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

Abstract

This study investigates crustal thickness and properties within the Libyan region. Results obtained from 15 seismic stations belonging to the Libyan Center for Remote Sensing and Space Science are reported, in addition to 3 seismic stations publically available, using receiver functions. The results show crustal thicknesses ranging from 24 km to 36 km (with uncertainties ranging between ±0.10 km and ±0.90 km). More specifically, crustal thickness ranges from 32 km to 36 km in the southern portion of the Libyan territory then becomes thinner, between 24 km and 30 km, in the coastal areas of Libya and thinnest, between 24 km and 28 km, in the Sirt Basin. The observed high Vp/Vs value of 1.91 at one station located at the AS Sawda Volcanic Province in central Libya indicates the presence of either partial melt or an abnormally warm area. This finding suggests that magma reservoirs beneath the Libyan territory may still be partially molten and active, thereby posing significant earthquake and volcanic risks. The hypothesis of an active magma source is further demonstrated though the presence of asthenospheric upwelling and extension of the Sirt Basin. This study provides a new calculation of unconsolidated sediment layers by using the arrival time of the P to S converted phases. The results show sediments thicknesses of 0.4 km to 3.7 km, with the Vp/Vs values ranging from 2.2 to 4.8. The variations in crustal thickness throughout the region are correlated with surface elevation and Bouguer gravity anomalies, which suggest that they are isostatically compensated.

Depths of magma chambers at three volcanic provinces in the Karlıova region of Eastern Turkey

“…Sanford and Einarsson 1982;Orcutt et al 1984;Macdonald 1986), as well as the locations of deep-seated reservoirs in the lower part of crust or at the crust-mantle boundary at depths ranging from 10 to 60 km (e.g. Gök et al 2003;Reed et al 2014;Lemnifi et al 2017b). However, fossil magma chambers and plutons cannot always be reliably traced using seismic tomography and geodetic methods (e.g.…”

Receiver function imaging of mantle transition zone discontinuities and the origin of volcanism beneath Libya

“…P-and S-wave velocity perturbations have been observed in previous studies [e.g., Grand, 2002;Simmons et al, 2012]. Shear wave splitting measurements obtained adjacent to North Africa [Miller et al, 2013;Lemnifi et al, 2014; are attributed to mantle flow and represent the horizontal movement of the African continent to the north with local deflection of the mantle flow [Lemnifi et al, 2015].…”

“…Tomography studies indicate that the volcanic areas in Libya are associated with a low-velocity mantle structure limited to the top 150 km [Lie´geois et al, 2005] as previously mentioned. Large positive velocity anomalies in the upper 100 km of North Africa were interpreted as the cratonic roots of cratonic terranes called the Sahara Metacraton [Grand, 2002;Lemnifi et al, 2015]. The delamination of cratonic roots have been proposed to explain the observed negative velocity anomalies at the depths of 100-175 km [Abdelsalam et al, 2011].…”

“…Libya has experienced a complex tectonic history comprised by the development of a subduction zone in its northern-most portion [Capitanio et al, 2009;Faccenna et al, 2014;Lemnifi et al, 2015;2017a], N-S and NW-SE oriented basement faults from the Pan-African Orogeny, and Hercynian compressional basement faults, which are also mainly orientated N-S or NW-SE [Hassan and Kendall, 2014;Lemnifi et al, 2015]. The region also hosts many volcanic provinces that were formed from the Miocene to the Holocene [e.g., Hoernle et al, 1995;Bardintzeff et al, 2012, Elshaafi andGudmundsson, 2017] (Figure 1).…”

AFRP20: New P‐Wavespeed Model for the African Mantle Reveals Two Whole‐Mantle Plumes Below East Africa and Neoproterozoic Modification of the Tanzania Craton

“…We account for crustal heterogeneity by making receiver‐side corrections to the residuals based on Moho depths within the Crust1.0 model (Laske et al., 2013) supplemented with receiver function constraints for African temporary seismic deployments where available (Akpan et al., 2016; Andriampenomanana et al., 2017; Ebinger et al., 2017; Fadel et al., 2018; Hosny & Nyblade, 2016; Lemnifi et al., 2017; Ogden et al., 2019). Details on generation of this crustal model and its effect on our tomographic inversion are presented in the supplementary material (Figures ).…”