EGS Special Sessions

InterRidge Office mac at ext.jussieu.fr
Wed Oct 21 17:02:04 EST 1998


     European Geophysical Society    XXIV General Assembly  
    
              The Hague, The Netherlands, 19-23 April 1999

Abstract Deadline: 15 December, 1998
Abstract submission instructions:
http://www.copernicus.org/EGS/egsga/41.htm
__________________________________________________________
                Special sessions relevant to mid-ocean ridge research

SE58    Composition and structure of the oceanic crust: constraints from
         seismic, gravity, geological and petrological observations
SE59    Extensional tectonics in the oceanic lithosphere; from
continental
        margins to mid-ocean ridges
SE60    Strain partitioning from continental margins to mid-ocean ridges
SE62    Melt generation beneath mid-ocean ridges and hotspots
OA8    The chemistry of hydrothermal systems and interactions with the
water
        column
__________________________________________________________
  
SE58    Composition and structure of the oceanic crust: constraints from
seismic, gravity, geological and petrological observations

Conveners: Dr. Timothy A. Minshull, minshull at esc.cam.ac.uk and Dr.
Daniel
Lizarralde, danl at mimer.dlc.ku.dk

Studies of oceanic crustal structure have provided us with important
insights into the composition, physical state, and dynamics of the
mantle.
While the first order processes governing oceanic crust formation are
understood, the detailed mechanism of magmatic accretion and the
interplay
of magmatism and tectonism are still not well known. In addition, many
important parameters - such as spreading rate, potential temperature,
proximity to a hot spot, etc. - have expressions which have not been
fully
characterized and influences which are not well understood. Research is
very
active in this area, and this session will bring together results from
recent studies aimed at characterizing oceanic crust composition and
structure with the goal of better understanding the processes
of oceanic crustal accretion under a variety of conditions. Papers
describing all types of studies are encouraged, including results from
seismic experiments, potential field studies, high-resolution mapping,
submersible investigations, dredging, drilling and ophiolite studies.
__________________________________________________________

SE59    Extensional tectonics in the oceanic lithosphere; from
continental
margins to mid-ocean ridges

Conveners: Dr. Mathilde Cannat, cannat at ccr.jussieu.fr and  Dr.Javier 
        Escartin,escartin at ccr.jussieu.fr

The session will focus on the modes of tectonic extension at passive
continental margins (continent to continent-ocean transition) and
mid-ocean
ridges. We seek contributions on brittle and ductile deformation
mechanisms,
rheology, quantification of strain, and on the interactions between
extensional tectonics and magmatic/ hydrothermal processes.
Contributions
addressing the origin and modes of formation of low angle detachment
faults
are particularly encouraged. Contributions addressing the geophysical
(gravity, seismics and magnetics) signature of tectonic structures are
also
welcome. This session is sponsered by InterRidge.
__________________________________________________________

SE60    Strain partitioning from continental margins to mid-ocean ridges

Convener: Dr. Luc L. Lavier, luc at ldeo.columbia.edu and Dr. John R.
Hopper,
jth at dlc.ku.dk

The more closely we look at areas of continental and oceanic extension,
the
more we see that all rifts are not created equal. Some from slowly, some
quickly. In areas of continental extension, there are wide rifts, narrow
rifts, volcanic rifts and failed rifts. Areas of oceanic extension are
markedly different in accordance with their spreading rates: fast
spreading
centers are marked by axial highs, slow spreading centers by axial
valleys
and intermediate spreading centers by both axial highs and valleys. For
both
oceanic and continental domains, the pattern of faulting is seen to vary
between different extended areas. In addition, the transition from
continental rift to oceanic rift and seafloor spreading is highly
variable:
some are defined as sharp boundaries while others are transition zones
that
span several 10's of km. Several processes have been implicated in the
production of this rift diversity from continent to ocean. These
include:
pre-existing strength heterogeneity, the initial thermal structure and
crustal thickness in a rifting region, strain rate dependent changes in
strength of rifts, and magmatism during rifting. We ask for contributed
papers that shed light on what processes control the development of
rifts or
classes of rifts. Papers concerning either observational constraints on
rift
structure and history or models of continental and oceanic extension, or
both, would be appropriate for this session.
__________________________________________________________

SE62    Melt generation beneath mid-ocean ridges and hotspots

Convener: Dr. Juan Pablo Canales, juan at sienna.whoi.edu

Melt generation beneath mid-ocean ridges and hotspots, fundamental
processes
closely related to the geodynamic and geochemical evolution of the
Earth,
continue to challenge geoscientists. Recent geophysical, petrological,
and
geochemical observations have improved our knowledge on melt extraction
and
mantle flow beneath mid-ocean ridges, and on the deep origin of mantle
plumes and its implications for models of mantle convection and the
evolution of mantle instabilities. The purpose of this session is to
bring
together researchers from all geoscience disciplines (seismology,
electromagnetic methods, geodynamic models, petrology, geochemistry) to
present and discuss their latest results on upwelling and mantle flow,
generation, extraction, and distribution of melt beneath mid-ocean
ridges,
and on the origin and evolution of mantle plumes. We encourage authors
to
present abstracts with a multidisciplinary approach. Papers on related
topics are also welcome.
__________________________________________________________

OA8    The chemistry of hydrothermal systems and interactions with the
water
column

Convener: Dr. Christopher R. German, cge at mail.soc.soton.ac.uk and 
        Dr. Joel Radford-Knoery, joel.radford.knoery at ifremer.fr 

This symposium aims to address current issues in submarine hydrothermal
circulation. New insights have emerged in recent years, at the European
and
wider international scale, concerning the relative importance of three
"end-member" types of hydrothermal venting:
a) spectacular high- temperature venting on mid-ocean ridge axes;
b) lower temperature, ore-forming diffuse flow along ridge-axes; and 
c) wide-spread low- temperature on- and off- axis circulation. 

All these styles of venting affect both thermal and chemical exchanges
between the solid earth and the overlying oceans and also support unique
ecosystems. The purpose of this symposium is to bring together
presentations
on state-of-the-art research from around the world's ridge-crests in
this
multi-disciplinary field. Papers are invited which address the physics,
chemistry and geology of hydrothermal systems themselves as well as the
fate
of material discharged from hydrothermal venting, in terms of physical,
chemical and biological processes in the oceans. Presentations may be
focussed upon any single aspect of submarine hydrothermal circulation,
on a
discipline-by-discipline basis, or may be chosen to address the subject
at a
multi-disciplinary scale.



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