Oceanic Core Complex die off and generation of enhanced mantle upwelling on the Mid-Atlantic Ridge - 22° N

EGU2011-13199 Images of crustal construction provide a key to understand the interplay of magmatism and tectonism while oceanic crust is build up. Bathymetric data show that the crustal construction is highly variable. Areas that are dominated by magmatic processes are adjacent to areas that are highly tectonised and where mantle rocks were found. The Mid-Atlantic Ridge at 22°N shows this high variability along the ridge axis, within the TAMMAR segment, and from segment to segment. However, this strong variability occurs also off-axis, spreading parallel, representing different times in the same area of the ridge. A fracture zone, with limited magma supply, has been replaced by a segment centre with a high magmatic budget. Roughly 4.5 million years ago, the growing magmatic active TAMMAR segment, propagated into the fracture zone, started the migration of the ridge offset to the south, and stopped the formation of core complexes. We present data from seismic refraction and wide-angle reflection profiles that surveyed the crustal structure across the ridge crest of the TAMMAR segment. These yield the crustal structure at the segment centre as a function of melt supply. The results suggest that crust is ~8 km thick near the ridge and decreases in thickness with offset to the ridge axis. Seismic layer 3 shows profound changes in thickness and becomes rapidly one kilometre thicker approx. 5 million years ago. This correlates with gravimetric data and the observed “Bull’s eye” anomaly in that region. Our observations support a temporal change from thick lithosphere with oceanic core complex formation to thin lithosphere with focussed mantle upwelling and segment growing. The formation of ‘thick-crust’ volcanic centre seems to have coincided with the onset of propagation 4.5 million years ago

Short Cruise Report RV POSEIDON Cruise P393 [POS393], Malaga, Spain – Faro, Portugal, 14 January – 24 January 2010

Objectives: The evolution of the Western Mediterranean Sea and the Gulf of Cadiz is inherently governed by (i) plate convergence between Nubia (Africa) / Eurasia and (ii) subduction related slab-roll back. Both processes are responsible for the surface features / topography of the Alboran Sea / Rif / Betic domain and deep-seated features related to the consumption of African lithosphere. The cruise is part of the ESF-EUROCORES programme TOPO- EUROPE (Project TOPO-MED) and is aiming to study the interrelation between convergence and major tectonic fault zones in the Alboran Sea (Trans-Alboran-Shear-Zone – the Alboran Ridge) and in the Gulf of Cadiz and Miocene subduction, causing deep-seated seismicity (40-150 km depth) under the western Alboran basin. Furthermore, active tectonic features and fault zones will mimic the plate boundary configuration between Europe/Iberia and Nubia/Morocco. Monitoring networks with ocean bottom seismometers (OBS) were installed in the Alboran Sea and in the Gulf of Cadiz, recording local and regional earthquakes. Two deployment periods of approx. 6 month (in total one year) were conducted. In August of 2009 30 OBS were deployed during the RV Poseidon cruise P389. Instruments were recovered now during the Poseidon cruise P393 and have been re-deployed in the Gulf of Cadiz (Fig. 1). The recovery of OBS deployed in the Gulf of Cadiz stations will be the main aim of the RV Maria S. Merian cruise MSMS15/5, scheduled for July of 2010. During the deployment in the Alboran Sea the ocean bottom seismic instruments recorded a wealth of local earthquakes (see Fig. 1). The distribution of seismicity is going to outline tectonically active features and faults. In addition, data will be used for tomographic inversion, providing seismic constraints on the structure of crust and mantle in the Gibraltar arc / Gulf of Cadiz area and the Alboran domain. Furthermore, land based monitoring networks operated during the time of the marine deployments will provide a regional coverage of the entire area between Morocco and Spain, including the northern Moroccan continent and southern Spain

1. Wochenbericht MSM15/5

1. Wochenbericht der Forschungsfahrt MSM15/5 des FS Maria S. Merian, Valletta nach Rostock 17. Juli 2010 bis 25. Juli 201

2. Wochenbericht SO181/1b

2. Wochenbericht der Forschungsfahrt Nr. SO181-1b des FS SONNE 17. Dezember 2004 bis 16. Januar 2005 Corral, Chile – Talcahuano, Chil

1. Wochenbericht SO181/1b

1. Wochenbericht der Forschungsfahrt Nr. SO181-1b des FS SONNE 17. Dezember 2004 bis 16. Januar 2005 Corral, Chile – Talcahuano, Chil

4. Wochenbericht SO181/1b

4. Wochenbericht der Forschungsfahrt Nr. SO181-1b des FS SONNE 17. Dezember 2004 bis 16. Januar 2005 Corral, Chile – San Vicente, Chil

4. Wochenbericht SO195

4. Wochenbericht der Forschungsfahrt Nr. SO195 des FS SONNE 7. Januar bis 15. Februar 200

3. Wochenbericht M115

3. Wochenbericht der Forschungsfahrt Nr. M115 des FS METEOR 1. April bis 28. April 2015 Kingston, Jamaika – Pointe à Pitre, Guadeloup

1. Wochenbericht M115

1. Wochenbericht der Forschungsfahrt Nr. M115 des FS METEOR 1. April bis 28. April 2015 Kingston, Jamaika – Pointe à Pitre, Guadeloup