Geophysical Studies near the Ascension Transform: Evolution of Ridge Segmentation and Crustal Structure - Auswertung

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In late 2004 Meteor cruise M62/4 will collect a large geophysical dataset in the region of the Ascension Transform fault with the aim of studying the segmentation of the spreading axis. Specific questions to be addressed are: the change in crustal and upper mantle structure moving from the centre of a spreading segment towards the end and between spreading segments with a well-developed median valley and a well-developed axial high; the asymmetry between segment ends adjacent to the active transform and the inactive fracture zone (inside and outside corners respectively); the evolution of oceanic core complexes (domal exposures of deep crustal and mantle rocks exhumed by movement along detachment faults and characterised by corrugated upper surfaces). Tools to be used include: wid-angle seismic profiles to determine crustal structure and in conjunction with existing gravity data to constrain the thermal structure of the uppermost mantle; high resolution seismic reflection studies (including a deep tow streamer) to image the structure of the upper oceanic crust (faulting and magma chambers); microseismicity and tomographic studies using a grid of ocean bottom instruments to determine local 3-D crustal structure and fault activity and mechanics; swath-bathymetry and magnetics. This proposal requests support to enable the complete analysis of these data.