Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada.
Astrobiology. 2013 Feb;13(2):163-76. doi: 10.1089/ast.2012.0887. Epub 2013 Feb 5.
Evaporation of silica-rich geothermal waters is one of the main abiotic drivers of the formation of silica sinters around hot springs. An important role in sinter structural development is also played by the indigenous microbial communities, which are fossilized and eventually encased in the silica matrix. The combination of these two factors results in a wide variety of sinter structures and fabrics. Despite this, no previous experimental fossilization studies have focused on evaporative-driven silica precipitation. We present here the results of several experiments aimed at simulating the formation of sinters through evaporation. Silica solutions at different concentrations were repeatedly allowed to evaporate in both the presence and absence of the cyanobacterium Synechococcus elongatus. Without microorganisms, consecutive silica additions led to the formation of well-laminated deposits. By contrast, when microorganisms were present, they acted as reactive surfaces for heterogeneous silica particle nucleation; depending on the initial silica concentration, the deposits were then either porous with a mixture of silicified and unmineralized cells, or they formed a denser structure with a complete entombment of the cells by a thick silica crust. The deposits obtained experimentally showed numerous similarities in terms of their fabric to those previously reported for natural hot springs, demonstrating the complex interplay between abiotic and biotic processes during silica sinter growth.
富含二氧化硅的地热水蒸发是温泉周围硅华形成的主要非生物驱动因素之一。本地微生物群落也在烧结结构的发展中起着重要作用，它们被石化并最终被包裹在二氧化硅基质中。这两个因素的结合导致了各种各样的硅结结构和结构。尽管如此，以前没有关于蒸发驱动二氧化硅沉淀的实验化石研究。我们在这里介绍了几项旨在通过蒸发模拟硅华形成的实验结果。不同浓度的二氧化硅溶液在存在和不存在蓝藻 Synechococcus elongatus 的情况下反复蒸发。没有微生物时，连续添加二氧化硅会形成分层良好的沉积物。相比之下，当存在微生物时，它们充当异质二氧化硅颗粒成核的反应表面；根据初始二氧化硅浓度，沉积物要么是多孔的，含有硅化和未矿化细胞的混合物，要么形成更密集的结构，细胞被厚厚的二氧化硅壳完全包裹。实验获得的沉积物在结构上与以前报道的天然温泉有许多相似之处，证明了在硅结生长过程中，非生物和生物过程之间的复杂相互作用。
