Flip-flop detachment tectonics at nascent passive margins in SE Afar

Geoffroy, Laurent; Gall, Bernard Le; Daoud, Mohamed Ahmed; Jalludin, Mohamed

doi:10.1144/jgs2013-135

Cited by 16 publications

(15 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Between the MI and AG active rift segments, the Mak'Arrassou transfer zone has been recognized as an oblique transfer zone with tectonic features consistent with the northwestern propagation of the AR (Tapponnier & Varet 1974;Manighetti et al 2001), when Le Gall et al (2011) and Geoffroy et al (2014) identify this region as a large monoclinal flexure, similar to those observed along the volcanic passive margin. Due to this spatial configuration of the GPS velocity field and in particular the lack of velocity vector northeast of the Mak'Arrassou, the strain rate tensor inversion shows that NEtrending extension occurs at the southern part of the Mak'Arrassou region, with a low counter-clockwise rotation rate (∼2.4 • /Myr) in agreement with low palaeomagnetic values (Manighetti et al 2001).…”

Section: The Aden Propagatormentioning

confidence: 85%

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

Doubre¹,

Déprez²,

Masson³

et al. 2016

Geophys. J. Int.

View full text Add to dashboard Cite

S U M M A R YKinematics of divergent boundaries and Rift-Rift-Rift junctions are classically studied using long-term geodetic observations. Since significant magma-related displacements are expected, short-term deformation provides important constraints on the crustal mechanisms involved both in active rifting and in transfer of extensional deformation between spreading axes. Using InSAR and GPS data, we analyse the surface deformation in the whole Central Afar region in detail, focusing on both the extensional deformation across the Quaternary magmato-tectonic rift segments, and on the zones of deformation transfer between active segments and spreading axes. The largest deformation occurs across the two recently activated Asal-Ghoubbet (AG) and Manda Hararo-Dabbahu (MH-D) magmato-tectonic segments with very high strain rates, whereas the other Quaternary active segments do not concentrate any large strain, suggesting that these rifts are either sealed during interdyking periods or not mature enough to remain a plate boundary. Outside of these segments, the GPS horizontal velocity field shows a regular gradient following a clockwise rotation of the displacements from the Southeast to the East of Afar, with respect to Nubia. Very few shallow creeping structures can be identified as well in the InSAR data. However, using these data together with the strain rate tensor and the rotations rates deduced from GPS baselines, the present-day strain field over Central Afar is consistent with the main tectonic structures, and therefore with the long-term deformation. We investigate the current kinematics of the triple junction included in our GPS data set by building simple block models. The deformation in Central Afar can be described by adding a central microblock evolving separately from the three surrounding plates. In this model, the northern block boundary corresponds to a deep EW-trending trans-tensional dislocation, locked from the surface to 10-13 km and joining at depth the active spreading axes of the Red Sea and the Aden Ridge, from AG to MH-D rift segments. Over the long-term, this plate configuration could explain the presence of the en-échelon magmatic basins and subrifts. However, the transient behaviour of the spreading axes implies that the deformation in Central Afar evolves depending on the availability of magma supply within the well-established segments.

show abstract

Section: The Aden Propagatormentioning

confidence: 85%

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

Doubre¹,

Déprez²,

Masson³

et al. 2016

Geophys. J. Int.

View full text Add to dashboard Cite

show abstract

“…A number of authors have suggested faults exist within highly magmatic settings. An asymmetric detachment fault has been observed in the Afar region, where two stages of extension over listric faults are inferred to have caused faulted rollover anticlines [ Geoffroy et al ., ]. This differs from our prediction of SDR evolution, where we propose the crust was thinned in just one stage.…”

Section: Discussionmentioning

confidence: 97%

Fault‐controlled lithospheric detachment of the volcanic southern South Atlantic rift

Becker

Tanner

Franke

et al. 2016

Geochem Geophys Geosyst

View full text Add to dashboard Cite

We present structural models of two exemplary conjugate seismic lines of the southernmost South Atlantic margins to examine their initial evolution, especially the seaward-dipping reflectors (SDRs). Modeling illustrates the different structure and inclination angles of the SDRs, which therefore require different subsidence histories. Since typical symmetrical subsidence models are not applicable, we suggest a model with a westward-dipping detachment fault that offsets the SDRs on the South American margin and we speculate on passively subsided SDRs on the South African margin. We propose a simple-shear rifting mechanism to explain the initial break-up of the South Atlantic.

show abstract

“…Thus, from a chronological point of view, the crust is “rethickened” after an extension phase. This may appear to be at odds with observations made at other onshore volcanic passive margins, such as the SE Afar rift in Djibouti [ Geoffroy et al ., ]. Here syn‐tectonic prisms of 8 to 2 Ma age (stage partly intermediate between Figures b and c) are thought to be controlled by rollover faults that are rooted in a detachment at depth that controls the location of future breakup.…”

Section: Discussionmentioning

confidence: 99%

“…Seismic studies show the presence of a broad mantle anomaly rooted at the core‐mantle boundary [ Ritsema and Allen , ; Simmons et al ., ; Bastow et al ., ; Li et al ., ; Ritsema et al ., ], and the Afar rift is therefore considered an example of rifting following impingement of a plume‐like thermal anomaly. The Afar rift system (Figure ) has been interpreted as an asymmetric rift, analogous to SDR, where strain and magmatism have migrated toward the rift center and play a major role in dyking [ Ebinger and Casey , ; Wolfenden et al ., ], or alternatively, as a detachment‐dominated rift [ Ghebreab and Talbot , ; Geoffroy et al ., ]. The relationship between normal faulting, dyking, and low‐angle faults therefore remains unclear.…”

Section: Introductionmentioning

confidence: 99%

Modes of rifting in magma‐rich settings: Tectono‐magmatic evolution of Central Afar

et al. 2016

View full text Add to dashboard Cite

International audienceRecent research in Afar (northern Ethiopia) has largely focused on the formation of the present-day ocean-continent transition at active segments (e.g., Manda Hararo). However, the Oligo-Miocene history of extension, from the onset of rifting at ~25 Ma to the eruption of the massive Stratoïd flood basalts at ~4 Ma, remains poorly constrained. Here we present new structural data and radiometric dating from Central Afar, obtained along a zone stretching from the undeformed Oligocene Ethiopian plateau to the Manda Hararo and Tat'Ale active volcanic segments. Basaltic and rhyolitic formations were mapped in two key areas corresponding to the proximal and distal parts of a half-rift. We present a balanced composite cross section of Central Afar, reconstructed using our new data and previously published geophysical data on the crustal structure. Our main findings are as follows: (1) Extension during the Mio-Pliocene corresponds to a “wide rift” style of rifting. (2) The lower crust has been underplated/intruded and rethickened during rifting by magmatic injection. (3) Our restoration points to the existence of midcrustal shear zones that have helped to distribute extension in the upper crust and to localize extension at depth in a necking zone. Moreover, we suggest that there is a close relationship between the location of a shear zone and the underplated/intruded material. In magma-rich environments such as Central Afar, breakup should be achieved once the initial continental crust has been completely replaced by the newly, magmatically accreted crust. Consequently, and particularly in Afar, crustal thickness is not necessarily indicative of breakup but instead reflects differences in tectono-magmatic regimes

show abstract

Flip-flop detachment tectonics at nascent passive margins in SE Afar

Cited by 16 publications

References 29 publications

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

Fault‐controlled lithospheric detachment of the volcanic southern South Atlantic rift

Modes of rifting in magma‐rich settings: Tectono‐magmatic evolution of Central Afar

Contact Info

Product

Resources

About