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1.
Lake Bogoria is a saline, alkaline, meromictic lake in a geothermally active part of the Kenya Rift Valley. Coring of the lake floor has shown two types of sedimentation – a shallow fan–deltaic clastic zone and a deeper zone with alternating organic muds and evaporites. The organic muds formed during periods of relatively high lake level and high microbial productivity, the evaporites during more arid phases. Analyses of the cores show many environmental fluctuations during the past 30000 years, related to regional climatic changes and to local tectonic and hydrological controls. 相似文献
2.
全球性的构造运动末期一般伴着海退和干旱的气候环境,而蒸发岩沉积与大地构造条件紧密相关。中亚卡拉库姆盆地、阿富汗_塔吉克盆地、塔里木盆地自晚侏罗世至中新世以来至少发生了3次大规模海侵_海退旋回,每次海侵_海退均受特提斯构造事件控制。卡拉库姆盆地、阿富汗_塔吉克盆地为晚侏罗世—早白垩世蒸发岩沉积、塔里木盆地的莎车次级盆地为晚白垩世—古新世蒸发岩沉积,库车次级盆地为古新世—中新世蒸发岩沉积,形成特提斯构造域自西向东蒸发岩沉积时代逐渐变新的盐湖链。中亚及塔里木盐湖链在海侵_海退旋回的控制下,至少发生5次大规模的蒸发岩沉积,发育2种不同的蒸发岩沉积序列,分别对应3次海退期蒸发岩沉积序列及2次断续海侵期蒸发岩沉积序列,具体为晚侏罗世晚期(海退期)卡拉库姆盆地、阿富汗_塔吉克盆地蒸发岩沉积;早白垩世—晚白垩世早期(断续海侵期)阿富汗_塔吉克盆地蒸发岩沉积;晚白垩世晚期(海退期)莎车次级盆地蒸发岩沉积;古新世—中新世(断续海侵期)莎车次级盆地、库车次级盆地蒸发岩沉积;中新世晚期—上新世早期(海退期)库车次级盆地蒸发岩沉积。塔里木与中亚古盐湖发育受控于特提斯构造事件及海侵_海退旋回,而海侵_海退旋回又控制2种不同的蒸发岩沉积序列。蒸发岩沉积序列、古盐湖演化阶段、蒸发岩物质来源、沉积环境决定了盐类矿物沉积类型(单一化学岩型、陆缘碎屑岩_化学岩型),卡拉库姆盆地、阿富汗_塔吉克盆地盐类矿物与塔里木盆地相比,种类简单,反映了盆地化学岩与陆源碎屑_化学岩沉积的区别及后期构造运动对盐类矿物种类的主控作用。 相似文献
3.
诸广山棉花坑铀矿深部矿化特征及找矿前景 总被引：4，自引：0，他引：4
有利的地质构造背景和深部构造环境、多期次构造岩浆活动和蚀变叠加、成群成组的成矿构造带以及花岗岩丰富的铀源等优越的成矿条件,使诸广山地区成为花岗岩型铀矿有利成矿区。通过分析棉花坑铀矿床舍矿构造带、热液脉体及物质组成、热液成分、矿石矿物及蚀变等在垂向上的变化规律以及深部矿化特征,说明区内深部有较大的找矿潜力。 相似文献
4.
Messinian evaporites, which resulted from the salinity crisis during the final closure of the Mediterranean Sea, are exposed in SE Turkey. These evaporites formed in two isolated sub-basins, Iskenderun-Arsuz (IA) and Hatay-Samanda? (HS), which belong to different depositional configurations and tectonic structures. The Neogene fill of these sub-basins consists of a thick sedimentary succession that started with Early Miocene terrestrial clastics, followed by reefs (Middle Miocene) and shallow water siliciclastics (Tortonian - Early to Late Miocene) and finally Messinian evaporates. These sub-basins accumulated in a diverse range of depositional environments from very shallow to deeper water. Evaporite facies in the IA sub-basin consist of sabkhas, saline lagoons and ponds. They are mainly represented by chemical deposits such as scattered gypsum nodules and balls, nodular bedded gypsum, laminated gypsum (Type-A) and selenites (Type-S1). Evaporites in the HS sub-basin mainly consist of detrital gypsum composed of gypsum laminae (Type-B, C), gypsum arenite-rudites and deeper water selenites (≤ 20 m), and resedimented selenites (Type-S2), which were deposited on a sulfate platform with a slope-basin transitional zone. Secondary gypsum with alabastrine and porphyroblastic textures as well as satin spar veins is commonly associated with the sabkha-type evaporites of the IA sub-basin. Deeper-water clastic evaporites of the HS sub-basin have generally remained as primary gypsum or have only been slightly affected by diagenetic alterations. The isotope values (87/86Sr; δ18O SMOW; and δ34S CDT) from the different kinds of gypsum lithofacies of the sub-basin are similar to those of the Messinian evaporites in other peri-Mediterranean basins, indicating an origin from marine water without external or basinal contributions.The Messinian evaporites examined in this paper are overlain by Early Pliocene (Zanclean) deposits composed of shallow- and deep-water siliciclastics and carbonates with local intercalations of Lago-Mare-type strata. Throughout the Messinian evaporitic stage, the IA sub-basin was mainly comprised of shallow water evaporites, while the HS sub-basin underwent deepening related to regional tectonics induced by the Dead Sea Fault during the construction of the Hatay Graben. 相似文献
5.
特提斯域是全球最重要的密西西比河谷型(MVT)铅锌矿床富集区,矿床广泛地分布在陆-陆碰撞造山带两侧的陆块上,就位于碰撞形成的褶皱-逆冲带和前陆带内,成矿通常发生在碰撞挤压作用晚期或之后、区域处于走滑或伸展的阶段。矿床、矿体的就位与张性断裂密切相关,主要控矿因素有蒸发盐底辟构造、碳酸盐岩溶蚀垮塌构造、蒸发盐溶蚀垮塌构造、高孔隙度白云岩、含重晶石地层等。油气流体在许多矿床和矿集区出现,其主要通过与硫酸盐发生反应为铅锌成矿提供还原硫。陆-陆碰撞的大地构造环境、大量的蒸发盐、丰富的油气流体是特提斯域富集MVT矿床的重要原因,域内寻找MVT矿床的潜力巨大。 相似文献
6.
本文通过对西天山研究区的遥感地质解译、野外实地验证和综合对比研究,认为西天山地区与邻区的穆龙套金矿、库姆托尔金矿同处一条巨型的构造带上,具有非常相似的大地构造环境、构造演化和赋金建造条件,尤其是分布于那拉提构造带南缘的弧形构造带和南北向贯穿那拉提构造带的横向断裂组是控矿的重要因素。区域上赋金层炭质岩系的存在和蚀变体的广泛发育,使金元素活化、富集成为可能。研究区内大量的金矿化、异常是金矿体存在的客观反映。据此,笔者预测出４处找矿有利地段。 相似文献
7.
Narjess El Euch-El Koundi Serge Ferry Jean-Pierre Suc Georges Clauzon Mihaela Carmen Melinte-Dobrinescu Christian Gorini Anissa Safra Fouad Zargouni 《地学学报》2009,21(1):41-48
Outcrops, offshore wells, electric logs and seismic profiles from northern Tunisia provide an opportunity to decipher the Messinian Salinity Crisis in the Strait of Sicily. Messinian deposits (including gypsum beds) near the Tellian Range reveal two successive subaerial erosional surfaces overlain by breccias and marine Zanclean clays, respectively. In the Gulf of Tunis, Messinian thick evaporites (mostly halite) are strongly eroded by a fluvial canyon infilled with Zanclean clays. The first erosional phase is referred to the intra-Messinian tectonic phase and is analogous to that found in Sicily. The second phase corresponds to the Messinian Erosional Surface that postdates the marginal evaporites, to which the entire Sicilian evaporitic series must refer. The Western and Eastern Mediterranean basins were separated during deposition of the central evaporites. 相似文献
8.
我国可地浸砂岩型铀矿成矿模式初步探讨 总被引：12，自引：4，他引：12
本文通过综合分析伊犁盆地南缘、吐哈盆地西南缘、鄂尔多斯盆地东北部地区等可地浸砂岩型铀矿重点成矿区的成矿环境和主要控制因素, 探讨了我国可地浸砂岩型铀矿的成矿模式, 认为伊犁盆地南缘、吐哈盆地西南缘层间氧化带型铀矿床主要受有利的构造、沉积建造和层间氧化带控制, 具有含矿建造铀预富集、表生后成改造成矿及矿后构造活动进一步叠加富集的特征, 而鄂尔多斯盆地东北部地区的铀矿化主要受古层间氧化带型铀矿化控制, 并遭受二次还原的改造作用, 其矿化规模显得较前者更大。 相似文献
9.
Stefan Schröder B. Charlotte Schreiber† Joachim E. Amthor‡ Albert Matter 《Sedimentology》2003,50(5):879-898
Abstract Six evaporite–carbonate sequences are recognized in the terminal Neoproterozoic–Early Cambrian Ara Group in the subsurface of Oman. Individual sequences consist of a lower, evaporitic part that formed mainly during a lowstand systems tract. Overlying platform carbonates contain minor amounts of evaporites and represent transgressive and highstand systems tracts. Detailed sedimentological and geochemical investigation of the evaporites allowed reconstruction of the depositional environment, source of brines and basin evolution. At the beginning of the evaporative phase (prograding succession), a shallow-water carbonate ramp gradually evolved into a series of shallow sulphate and halite salinas. Minor amounts of highly soluble salts locally record the last stage of basin desiccation. This gradual increase in salinity contrasts sharply with the ensuing retrograding succession in which two corrosion surfaces separate shallow-water halite from shallow-water sulphate, and shallow-water sulphate from relatively deeper water carbonate respectively. These surfaces record repeated flooding of the basin, dissolution of evaporites and stepwise reduction in salinity. Final flooding led to submergence of the basin and the establishment of an open-water carbonate ramp. Marine fossils in carbonates and bromine geochemistry of halite indicate a dominantly marine origin for the brines. The Ara Group sequences represent a time of relatively stable arid climate in a tectonically active basin. Strong subsidence allowed accommodation of evaporites with a cumulative thickness of several kilometres, while tectonic barriers simultaneously provided the required restricted conditions. Subsidence allowed evaporites to blanket basinal and platform areas. The study suggests a deep-basin/shallow-water model for the evaporites. 相似文献
10.
Stefano Carruba Raffaele Casnedi Cesare R. Perotti Milly Tornaghi Giorgio Bolis 《International Journal of Earth Sciences》2006,95(4):665-683
The Periadriatic foredeep (Italy) was generated by Neogene downbending of the Adria Plate under the Apennine Chain. The basin is filled with Plio-Pleistocene siliciclastic turbidites. Its substratum consists of the carbonate succession of the southwestern Adria Plate margin. The influence of the basin’s morphology on sedimentation and subsequent tectonic evolution is investigated in the Abruzzo sector of the foredeep (Cellino Basin). The substratum is composed of Messinian evaporites that dip towards the Apennines (W). A NNW component along the depocentral axis is divided into four blocks with different depths. The substratum was also affected by a Messinian extensional fault system, not involving the overlying Pliocene sequence. This morphology controlled the distribution of the turbidites in the lower part of the Cellino Basin. The Plio-Pleistocene compressional deformation of the foredeep produced an inner complex structure (Internal Structure), involving the foredeep substratum and an outer imbricate thrust system (Coastal Structure), detached over the faulted Messinian evaporites. This thrust system is parallel to the extensional faults, suggesting a strong influence of the substratum morphology on the development of the compressional structures. The overall structural setting was validated with a balanced cross-section. Out-of-sequence thrusting and non-coeval deformation within each thrust sheet characterize the local tectonic history. 相似文献
11.
Deep-water clastic evaporites deposition in the Messinian Adriatic foredeep (northern Apennines,Italy): did the Mediterranean ever dry out? 总被引：1，自引：0，他引：1
A new genetic facies model for deep-water clastic evaporites is presented, based on work carried out on the Messinian Gessoso-solfifera Formation of the northern Apennines during the last 15 years. This model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts. The model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites, representing the most common evaporite facies of the northern Apennines, and the definition of the genetic and stratigraphic relationship with primary shallow-water evaporites formed and preserved in marginal settings. Due to the severe recrystallization processes usually affecting these deposits, petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity-driven deposits ranging from debrisflow to low-density turbidites. Almost all the laminar ‘balatino’ gypsum, previously considered a deep-water primary deposit, is here reinterpreted as the fine-grained product of high to low-density gravity flows. Facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the Apennine foredeep basin. The Messinian Salinity Crisis occurred during an intense phase of geodynamic reorganization of the Mediterranean area that also produced the fragmentation of the former Miocene Apennine foredeep basin. In this area, primary shallow-water evaporites equivalent to the Mediterranean Lower Evaporites, apparently only formed in semi-closed thrust-top basins like the Vena del Gesso Basin. The subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins. Vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the Messinian tectonic evolution of the Apennine thrust belt and related exhumation–erosional processes. The facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts; the importance of clastic evaporites deposits has been overlooked in the study of other Mediterranean areas. Based on the Apennine basins experience, it is suggested here that evaporites diffused into the deeper portions of the Mediterranean basin may consist mainly of deep-water resedimented deposits rather than shallow-water to supratidal primary evaporites indicative of a complete basin desiccation. 相似文献
12.
彭山地区燕山晚期形成的钙碱性花岗岩体与区内有色金属矿产的形成具有直接成因上的联系。四个典型矿床的地质特征及控岩控矿特点反映出矿床均受到了穹窿体系中层间滑动断裂及次级断裂的控制。矿田中部分矿床的硫同住素、铅同住素的分析数据表明，矿床的Sn，Pb，Zn矿物质与岩体具有同源性，岩体的侵位过程为矿床的形成带来大量的矿物质。对成矿机制的研究显示板块作用产生的剪切力是造成区内深部岩石重熔的源动力，而早期形成的断裂体系及后期形成穹窿构造为矿物质的运移提供了有利的通道，在完善的循环对流机制配合下，成矿物质在迁移过程中发生较为充分的分异作用，各类矿物质在相应的物化环境中结晶沉淀，并在有利的构造部位富集成矿。 相似文献
13.
二连盆地马尼特坳陷西部幕式裂陷作用对铀成矿的影响 总被引：1，自引：0，他引：1
二连盆地包括马尼特坳陷早白垩世具有幕式裂陷特点。裂陷幕不同阶段控制铀储层的垂向分布并且控制砂岩型铀矿的垂向分布。在马尼特坳陷西部,有利的储矿层位、有利的铀储层的成因类型和砂岩型铀矿的形成过程都与盆地的幕式演化密切相关。赛汉组为断拗转换期,为最有利的铀储层发育层位;裂陷幕的末期通常伴随弱构造反转,多幕弱构造反转形成的构造斜坡控制古水文地质系统并控矿;不同裂陷幕阶段之间的不整合面和剥蚀作用是氧化带和砂岩型铀矿发育的有利时期;幕式裂陷决定了石油-天然气、煤和砂岩型铀矿的时空配置。根据二连盆地幕式裂陷不同阶段的构造、沉积特征可以明确重点勘探层位、找矿类型和有利找矿部位。 相似文献
14.
本文通过对柴东盆地各地质体（层）物性参数和重磁场特征分析，推断解释盆地的基底结构、岩相特征，磁源体埋深，断裂构造性质及其控盆作用和对沉积覆盖层凹凸格局的影响，对柴东盆地的基底及盖层构造单元进行了划分。笔者建议在相对稳定的地区，寻找基底埋藏浅、沉积盖层厚度较薄，有利于轴成矿的斜坡带。 相似文献
15.
陕西北秦岭地区具有多旋回构造发展史及多旋四成矿作用。主要表现:断裂构造作用的多期性,板块多次俯冲碰撞,构造带多次由北向南迁移以及多期次岩浆活动和变质作用等方面。其结果使得该区显示出由北向南的构造发展规律,并形成了最终的构造格局。根据该区多旋回的构造发展历史,可将该区铀及其有关矿产分为五个矿化旋回期:太古代,元古代、早古生代、晚古-中生代和新生代。其中早古生代、晚古-中生代和新生代,是区内三个主要矿化旋回期。深大断裂带系统在成岩成矿中占有相当重要的地位,它们不但控制了区内内生矿化的形成,而且是控制变质怍用与矿化的重要因素。断裂作用破坏了地壳岩石的完整性,使处于封闭状态的铀及其它成矿元素得以活化转移,从而形成了矿化作用的有利条件。燕山-喜山期构造和岩浆活化作用,对原有地质构造和矿化进行了强烈的改造。形成了新的矿化排列组合及新类型矿化。铀矿化则以淋积型为主。该区有利的找矿方向是:地台边缘冒地槽区,深大断裂带通过富铀建造的地区,北东向隆起一沉降过渡区。 相似文献
16.
江陵凹陷古近系厚层蒸发盐对区域构造和气候变化的响应机制仍然不明确。本文基于获取的江陵凹陷深钻SKD1岩芯和已有的研究资料,探讨了江陵凹陷古近系蒸发盐的矿物特征以及成盐环境,重建了蒸发盐的时空分布演化。研究结果表明,沙市组时期构造活动强烈,较快的沉降速率以及极端暖旱的气候使蒸发盐首先在凹陷北部沉积;新沟咀组下段沉积时,构造活动减弱,季节性干旱气候以及沉降中心向西南方向迁移等诸多因素共同导致膏盐岩在凹陷南部沉积,进一步指示在南部次级洼陷中找钾的前景。 相似文献
17.
陇南地区白龙江下游冯坪子位于西秦岭复杂构造带中,广泛发育碧口群绿片岩系,为含金初始矿源岩,第四纪以来,白龙江流域长期隆起剥蚀,对矿金运移富集提供了良好的地质环境,断陷带、构造谷负向部位成为砂金储集场所,冯坪子河漫滩采样分析结果表明,深度增加金品位增高,3.5～5m,7.5～11m为金富集段。 相似文献
18.
赣杭构造带及其地质意义 总被引：6，自引：4，他引：6
赣杭构造带主要受赣抗断裂带控制。它主要由永丰-诸暨坳陷带、赣杭构造火山活动带和赣杭红盆断陷带构成。赣抗断裂带是由绍兴-江山深断裂发展演化而来,它主要由绍兴-江山、广丰-东乡和抚州-永丰三条深、大断裂构成。该断裂带是一条长期活动带,但各时期地质构造的表现形式和各段动的强烈程度、深度、形成时间并不完全相同。赣抗构造带具明显的继承性。自加里东运动以来,它长期屎持相对坳陷或低地特点。这一特殊构造环境,对铀成矿有利。区内铀成矿经历了漫长的复杂过程,这些过程均与赣杭断裂带活动密切相关。 相似文献
19.
Evaporites through time: Tectonic,climatic and eustatic controls in marine and nonmarine deposits 总被引：3，自引：0，他引：3
John K. Warren 《Earth》2010,98(3-4):217-268
Throughout geological time, evaporite sediments form by solar-driven concentration of a surface or nearsurface brine. Large, thick and extensive deposits dominated by rock-salt (mega-halite) or anhydrite (mega-sulfate) deposits tend to be marine evaporites and can be associated with extensive deposits of potash salts (mega-potash). Ancient marine evaporite deposition required particular climatic, eustatic or tectonic juxtapositions that have occurred a number of times in the past and will so again in the future. Ancient marine evaporites typically have poorly developed Quaternary counterparts in scale, thickness, tectonics and hydrology. When mega-evaporite settings were active within appropriate arid climatic and hydrological settings then huge volumes of seawater were drawn into the subsealevel evaporitic depressions. These systems were typical of regions where the evaporation rates of ocean waters were at their maximum, and so were centred on the past latitudinal equivalents of today's horse latitudes. But, like today's nonmarine evaporites, the location of marine Phanerozoic evaporites in zones of appropriate adiabatic aridity and continentality extended well into the equatorial belts.Exploited deposits of borate, sodium carbonate (soda-ash) and sodium sulfate (salt-cake) salts, along with evaporitic sediments hosting lithium-rich brines require continental–meteoric not marine-fed hydrologies. Plots of the world's Phanerozoic and Neoproterozoic evaporite deposits, using a GIS base, shows that Quaternary evaporite deposits are poor counterparts to the greater part of the world's Phanerozoic evaporite deposits. They are only directly relevant to same-scale continental hydrologies of the past and, as such, are used in this paper to better understand what is needed to create beds rich in salt-cake, soda-ash, borate and lithium salts. These deposits tend be Neogene and mostly occur in suprasealevel hydrographically-isolated (endorheic) continental intermontane and desert margin settings that are subject to the pluvial–interpluvial oscillations of Neogene ice-house climates. When compared to ancient marine evaporites, today's marine-fed subsealevel deposits tend to be small sea-edge deposits, their distribution and extent is limited by the current ice-house driven eustasy and a lack of appropriate hydrographically isolated subsealevel tectonic depressions.For the past forty years, Quaternary continental lacustrine deposit models have been applied to the interpretation of ancient marine evaporite basins without recognition of the time-limited nature of this type of comparison. Ancient mega-evaporite deposits (platform and/or basinwide deposits) require conditions of epeiric seaways (greenhouse climate) and/or continent–continent proximity. Basinwide evaporite deposition is facilitated by continent–continent proximity at the plate tectonic scale (Late stage E through stage B in the Wilson cycle). This creates an isostatic response where, in the appropriate arid climate belt, large portions of the collision suture belt or the incipient opening rift can be subsealevel, hydrographically isolated (a marine evaporite drawdown basin) and yet fed seawater by a combination of ongoing seepage and occasional marine overflow. Basinwide evaporite deposits can be classified by their tectonic setting into: convergent (collision basin), divergent (rift basin; prerift, synrift and postrift) and intracratonic settings.Ancient platform evaporites can be a subset of basinwide deposits, especially in intracratonic sag basins, or part of a widespread epeiric marine platform fill. In the latter case they tend to form mega-sulfate deposits and are associated with hydrographically isolated marine fed saltern and evaporitic mudflat systems in a greenhouse climatic setting. The lower amplitude 4 and 5th order marine eustatic cycles and the greater magnitude of marine freeboard during greenhouse climatic periods encourages deposition of marine platform mega-sulfates. Platform mega-evaporites in intracratonic settings are typically combinations of halite and sulfate beds. 相似文献
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陆相拗陷湖盆陡坡带具有坡度陡、构造活动强烈、物近源、多物源、相变快等特点。勘探实践表明,与拗陷湖盆陡坡带相关的各类砂体,由于具有良好的油源条件、储集条件和油气运移条件,是油气聚集成藏的极有利场所。鄂尔多斯盆地三叠纪时期为典型的内陆大型拗陷盆地,陇东地区三叠纪延长期时在西缘逆冲带的影响下处于陡坡带,该区有两种物质聚集模式,一是从长10-长7退积型三角洲模式,二是从长6-长1进积型三角洲模式。并且在盆地形成演化过程中,伴随着基准面的升降变化,不同相区、不同时期可容纳空间和沉积物供应之间的比值发生相应的变化,从而表现为不同的地层充填样式。 相似文献