Abstract This study gives insight into the mechanisms of formation of palygorskite-sepiolite minerals that have remained elusive for many years. The occurrence of palygorskite-sepiolite and minor smectite in association with a variety of authigenic sulphates and Ca-Mg carbonate mineral deposits was identified in silicon-poor, saline to hypersaline ephemeral lakes in Central Spain. By a combination of sedimentological, mineralogical and petrological techniques (XRD, SEM, FEGSEM and TEM) it is shown that very small, poorly ordered palygorskite-sepiolite crystals resulted from the aggregation of nanocrystals within the matrix of the microbial mats (EPS) as it dehydrates. The Mg-rich clays nucleated on Mg-enriched EPS that also contain variable amounts of Si, Mg, Al and Fe, mostly derived from the degradation of siliciclastic minerals. The crystals have a broad compositional and textural range, from poorly ordered palygorskite laths to pure sepiolite bundles, suggesting that they grow through successive stages. Changes in the chemical composition of the fibers occur even at microscale, which is explained by the variability of the biogeochemical conditions prevailing in the microenvironments where the crystals grow. The overall results provide evidence for a biomediated-crystallization of palygorskite-sepiolite in microbial sediments.

中文翻译：

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现代高盐度湖泊中微生物诱导的坡缕石-海泡石自生（西班牙中部）

摘要 这项研究深入了解了多年来一直难以捉摸的坡缕石-海泡石矿物的形成机制。在西班牙中部贫硅、盐碱至高盐度的短暂湖泊中发现了坡缕石-海泡石和少量蒙脱石与各种自生硫酸盐和钙镁碳酸盐矿床有关。通过沉积学、矿物学和岩石学技术（XRD、SEM、FEGSEM 和 TEM）的组合，表明非常小、有序的坡缕石-海泡石晶体是由于微生物垫 (EPS) 基质内纳米晶体的聚集造成的。脱水。富含镁的粘土在富含镁的 EPS 上成核，其中还含有不同数量的 Si、Mg、Al 和 Fe，主要来自硅质碎屑矿物的降解。这些晶体具有广泛的成分和质地范围，从排列不良的坡缕石板条到纯海泡石束，表明它们是通过连续阶段生长的。即使在微观尺度上，纤维的化学成分也会发生变化，这可以通过晶体生长的微环境中普遍存在的生物地球化学条件的可变性来解释。总体结果为微生物沉积物中坡缕石-海泡石的生物介导结晶提供了证据。这可以通过晶体生长的微环境中普遍存在的生物地球化学条件的可变性来解释。总体结果为微生物沉积物中坡缕石-海泡石的生物介导结晶提供了证据。这可以通过晶体生长的微环境中普遍存在的生物地球化学条件的可变性来解释。总体结果为微生物沉积物中坡缕石-海泡石的生物介导结晶提供了证据。