关于我国的盐溶角砾岩

盐溶角砾岩可分为溶解-崩塌角砾岩和塑变-交代角砾岩两种类型。它们的主要鉴定特征是分布的层位稳定、角砾成分单一,而且无例外地均和易溶蒸发盐岩伴生。我国主要成盐期的地层中,均有盐溶角砾岩分布,不过发育的程度和特点略有不同。     

陕南下中三叠统“膏溶角砾岩”特征、成因及其找矿意义

<正> 陕南早中三叠世地层中广泛分布着一套与碳酸盐岩-蒸发岩有关的非原生沉积的“角砾岩”,由于它们直接或间接地与盐溶作用有关,故常称之为“膏溶角砾岩”或“盐溶角砾岩”或“岩溶角砾岩”等。关于其地质特征及成因,我们通过对陕南下中三叠统中分布的“膏溶角砾岩”的研究,得出以下几点认识:1.“膏溶角砾岩”的地质特征、成因及其找矿指示意义等各有不同,不能一概称之为“膏溶角砾岩”。因此,我们将其划分为:膏溶残余角砾状碳酸盐岩;坍塌角砾状碳酸盐岩及喀斯特角砾状碳酸盐岩。     

论中国的盐溶角砾岩

<正> 岩石学中常把直径大于2mm 的未磨圆的各种岩石碎屑,经胶结组成的碎屑岩总称为角砾岩。角砾岩有多种类型,如压碎角砾岩、火成碎屑角砾岩、撞击或回落角砾岩、假角砾岩、地滑和滑坍角砾岩、构造角砾岩、崩坍(坍落)和溶解角砾岩、塌陷角砾岩等。在众多的角砾岩中,有一种角砾岩是与蒸发岩有关的。这种角砾岩是蒸发岩在地表或近地     

下扬子地区青龙群上部角砾岩成因问题

1989—1990年,安徽省地质科学研究所与德国下萨克森州不伦瑞克大学地质古生物研究所在下扬子地区合作进行了中三叠统的蒸发岩沉积特征及含钾性评价的研究,对下扬子地区青龙群上部(东马鞍山组)地表角砾岩层进行了详细的野外地质工作。我们认为这套以往一直被看作盐溶倒塌成因的角砾岩,主要是碎屑流沉积的结果,有少量构造角砾岩、膏溶崩坍角砾岩。碎屑流沉积发育于长江北岸的宿松、安庆、巢湖、无为和长江南岸的贵池、铜陵、繁昌、南京、镇江、溧阳等地,呈北东—南西向带状展布,分布广泛、规模大,最大沉积厚度超过百米以上,十分引人注目。     

华北地区中奥陶统蒸发盐岩溶解坍塌角砾岩化作用

华北地区中奥陶统下马家沟组第二、四段及上马家沟组第三段广泛分布着三层角砾岩。角砾岩系由蒸发盐溶解致使其白云岩夹层及残留蒸发盐岩沉陷坍塌所形成。这是一个复杂的过程,可划分为四个阶段:1.蒸发盐岩层塑性变形和矿物相的转变导致原生沉积构造破坏和部分角砾岩化;2.形成具蒸发盐和白云石基质的角砾岩;3.形成具白云石基质的角砾岩;4.形成细-粗晶石灰岩、角砾灰岩。     

中上扬子寒武系蒸发岩岩相古地理

中上扬子区寒武系蒸发岩层位上属龙王庙阶和毛庄阶至张夏阶,分布在成都以东、贵州遵义以北和武陵山以西,形成四川长宁、重庆永川-江津、湖北利川、武汉4个沉积中心,是早古生代海相油气的重要盖层。经深井揭露,寒武系蒸发岩为石膏和石膏夹石盐,有三种岩石类型:粉砂质白云岩、白云岩与石膏互层、石膏夹石盐。地表以盐溶角砾岩、石盐假晶、次生石膏为标志,川东有少量盐泉出露。寒武纪时中上扬子区蒸发岩沉积具有构造和古地理障壁及岩相障壁,西部除龙门山前分布有岛链状的古陆外,早寒武世末川中古隆起已具雏形,并由西向东迁移扩大;黔中古隆起至中晚寒武世可能为水下无沉积区,具有局限障壁作用。早中寒武世碳酸盐浅滩分布在构造障壁的东侧。构造、古地理和沉积相展布,使中上扬子区转化为局限、封闭或半封闭构造古地理环境,是该区沉积蒸发岩的关键条件。     

陕西柞山地区钠长石碳酸盐角砾岩的地质特征与矿产

柞山地区钠长石碳酸盐角砾岩的地质特征表明,它既非同生沉积有砾岩,也非构造角砾岩或盐溶塌陷角砾岩,而是一种与岩浆活动密切关联的流体隐爆角砾岩。已发现钠长石碳酸盐角砾岩与金,铜,镍,钴,铅,锌等多种矿产有关。     

中酸性隐爆角砾岩、次火山(超浅成)岩与成矿的关系——以广西贵港新民—吉塘铜银矿区为例

研究了隐爆角砾岩与断层角砾岩、火山爆破角砾岩的区别,隐爆岩筒上、中、下部隐爆角砾岩的区别,含矿隐爆角砾岩筒特征,以及与隐爆、成矿作用有关的次火山(超浅成)岩特征。     

遂渝高铁无砟轨道综合试验段盐溶角砾岩工程地质特征试验研究及防治措施综述

遂渝高铁无砟轨道综合试验段对地质勘察工作提出了高要求，场区大面积分布盐溶角砾岩具诸多不利工程地质特性，通过区域地质、现场调绘、地质钻探、原位测试及取样试验分析等综合工程地质勘察，对场区盐溶角砾岩分布和工程特性分析研究和提出防治措施，为设计和施工处理提供地质参数和依据。对类似工程地质条件的西南山区高速铁路勘察设计有一定借鉴意义。     

东准噶尔成矿带岩浆隐蔽爆破作用与成矿

新疆东准噶尔地区乌伦布拉克铜矿、老山口铜—铁—金矿两地皆存在花岗质岩浆隐蔽爆破作用。前者形成了与潜火山英安玢岩侵入体密切伴生的英安玢岩质隐爆角砾岩,后者形成了与潜火山闪长玢岩侵入体相伴生的闪长玢岩质隐爆角砾岩和闪斜煌斑岩质隐爆角砾岩。岩浆隐蔽爆破作用是伴随该区华力西中晚期—晚期地槽褶皱造山运动而发生的一种超浅成岩浆作用,其与铜、金等金属成矿的关系密切;与其有关形成了隐爆角砾岩筒型铜(金)矿和破碎带蚀变岩型金矿。两种类型的矿床都显示出广阔的找矿前景。     

Diagenetic evolution of Aptian evaporites in the Namibe Basin (south‐west Angola)

The widespread and dissected nature of the Angolan gypsiferous salt residuals offers a uniquely detailed view of the lateral and vertical relations inherent to secondary evaporite textures, which typify exhumed salt masses worldwide. Such secondary textures are sometimes misinterpreted as primary evaporite textures. Thin, metre‐scale and patchy, dome‐like gypsum accumulations are well‐exposed within strongly incised present‐day river valleys along the eastern margin of the Namibe and Benguela basins (south‐west Angola). These sections are time equivalent to the main basinward subsurface evaporites (Aptian Loeme Formation) which mostly consist of halite. The gypsum (here called the Bambata Formation) is interpreted to represent the final residual product of fractional dissolution and recrystallization of the halite mass that occurred during Late Cretaceous margin uplift and continues today. This halite underwent multiple episodes of diagenetic alteration between its deposition and its final exhumation, leading to the formation of various secondary gypsum fabrics and solution‐related karst and breccia textures that typify the current evaporite outcrop. Four different diagenetic gypsum fabrics are defined: thinly bedded alabastrine, nodular alabastrine, displacive selenite rosettes and fibrous satin‐spar gypsum. Current arid conditions are responsible for a thin weathered crust developed at the top of the outcropping gypsum, but the fabrics in the main core of the current at‐surface evaporite unit mostly formed during the telogenetic stage of uplift prior to complete subaerial exposure. Alteration occurred as various dissolving and rehydrating saline minerals encountered shallow aquifers in the active phreatic and vadose zones. Geomorphological and petrographic analyses, mostly based on the cross‐cutting relations and crystallographic patterns in the outcrop, are used to propose a sequence of formation of these different fabrics.     

中国蒸发岩研究中几个值得重视的地质问题的讨论

本文概括地介绍了近一个多世纪以来蒸发岩成因理论发展过程。根据现代盆湖的实际资料,强调了深部水是成盐物质来源的重要方面之一,指出含盐盆地天然水循环是研究蒸发岩成因理论的重要方面,讨论了卤水演化,特别强调我国应积极开展矿相学、蒸发岩测年和盐类矿物流质色裹体的研究。     

A barred-basin marine evaporite in the Upper Proterozoic of the Amadeus Basin, central Australia

The Ringwood evaporite is part of the 900 m.y. old Bitter Springs Formation, a warm-water shallow-marine sequence of stromatolitic dolomite and limestone, microfossiliferous chert, red beds, quartzite, and evaporites. The evaporite at Ringwood comprises two parts: (i) a lower 127 m characterized by brecciated pyritic bituminous dolomite, together with smaller amounts of dolomite-gypsum breccia, friable chloritic dololutite, coarsely crystalline anhydrite, and satin-spar gypsum; and (ii) an upper 133 m which is similar except that bituminous dolomite forms only one bed, and the characteristic rock-type is dolomite-gypsum breccia. The evaporite is overlain by limestone breccia and massive stromatolitic limestone, interpreted as an algal reef. Gypsum is secondary after anhydrite, and the ratio of gypsum to anhydrite increases upwards. The evaporite shows none of the features of a sabkha or desiccated deep ocean basin deposit, and instead is interpreted as the filling of a barred basin which was cut off from the ocean by growth of an algal barrier reef. As circulation became restricted, bituminous dolomite deposited in the lagoon behind the reef, together with pyrite from the destruction by anaerobic bacteria of algal debris derived from the reef. With continued evaporation, brine concentration increased and gypsum precipitated. Occasional dust storms contributed wind-blown clay to the deposit. The barrier reef transgressed diachronously across the evaporite lagoon, and was eventually drowned when normal marine conditions became established. Burial of the evaporite to about 7000 m beneath the succeeding sediments of the Amadeus Basin converted gypsum to anhydrite, and formed chlorite by reaction of clay with dolomite. Late Palaeozoic tectonism folded and brecciated the rocks, and was followed by erosion which eventually exposed the evaporite to ingress of meteoric water. Hydration of anhydrite to gypsum ensued, the reaction becoming less complete with increasing depth from the ground surface.     

Salt Crystallization Sequences of Nonmarine Brine and Their Application for the Formation of Potassium Deposits

The salt assemblages precipitated during evaporation of concentrated brine collected from Gasikule Salt Lake (GSL) were studied to better understand the formation of potassium deposits in the Qaidam Basin. The study included isothermal evaporation at 25 °C in the laboratory and solar evaporation in the ponds at GSL field. Brines increased in density and became moderately acidic (pH?≈?5.30) while major ion geochemistry and precipitate mineralogy all showed broad agreement between both systems. Four salt assemblages were identified in the isothermal evaporation experiment: halite?→?halite?+?hexahydrite?→?halite?+?bischofite?+?carnallite?→?bischofite. Alternately, three salt assemblages were recognized in the solar evaporation: halite?→?halite?+?epsomite?+?carnallite?→?halite?+?carnallite?+?bischofite. The key difference in salt assemblages between the two systems is attributed to differences in relative humidity and temperature conditions. Although the GSL has deep spring inflow recharge, the high abundance of MgSO₄ salts demonstrates that the salt assemblages are similar to normal seawater evaporation. Thus, different proportions of deep spring inflow and river water could form both MgSO₄-deficient potassium evaporite and normal seawater potassium evaporites. Therefore, nonmarine water may form diverse potassium evaporite deposits in continental basins when the geological structure as well as hydrogeological and climatic conditions is appropriate.     

Petrography and geochemistry of the Belle Roche breccia (lower Visean, Belgium): evidence for brecciation by evaporite dissolution

The lower Visean Belle Roche breccia (east Belgium) displays a number of features that indicate brecciation by evaporite dissolution collapse: the sharp lower contact of the breccia, the gradual transition into the overlying strata, the presence of semi-continuous beds within the breccia giving it a crude ‘stratification’, and the existence of several types of (calcite, dolomite and silica) evaporite pseudomorphs. Furthermore, the majority of the breccia fragments indicates hypersaline to lagoonal sedimentation conditions. Most of these fragments display an interlocking fabric. The interpretation is also supported by the existence of continuous evaporite beds replaced by carbonates (calcite and dolomite) both under and overlying the breccia. The brecciation history is characterized by gradual subsidence. Multiple brecciation episodes are recognized, and are best seen in the lower breccia which underwent at least two major brecciation episodes. Here, brecciated and veined breccia fragments occur within a microsparite (neomorphosed mud) matrix. Brecciation of these strata was due to the dissolution of interlayered evaporites. The second brecciation event relates to infiltration of meteoric water and to the dissolution of the remaining evaporites. This infiltration was probably triggered by the orogenic event at the end of the Visean (Sudetic orogenic phase). The whole breccia was finally cemented by a blocky calcite. The different lithologies and cements were characterized by their trace element (Mg, Sr, Na, Fe, Mn, K), insoluble residue and organic matter content. Carbon/oxygen isotope data of the cements and replaced evaporite layers helped to place the multiple collapse episodes within a general diagenetic model. Solution-reprecipitation processes within the original aragonite-dominated mud fragments, as well as in the early diagenetic dolomite fragments, have been recognized. The geochemical data show that these transformation processes occurred in equilibrium with the same fluid. These processes may have occurred within a freshwater lens very early in the diagenetic evolution or under shallow burial conditions. Cementation of blocky calcite occurred in a meteoric realm under burial conditions.     

蒸发岩非传统稳定同位素研究综述

蒸发岩是海水/卤水蒸发浓缩的产物,不同的水化学环境下析出的蒸发岩类型不同,其在不同的地质历史时期都有分布,是重要的古海水和古环境记录载体。蒸发岩研究的主要问题包括:蒸发岩的物质来源、形成时代、蒸发盆地和卤水的演化历史、蒸发岩矿物所记录的环境变化。一些矿物、元素及同位素指标可用于解决这些问题,其中稳定同位素对于示踪蒸发岩的物质来源与形成过程具有不可替代的作用。近20年来,非传统稳定同位素地球化学获得快速发展,并在蒸发岩研究中获得成功应用,这些同位素体系包括阴离子元素B、Cl和Br,以及阳离子元素Mg、K和Ca。本文综述了多个非传统稳定同位素在蒸发岩领域的研究,主要包括:蒸发岩矿物与溶液之间的同位素分馏系数、蒸发岩的同位素信息重建古海水同位素组成及示踪蒸发岩成因和时代等。     

上扬子区(四川盆地)寒武系的含盐性与地质背景

据记载,分布于上扬子区寒武系的石膏岩仅有零星资料。如今,大量蒸发岩如溶蚀角砾岩、硬石膏、石盐岩及富钾卤水等已被发现。沉积相经历了从盆地相、台地相到蒸发岩相的演化过程。在中、下寒武统中找到海退沉积序列。古构造-古地理背景是蒸发岩沉积的重要控矿条件之一。周边板块运动及塑性基底的褶皱,导致台缘隆起及台内坳陷的形成。岩相古地理图展示从碳酸盐、硫酸盐到氯化物盐类的“泪滴式”沉积相带。蒸发岩沉积于台缘隆起及礁生长进入堰塞潟湖至盐湖阶段。在稳定坳陷区沉积盆地中蒸发岩系发育;石盐岩较厚,其溴氯比值为0.2—0.4;古气候炎热、干燥;在蒸发岩体周围有沉积(封层)水及溶滤水,其含钾(K~+)量为0.10—4.76g/L;水文地球化学比值(如钾氯比值、钾盐比值及钾溴比值等)指示含钾异常;盐湖浓缩卤水达到氯化物盐类沉积阶段及相应的构造封闭程度;含盐地质标志广泛分布等等。鉴于上述,估计该区可能具备钾盐成矿条件。然而目的层埋藏太深,因此笔者建议,应在浅埋部位进行有效的成矿预测,为普查指出远景区。     

塔西南坳陷中新生代蒸发岩沉积初探

通过资料搜集、蒸发岩野外露头地质调查、石盐岩沉积特征分析及盐类矿物学研究,对塔里木盆地塔西南坳陷中新生代蒸发岩的分布、层位、盐类矿物组合、成因进行了初步探讨。塔西南坳陷石盐岩沉积呈透镜体状,主要沿西昆仑山前分布,常含有褐红色、灰绿色泥砾,泥砾岩性与吐依洛克组下段岩性一致,推测应为吐依洛克组沉积晚期海退期成盐,其层位应归属于吐依洛克组上段。石盐岩透镜体在横向分布上不连续,反映了当时塔西南坳陷内部可能存在多个古盐湖次级凹地,其在干旱气候条件下经浓缩蒸发成盐。蒸发岩矿物除石盐、石膏外,还见有杂卤石、钙芒硝等,其中杂卤石可能为后期富钾卤水交代原生石膏的产物,而乌泊1井石盐表面大量的次生钙芒硝可能为盐湖后期石盐析出阶段含钙地下水缓慢持续补给盐湖的产物。     

GIS and ANN coupling model: an innovative approach to evaluate vulnerability of karst water inrush in coalmines of north China

Evaporites, including rock salt (halite) and gypsum (or anhydrite), are the most soluble among common rocks; they dissolve readily to form the same types of karst features that commonly are found in limestones and dolomites. Evaporites are present in 32 of the 48 contiguous states in USA, and they underlie about 40% of the land area. Typical evaporite-karst features observed in outcrops include sinkholes, caves, disappearing streams, and springs, whereas other evidence of active evaporite karst includes surface-collapse structures and saline springs or saline plumes that result from salt dissolution. Many evaporites also contain evidence of paleokarst, such as dissolution breccias, breccia pipes, slumped beds, and collapse structures. All these natural karst phenomena can be sources of engineering or environmental problems. Dangerous sinkholes and caves can form rapidly in evaporite rocks, or pre-existing karst features can be reactivated and open up (collapse) under certain hydrologic conditions or when the land is put to new uses. Many karst features also propagate upward through overlying surficial deposits. Human activities also have caused development of evaporite karst, primarily in salt deposits. Boreholes (petroleum tests or solution-mining operations) or underground mines may enable unsaturated water to flow through or against salt deposits, either intentionally or accidentally, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures can cause land subsidence and/or catastrophic collapse. Evaporite karst, natural and human-induced, is far more prevalent than is commonly believed.