Biological mediation in ocean crust alteration; how deep is the deep biosphere?

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doi: 10.1016/S0012-821X(99)00005-9
Author(s): Furnes, Harald; Staudigel, Hubert
Author Affiliation(s): Primary:
University of Bergen, Geological Institute, Bergen, Norway
Scripps Institution of Oceanography, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 166(3-4), p.97-103. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 21 refs.; illus.
Summary: Biological mediation has been suggested as a control of the chemical exchange between the oceanic crust and seawater, but very little is known about its distribution within the oceanic crust and the relative importance of biotic and abiotic processes. Alteration textures in glassy pillow lava margins record the proportions of biotic and abiotic alteration, and the fraction of biotic alteration may be determined by point counting methods. We used this method at DSDP/ODP Sites 417D and 418A (110 Ma crust south of Bermuda Rise) and Holes 504B and 896A (5.9 Ma Costa Rica Rift). Biotic alteration dominates glass alteration in the upper 250 m of the oceanic crust (60-85% of the total glass alteration) and steadily declines in importance down to 10-20% at 500 m. The consistency of data between two crustal sections of very different age and tectonic setting suggest that microbially mediated glass alteration may be largely confined to the upper oceanic crust. However, both sites studied are sealed by thick sedimentary layers and, thus, are typical for ocean crust underlying the oceanic basins, rather than crust at mid-ocean ridges with possibly deep and rapid hydrothermal circulation. Down-hole temperature measurements at the Costa Rica Rift suggest that glass-altering microbes are hyperthermophilic and thrive at least up to temperatures of about 90°C. Microbial activity does occur at higher temperatures (up to about 110°C) but with reduced apparent abundance. Abstract Copyright (1999) Elsevier, B.V.
Year of Publication: 1999
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; 18 Geophysics, Solid-Earth; Alteration; Atlantic Ocean; Basaltic composition; Bermuda Rise; Biogenic processes; Biosphere; Costa Rica Rift; Crust; DSDP Site 417; DSDP Site 418; DSDP Site 504; Deep Sea Drilling Project; Depth; East Pacific; Glasses; Halmyrolysis; Hydration; Hydrothermal alteration; IPOD; Igneous rocks; Lava; Leg 102; Leg 111; Leg 137; Leg 140; Leg 148; Leg 51; Leg 52; Leg 53; Leg 69; Leg 70; Leg 83; Leg 92; Metasomatism; Microorganisms; North Atlantic; ODP Site 896; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Permeability; Pillow lava; Porosity; Statistical analysis; Temperature; Textures; Upper crust; Volcanic glass; Volcanic rocks; Water-rock interaction
Coordinates: N250000 N250000 W0680000 W0680000
N250205 N250207 W0680326 W0680327
N011335 N011338 W0834348 W0834357
N011301 N011301 W0834323 W0834323
Record ID: 1999023729
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands