Spatial variations of crustal characteristics beneath the Hoggar swell, Algeria, revealed by systematic analyses of receiver functions from a single seismic station

Abstract

[1] The Hoggar swell in Algeria is one of the significant massifs of northwest Africa. The paucity of highresolution geophysical studies of the crust and mantle beneath the massifs is mostly responsible for the heated debates about the depth of the source region of the Cenozoic volcanism and the closely related uncertainty about the mechanism that formed and maintains the high elevation of the swells. Here we report results from a systematic study of 1386 high-quality receiver functions (RFs) recorded by station TAM, the only permanent broadband seismic station on the Hoggar swell. The resulting crustal thickness is about 34 km and the V p /V s is 1.77 when all the RFs from the station are stacked. Our study reveals a sharp contrast in the amplitude of the P-to-S converted phases between the volcanic, highly-fractured Tefedest terrane and the non-volcanic, less fractured Laouni terrane. The former has a stacking amplitude that is comparable to typical cratonic areas, and the latter has an amplitude that is only about 25% as large. Spatially consistent crustal thickness and an intermediate-mafic crust are inferred on the Tefedest terrane, while spatially variable crustal thickness and a felsic crust is inferred beneath the Laouni terrane. The observations can be best explained by a mantle-derived underplated magmatic layer beneath the mechanicallystronger Laouni terrane, and magmatic diking and resultant volcanism associated with the mechanically weaker Tefedest crust. The study demonstrated the significance of a long-running station in the investigation of spatial variations of crustal characteristics.

Physical State and Structure of the Crust Beneath the Western‐Central United States From Multiobservable Probabilistic Inversion

“…The V p / V s ratio for common rock types varies from ∼1.63 for felsic rocks to ∼2.1 for mafic and ultra mafic rocks or uncosolidated sediments (Christensen, ; Fountain et al, ; Wang et al, ; Zandt & Ammon, ) and is commonly considered a useful proxy for bulk crustal composition (Chevrot & Van Der Hilst, ; Christensen, ; Gercek, ; Liu & Gao, ; Nair et al, ; Shillington et al, ; Tarkov & Vavakin, ; Zandt & Ammon, ). However, it also known that the presence of melts/fluids can significantly affect the V p / V s ratio and mask the bulk compositional signature (Caricchi et al, ; Chatterjee et al, ; Hacker et al, ; Johnson & Poland, ; Nakajima et al, ; Owens & Zandt, ; Takei, ; Tripoli et al, ; Ueki & Iwamori, ; Zhang et al, ).…”

Crustal Thickness Beneath Libya and the Origin of Partial Melt Beneath AS Sawda Volcanic Province From Receiver Function Constraints

“…(a) Radial RFs plotted against the back azimuth, with a simple time series stack (red) before sediment moveout, (b) same as Figure a but after resource‐removal filtering, and (c) H ‐ κ grid plot for normalized stacking amplitude after the sediment moveout correction. The red line represents stacking amplitudes for κ = 1.73 (which is the mean κ for crustal rocks; Liu & Gao, ), the dashed blue line represents stacking amplitudes for the optimal κ and stacking amplitude along the dashed white. The optimal H and κ pair is indicated by a black dot.…”

“…The North African portion of the subcontinental lithospheric mantle has undergone a series of complex tectonic processes, where the most notable being the Pan‐African events. The Pan‐African events (Late Proterozoic to Early Paleozoic) developed continental‐scale convergence structures, such as crustal thickening, and may be related to volcanic arcs and possibly deeper alterations indicated by drop a Bouguer gravity anomaly (Doucouré & de Wit, ; Liégeois et al, , ; Liu & Gao, ; Van Der Meijde et al, ). Libya includes a portion of the largest Archean craton of Africa, which is the Sahara Metacraton (SMC).…”

Receiver function constraints on crustal seismic velocities and partial melting beneath the Red Sea rift and adjacent regions, Afar Depression

“…Our recent applications of the procedure can be found in Nair et al [2006], Liu and Gao [2010], and Bashir et al [2011]. The weighting factors used for the stacking are 0.5, 0.4, and 0.1 for the P m S, PP m S, and PS m S phases, respectively.…”