences on the basin margins is directly linked to the recurrence of sedimentary breaks. The geochemical data show that the host sediment corresponds to a pelagic setting, far from hydrothermal influences, but generally in a restricted, dysoxic to suboxic, depositional environment. The sulphur isotopic composition of the barite sulphate (+16 to +76‰ rel. CDT) supports the hypothesis of an early diagenetic origin of the barite nodules. Their genesis may be explained by the fixation of a diagenetic front corresponding to the penetration of a sulphate reduction zone from the seawater–sediment interface down in the sediment which is in contact with barium-rich porewaters expelled upwards as a consequence of compaction. The barium of biogenic origin, initially stored in the underlying black shale, was mobilized under strongly reducing conditions. Such fixation is normally induced by a pause or a stop in sedimentation due to starvation or renewed bottom-water circulation. Together with other concretions, the barite nodules mark condensed stratigraphic intervals and often represent major breaks. As such they shed light on variations in sedimentary activity and their importance in the sedimentology and stratigraphy of pelagic marly sequences cannot be ignored.     

砂岩早期核心式碳酸盐胶结作用的成像测井证据

早期碳酸盐胶结作用是库车坳陷新生界浅埋藏河流相砂岩内除机械压实外目前正在进行的主要成岩作用,高分辨率电阻率成像测井资料为研究其特征及成因提供了重要的地球物理证据。在电阻率成像测井图像上,早期碳酸盐胶结物呈圆形、椭圆形或不规则斑块状、葡萄状等形态出现,多数顺层理方向分布,其产状有孤立状或分散状斑块、断续胶结纹层和连续胶结纹层等。它们可以发育于砂岩层顶部或底部,也可以与疏松未胶结或弱胶结砂岩呈互层或夹层状交替分布。早期碳酸盐胶结物的沉淀采取核心式胶结模式,即胶结物首先围绕少数核心沉淀,呈斑块状逐渐向外增生,直至从各个核心生长出来的碳酸盐胶结斑块相互靠近和连生导致砂岩层被完全胶结为止。砂体或砂层被碳酸盐胶结的过程遵循由外向内 (由砂体边缘向砂体中心 )、由高渗透纹层向低渗透纹层、由局部胶结核心向周围孔隙增生的规律.     

丹池晚古生代盆地的沉积和构造演化*

丹池盆地属右江裂谷带靠近江南古陆南缘的次级裂陷盆地,其中的沉积可分为五个相区,十三种相类型。研究认为丹池盆地的形成、沉积作用、相和相序的分布均明显受到同沉积期断裂活动的影响。构造演化从泥盆纪初开始即有北西向丹池断裂的张裂作用,此种张裂与其派生的北北东向走滑断裂的复合作用,到二叠纪时,演变为北西向断裂的走滑活动,丹池盆地最初由半地堑式发展为地堑式盆地,到二叠纪成为-走滑盆地。     

Paleoceanographic Setting and Preservation of Buried Manganese Deposits in DSDP/ODP Cores

Abstract. The occurrence, lithology, and stratigraphic setting of buried manganese deposits and associated host sediments in cores obtained on Legs 123–210 of the Ocean Drilling Program (ODP) are examined in order to establish the formative environment and conditions of preservation. Fossil manganese nodule and crusts are found to have formed or deposited throughout the period from 100 Ma to the present, with an additional example of formation near 137 Ma, suggesting that the deep-sea environment has been oxic and suitable for the formation of manganese nodules and crusts since the Cretaceous. Many manganese nodules and crusts occur on horizons corresponding to hiatuses in sedimentation or periods of slow sedimentation, consistent with the environment in which modern nodules form (sedimentation rate less than 10 m/m.y.). Sediments overlying the fossil nodules and crusts are oozes or biogenic sediments with sedimentation rates of 1–18 m/m.y. Low total organic carbon (<0.1 wt%) in the overlying sediments and high sulfate content (>25 mM) in interstitial water around the manganese horizon suggest that no strong reduction occurred within the overlying sediments. Coverage by biogenic sediments containing only small amounts of organic matter is therefore considered important for the preservation of manganese nodules and crusts. Manganese carbonate occurs sporadically as nodules, concretions or thin layers in various host sediments, including clay, calcareous ooze and siliceous ooze with sedimentation rates of 6–125 m/m.y. Hiatuses are rare around the host sediments of manganese carbonate. Higher total organic carbon (0.2–1.8 wt%) in the host sediments and lower sulfate content (0–25 mM) in interstitial water around the manganese carbonate horizon suggest that reduction in association with decomposition of organic matter would have proceeded in the host sediments.     

四川地区海泡石粘土矿的地质特征及分布规律

海泡石(sepiolite)是很有发展前途的一门新兴矿种,是当今世界上用途很广的非金属矿物原料之一。在石油、油脂、酿造、轻工、化工、医药、国防、农牧业、环保、橡胶、涂料以及深井钻探泥浆等方面都有应用,就目前所知,其用途广达130余种,随着科学技术的发展,其用途还将不断地扩大。由于海泡石具有特殊的晶体结构、较好的纤维性质、较高的负电动电位、低的比磁化率,以及一定的耐酸碱腐蚀性、过滤性、阳离子交换性及吸附性等,因而世界上许多国家已越来越重视该矿物的找矿、开发和应用。我国在海泡石的找矿方面已有较大的进展,已找到海泡石矿床(点)五十余处,其中大型矿床六个,分布在江西、湖南、陕西等省。与四川邻近的陕西宁强、湖南石门陈家湾等都是大