Diversity of biogenic minerals in lowtemperature ... - Wiley Online Library

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abiogenic processes (e.g., silica supersaturation and poly- merization) in seafloor hydrothermal vent fields [Renaut et al., 2002; Yee et al., 2003; Konhauser et al.
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, G03030, doi:10.1029/2011JG001691, 2011

Diversity of biogenic minerals in low‐temperature Si‐rich deposits from a newly discovered hydrothermal field on the ultraslow spreading Southwest Indian Ridge Xiaotong Peng,1 Shun Chen,1 Huaiyang Zhou,1 Lixue Zhang,1 Zijun Wu,1 Jiangtao Li,1 Jiwei Li,1 and Hengchao Xu1 Received 17 February 2011; revised 8 May 2011; accepted 24 May 2011; published 8 September 2011.

[1] A newly discovered hydrothermal field on the ultraslow spreading Southwest Indian Ridge expands the known ranges of biogenic minerals, microbes, and hydrothermal deposits. The deposits from this vent site show typical characteristics of low‐temperature hydrothermal deposits. Rare earth element fractionation might be partly influenced by bacterial activity. A physicochemical gradient is present across the layer of deposits, providing suitable microhabitats for various microbes. Molecular phylogenetic analysis demonstrates a diverse range of bacteria, some of which are involved in sulfur, iron, and nitrogen metabolism. A high diversity of biogenic Fe and Si minerals are present in the deposits. Biogenic silica, Fe‐sulfides, and Fe‐oxides with distinctive morphologies are closely related to microbes. Several novel Fe‐oxide structures are found and attributed to new types of biogenic minerals. The precipitation of porous silica spherules and Fe‐ sulfides can be strongly promoted by extracellular polymer saccharides. Biomineralization features indicate that these deposits evolved through four stages. These results help us to better understand the formation of biogenic minerals and low‐temperature deposits associated with microbes in the Earth’s modern and ancient seafloor hydrothermal vent fields. Citation: Peng, X., S. Chen, H. Zhou, L. Zhang, Z. Wu, J. Li, J. Li, and H. Xu (2011), Diversity of biogenic minerals in low‐ temperature Si‐rich deposits from a newly discovered hydrothermal field on the ultraslow spreading Southwest Indian Ridge, J. Geophys. Res., 116, G03030, doi:10.1029/2011JG001691.

1. Introduction [2] Seafloor hydrothermal activity is one of the fundamental processes by which heat and chemical species are transferred from the lithosphere to the ocean. Since 1977, more than 200 seafloor vent fields have been investigated. Most interest in the mid‐oceanic ridge has been focused on the hydrothermal activities in the fast, slow, and intermediate spreading ridges [Hannington et al., 2005]. The search for hydrothermal sites on the ridges, however, has been largely constrained to the ultraslow spreading ridge where full spreading rates are