Special Session T19 of the 2007 AGU Fall Meeting is entitled
“The Generation Of Oceanic Lithospheric in Areas of Low Effusive Magmatism:
Where Has All The Crust Gone?”
The aim is to discuss recent discoveries of the structures and processes
associated with the generation and early evolution of oceanic crust and
lithosphere in regions of apparently low effusive volcanism, extensive
detachment faulting or oceanic core complexes. As convenors of this
session, we encourage workers from any relevant discipline in any
geographical area to submit a presentation to the session. The session
description is given below, and further details are available at
http://www.agu.org/meetings/fm07/ under “Preplanned Sessions”.
Please note that the abstract submission deadline is September 6.
Session description:
Recent years have seen increasing interest in the processes associated with
the generation and early evolution of oceanic crust and lithosphere in
regions of apparently low effusive volcanism and/or extensive detachment
faulting. Such regions are mostly, though not entirely, associated with low
spreading rates such as the Gakkel Ridge and Southwest Indian Ridge, but
include the somewhat faster spreading Mid-Atlantic Ridge at 12ºN – 17ºN,
segment ends elsewhere on the Mid-Atlantic Ridge, the relatively fast
spreading Parece Vela ridge in the Philippine Sea, and perhaps areas of very
slow-spread crust in otherwise fast-spreading regions such as Pito Deep on
the boundary of the Easter Microplate. The processes and related scientific
questions include the degree of mantle melting, melt transport mechanisms,
routes and final destinations of melt (e.g. is lack of effusive volcanism
balanced by greater degrees of deep gabbro intrusions?); the nature and
geometry of peridotite upwelling and incorporation into the lithosphere; the
architecture and evolution of oceanic core complexes; early alteration of
the crust/lithosphere; and the properties and bio-geo-chemical consequences
of peridotite-hosted hydrothermal systems.
Many studies of these areas and processes have either just come to fruition
(e.g., ODP Leg 209 drilling of peridotite exposures on the MAR at 15ºN, IODP
Leg 304/305 drilling of the Atlantis Massif Oceanic Core Complex, work on
the Gakkel and Southwest Indian Ridges), or have started recently and are
ready for preliminary presentation and discussion (e.g., recent US
expeditions to Pito Deep, oceanic core complexes at Kane Fracture Zone and
MAR 12ºN-14ºN, and British, French, German and Russian expeditions
investigating oceanic core complexes, low-effusive spreading and
peridotite-hosted hydrothermal vents at MAR 12ºN-17ºN).
A wide range of disciplines is involved in addressing these questions; we
invite contributions from multi-disciplinary and multi-regional perspectives
that are important for attaining solutions.
Roger Searle, Durham University, [log in to unmask];
Eric Hellebrand, SOEST - University of Hawaii, [log in to unmask];
Maurice Tivey, Woods Hole Oceanographic Institution, [log in to unmask];
Benoit Ildefonse, CNRS - Université Montpellier 2,
[log in to unmask]
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