成都市白垩系灌口组富膏盐红层溶蚀特征与机理

成都市白垩系灌口组近地表红层富膏盐地层因富含膏盐、钙芒硝等易溶矿物普遍发育红层类岩溶现象,制约着地下空间的开发利用。为梳理出成都市域灌口组富膏盐红层溶蚀规律与机理,防范红层硫酸盐岩溶相关的工程地质问题,综合利用钻孔岩芯、物探、测井、物性测试、溶解实验等资料,分析区域内富膏盐地层的分布规律、富膏盐红层溶蚀特征、溶蚀发育的影响因素和红层硫酸盐岩溶机理。综合研究表明,成都市白垩系灌口组富膏盐红层溶蚀现象普遍发育于低丘台地区及平原河谷区。红层硫酸盐岩溶受地形、构造、地下水活动、断裂等多种因素的综合影响,地下水活动和断裂系统是最关键因素。存在两种不同的溶蚀模式:在高于平原区的低丘地区,地表水透过第四系松散卵砾石层,入渗至裂缝发育、岩体破碎的强-中风化以及富含膏盐的白垩系灌口地层,溶蚀钙芒硝、石膏、硬石膏等矿物后,地下水顺流至低洼的平原、河谷地带或汇入地表径流,促使溶蚀作用的持续发生;在低于平原区的较深部,地表径流沿向斜翼部侧向顺层流动或沿断裂系统入渗补给地下水,导致60 m以深的较深部发生溶蚀现象。     

滇中红层膏盐溶蚀特征及其对水质的影响

滇中红层多含有石膏、岩盐等可溶盐矿物,在可溶盐富集地段,地下水往往表现为咸水或微咸水而不适宜饮用。文章以楚雄市谢家河河谷为例,基于钻探、物探、测井、水质分析等综合勘察资料,研究红层膏盐在地下水循环中的溶蚀特征并分析膏盐溶蚀对水质的影响。结果表明:膏盐溶蚀形式主要为散点状膏盐的溶蚀孔洞和裂隙状石膏的溶蚀裂隙,溶蚀强度主要受控于含水介质孔隙发育程度和地下水循环速度;浅层地下水循环速度快,虽可溶盐溶蚀强烈,但对地下水水质影响较弱,水质超标面较小;深层地下水循环速度慢,可溶盐溶蚀后富集于深层承压含水层中,导致地下水水质超标面大;断裂及其影响带导水造成深层承压水向浅层地下水越流,导致浅层地下水水质变差。      

西宁石膏岩对水工建筑物危害的探讨

西宁石膏岩赋存于第三系中新统西宁组中段,分布于南、北两山的前山带。为了确保水工建筑物的安全和效益,在水工建筑物及其基础分布处,必须隔离石膏岩体与水体,尽量不让两者直接接触,防止石膏岩被溶蚀及由此产生渗漏而造成溃坝事故。（１）西宁石膏岩的溶蚀性石膏岩体...     

江西红层含水特征

江西红层包括白垩系到第三系,出露面积近三万平方公里(另有一万平方公里隐伏于第四系之下)。为巨厚的红色碎屑岩建造,含石膏、岩盐等。     

我国红层岩溶与红层岩溶塌陷刍议

中国岩溶地区面积广阔,岩溶地貌和现象类型多样。其中我国南方地区红层中出现的岩溶现象较为特殊:可溶岩类型复杂,成岩作用差,溶蚀机理多样,还易风化崩解。近年来红层岩溶塌陷多有发生,成为一个不可回避的问题。文章对我国红层岩溶与红层岩溶塌陷研究现状进行了系统梳理。红层岩溶主要存在于以可溶物质胶结的或含碳酸盐岩砾石的红色沉积岩为主的地区。红层岩溶的特点可以概括为:(1)可溶岩类型复杂,溶蚀机理多样;(2)成岩作用差,力学强度低,易风化崩解;(3)与地质构造密切相关。红层岩溶地区不但会出现覆盖型岩溶区的土层塌陷,而且由于其特殊的岩溶作用还可能出现基岩塌陷。根据红层岩溶地区地质结构,其塌陷模式可概化为红层上覆松散层塌陷、红层溶洞顶板垮塌以及红层整体垮塌三类。今后有必要从红层溶蚀特点和红层岩溶塌陷模式出发,开展红层溶蚀对岩溶塌陷作用机理的专项研究,为红层地区岩溶塌陷地质灾害的风险评估和防治处理提供科学依据和技术支撑。     

成都地区含膏红层软岩溶蚀特性研究

针对成都地区红层软岩溶蚀空洞现象,以成都半岛城邦项目场地的红层软岩为例,选取不同深度的岩样进行室内浸水试验、淋滤试验和溶蚀试验,观察岩样在不同类型环境水下的作用性状和溶蚀特征,分析经历不同作用的含膏红层软岩 可溶成分的流失程度及其对环境水的影响。结果表明,红层软岩中的石膏含量随着深度的增加而增加,含膏红层及其环境水的腐蚀性显著增强;遇水后,红层软岩中的可溶成分逐渐溶解、流失,随着时间的积累;红层软岩孔隙增大,渗透性增强,红层的完整性丧失,强度衰减;在酸性环境水的作用下红层软岩中的钙质胶结物流失加剧,结构连接破坏严重,对红层的结构强度影响较大。对浸泡、淋滤和溶蚀作用后的试样,重点测试了抗压强度、波速等参数。试验结果表明,红层软岩经硫 酸溶液腐蚀后岩样的结构被破坏,单轴抗压强度从8.5 MPa降低到2 MPa,降低了76%;波速明显减小,从2 204 m/s减小至1 355 m/s,减小了40%;红层试样的pH与电导率变化也比较显著,pH值从8.77减小至7.29;电导率从55 ?s/cm增加到1 100 ?s/cm。     

甘肃红层泥岩耐崩解试验与矿物夹杂效应研究

为探究干湿作用下甘肃红层质泥岩加速崩解机制,针对典型的石膏质泥岩,开展浸水及快速崩解试验,并通过与泥质砂岩、页岩和石膏岩的对比,分析了影响岩石耐久性的主要因素,对崩解过程中的矿物夹杂效应进行了讨论。研究结果表明：原状石膏质泥岩浸水自然崩解速度较慢,3 h崩解量为0.11,但高温(>163℃)干燥后夹杂的石膏矿物将完全脱水硬化,体积收缩,再次遇水后岩块于2 h内完全崩解。石膏质泥岩的二次循环耐崩解指数I_d2为0.80,属于高耐久性岩石,但在干湿过程中有加速崩解的趋势,第5次循环时的相对崩解指数I₅达到了0.56。岩石的耐久性受矿物成分和胶结强度影响较大,矿物膨胀驱使岩块崩解的过程中,泥质岩块易发生均匀破碎而砂质岩块易出现非均匀破碎。石膏质泥岩中黏土矿物夹杂密实,干湿作用下易崩解,所夹杂的石膏矿物具有溶蚀性,且溶蚀后崩解液显弱酸性,石膏溶蚀产生的微裂隙和酸性环境下钙质结核的脱落是导致石膏质泥岩加速崩解的主要原因。     

广东的红层岩溶及其机制

广东岩溶红层主要为砾屑石灰岩和钙质砂岩、砾岩,形成裸露型、覆盖型红层岩溶地貌。红层中有以溶蚀为主的岩溶,也有溶蚀、潜蚀同等重要的假岩溶。存在两种红层岩溶形成机制。岩溶发育程度和岩石中方解石白云石含量与岩溶／假岩溶的比值有关。      

贵州高原分散小型红色盆地堆积物的划分与对比

一、问题的提出自王长生(1975)报导了四川黔江正阳盆地红层中首次发现鸭嘴龙动物群以来,为一向归下第三系(东湖群)的红层,提出了归晚白垩世的有力证据。他还提出川、鄂、湘、黔交境附近的红盆堆积物应与正阳盆地相比,引起了地质工作者的注意。毛志中等(1979)在贵州盘县特区石脑公社所在的红层(原定上第三系)中发现了始新世脊椎动物化石,并将其与茅台群及全省习称的下第三系相比。同年,我队秦守荣同志在修文扎佐黑山水库主坝附近的红层中,发现了大量晚白垩世安陆孔轮藻植物化石等,为黔中地区红色盆地的地层时代提供了重要古生物依据。     

石膏原岩静水溶蚀时间-温度效应试验初步研究

文章对石膏原岩在静水溶蚀条件下的时间-温度效应进行了初步研究,并从微观角度对石膏岩溶蚀破坏机理进行分析。试验发现随着溶液温度的升高、溶蚀时间的延长,石膏岩溶蚀破坏加剧。具体表现为:石膏岩失重率随温度升高、时间延长而增大,溶蚀速率均值随温度升高而增大;溶液中Ca^2+浓度随温度升高、时间延长而增大,Ca^2+浓度增长速率均值随温度升高而增大。Fick扩散及溶胀应力是石膏岩溶蚀破坏的主要原因。静水溶蚀条件下,石膏原岩主要溶蚀破坏形式为:溶胀裂缝、柱状劈裂及片状剥离。     

库车盆地古-新近纪蒸发岩沉积对喜马拉雅构造运动期次的响应

库车盆地在古—新近纪时期发育巨厚的蒸发岩沉积,自下而上蒸发岩沉积地层主要有:古近系的库姆格列木组、苏维依组;新近系下部的吉迪克组,依据部分钻井剖面资料,可识别出5个蒸发岩沉积旋回。库姆格列木时期巨厚的蒸发岩沉积（Ⅰ1、Ⅰ2沉积旋回期）是燕山后期相对宁静的大地构造环境反映;苏维依时期蒸发岩沉积（Ⅰ3沉积旋回期）在岩性、沉积范围上发生明显改变,反映了早喜马拉雅构造环境下的不稳定沉积,吉迪克早期巨厚的盐、膏沉积（Ⅰ4沉积旋回期）及沉积区域的继续迁移则反映了早喜马拉雅构造影响仍然存在但已经减弱;吉迪克中期（Ⅰ5沉积旋回期）蒸发岩沉积结束,盐湖沉积转变为陆源碎屑岩夹薄层石膏沉积,以砂、砾为主的山麓相沉积指示了当时山体抬升、遭受剥蚀、快速堆积的沉积环境,反映了相对活动的大地构造环境,是中喜马拉雅构造运动时期的开始。可见,库车盆地的蒸发岩沉积与喜马拉雅构造运动有较好的对应关系,是大区域的构造运动在小区域范围内的地质事件反映。     

人类活动影响下娘子关岩溶水系统地球化学演化

娘子关泉是我国北方最大的岩溶泉之一,也是阳泉市工农业生产和人民生活的重要供水水源。地下水地球化学演化分析表明,在地下水由补给区向排泄区运移过程中,除固有的水岩相互作用外,由于受采矿活动和地表水入渗补给的影响,岩溶水由低离子含量的HCO3-SO4或HCO3型水逐渐成为SO4型、SO4-HCO3型和SO4-HCO3-Cl型水。在泉群集中排泄区,区域流动系统与局部流动系统的地下水发生混合作用,最终形成了水质相对良好的HCO3-SO4型或SO4-HCO3型岩溶泉水。在此过程中,地下水对方解石和白云石也由最初的溶解作用演变为沉淀再结晶。尽管石膏呈持续溶解现象,但在采煤活动严重影响区域,石膏的沉淀也可能出现。地球化学模拟表明,在岩溶含水层中,地下水首先以方解石（白云石）的溶解为主;随着石膏溶解数量的增加,方解石（白云石）的溶解开始受到抑制,进而发生沉淀,石膏的溶解成为控制地下水水化学的主导过程。当矿坑水混入时,地下水相对石膏过饱和,地下水对碳酸盐岩含水介质的溶蚀能力得到增强。随着水岩反应的演进,铁氢氧化物大量沉淀,通过共沉淀和吸附作用去除了地下水中的重金属类污染物。      

Discovery,Genesis and Significance of Metallic Minerals in Evaporate Series in the Kuqa Basin

A large-scale evaporate series is developed in Paleogene-Neogene strata in the Kuqa basin. The series is composed mainly of evaporate with thin beds of clastic rock (mainly mudstone and siltstone). In grayish white medium- and coarse-grained sandstone in Miocene strata, the formation of copper minerals is in close connection with brine. In joint planes, which are developed in vertical strata, are filled with gypsum. Gypsum and copper-mineralized sandstone contains enormous copper minerals, mainly atacamite. According to the SEM analysis for salt rock, gypsum rock, limestone, grayish green siltstone, grayish white medium-coarse-grained sandstone, some minerals are composed of metallic elements including Au, Ag, Cu, Zn, Pb, Co, Ni and U etc., in which Au occurs in a native form, Cu occurs in a native form or as atacamite in salt rock, gypsum rock and limestone, Ag occurs as silver sulfide in gypsum, and Zn, Pb, Co, Ni, U occur as compounds along with the above metallic ions in evaporate or clastic rock. From SEM images, we can see that metallic elements or their compounds (oxides or sulfides) “take root” as grains in salt or gypsum crystals, which belong to primary chemical sedimentation along with evaporate, while some grains “float” on surface of salt or gypsum. In the former case, mineral grains were formed together with salt (gypsum) crystals; while in the latter case, minerals were enriched from internal metallic ions (Paleogene evaporate samples) or external metallic ions (Neogene gypsum samples) in the late stage of evaporate formation. The metallic ions in Paleogene evaporate samples might originate from weathered or denudated materials in the south Tianshan Mountains. The metallic ions in the Neogene evaporate samples might be from metal-bearing brine, which migrated upward to surface along fractures and leached into evaporate (gypsum). Occurrence of metallic minerals and their compounds (elementary substance) in Paleogene evaporate proves that diversified metallic minerals exist in evaporate. The source of metallic ions in the Neogene evaporate series shows that evaporate could provide materials for late-stage metallic mineralization.     

库车盆地古近系-新近系蒸发岩沉积旋回识别及对比

库车盆地古近纪-新近纪发育巨厚的蒸发岩沉积,根据蒸发岩沉积旋回的变化,即由于盐湖水体
从淡-咸-盐-咸-淡的旋回变化,相应地沉积物发生由碎井的屑岩-膏岩-盐岩-膏岩-碎屑岩的变化。考
虑钻井的分布位置及其剖面在时代上的完整性,选取盆地中 13口井的钻井剖面进行沉积旋回识别和对比,共识
别出 5个蒸发岩沉积旋回,其中库姆格列木群两个,苏维依组一个,吉迪克组两个。通过对比,确立了以东秋8井剖面为库车盆地蒸发岩沉积旋回对比的标准剖面,初步分析认为,盆地蒸发岩沉积旋回的沉积区迁移特征,
应受盆地基底控制和南北向构造挤压应力变化的影响。古近系蒸发岩主要分布在盆地西部,新近系吉迪克组沉
积时期,盆地西北部转为陆源碎屑岩沉积 （ 西南部发育少量蒸发岩） ,而东部发育巨厚的蒸发岩,显示出东西分
带的特点。在始新世末印度板块和欧亚板块碰撞的远距离效应影响下,库车盆地自苏维依组沉积时期蒸发岩沉
积中心就已经开始迁移,迁移中心一分为二,自盆地北西分别向南、向东移动,形成两个沉积区,吉迪克组沉
积时期在上述两个沉积区继续发育盐岩、膏岩沉积。     

Diagenetic formation of gypsum and dolomite in a cold‐water coral mound in the Porcupine Seabight,off Ireland

Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold‐water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore‐water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21·6% and 28·6% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment‐water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate‐rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds.     

地热系统作用下红层软岩力学性能试验研究

地热能源是目前绿色建筑的发展趋势,但红层软岩分布地区出现的系列建筑地基病害问题与地源热系统关系尚不清楚。依托成都某建筑群事故调查项目,研究了有无地热系统作用下泥岩、石膏岩的工程特性,并基于室内试验模拟,研究了不同加热方式、不同温度及不同浸水时间等因素下岩石宏观力学特性和微观结构特征。结果表明：（1）同一场地有无地热系统对岩石力学性质影响甚微,但有地热系统时岩体中裂隙发育数量明显增多,累积张开度明显增大;（2）随着浸泡时间增加,泥岩最大含水率可达30%以上,石膏岩含水率超不过15%,泥岩浸水软化效应较石膏岩显著,二者力学指标随含水率增加呈负指数型下降,石膏岩因晶粒大小不同,离散性大;（3）天然状态下石膏岩呈脆性破坏,泥岩呈延性破坏,石膏岩水岩界面溶蚀作用效应显著,随着石膏岩由表及里溶蚀加剧,温度变化效应对岩体内生裂隙萌发起一定促进作用;（4）在20～50 ℃温度变化范围内,石膏岩抗压强度随温度呈抛物线变化,而泥岩单调升高;（5）地热管与岩体间填筑不密实容易形成渗水通道,改变水动力条件,动水作用下使石膏岩裂隙及软弱夹层溶蚀加剧,形成更大空洞,从而诱发沉降。     

石膏对白云岩溶解影响的实验模拟研究

表生到埋藏成岩作用的温度与压力（４０-１３０℃、常压－３０ＭＰａ）条件下，含膏与不含膏白云岩的溶解实验证明:在表生与相对浅埋藏的温压条件（低于７５℃，２０ＭＰａ）下，石膏（或硬石膏）的存在可不同程度地加速白云岩的溶解，随着实验温度和压力的升高，石膏（或硬石膏）对白云岩溶解的这种积极作用逐渐降低。在相对深埋藏的温压条件（高于７５℃、２０ＭＰａ）下，石膏（或硬石膏）的存在显著阻止白云岩的溶解，随着实验温度和压力的继续升高，石膏（或硬石膏）对白云岩溶解的这种消极作用也逐渐增加。从实验的这种结果可以预测，在近地表条件下和埋藏成岩作用的早期阶段，由溶解作用造成的含膏白云岩地层的次生孔隙将比不含膏的白云岩地层更为发育，因而在经历了古风化作用的地层中，含膏白云岩层更易形成良好的储层；与之相反，在相对高温高压的深埋藏成岩阶段，不含膏的白云岩地层中将更容易因酸性水的溶解作用而形成次生孔隙。因而在非蒸发沉积环境中形成的白云岩体（如正常海沉积环境的灰岩中的白云岩透镜体）更易因深埋藏溶蚀作用而形成良好的储层。     

Computational analysis of the experimental physical model: Karstic layer in dam foundation

Karstic rocks (soluble rocks) exist in different areas of the world having useful/harmful structural and environmental impacts. One of the useful aspect is availability of rich water resources in some regions. An important defect of this kind of rocks is their low strength against water flows. These rocks usually dissolve in acidic water and as a result abundant caverns are created inside them. The gypsum and salt present in these rocks dissolve even in non-acidic water. Presence of these rocks in different foundations and reservoirs especially in dams could be potentially dangerous and cause enormous problems. If dams are located above soluble rocks like limestone, dolomite or gypsum they are endangered by karstification. Karstification is a dynamic process resulting in voids within the rocks due to dissolution. This dissolution leads to the formation of a pipe system within the sub-surface In the physical modeling, effects of cut-off wall height within gypsum layer were examined and monitored. Then with GeoStudio and Flac software, results of physical modeling are analyzed. In each experiment, cut-off wall height was changed. The result of the experiments indicated that as the gypsum Karst is very weak against water, cut-off wall must continue completely within the gypsum layer, as a complete positive cut-off wall.     

Neogene evaporites in desert volcanic environments: Atacama Desert, northern Chile

The Upper Miocene and Pliocene evaporite deposits of the Atacama Desert of northern Chile (Hilaricos and Soledad Formations) are among the few non‐marine evaporites in which aridity not only formed the deposits, but has also preserved them almost unaltered under near‐surface conditions. These deposits are largely composed of displacive Ca sulphate and halite together with minor amounts of glauberite, thenardite and polyhalite. However, at the base and top of these deposits, there are also beds of gypsum crystal pseudomorphs that originally formed as free‐growth forms within shallow brine bodies, rather than as displacive sediments. The halite is present as interstitial cement, displacive cubes and shallow‐water, bottom‐growth chevron crusts. Most of the calcium sulphate is presently anhydrite, pseudomorphous after gypsum, that was the primary depositional sulphate mineral. The secondary anhydrite formed under early diagenetic conditions after slight burial (some metres) resulting from the effect of strongly evolved pore brines. The anhydrite has been preserved without rehydration during late diagenetic and exhumation stages on account of the arid environment of the Atacama Desert. Both the Hilaricos and the Soledad Formations contain geochemical markers indicating that these Neogene evaporites had a largely non‐marine origin. Bromine content in the halite is very low (few p.p.m.), indicating neither a sedimentological relation with sea water nor the likelihood of direct recycling of prior marine halites. Moreover, the δ³⁴S of sulphates (+4·5‰ to +9‰) also reflects a non‐marine origin, with a strong volcanic influence, although some recycling of Mesozoic marine sulphates cannot be ruled out. δ³⁴S of dissolved sulphate from hot springs and streams in the area commonly displays positive values (+2‰ to +10‰). Leaching of oxidized sulphur and chlorine compounds from volcanoes and epithermal ore bodies, very common in the associated drainage areas, have been the main contribution to the accumulation of evaporites. The sedimentary and diagenetic evolution of the Hilaricos and Soledad evaporites (based on lithofacies analysis) provides information about the palaeohydrological conditions in the Central Depression of northern Chile during the Neogene. In addition, the diagenesis and exhumation history of these evaporites confirms the persistence of strongly arid conditions from Late Miocene until the present. A final phase of tectonism took place permitting the internal drainage to change and open to the sea, resulting in dissolution and removal of a significant portion of these deposits. Despite the extensive dissolution, the remaining evaporites have undergone little late exhumational hydration.     

Subsidence hazards due to evaporite dissolution in the United States

Evaporites, including gypsum (or anhydrite) and salt, are the most soluble of common rocks; they are dissolved readily to form the same type of karst features that typically are found in limestones and dolomites, and their dissolution can locally result in major subsidence structures. The four basic requirements for evaporite dissolution to occur are: (1) a deposit of gypsum or salt; (2) water, unsaturated with CaSO₄ or NaCl; (3) an outlet for escape of dissolving water; and (4) energy to cause water to flow through the system. Evaporites are present in 32 of the 48 contiguous states of the United States, and they underlie about 35–40% of the land area. Karst is known at least locally (and sometimes quite extensively) in almost all areas underlain by evaporites, and some of these karst features involve significant subsidence. The most widespread and pronounced examples of both gypsum and salt karst and subsidence are in the Permian basin of the southwestern United States, but many other areas also are significant. Human activities have caused some evaporite–subsidence development, primarily in salt deposits. Boreholes may enable (either intentionally or inadvertently) unsaturated water to flow through or against salt deposits, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures above the cavity can cause land subsidence or catastrophic collapse.