东营凹陷古近系湖相细粒混积岩沉积成岩特征

东营凹陷古近系湖相细粒混合沉积岩相类型、沉积环境和成岩演化等方面有待深入研究,利用岩心观察、薄片、X衍射和碳氧同位素等分析手段,明确了细粒混积岩相类型和沉积成岩特征.研究认为:岩石矿物组分和古生物含量的纵向变化较好地反映了沉积环境的变化和混合沉积成因过程,可作为细粒沉积层序四级界面识别标志.泥晶和亮晶方解石经历过显著的碳氧同位素分馏,证实了混积岩中泥晶方解石主要隶属于与甲烷细菌活动生成生物气有关的碳酸盐,透镜状和纹层状亮晶方解石纹层源自脉体方解石充填微裂缝,微裂缝和方解石脉集中形成于早期次干气-生油阶段.阐述了从生烃增压、微裂缝形成、有机质热演化排出有机酸、溶蚀泥晶方解石、方解石重结晶和脉体形成,直至影响临近砂体胶结作用的整个同生演化过程,对中深层页岩油气成藏研究具有重要指导意义.      

湘南多金属矿床方解石形态及表面微形貌的研究

对湘南多金属成矿区方解石的研究表明，产于钨矿床中的方解石以层状晶体发育为特征，晶体形态主要为｛０００１｝和｛０１２｝＋｛１０１０｝，晶体表面具有菱形生长阶梯；产于铅锌矿床中的方解石一般不出现层解石，晶体形态主要为｛２１３１｝，｛０１１２｝＋｛１０１０｝和｛０００１｝＋｛１０１０｝＋｛０１１２｝，晶体表面平行纹发育；远矿正常灰岩内方解石晶体形态主要为｛４０４１｝。     

贵州水银洞卡林型金矿床方解石稀土元素地球化学特征与找矿意义

水银洞是滇黔桂地区最大的、隐伏的、层控型卡林型金矿床。本文以水银洞金矿床为例,采集矿体裂隙、无矿围岩、断层破碎带、中上二叠统之间构造蚀变体和远离水银洞金矿床无矿区域地表裂隙等5种空间部位中的方解石,分析其稀土(REE)和As、Sb、Tl、Y等微量元素组成,以期能揭示成矿流体地球化学信息,并挖掘方解石用于滇黔桂地区隐伏矿找矿的地球化学指标。矿体裂隙中充填的与成矿作用相关的方解石具有中稀土(MREE)富集的配分模式和正Eu异常(δEu=1.01～1.51)的显著特征,显示了成矿流体是一种MREE相对富集,超常富Eu的还原性流体。其它空间部位方解石的REE配分模式和Eu异常特征(δEu=0.60～1.58)复杂多样,显示了这些方解石的多来源性、多期性和复杂性。不同空间部位方解石的As、Sb、Tl含量没有明显的区别,无法根据成矿相关元素(如As、Sb、Tl等)含量的高低,识别其与成矿作用的关系。在?MREE-δEu和Y/Ho-La/Ho图解中,矿体裂隙中的方解石可与其它空间部位的方解石区分,可大致判断方解石与成矿作用的相关性。成矿流体在经历Au沉淀成矿作用后,可能沿着各种断裂和微裂隙继续运移,...     

论川北砂岩型铀矿床方解石脉与铀矿成矿关系

对以303和1210两矿床为代表的川北砂岩型铀矿床的野外调查、方解石脉的岩矿鉴定、包裹体测试、微量元素和铀含量分析、脉体与矿化围岩蚀变关系的研究得出:方解石脉由中低温热水充填裂隙形成,热水同时活化汲取围岩中的铀,搬迁到构造裂隙发育、富含有机质的地段再沉淀富集。迭加成矿,川北砂岩型铀矿床为热水改造成因     

方解石脉双晶纹方法在工程勘察中的应用

在工程区基岩被第四纪土、江水等覆盖的情况下，如何充分利用好获得的钻孔岩芯来分析断层的发育和活动性情况就显得非常重要。为此，地基勘察中引入一种显微构造分析方法，即方解石脉双晶纹分析方法。方解石脉双晶纹能解决断层的活动期次、每一期次的强度、断层应力场、断层性质、断层活动时的环境条件和最后一次活动的时代等问题。由于方解石脉双晶纹发育的广泛性，使之具有推广价值。     

法国罗瓦尔河口悬移质中的石膏颗粒及表面新生方解石霰石晶体描述

本文介绍在暖温带河口悬移质中发现的石膏颗粒及其表面的新生方解石和霰石晶体。石膏颗粒经受了不同程度的化学和生物化学风化。在一部分风化石膏表面,存在大量的数微米到数十微米大小的方解石和霰石晶体,某些晶体还呈现出亲岩生物遗留的生长纹。由于河口水的溶蚀作用,一部分石膏颗粒已充分碳酸钙化。     

济阳坳陷古近系黑色页岩中纹层状方解石脉的成因探讨

在济阳坳陷3000m以下的古近系中,可见含纹层状方解石脉的黑色页岩,往往与钙质纹层页岩、油页岩、钙质页岩相伴生或薄互层出现。镜下研究表明,这些纹层状方解石脉干净、明亮,晶粒垂直纹层生长,具有明显的近距离经溶解再重结晶的特征,而且与有机质的含量密切相关,页岩中并无石膏的发育和残留。在岩石地球化学上,较相邻的其他页岩,Mg/Ca、Mn/Ca值明显降低,而Sr/Ca值则明显升高,同时碳酸盐的δ18O明显降低,δ13C小幅上升或波动。这些证据表明黑色页岩中的纹层状方解石脉是钙质纹层页岩或富碳酸盐油页岩在晚成岩期随有机质的热演化经溶解和再沉淀作用的产物,并随孔隙水的排出伴有碳酸盐的流失。     

德国哈茨山St.Andreasberg热液矿床方解石巨晶的碳氧同位素研究

在德国哈茨山Ｓｔ．Ａｎｄｒｅａｓｂｅｒｇ热液Ｐｂ－Ｚｎ矿床的方解石脉中,发现了一个方解石巨晶。对该方解石三个不同方向上的Ｃ和Ｏ同位素分析发现,方解石晶体内部存在明显的Ｃ－Ｏ同位素环带。通过对方解石同位素环带的理论模拟,发现在方解石生长过程中,有三种流体参与了作用。它们分别为Ａ：温度约为６０℃的近地表流体,δ＾１３Ｃ＝－１８．５‰,δ＾１８Ｏ＝０‰;Ｂ：温度约为１４０℃的深源流体,δ＾１３Ｃ＝-7.0％O,δ＾１８Ｏ=+10.0％o;C：温度小于20℃。δ＾１８Ｏ≤％O ,δ＾１3C≥ 14.0％o的大气降水 作用过程有四个阶段：① 方解石在流体A中等温生长;② 流体B开始与流体A在封闭体系内均匀混合;③ 流体B缓慢注入的同时,发生了一次性流体C的快速不均匀混合;④ 流体B继续与A缓慢混合,混合体系开放。流体混合的发现,为认识St Andreasberg热液矿床的形成机制提供了颟的视野。     

西秦岭大水金矿床方解石Sm-Nd等时线年龄及其地质意义

大水金矿床位于西秦岭造山带南缘,矿床中金矿化与硅化、去碳酸盐化和方解石化密切相关。硅化主要表现为石英或玉髓交代(白云质)灰岩,在石英中常见灰岩或白云质灰岩的交代残余碎屑,在石英颗粒内或裂隙中见有自然金颗粒,说明硅化、去碳酸盐化和金矿化是同步的;成矿期的脉状-网脉状载金方解石主要分布于硅化-去碳酸盐化蚀变带的边缘或附近裂隙中,说明方解石的结晶与金矿化同步或稍晚。对该矿床成矿期的8件载金方解石样品进行了Sm-Nd同位素定年体系研究,方解石的147Sm/144Nd值变化于0.069 489~2.243 873,143Nd/144Nd值变化于0.511 673~0.514 369,获得Sm-Nd等时线年龄为(189.4±1.4)Ma,代表了大水金矿床的成矿年龄。大水金矿床的成矿时限与秦岭造山运动相关的碰撞型花岗闪长岩岩浆活动时限一致;此外,前人的稀土元素地球化学、黄铁矿Co/Ni比值及H-O同位素研究亦表明成矿物质来源与花岗闪长岩岩浆活动关系密切,因而本次获得的大水金矿床成矿年龄,在一定程度上为"大水金矿床的金成矿与花岗闪长岩岩浆活动存在成因联系"提供了年代学证据。     

地层水条件下碳酸盐矿物热力学平衡条件及其在克拉2气田的应用

基于热力学平衡理论及库车盆地的实际,建立了该区地层水温度、压力条件下方解石溶解、白云石对方解石交代作用的热力学平衡条件,并根据地层水介质特征探讨了该区方解石溶解、白云石交代方解石的具体成岩反应状况,认为该区地层水条件下正进行着方解石溶蚀及白云石对方解石的交代作用,方解石的溶蚀是形成该区深层次生孔隙的根本因素。      

构造驱动大巴山前陆烃类流体排泄:含烃包裹体纤维状方解石脉证据

含烃包裹体纤维状方解石脉被认为是超高压下油气流体形成和排泄的标志。大巴山前陆构造带一些断裂和下古生界黑色泥岩和泥灰岩烃源岩微裂隙中分布有含烃包裹体纤维状方解石脉,成分分析表明其为低镁方解石。纤维状方解石脉δ13CVPDB和δ18OVPDB比围岩碳酸盐岩的明显变轻,前者δ13CVPDB和δ18OVPDB变化范围分别为-1.9%～-4.8‰和-8.4%～-12.8‰,后者分别为-1.7%～+3.1‰和-8.7%～-4.5‰,且δ13C与δ18O具有明显的线性关系,反映出纤维状方解石脉具有成岩有机流体与浅部流体混合的流体特征。纤维状方解石脉含有共生的固体沥青包裹体、含甲烷液相包裹体和气液二相盐水包裹体等多相态包裹体,其中沥青包裹体为油气运移的残余沥青。气液二相盐水包裹体均一温度主要位于140℃和196℃之间（峰值为179℃）,盐度较高（平均为9.7wt% NaCl）。分别应用盐水包裹体和甲烷包裹体等溶线P-T相图确定出含烃包裹体纤维状方解石脉形成的流体压力为150~200 MPa,属于异常超高压流体。地质和地球化学特征分析认为,大巴山含烃包裹体纤维状方解石脉不具有泥岩因压实成岩作用而形成的超高压流体特征。结合沉积和构造演化历史分析认为,印支碰撞造山运动和燕山前陆构造作用导致大巴山褶皱隆起并伴随天然气藏破坏和改造,挤压环境下的超高压构造应力驱动天然气流体排泄,大巴山前陆构造带含烃包裹体纤维状方解石脉就是超高压构造应力驱动天然气排泄的产物。     

海南岛南部一地全新世生物屑灰岩的成岩作用

引言研究标本由我所碳酸岩组采自海南岛南部的一个地点。在那里,沿岸覆于原生礁之上有一套由生物骨屑(主要是珊瑚)砂、砾所组成的、已被碳酸盐胶结的岩层,其厚约3米左右(图1)。此岩层一般称为“次生礁”。它是由当时原生礁盘上的生物被海浪击碎并冲带到礁盘上沉积下来的,这里属连岛砂堤沉积,它现已完全暴露地表。次生礁在它抬升过程中,下部被海蚀形成海蚀龛。     

Molar tooth structures of the Neoarchean Monteville Formation, Transvaal Supergroup, South Africa. I: Constraints on microcrystalline CaCO3 precipitation

Molar tooth (MT) structures are enigmatic, contorted millimetre‐ to decimetre‐long veins and spheroids of microcrystalline calcite that formed during very early diagenesis in Precambrian sediments. MT structures in the ca 2·6 Ga Monteville Formation are 600–800 Myr older than previously reported occurrences and establish that conditions necessary for MT genesis were met locally throughout much of the Precambrian. In the Monteville Formation, MT structures were formed shallow subtidally, extending to depths near storm wave base, in shale host sediments intercalated with storm‐generated carbonate sand lenses. They are filled with microcrystalline calcite and rare pyrite. Microcrystalline calcite identical to that in MT structures fills other pore space, including porosity between grains in carbonate sand lenses, moldic porosity in sand grains, sheet cracks in columnar stromatolites, and shallow cracks on sandy bedding planes. Relationships in the Monteville Formation demonstrate that microcrystalline CaCO₃ precipitated in fluid‐filled cracks and pores; microcrystalline calcite characteristics, as well as the paucity of carbonate mud in host rocks, are inconsistent with injection of lime mud as the origin of MT structures. Locally, MT cracks were filled by detrital sediment before or during precipitation. Precipitation occurred in stages, and MT CaCO₃ evolved from granular cores to a rigid mass of cores with overgrowths – allowing both plastic and brittle deformation of MT structures, as well as reworking of eroded MT structures as rigid clasts and lime mud. Crystal size distributions and morphology suggest that cores precipitated through nucleation, Ostwald ripening and size‐dependent crystal growth, whereas overgrowths formed during size‐independent crystal growth.     

滇东北会泽地区南红玛瑙产出特征及成因分析

会泽地区的南红玛瑙矿主要产于上三叠统飞仙关组的中上部砾岩层、上二叠统宣威组底部砾岩层以及晚二叠世峨眉山组杏仁状玄武岩中。玛瑙新鲜面多为红色、浅红色及灰白色;呈椭球状或扁球状分布于砾岩之中,分布不均匀,局部富集;玛瑙砾石大小不一,玛瑙粒径多集中在0.5~5 cm,偶见大于6 cm。会泽地区的南红玛瑙矿形成可分为三个阶段：1）晚二叠世时期,玄武质火山岩（P₃e）中的含硅质热液在晚期充填于玄武岩气孔或裂隙中,经过（快速）冷却形成隐晶质石英或晶质石英集合体——玛瑙,即原生玛瑙;2）晚二叠世晚期的华力西运动和印支运动早期的地壳继续隆升,使得含玛瑙玄武岩遭受风化-剥蚀作用,两次剥离出来的玛瑙单体经流水搬运作用及河湖相沉积作用,形成宣威组（P₃x）、飞仙关组（T₁f）含玛瑙砾石层——沉积砾岩型玛瑙矿产;3）近-现代地质作用,使得二叠纪玄武岩气孔中原生玛瑙和宣威组、飞仙关组沉积砾岩层中的次生玛瑙砾石,再次受到风化-剥蚀作用,玛瑙砾石经流水搬运至现代河流或湖泊中,形成次生玛瑙砂矿。     

Genesis and diagenesis of hiatus- and breccia-concretions from the mid-Cretaceous of Texas and northern Mexico

A study of septarian concretions from late Cretaceous shale sequences of Texas and northern Mexico reveals complex burial-exhumation histories. First generation concretions and pre-fossilized moulds formed in silty clays before significant compaction occurred. Syneresis cracks developed and were filled by length slow fibrous calcite with a decrease in iron content toward the centre of each vein; in some cases this was succeeded by growth of equant or bladed calcite. Subsequent erosion of enclosing sediment caused collapse and break up of concretions, leaving fragments and some unbroken concretions exposed to encrustation and boring on the sea floor. These were subsequently buried and enclosed in a second generation of concretions, which also developed syneresis cracks. The calcite that filled these latter cracks was generally bladed (sometimes followed by equant calcite) and contains more iron toward the centre of the vein. Differences between the calcite filling first and second generation septarian veins indicates changing diagenetic regimes during burial in the marine environment, without a major shift in diagenetic conditions, such as the introduction of meteoric waters. These conclusions have significant implications to cementation in ancient limestones, which show textural and chemical sequences similar to those present in the septarian concretions described.     

Shallow-marine carbonate cementation in Holocene segments of the calcifying green alga Halimeda

Early-diagenetic cementation of tropical carbonates results from the combination of numerous physico-chemical and biological processes. In the marine phreatic environment it represents an essential mechanism for the development and stabilization of carbonate platforms. However, diagenetic cements that developed early in the marine phreatic environment are likely to become obliterated during later stages of meteoric or burial diagenesis. When lithified sediment samples are studied, this complicates the recognition of processes involved in early cementation, and their geological implications. In this contribution, a petrographic microfacies analysis of Holocene Halimeda segments collected on a coral island in the Spermonde Archipelago, Indonesia, is presented. Through electron microscopical analyses of polished samples, this study shows that segments are characterized by intragranular cementation of fibrous aragonite, equant High-Mg calcite (3.9 to 7.2 Mol% Mg), bladed Low-Mg calcite (0.4 to 1.0 Mol% Mg) and mini-micritic Low-Mg calcite (3.2 to 3.3 Mol% Mg). The co-existence and consecutive development of fibrous aragonite and equant High-Mg calcite results initially from the flow of oversaturated seawater along the aragonite template of the Halimeda skeleton, followed by an adjustment of cement mineralogy towards High-Mg calcite as a result of reduced permeability and fluid flow rates in the pores. Growth of bladed Low-Mg calcite cements on top of etched substrates of equant High-Mg calcite is explained by shifts in pore water pH and alkalinity through microbial sulphate reduction. Microbial activity appears to be the main trigger for the precipitation of mini-micritic Low-Mg calcite as well, based on the presumable detection of an extracellular polymeric matrix during an early stage of mini-micrite Low-Mg calcite cement precipitation. Radiocarbon analyses of five Halimeda segments furthermore indicate that virtually complete intragranular cementation in the marine phreatic environment with thermodynamically/kinetically controlled aragonite and High-Mg calcite takes place in about 100 years. Collectively, this study shows that early-diagenetic cements are highly diverse and provides new quantitative constraints on the rate of diagenetic cementation in tropical carbonate factories.     

浙江桐庐二叠纪海绵生物丘的沉积环境和成岩环境

浙江桐庐二叠纪茅口期海绵丘发育于碎屑陆棚上，呈透镜状，无礁前和礁后相。由于当时相对频繁的海进海退，使该丘在生长过程中出现三次成礁期，海进成礁，海退消亡。其主要的礁岩类型为海绵（或水螅）障积岩，在上部出现纹层藻和古石孔藻粘结岩，最后为潮坪相叠层石灰泥岩所覆盖。该丘经历了早期海底、海水潜流带、混合水和大气淡水成岩环境。早期成岩作用以灰泥淀积作用为主，大部分孔隙都为灰泥所充填，少量残余孔隙中可见形成于早期海底成岩环境的纤状和针状方解石胶结物。     

四川渠县三叠系膏盐的同生、成岩、后生及表生变化

本文论述了四川渠县三叠系的膏盐在沉积后的不同阶段所发生的各种变化,并提出根据膏盐的变化特征推测它们的原生沉积条件、卤水咸化程度及研究区的矿床保存条件。     

巴布亚新几内亚合恩半岛晚第四纪上升珊瑚礁造礁珊瑚的成岩历史

更新世以来,剧烈的构造运动已将巴布亚新几内亚合恩半岛东北海岸的晚第四纪珊瑚礁阶地抬升上千米.阶地中造礁珊瑚的成岩变化和成岩产物的组构特征反映了该礁的成岩历史,充分体现该区快速构造上升的影响.海水潜流带和淡水渗流带为上升礁的主要成岩环境.生物钻孔、生物碎屑填隙、珊瑚文石针粗化、珊瑚骨骼的溶解和新生变形转化,以及其不同矿物成分和组构的种种胶结物的胶结作用是造礁珊瑚经历的主要成岩作用.地球化学资料表明其成岩变化发生于开放的化学体系之中.     

贵州中三叠统上部垄头组的沉积性质——再论其钙结壳的成因

钙结壳是土壤层之下的岩石在出露地表渗流带环境内受大气雨水的溶解,并通过上覆土壤层的淋滤而成的产物。由于雨水的不断的溶解,使原始的岩石或沉积物发生破裂,从而形成各种大小的砾块或砾石。随着雨水不断的溶解,雨水逐渐增加 CaCO_3的含量。这些富含碳酸钙的雨水,当它流到位于潜水面之上的下渗流带时,就在土壤层之下、原来岩石之上沉积了特殊的、层纹状方解石胶结物。它们往往覆盖岩石表面或沿着砾石的外缘、呈包覆状沉积,从而形成典型的层纹状钙结壳。渗滤豆粒的外皮也属于层纹状钙结壳的性质,这些外皮有向下方加厚的趋势,这表明渗流带的含碳酸钙的雨水,受重力作用影响下,具有往下悬垂现象,类似于洞穴内的钟乳石。豆粒之间的相互衔接呈多边形构造,也表明它是受重力作用而形成的构造。