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1.
弄清钙华生物沉积作用有助于更好地理解钙华微岩相结构和地球化学特征的气候环境指示意义。总结和综述了与钙华沉积相关的生物群落、生物成因钙华微岩相结构、钙华生物沉积作用过程及其对钙华地球化学特征影响的研究进展,并展望了未来的研究重点。细菌、藻类和苔藓等广泛参与到钙华沉积中,形成了许多不同类型的孔隙结构、晶体结构和纹层结构。生物沉积过程主要包括:①生物生长扰动水流使得CO2逸出;②代谢作用(如光合作用)过程诱导碳酸钙沉积;③"表面控制"过程影响晶体成核及生长。生物沉积作用驱动了元素的迁移转化,对沉积水体和钙华地球化学特征具有重要影响。钙华在地球生物学研究中具有重要潜力,未来需要加强现代钙华沉积中的物理化学和生物过程相互作用机制及其各自贡献的量化研究,以便准确地解译钙华沉积记录。 相似文献
2.
A combination of both water chemistry and sedimentological information was used to investigate the carbonate-producing mechanism
in Littlefield Lake, a small lake located in Isabella County, central Michigan. Data on temperature, dissolved oxygen, pH,
calcium carbonate (CaCO3) saturation, alkalinity, calcium, and magnesium were obtained on a monthly basis over a 13-month period, with each parameter
determined at 1m intervals over a depth range of 20m. The loss of dissolved carbon dioxide (CO2) from warm surface waters during direct degassing, and to a lesser extent during photosynthetic uptake by lacustrine macrophytes
and phytoplankton during the summer, results in massive precipitation of the low-magnesium calcite which predominates in all
Littlefield Lake sedimentary facies However, despite the fact that carbonate precipitation in this rather typical temperate-region
marl lake is directly related to, and may be driven by, seasonal variation in these physiochemical parameters, most calcite
forms as encrustations around cyanophytic and chlorophytic macrophytes. Such relationships demonstrate that carbonate precipitation
in marl lakes may result from complex interactions between both biochemical and physiochemical processes. As such, marl formation
in this, and probably many other calcareous lake systems, can not be simply ascribed to one or the other of these two general
mechanisms. 相似文献
3.
The source of whitings on the Great Bahama Bank and their relationship to major changes in the chemistry of Bank waters have been among the longest and most hotly debated topics in carbonate geochemistry. In this paper, we demonstrate that the reaction kinetics of calcite with Bank waters for a given saturation state are similar to, but somewhat slower (2 to 3 times) than with Gulf Stream water. The interpretation of the reaction kinetics of suspended Bank sediment with Bank water requires that the precipitating phase be about twice as soluble as aragonite. Good agreement at equivalent saturation states was found between experimental precipitation rates and those calculated for the rate of change of Bank water chemistry in the region of whitings. These results indicate that the dominant mode of carbonate removal is via precipitation on resuspended sediments rather than the rapid pseudo-homogeneous precipitation of calcium carbonate in the water column resulting in the formation of a whiting. Estimates indicate that single aragonite needles may be resuspended many times over a period of decades during which they experience repeated overgrowth. A major portion (>98%) of suspended calcium carbonate is outside the visually dramatic whitings. Thus, as visually spectacular as they are, whitings do not represent a short-term locally massive precipitation of carbonate on the Great Bahama Bank, nor are they even likely to be the dominant sites of carbonate removal in this region. Although future refinements are needed that include seafloor processes, we have at this point arrived at a mechanistic kinetic model that provides a reasonably quantitative explanation for the hydrochemistry of the carbonate system on the northern Great Bahama Bank. 相似文献
4.
The investigation of biological processes responsible for travertine deposition allows us to better understand the travertine petrographic and geochemical signatures as proxies of climatic and environmental change. This paper reviewed the organisms associated with travertines, the biotic micro-fabrics formed within travertines, the biological processes associated with travertine precipitation and their controls on travertine geochemical properties. Prospects of the future research on biological processes responsible for travertine precipitation were provided. Bacteria, algae and mosses are the most important organisms that involve in the precipitation of travertines. The growth of these organisms leads to the formation of a range of various porosity, crystal fabrics and lamination within travertines. Three main biological processes responsible for travertine deposition can be classified, including a process of aquatic plant growth generating a turbulent condition and consequent CO2 evasion, a metabolic (mainly photosynthetic) process mediating carbonate precipitation and a ‘surface-control’ process influencing nucleation and crystal growth. These processes play an important role in the migration and transformation of elements in travertine-depositing system and thus determine the properties of water chemistry and geochemistry of carbonate deposits. Travertine deposits have great potential to be valuable records for the geobiological study. Further investigation is required to simultaneously track biotic and abiotic interactions in modern travertine-depositing environments and quantify the contribution of these two processes and apply the results to accurately interpret travertine records. 相似文献
5.
《Russian Geology and Geophysics》2007,48(8):659-667
The subject of study was the chemical composition of common fresh-water springs precipitating travertines in tectonically passive regions of the Kolyvan'-Tomsk folded area and northwestern Salair. Attention was paid to the specific character of manifestation, mineralogy, and petrography of the produced travertines. Results of the study of isotopic composition of carbon in hydrocarbonate ion of waters and carbonate travertines are reported. It is shown that the genetic type of CO2 accompanying the formation of travertines is biogenic. Study of the equilibrium of the underground waters with aluminosilicate and carbonate minerals has shown that the travertines are the product of evolution of an equilibrium-nonequilibrium water-rock system. New mechanisms of travertine formation from cool fresh waters are proposed. 相似文献
6.
Travertine formation in Plitvice National Park, Yugoslavia: chemical versus biological control 总被引：5，自引：1，他引：5
Hydrochemical studies of the Plitvice Lakes and their tributaries (Croatia/Yugoslavia) were coupled with micromorphological investigations on carbonate lake sediments and recent travertines. Karst springs discharge water from aquifers in Triassic and Jurassic dolomites and limestones and collect in lakes, which are ponded behind accreting travertine dams. Waters at springs have a high CO2 partial-pressure (greater than 7000 ppm) and are slightly undersaturated with respect to calcite (saturation index less than —0·03). CO2 partial pressure is quickly reduced in swift running streams, leading to very high supersaturation with carbonate minerals (saturation indices between 0·74 and 0·53). Calcite deposition, however, is restricted to the lake bottoms (formation of lake marl) and to the tufa dams. The annual carbonate precipitating capacity of the system based on water balance and downstream loss of dissolved ions is estimated to be on the order of 10 000 t CaCO3 as cascade deposits (tufa dams) or as micrite in lakes behind the travertine dams. The initial stages of travertine formation as a result of morphological, biological, and chemical factors are (i) moss settling on small ridges in the creek courses, (ii) epiphytes (diatoms and cyanobacteria) settling on the moss surface, (iii) micrite particles resuspending from lake bottoms and being trapped on mucous excretions from bacteria and diatoms, and (iv) inorganic calcite precipitating as sparite at nucleation sites provided by these crystal seeds. Geochemical studies of the lake marl and tufa dams show that amino acids are dominated by aspartic acid. Carbohydrates come from structural polysaccharides of diatoms. The sticky excretions, rich in aspartic acid, are necessary for the initiation of calcite precipitation. They may be a response of algal and bacterial metabolism to environmental stress by either nutrient depletion or high calcium concentrations in ambient waters. The formation of tufa and micrite (lake marl) appears to be initiated by localized biological factors and is not governed by mere calcite supersaturation of the water. Oligotrophy may be an essential precondition for the formation of fresh water carbonate deposits. 相似文献
7.
温泉钙华沉积的影响因素 总被引：2，自引：2，他引：0
钙华是在泉水、河水、湖水、洞穴周围沉积的非海相碳酸钙沉积物。钙华是陆地水循环过程中物质迁移的一种表现形式,研究钙华的形成有助于了解局部水文循环中的物质迁移规律并间接了解古气候与古水文地质条件。部分温泉的泉口附近沉积有形态多样的钙华。本文综述温泉钙华的形成过程、钙华沉积的主要影响因素和它们之间的相互影响关系。水化学条件是钙华沉积的物质基础和必要条件,水动力条件是钙华沉积的充分条件,生物效应对钙华沉积起到加强的作用,沉积环境通过影响水化学条件或水动力条件间接控制钙华的沉积。 相似文献
8.
单生卵囊藻对DIC的利用及其对CaCO3沉积影响的研究 总被引：4，自引：0，他引：4
以生长在钙华池中的单生卵囊藻（Oocystis solitaria Wittr）为研究对象,利用pH漂移方法,探讨了封闭系统中单生卵囊藻在岩溶水和非岩溶水环境下对溶解无机碳（DIC）利用及其对水体Ca^2＋沉积影响的差异。结果表明,单生卵囊藻在低CO2浓度时,通过胞外碳酸酐酶的催化,以HCO3^-作为无机碳源进行光合作用。在岩溶水环境下单生卵囊藻DIC利用能力要高于非岩溶水环境（4．78倍）,而在此过程中对水体中Ca^2＋沉积的影响也更高（2．13倍）。在岩溶水（非岩溶水）环境下,有42．6％（8．9％）的Ca^2＋通过物理化学效应以CaCO3形式沉积,其余Ca^2＋可能被藻体生长而吸收利用．． 相似文献
9.
碳酸盐生物沉积作用的研究现状与展望 总被引：6，自引：2，他引：4
碳酸盐矿物是地球上最丰富的矿物之一,碳酸盐沉积在许多地质过程中起着非常重要的作用.生物沉积碳酸盐的现象在自然界普遍存在,其中又以生物沉积碳酸钙(CaCO3)为主.生物从周围环境中选择性地吸取元素,在严格的生物控制下,组装成功能化的碳酸盐结构;生物也可以通过改变周围的环境诱导碳酸盐的沉积或自身参与碳酸盐的沉积.不同生物对碳酸盐沉积的作用扣机理不同,综述了海洋动植物、藻类生物、菌类生物对碳酸盐的沉积作用及其机理以及实验室模拟调控CaCO3生物矿化方面的一些研究成果和研究现状,提出未来亟待解决的一些重要问题,并指出生物沉积碳酸盐研究所具有的巨大应用前景. 相似文献
10.
ROBIN W. RENAUT R. BERNHART OWEN BRIAN JONES JEAN‐JACQUES TIERCELIN CORINNE TARITS JOHN K. EGO KURT O. KONHAUSER 《Sedimentology》2013,60(2):428-468
Travertine is present at 20% of the ca 60 hot springs that discharge on Loburu delta plain on the western margin of saline, alkaline Lake Bogoria in the Kenya Rift. Much of the travertine, which forms mounds, low terraces and pool‐rim dams, is sub‐fossil (relict) and undergoing erosion, but calcite‐encrusted artefacts show that carbonate is actively precipitating at several springs. Most of the springs discharge alkaline (pH: 8·3 to 8·9), Na‐HCO3 waters containing little Ca (<2 mg l?1) at temperatures of 94 to 97·5°C. These travertines are unusual because most probably precipitated at temperatures of >80°C. The travertines are composed mainly of dendritic and platy calcite, with minor Mg‐silicates, aragonite, fluorite and opaline silica. Calcite precipitation is attributed mainly to rapid CO2 degassing, which led to high‐disequilibrium crystal morphologies. Stratigraphic evidence shows that the travertine formed during several stages separated by intervals of non‐deposition. Radiometric ages imply that the main phase of travertine formation occurred during the late Pleistocene (ca 32 to 35 ka). Periods of precipitation were influenced strongly by fluctuations in lake level, mostly under climate control, and by related changes in the depth of boiling. During relatively arid phases, meteoric recharge of ground water declines, the lake is low and becomes hypersaline, and the reduced hydrostatic pressure lowers the level of boiling in the plumbing system of the hot springs. Any carbonate precipitation then occurs below the land surface. During humid phases, the dilute meteoric recharge increases, enhancing geothermal circulation, but the rising lake waters, which become relatively dilute, flood most spring vents. Much of the aqueous Ca2+ then precipitates as lacustrine stromatolites on shallow firm substrates, including submerged older travertines. Optimal conditions for subaerial travertine precipitation at Loburu occur when the lake is at intermediate levels, and may be favoured during transitions from humid to drier conditions. 相似文献
11.
微生物诱导碳酸钙沉淀(microbially induced calcium carbonate precipitation, MICP)是一种在自然界中广泛存在的生物矿化过程。由于MICP具有反应速度快、环境条件要求低、应用范围广、温室气体减排效应显著等特点,在地质、土木、水利、环境多个领域中广泛推广应用。文章在分析国内外相关研究成果的基础上,归纳整理出反硝化过程、硫酸盐还原作用、尿素分解作用等多种微生物诱导下碳酸钙矿化途径和作用机制。以尿素分解菌为代表,重点讨论微生物诱导碳酸盐沉淀过程中pH、温度、离子浓度等环境因素对生成矿物晶型晶貌等方面的影响,总结了MICP的环境应用机制,即环境中的重金属元素通过替换作用替换矿化矿物中的Ca2+或CO32?从而被固定。MICP作为一种简单高效的地质环境过程,在生态环境修复领域具有广阔的应用前景。 相似文献
12.
Zhou Haiyan Zhou Xun Chai Rui Yu Lan Liu Chunhui Li Liangping 《Environmental Geology》2008,53(7):1483-1489
Thermal groundwater occurs in bedrock aquifers consisting of the dolomite of the Wumishan Group of the Jixianin System and
the Cambrian carbonate in the Xiaotangshan geothermal field near the northern margin of the North China Plain, China. The
hot water in the geothermal field of basin-type discharges partly in the form of the Xiaotangshan hot spring under natural
conditions. The hot water has TDS of less than 600 mg/L and is of Na·Ca-HCO3 type. The geothermal water receives recharge from precipitation in the mountain area with elevation of about 500 m above
sea level to the north of the spring. Thermal groundwater flows slowly south and southeast through a deep circulation with
a residence time of 224 years estimated with the Ra–Rn method. The Xiaotangshan hot spring dried up in the middle of the 1980s
owing to the increasing withdrawal of the hot water in the geothermal field in the past decades. The water level of the geothermal
system still falls continually at an annual average rate of about 2 m, although water temperature changes very little, indicating
that the recharge of such a geothermal system of basin-type is limited. Over-exploitation has a dramatic impact on the geothermal
system, and reduction in exploitation and reinjection are required for the sustainable usage of the hot water. 相似文献
13.
微生物沉积碳酸钙固化砂质黏性紫色土试验研究 总被引：1，自引：0，他引：1
重庆紫色土是一种砂质黏性土,地区降雨集中,水力冲蚀作用剧烈,极易产生水土流失,微生物诱导方解石沉积(MICP)技术因能耗低、污染小而广泛应用于土体加固中。通过正交试验优化了巨大芽孢杆菌(BNCC 336739)的培养基和培养条件,活菌数增长126%,活性良好。采用巨大芽孢杆菌,进行低水压(9.8kPa)灌注固化砂质黏性紫色土试验,探究了固化效果的变化规律。结果表明:随固化次数增加,碳酸钙生成量和干密度逐级增加,无侧限抗压强度与碳酸钙生成量正相关;碳酸钙有效沉积越来越少,强度提高趋于稳定,固化9次后强度提高77%;随孔隙被碳酸钙填充和上下碳酸钙硬壳的形成,渗透性不断降低,最终下降两个数量级;通过试样上、中、下三部分碳酸钙生成量C的样本标准差s来反映碳酸钙分布离散程度,发现割线弹性模量在s的影响下随C增加而波动上升,波动表现为在C相近或s相差很大时,s越小割线弹性模量越大。研究成果可以为MICP技术在紫色土地区的地基、边坡加固和水土流失防护等工程应用提供科学依据和参考。 相似文献
14.
This paper deals with the hydrogeological relationship between base levels of saline lakes and the formation of sub-horizontal caves. The mechanism presented here suggests that many horizontal cave levels in carbonate sequences are created adjacent to the saline lakes shorelines because of the converging of the groundwater flow above the fresh–saline water interface. The main factors that control enhanced carbonate dissolution and cave formation are high groundwater flow velocities in the shallow phreatic zone during a relative long steady state of the water table. High groundwater flow velocities are evident close to the Dead Sea due to the convergent fast flows above the shallow interface adjacent to the shoreline. The same could prevail in the case of previous paleo-lakes that existed in the basin. The synergetic combination of the above preconditions for enhanced cave formation seems to be responsible for the formation of elevation-controlled alignment of paleo-near shore cave levels in the central and southern (Dead Sea) portion of the study area. These are found on the western fault escarpment and basin margin in different stratigraphic horizons of carbonate lithology. Many of the cave levels can be linked to late Quaternary–Holocene lake levels obtained from dated lake sediments within the basin. The most common cave’s elevation was found to be around 200 m below sea level which was the elevation of the Lisan Lake during part of its history. On the other hand, the Hula Basin in the northern part of the Dead Sea Basin was not occupied by saline water bodies since its formation as a base level, and thus the above preconditions for enhanced cave formation did not prevail. Indeed, this is evident by the lack of horizontal cave levels on its western carbonate margins unlike the situation in the south. 相似文献
15.
New insights into biological influence on the geochemistry of freshwater carbonate deposits 总被引：2，自引：0，他引：2
Ambient temperature freshwater carbonates (“tufas”) have outstanding potential as palaeoclimate archives. However, it has proven difficult to constrain the behaviour of the geochemical parameters on which important proxy systems rely. Current thinking on the development of trace element ratios in tufa rests upon an assumption of precipitation driven by degassing of CO2, with the final precipitate being in equilibrium with ambient river water. This study provides evidence that although supersaturation is largely regulated by degassing, precipitation in sterile flowing systems does not occur throughout the air-water interface, but only at lines of intersection between this interface and a solid surface. Precipitation at the bottom, as is normal in river sites, is not found to occur. However, when benthic microbial communities (“biofilms”) are present, extensive precipitation does occur within them in preference and/or addition to that at the air-water interface. Precipitation is therefore not purely a consequence of degassing, and some microbiological influence is necessary to generate precipitates analogous to nature.We further investigate whether these biofilms alter the behaviour of trace elements within tufa systems, in addition to modulating the sites and mechanisms of precipitation, via a series of experiments. Biofilms are shown to accumulate large inventories of calcium and other dissolved ions (Ba, Sr, and Mg), and we demonstrate that this process is chemoselective in favour of ions with low charge densities. These observations have consequences for interpretation of trace element records from tufas based on an assumption of equilibrium with river water, and also for other carbonate deposits associated with biofilm activity (travertines, marine stromatolites, lacustrine and soil carbonates, speleothems). Conversely, our study provides new insight into the reasons for discrepancy of tufa Mg/Ca ratios from expectation, and thus provides encouragement for the potential of Mg/Ca palaeothermometry in freshwater carbonate systems. 相似文献
16.
Microbially mediated carbonate precipitation in a hypersaline lake,Big Pond (Eleuthera,Bahamas) 总被引：1，自引：0，他引：1
CHRISTINA GLUNK CHRISTOPHE DUPRAZ OLIVIER BRAISSANT KIMBERLEY L. GALLAGHER ERIC P. VERRECCHIA PIETER T. VISSCHER 《Sedimentology》2011,58(3):720-736
Microbial metabolism impacts the degree of carbonate saturation by changing the total alkalinity and calcium availability; this can result in the precipitation of carbonate minerals and thus the formation of microbialites. Here, the microbial metabolic activity, the characteristics and turnover of the extracellular polymeric substances and the physicochemical conditions in the water column and sediments of a hypersaline lake, Big Pond, Bahamas, were determined to identify the driving forces in microbialite formation. A conceptual model for organomineralization within the active part of the microbial mats that cover the lake sediments is presented. Geochemical modelling indicated an oversaturation with respect to carbonates (including calcite, aragonite and dolomite), but these minerals were never observed to precipitate at the mat–water interface. This failure is attributed to the capacity of the water column and upper layers of the microbial mat to bind calcium. A layer of high Mg‐calcite was present 4 to 6 mm below the surface of the mat, just beneath the horizons of maximum photosynthesis and aerobic respiration. This carbonate layer was associated with the zone of maximum sulphate reduction. It is postulated that extracellular polymeric substances and low molecular weight organic carbon produced at the surface (i.e. the cyanobacterial layer) of the mat bind calcium. Both aerobic and anaerobic heterotrophic microbes consume extracellular polymeric substances (each process accounting for approximately half of the total consumption) and low molecular weight organic carbon, liberating calcium and producing inorganic carbon. The combination of these geochemical changes can increase the carbonate saturation index, which may result in carbonate precipitation. In conclusion, the formation and degradation of extracellular polymeric substances, as well as sulphate reduction, may play a pivotal role in the formation of microbialites both in marine and hypersaline environments. 相似文献
17.
In this study, we investigate the geochronological, geochemical and isotopic characteristics of two travertine sites surrounded by Quaternary eruption centres in central Anatolia with ample palaeo-eruption records. High-resolution carbonate precipitation records, revealed by U-Th dating, are clustered around 5–35, 60–100 and 120–170 ka and are well correlated with the dataset on eruptions as well as the position of fractures related to the volcanic centres. Syn-eruptive carbonate precipitation seems to occur due to the circulation of CO2-rich fluids along the extensional fracture systems aligned tangentially to the related volcanic conduit and, therefore, the study of this system could be an alternative technique for the reconstruction of palaeo-eruptions. δ18O values of the studied travertines are within the range of meteogene fluids. Oxygen isotope compositions at around 130 ka match well with Glacial Termination II that is also recorded by climate proxies in various cave and benthic deposits throughout the world. It is likely that the studied carbonates were precipitated under similar fluid circulation conditions which are represented by a high rate of dilatation followed by a meteoric water influx into the extensional fractures. 相似文献
18.
B. Levent Mesci 《Geodinamica Acta》2013,26(1-2):12-25
Several geothermal fields are located in a NE-SW trend along a structural lineament around the Sivas basin; one of those is the Ortaköy travertines situated 83?km south-west of Sivas. There are eight fissure-ridge-type travertine localities in the area, although eroded-sheet-type travertines constitute many of the travertines of the region. By evaluating the rocks of the Late Miocene-Early Pliocene K?z?l?rmak Formation, it was determined that fissure axes developed within fissure-ridge-type travertines, and that the structural elements obtained from satellite images together with the fissures that form the fissure-ridge-type travertines are shear and tension fissures, and the NE-SW-oriented opening of the fissures, were a result of NW-SE-directed compression, which was also responsible for the formation of the Sivas Backthrust. Ground-penetrating radar studies have shown that the thickness of fissure fills within the fissure-ridge-type travertines of the Ortaköy geothermal field increase with depth, and that the hydrothermal fluids which brought about the formation of the travertines moved surfaceward via fissure systems. The results of U/Th radiometric dating indicate that the youngest travertine in the region is 17,761 (?268/+269) years old and the oldest 128,286 (?3537/+3662) years old. Using the widths of banded travertines within the fissure-ridge-type travertines as well as these age results, the opening rate of the Sivas Basin was determined to be .06 (?.01/+.05) mm/year. 相似文献
19.
20.
Late Pleistocene travertines up to 40 m thick near Rapolano Terme in Tuscany, central Italy, were precipitated by hot water issuing from springs on hillsides and flowing into adjacent depressions to mix with rainwater. Proximal light-coloured slope and terrace travertines pass distally into darker reed mound and depression-fill travertines. Lithotypes include crystalline crust, shrub, pisoid, paper-thin raft, coated bubble, reed, and lithoclast-breccia. High precipitation rates resulted in rapid slope aggradation and progradation. Dilution by rainwater likely lowered precipitation rates in depressions, but deposition was augmented by allochthonous material eroded from upslope travertines. Slope Depositional Systems consist of Smooth and Terrace Slope facies characterized by white crystalline crusts, with diverse additional lithotypes in terrace pools. Depression Depositional Systems have mixed light and dark travertines with horizontal to gently concave stratification. Extensive light-coloured Shrub Flat travertine is dominant; darker Marsh-Pool Facies composed of fine lithoclast and reed travertine is localized. Reed Mounds composed of mixed light and dark travertines localized by abundant reed growth, formed where spring water emerged near the bases of low angle slopes. Distal reduction in accretion rate was the major influence on sequence development. Light-coloured slope travertines interdigitate with darker depression deposits. Vertical aggradation of slope deposits, mound progradation, and filling of topographic depressions is expressed by advance and retreat of facies. Evolution from depression to slope or mound sequences is termed ‘steepening up’. Up-sequence change from slope or mound to depression facies is termed ‘levelling up’. Exposure surfaces associated with palaeosols are common in all facies and often constitute sequence boundaries. They are more closely spaced in depression sequences, reflecting slower and possibly also more discontinuous accumulation at sites furthest from hot springs. 相似文献