We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Fault attribute analysis for unraveling rifting processes at a Continent-Ocean Transition rift: example of Dabbahu-Manda-Hararo (Ethiopian Afar).
- Authors
Dumont, Stéphanie; Klinger, Yann; Socquet, Anne; Escartín, Javier; Grandin, Raphaël; Jacques, Eric; Medynski, Sarah; Doubre, Cécile
- Abstract
Analyses of fault attributes help us understand fault growth processes in diverse tectonicsettings. Here we present a detailed analysis of a fault population integrated at the scale of theDabbahu-Manda-Hararo (DMH) rift segment (Central Afar, Ethiopia), a rift in a late phase ofthe continent-ocean transition. We investigate the along-rift axis variations in faultingprocesses, and compare these to those observed at oceanic ridges so as to better unravel theprocesses leading to the continental breakup. We quantify fault azimuth, length, and throw attributes for 668 normal faults we mapped.Along DMH rift, the mean fault density is 0.87 ± 0.7 km/km2 and the mediantectonic strain ranges from 1.8% to 3.1% assuming fault dip of 60˚ and 45˚,respectively. North of the transversal Ado Ale volcanic chain, between N12.35˚ andN12.45˚, the azimuth of DMH rift changes from N150º to N165º accommodated bythe fault population. This rift section also reaches the maximum tectonic strainobserved along the rift (∼12% and ∼20% assuming a 60˚ and 45˚ dipping fault) andis also characterized by long faults (4-12 km) distributed evenly at the rift axisand margins. Combined to scaling laws and morphological analysis, these resultssuggest specificities of the northern part of the rift that cannot be explained byregional processes such as changes in the direction of extension between Nubia andArabia tectonic plates. Instead, our observations suggest that the Dabbahu volcanoinfluences rift development. Using thermomechanical arguments, we suggest that crustalmagma chambers act as stress concentrators. Hence, the Dabbahu volcano, locatedat the northern tip of the rift, has captured the propagating Manda-Hararo rift inthe last ∼100 kyr resulting in a different rifting stage in the northern part of therift. The morphotectonic analysis reveals numerous common features (segment length,spreading rate, associated magmatic system, tectonic strain, fault growth) withslow-spreading ridge segments, such as the Lucky Strike oceanic spreading center(LS-OSC) at the Mid-Atlantic ridge. The comparison led between DMH rift andLS-OSC segment shows that the upper crustal extension is accommodated at first-ordersimilarly at both extensional systems, represented at ∼80% by diking and ∼10-20% byfaulting. A further analysis of the lithospheric structure and dynamics of these twoextensional systems using observations from the literature suggests 1) a decoupling ofthe lithospheric crust/mantle at DMH rift and 2) a decoupling of the lithosphericcrust/mantle at LS-OSC segment center and decoupling at the segment ends. Thesevariations are related to the different thermal conditions that characterize the transitionalcontinental lithosphere and oceanic ridges. These common features and differences resultfrom the depth-dependent extension and induced feedback that likely determine thetransitional present-day surface expression of late rifting stages like at DMH rift.
- Subjects
MID-Atlantic Ridge; NUBIA; RIFTS (Geology); GEOLOGIC faults; PLATE tectonics; LITHOSPHERE; VOLCANOES
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article