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首页> 外文期刊>Sedimentology: Journal of the International Association of Sedimentologists >Authigenic replacement of cyanobacterially precipitated calcium carbonate by aluminium-silicates in giant microbialites of Lake Van (Turkey)
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Authigenic replacement of cyanobacterially precipitated calcium carbonate by aluminium-silicates in giant microbialites of Lake Van (Turkey)

机译：铝合金铝硅酸盐（土耳其）铝 - 硅酸盐含铝硅酸钙的Athegenic替代碳酸钙

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Studies of modern cyanobacterial mats and biofilms show that they can precipitate minerals as a consequence of metabolic and degradational activities paired with ambient hydrochemical conditions. This study looked at modern microbial mats forming giant, tower-like, groundwater-fed, calcareous microbialites in the world's largest, highly alkaline lake; Van Golu (Lake Van), East Turkey. Results show that microbial systems play a role not only in carbonate precipitation but also in the formation of siliceous mineral phases. Transmitted light microscopy, scanning electron microscopy and spectral observations revealed that, within the extracellular polymeric substances excreted by the mats abundant minute aragonite grains precipitated first invivo. These minute grains were quickly succeeded and/or supplemented in the dead biomass of the cyanobacterial mat by authigenic Al-Mg-Fe siliceous phases. Silicon dioxide is available in large concentrations in the highly alkaline water of Lake Van. Divalent cations (Ca and Mg) are delivered to the microbialites mostly by groundwater springs. The precipitation of the fine-grained siliceous phases is probably mediated by bacteria degrading the cyanobacterial biomass and complexing the excessive cations with their extracellular polymeric envelopes. The bacteria serve as nucleation centres for the subsequent precipitation of siliceous mineral phases. Generally, the biphasic (calcareous and siliceous) mineralization - characterizing Lake Van microbialites - is controlled by their interior highly dynamic hydrogeochemical situation. There, the dramatically different alkaline lake water and the Ca-Mg-charged groundwater mix at various rates. The early diagenetic replacement of the invivo aragonite by authigenic siliceous phases significantly increases the fossilization potential of the mat-forming cyanobacteria. Lake Van and its giant microbialite tufa towers act as a model explaining the transformation of early diagenetic mineral phases
机译：对现代蓝杆菌和生物膜的研究表明，由于与环境水化学条件配对的代谢和降解活性，它们可以沉淀矿物质。这项研究看着现代微生物垫形成巨型，塔式，地下水，世界上最大的高度碱性湖泊的钙质微生物; van golu（瓦车），东土耳其。结果表明，微生物系统不仅在碳酸盐沉淀中起作用，而且在硅质矿物相的形成中起作用。透射光学显微镜，扫描电子显微镜和光谱观察显示，在由垫子排泄的细胞外聚合物物质内，沉淀着沉淀的首次invivo沉淀了。这些微小的晶粒迅速成功和/或通过AheraIgenic Al-Mg-Fe Siliceous阶段迅速成功地成功和/或补充在树脂酸的死生物量中。二氧化硅以大型湖泊的高碱性水分提供大浓度。二价阳离子（Ca和Mg）主要由地下水弹簧递送至微生物岩。细菌沉淀阶段的沉淀可能是由细菌介导的，细菌降解蓝藻生物质并与细胞外聚合物包络络合过量的阳离子。细菌用作随后沉淀硅质矿物相的核心中心。通常，双相（钙质和硅质）矿化 - 表征Van Microbialites Lake Lake Microbialites - 由其内部的高动态水文地理化。在那里，大幅不同的碱性湖水和Ca-Mg带电的地下水混合在各种速率下。 Actigenic癫痫阶段的InvivoAnigate的早期成岩替代性显着提高了垫形成的蓝细菌的渗透潜力。瓦车及其巨型微生物Tufa Towers作为一种模型，解释了早期成岩矿物阶段的转化

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