We would like to alert the structure/tectonics community to a topical
session that has been approved for the upcoming GSA Annual Meeting in
Boston. Please consider submitting to this session -- we would like to
make it as interdisciplinary as possible. Please pass this announcement
along to anyone else who might be interested.
TOPICAL SESSION ANNOUNCEMENT, BOSTON GSA MEETING, NOVEMBER 5-8, 2001
Topical session T59:
"Rheological effects of fluid-rock interactions at depth: From experimental
constraints to interpretations of field observations"
Convenors:
Tim Wawrzyniec
Bureau of Economic Geology, University of Texas
[log in to unmask]
Jane Selverstone
University of New Mexico
[log in to unmask]
Sponsors: GSA Structural Geology and Tectonics Division, GSA Geophysics
Division.
The invited speakers list is still being finalized.
Scientific categories: Structural Geology/Tectonics; Experimental
Petrology; Geophysics (NOTE: the categories listed in the March issue of
GSA Today were incorrect...).
Recent investigations have demonstrated that fluid *composition* may be a
rarely recognized but important variable in dictating the position of the
brittle-ductile transition. This transition has been described as a broad
zone, possibly several kilometers thick, where deformation may occur by
either brittle or ductile deformation mechanisms. The position of this
transition is dictated by temperature, mineralogy, grain size, strain rate,
degree of work hardening, and the orientation of brittle structures with
respect to the regional stress field. However, recent advances in
experimental petrology have shown that the presence of an interstitial
fluid and the composition of that fluid can also have a profound effect on
the rheology of a deforming body of rock. For a fluid in textural
equilibrium with the host phases, the surface energy characteristics
between the fluid and the mineral grains determine whether a fluid is
wetting or nonwetting. A wetting fluid is capable of being transmissive
and therefore can enhance diffusion processes, which may ultimately favor
or enhance a plethora of ductile mechanisms. In contrast, a nonwetting
fluid may become nontransmissive, ultimately leading to an increase in
fluid pressure and the ultimate stabilization of brittle deformation.
Shifts from wetting to nonwetting behavior can occur over very narrow
ranges of fluid composition and clearly vary depending on bulk fluid and
bulk rock composition. The purpose of this session is to bring together a
series of talks from the fields of experimental petrology and
microstructural analysis, structural geology, applied fluid inclusion
analysis, and economic geology to explore the relatively unrecognized but
significant role of fluid composition in dictating the position of the
brittle/ductile transition. This exploration in turn may provide insight
into seismogenic processes and shear zone initiation.
We encourage contributions from experimental and applied petrology,
microstructural studies, field based kinematic studies, fluid inclusion
studies of shear zone rocks, and studies of rheologic changes associated
with boiling fluids.
If there are a sufficient number of contributions, we hope to have both an
oral session and a poster session on this topic.
THE DEADLINE FOR SUBMITTING ABSTRACTS FOR THE MEETING IS JULY 24.
Information on the meeting and on electronic abstract submission is
available at:
http://www.geosociety.org/meetings/2001/index.htm
____________________________________________________
Jane Selverstone, Professor
Dept. of Earth & Planetary Sciences
Northrop Hall, 200 Yale Blvd. NE
University of New Mexico
Albuquerque, NM 87131-1116
[log in to unmask]
505-277-6528 or -4204; 505-277-8843 fax
http://epswww.unm.edu/facstaff/selver/home.htm
|