Modeling Heat
and Mass Transfer Along the Muroto Transsect, Nankai Trough, Combining 2D-Basin
and Structural Modeling and its Importance for the Deep Biosphere
Ondrak, Robert1, Christoph
Gaedicke2, Brian Horsfield3 (1) GeoForschungsZentrum,
Potsdam, Germany (2) Federal Institute for Geosciences and Natural Resources
(BGR), Germany, Hannover, Germany (3) GeoForschungsZentrum-Potsdam, Potsdam,
Germany
The Nankai trough located southeast of balanced
cross-sections
defining the sections before and after overthrusting as
input
for 2d-basin
modeling. We can show that rapid burial and over thrusting during the
Quaternary is not sufficient to explain measured maturity of organic material
in the sediments. The observed maturity levels are reached only in combination
with very high heat flow during the phase of rapid burial. Today's heat flow
distribution is not purely conductive but modified by hydrothermal convection.
This is in agreement with previous studies observing a large scatter in heat
flow which can only be explained by transient effects due to hydrothermal
convection in the compressional regime of the Nankai accretionary prism.
Present day temperatures reach 110°C at a depth of about 1100m below sea floor
in 5800m water depth. The model predicts that generation proceeds at 5200-5600m
depth, depending on well location. We used published and laboratory determined
kinetic parameters for total hydrocarbon generation and carbon dioxide
generation, in order to predict the timing of generation of these substances in
time and space. An overlap was observed between generation zones and subsurface
microbial communities, pointing to bio-geo coupling feeding the deep biosphere.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California