How does the Earth`s crust grow at divergent plate boundaries? A unique opportunity in Afar, Ethiopia

Abstract

We undertook our first field season on this project in January/February 2008, collecting data along a profile crossing the currently active Dabbahu magmatic segment (see loan application). The area is remote and inaccessible, and conditions there are harsh. Most sites were accessed by a commercially hired helicopter (Figure 1). We made very efficient use of this resource by having access to digital SPOT imagery, which enabled us to identify and obtain the coordinates of ~100m diameter sandy patches suitable for MT deployment within the otherwise bare rock rift (Figure 2) at suitable spacings along the profile line.Despite the difficulty of the terrain and the loss of our sealed gel batteries in customs, we successfully occupied 17 sites along a ~56km profile approximately perpendicular to the axis of dyking (Figure 3). The data quality at a couple of the sites is poor (environmental/equipment problems), and is limited by battery problems to shorter periods at others (Figure 4). We were able to deploy two MT sites simultaneously, each occupied for 1-3 days, using GEF broadband coils, its SPAM III (Ritter et al, 1998), and a recording system loaned from Oliver Ritter (GFZ, Potsdam). (A second instrument loaned from GFZ failed in the field.) TEM data were collected using the GEF PROTEM system at 10 of the sites, using a loop size of 100m square (at site 801 we also collected data with a 50m square loop).