Strain Accommodation by Intrusion and Faulting in a Rift Linkage Zone: Evidences From High‐Resolution Topography Data of the Afrera Plain (Afar, East Africa). Issue 6 (31st May 2022)

• Record Type: Journal Article
• Authors: La Rosa, Alessandro; Pagli, Carolina; Hurman, Gareth L.; Keir, Derek
• Is Part Of: Tectonics. Volume 41:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-31
• Subjects: rift systems -- Pléiades‐1 -- DEM -- transfer zone -- Afar; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2021TC007115
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: At mature magma‐rich continental rifts, extension focuses along discrete axial segments where magmatism and diking are important in accommodating plate divergence. However, the role of magma in influencing the deformation at rift–rift offsets is still unclear as direct observations are rare. Here, we exploited high‐resolution Pléiades‐1 tri‐stereo imagery to produce the first 1 m Digital Elevation Model of the Afrera Plain linkage zone between the Erta Ale and Tat Ali magmatic segments in Northern Afar. We carried out a detailed structural analysis of both tectonic and magmatic features in the area and observed different trends and kinematics of these features. Magmatic features at Afrera strike N160°E ± 5°E, similar to the Erta Ale segment and perpendicular to the extension direction. Conversely, tectonic features fall into two families of ∼NW‐SE‐ and ∼NS‐striking oblique faults with right‐lateral and left‐lateral components, respectively, as shown by Riedel shears. We interpret the extension direction of tectonic features using observed opening of fractures, previous seismic, and InSAR‐based fault models and from that expected for the mapped conjugate fault pattern. While the results show scatter in the range of N46°E–N68°E, it is similar within error to the regional extension direction. The simplest model that explains our data is that in the linkage zone there is both extensional and shear strain. The dikes accommodate only extension, while conjugate oblique faults accommodate extension and shear strain. Our study shows that both magmatism and faulting are important during rift segment interaction and linkage. Plain Language Summary: When two tectonic plates separate, the lithosphere extends through the intrusion of molten rock (magma) rising from depth and with brittle faulting occurring in the upper crust. As extension proceeds, the magma emplacement focuses in ∼50–100‐km‐long, and tens‐of‐kilometers‐wide linear segments (magmatic segment) of the rift valley floor, with a sideways step (lateral offset) commonly present in‐between adjacent segments. However, the style of faulting and the role of magmatic activity in influencing the deformation in the lateral offsets between magmatic segments are not well understood. In this study, we addressed this open question by creating high‐resolution combined three‐tridimensional models of the Earth surface and interpreting it with high‐resolution satellite images. We map fractures and other structures related to magmatic activity and collect measurements showing that two different types of coexisting deformation can be accommodated by either magmatic and or nonmagmatic processes. Key Points: We carried out a detailed structural analysis of the Afrera Plain linkage zone using 1 m Digital Elevation Models obtained from tri‐stereo Pléiades‐1 imagery Dikes and faults are coeval and both accommodate strain in the linkage zone Diking accommodates pure extension, while conjugate faults accommodate both shear and extension during rift–rift interaction