Magnetic constraints on the emplacement of lower crustal and upper mantle
materials at slow spread ridges

by Jeff Gee
SIO GRD
University of California, San Diego

3-4pm
Friday April 18, 2003
Refreshments served at 2:45pm
Munk Conference Room
Cecil and Ida M. Green Institute of Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
http://mahi.ucsd.edu/seminar/

Abstract

Extensive exposures of gabbroic rocks and associated mantle-derived
ultramafic lithologies have been documented at a number of localities
on the flanks of slow-spreading ridges. Most current models for the
uplift of lower crust and upper mantle involve substantial exhumation
through detachment faulting, though the precise kinematic history of this
fault-related thinning remains uncertain. Magnetic anomaly data and the
remanent magnetization of samples can provide valuable information both
on the thermal history (and hence rheology) as well as the deformation
history of such lower crustal/upper mantle lithologies. I will focus
primarily on results from a near bottom magnetometer survey over an
oceanic core complex near 30N on the Mid-Atlantic Ridge. Here, a series
of ridge parallel anomaly lineations apparently continue from the exposed
peridotite/gabbro massif to more normal crust to the north, presumably
providing a record of uplift, cooling and magnetization acquisition in
the massif. Remanent magnetization data from similar exposures sampled
by drilling will be used to illustrate how such data can constrain the
thermal and tectonic history of lower crustal/upper mantle exposures.