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Subduction zone forearc serpentinites as incubators for deep microbial life

Artikel i vetenskaplig tidskrift
Författare O. Plumper
H. E. King
T. Geisler
Y. Liu
S. Pabst
I. P. Savov
D. Rost
Thomas Zack
Publicerad i Proceedings of the National Academy of Sciences of the United States of America
Volym 114
Nummer/häfte 17
Sidor 4324-4329
ISSN 0027-8424
Publiceringsår 2017
Publicerad vid Institutionen för geovetenskaper
Sidor 4324-4329
Språk English
Länkar dx.doi.org/10.1073/pnas.1612147114
Ämnesord deep biosphere, serpentinization, subduction zone, forearc, HYDROTHERMAL CIRCULATION, METHANE FORMATION, MUD VOLCANISM, LOST CITY, HEAT-FLOW, MARIANA, MANTLE, PLATE, DEVOLATILIZATION, ENVIRONMENT
Ämneskategorier Geovetenskap och miljövetenskap

Sammanfattning

Serpentinization-fueled systems in the cool, hydrated forearc mantle of subduction zones may provide an environment that supports deep chemolithoautotrophic life. Here, we examine serpentinite clasts expelled from mud volcanoes above the Izu-Bonin-Mariana subduction zone forearc (Pacific Ocean) that contain complex organic matter and nanosized Ni-Fe alloys. Using time-of-flight secondary ion mass spectrometry and Raman spectroscopy, we determined that the organic matter consists of a mixture of aliphatic and aromatic compounds and functional groups such as amides. Although an abiotic or subduction slab-derived fluid origin cannot be excluded, the similarities between the molecular signatures identified in the clasts and those of bacteria-derived biopolymers from other serpentinizing systems hint at the possibility of deepmicrobial life within the forearc. To test this hypothesis, we coupled the currently known temperature limit for life, 122 degrees C, with a heat conduction model that predicts a potential depth limit for life within the forearc at similar to 10,000 m below the seafloor. This is deeper than the 122 degrees C isotherm in known oceanic serpentinizing regions and an order of magnitude deeper than the downhole temperature at the serpentinized Atlantis Massif oceanic core complex, Mid-Atlantic Ridge. We suggest that the organic-rich serpentinites may be indicators for microbial life deep within or below the mud volcano. Thus, the hydrated forearc mantle may represent one of Earth's largest hidden microbial ecosystems. These types of protected ecosystems may have allowed the deep biosphere to thrive, despite violent phases during Earth's history such as the late heavy bombardment and global mass extinctions.

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