Crustal structure of the propagating TAMMAR ridge segment on the Mid-Atlantic Ridge, 21.5°N.

Dannowski, Anke , Grevemeyer, Ingo , Phipps Morgan, Jason, Ranero, César R., Maia, M. and Klein, Gerald (2011) Crustal structure of the propagating TAMMAR ridge segment on the Mid-Atlantic Ridge, 21.5°N. Open Access Geochemistry, Geophysics, Geosystems, 12 . Q07012. DOI 10.1029/2011gc003534.

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Abstract

Active ridge propagation frequently occurs along spreading ridges and profoundly affects ridge crest segmentation over time. The mechanisms controlling ridge propagation, however, are poorly understood. At the slow spreading Mid-Atlantic Ridge at 21.5°N a seismic refraction and wide-angle reflection profile surveyed the crustal structure along a segment controlled by rapid ridge propagation. Tomographic traveltime inversion of seismic data suggests that the crustal structure along the ridge axis is controlled by melt supply; thus, crust is thickest, 8 km, at the domed segment center and decreases in thickness toward both segment ends. However, thicker crust is formed in the direction of ridge propagation, suggesting that melt is preferentially transferred toward the propagating ridge tip. Further, while seismic layer 2 remains constant along axis, seismic layer 3 shows profound changes in thickness, governing variations in total crustal thickness. This feature supports mantle upwelling at the segment center. Thus, fluid basaltic melt is redistributed easily laterally, while more viscose gabbroic melt tends to crystallize and accrete nearer to the locus of melt supply. The onset of propagation seems to have coincided with the formation of thicker crust, suggesting that propagation initiation might be due to changes in the melt supply. After a rapid initiation a continuous process of propagation was established. The propagation rate seems to be controlled by the amount of magma that reaches the segment ends. The strength of upwelling may govern the evolution of ridge segments and hence ultimately controls the propagation length.

Document Type: Article
Keywords: Meeresgeologie; Volcanology; Geophysics; Crustal structure; mid-ocean ridges; ridge propagation; seismic traveltime tomography; marine seismics; mid-ocean ridge processes
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2011gc003534
ISSN: 1525-2027
Related URLs:
Projects: Future Ocean, COSTMAR
Date Deposited: 27 Jul 2011 08:45
Last Modified: 13 Mar 2018 11:29
URI: http://oceanrep.geomar.de/id/eprint/11988

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