Experimental evidence of microbially catalyzed smectite-illite reaction at high pressure and high temperature: Analogy in the Nankai Trough
Abstract
Microbial Fe-reduction in smectite structure plays a significant role in illitization accompanying with the structural/chemical modification of smectite closely linked to the petrophysical properties of sediment, elemental cycles, fault behavior, and deep biosphere.
The present study demonstrates evidence of microbially catalyzed S-I reaction at high pressure and high temperature (55 MPa and 80-140℃) to analogy in the modern mudstone of Nankai Trough. The sediment of lower Shikoku basin (660-855 mbsf) from the Site C0023 (32⁰22.0018' N, 134⁰57.9844' E) which was conducted by Expedition 370 of International Ocean Discovery Program (IODP), was incubated at various temperature (80, 95, 110, 125, and 140℃) to examine the changes in mineralogy, particularly structural/geochemical modification in smectite and illite. The X-ray diffraction profiles showed a modification in intensity of d001 peak of smectite as well as a detection of mixed layer (I/S) in 2θ=9.84° that may indicate the S-I reaction has been progressed by microbial respiration and/or thermal diagenetic process. Additionally, changes in Al/Si ratio, K contents and oxidation state of structural Fe of smectite and illite were measured by transmission electron microscopy with energy dispersive X-ray spectroscopy and electron energy loss spectroscopy to determine the progress in illitzation at nano-scale. Furthermore, Al, Si, and Fe concentration in supernatant was measured to verify the dissolution of clay mineral. The detail evidences to reveal the microbially catalyzed S-I reaction in deep subseafloor environment will be discussed.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B23E2544K
- Keywords:
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- 0444 Evolutionary geobiology;
- BIOGEOSCIENCESDE: 0495 Water/energy interactions;
- BIOGEOSCIENCESDE: 4805 Biogeochemical cycles;
- processes;
- and modeling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICALDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS