Скачать или смотреть InterRidge 2022 February webinar by Yohey Suzuki

InterRidge 2022 Webinar Series - Earth Science, Life Science and Our Future

-Title: Unveiling Microbial Life in the Deep Rocky Biosphere
-Lecturer: Yohey Suzuki (Associate Professor, The University of Tokyo)
-Day: 24th February, 2022

High-temperature rock-water interactions produce vast chemical energy for life at the mid-ocean ridge. The transition from high- to low-temperature hydrothermal ridge flank systems substantially reduces the production of chemical energy in the oceanic crust after 10 million years after formation (Ma). In addition, the weakness of fluid circulation in the more than 10-Ma oceanic crust hinders fluid sampling from borehole-based observatories unlike young crust sites such as the Juan de Fuca Ridge (3.5 Ma) and North Pond (8 Ma). Oceanic crust sites (13.5, 33 and 104 Ma) were drilled into the basaltic basement in the South Pacific Gyre during IODP Expedition 329. Without sampling crustal fluids, it was technically challenging to characterize microbes in drilled basaltic cores. The first attempt was made for estimating the habitability of the rock interior by characterizing diagnostic products of low-temperature rock-water reactions such as smectite group minerals. We noticed Fe(III)-bearing smectite (nontronite) is not observed in 13.5-Ma core samples but in 33- and 104-Ma core samples (Yamashita et al. 2019). The second attempt was made to visualize microbial cells in association with Fe(III)-bearing smectite by developing a new method (details provided during the webinar!!). As a result, it was surprisingly unveiled that microbial cells were densely enrobed within smectite aggregates (Suzuki et al. 2020). Dense microbial cells were also observed in association with Fe(II)-bearing smectite (saponite), indicating that the anaerobic rock interior is also habitable at the 104-Ma site. These results support the habitability of the upper oceanic crust from the ridge to subduction zones. Hopefully, a next big question about “how deep” will be investigated by future deep drilling to the mantle.

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