Volcano-tectonics of the Al Haruj Volcanic Province, Central Libya

Elshaafi, Abdelsalam; Guðmundsson, Ágúst

doi:10.1016/j.jvolgeores.2016.06.025

Cited by 25 publications

(17 citation statements)

References 39 publications

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“…However, there is little evidence of post‐Eocene extensional normal faulting within the basin (Abadi et al, 2008). For this reason, alternative models which combine mild lithospheric thinning with elevated mantle temperatures have also been proposed (Beccaluva et al, 2008; Bardintzeff et al, 2012; Cvetković et al, 2010; Elshaafi & Gudmundsson, 2016; Lustrino et al, 2012; Radivojević et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Quantifying Asthenospheric and Lithospheric Controls on Mafic Magmatism Across North Africa

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Masoud

et al. 2019

Geochem Geophys Geosyst

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African basin‐and‐swell morphology is often attributed to the planform of subplate mantle convection. Across North Africa, the coincidence of Neogene and Quaternary (i.e., <23 Ma) magmatism, topographic swells, long wavelength gravity anomalies, and slow shear wave velocity anomalies within the asthenosphere provides observational constraints for this hypothesis. Admittance analysis of topographic and gravity fields corroborates the existence of subplate support. To investigate quantitative relationships between intraplate magmatism, shear wave velocity, and asthenospheric temperature, we collected and analyzed a suite of 224 lava samples from Tibesti, Jabal Eghei, Haruj, Sawda/Hasawinah, and Gharyan volcanic centers of Libya and Chad. Forward and inverse modeling of major, trace, and rare Earth elements was used for thermobarometric studies and to determine melt fraction as a function of depth. At each center, mafic magmatism is modeled by assuming adiabatic decompression of dry peridotite with asthenospheric potential temperatures of 1300‐1360 °C. Surprisingly, the highest temperatures are associated with the low‐lying Haruj volcanic center rather than with the more prominent Tibesti swell. Our results are consistent with earthquake tomographic models which show that the slowest shear wave anomalies within the upper mantle occur directly beneath the Haruj center. This inference is corroborated by converting observed velocities into potential temperatures, which are in good agreement with those determined by geochemical inverse modeling. Our results suggest that North African volcanic swells are primarily generated by thermal anomalies located beneath thinned lithosphere.

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Section: Introductionmentioning

confidence: 99%

Quantifying Asthenospheric and Lithospheric Controls on Mafic Magmatism Across North Africa

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Masoud

et al. 2019

Geochem Geophys Geosyst

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“…Volcanism in Libya began in the Eocene and continued developing into the late Pleistocene. Some evidence suggests volcanism continued along the western and southwestern margins of the Sirt Basin into the Holocene (Elshaafi & Gudmundsson, , ; Nixon et al, ). Volcanic units of the Al‐Haruj province of Libya are dominated by primarily olivine‐ and clinopyroxene‐rich magma types, which were likely sourced from the juvenile asthenosphere (Cvetković et al, ).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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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.

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“…The uncertainties or errors for our measurements are estimated at 5% partly based on comparison between measurement in the field and from satellite imagery (cf. Elshaafi and Gudmundsson 2016). The rough elliptical surface expression of most collapse dolines on the satellite imagery and in the field may be taken as an indicator of ellipsoidal geometry chamber of dolines (Figs.…”

Section: Size and Distribution Of Collapse Dolinesmentioning

confidence: 99%

Development of collapse dolines in Al Jabal Al Akhdar, NE Libya: geomorphic analysis and numerical modeling-based approach

Elshaafi

Bilal

Awami³

et al. 2021

Carbonates Evaporites

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Al Jabal Al Akhdar anticlinorium, NE Libya, has the most extensive and diversified karstic features. Collapse dolines are among the most prominent karst phenomena with many of them developed during the Holocene. This research uses field observations and numerical modelling to understand the geometry and formation mechanisms of these dolines. Detailed measurements of 66 collapse dolines including locations, elevations and dimensions (diameters and depths) are documented herein. The dolines have diameters ranging from several meters to tens of meters, while their depths vary from few meters to over a hundred meters. Some giant dolines can be classified as "Tiankengs". The dolines have average diameter of 55 m and height/depth of 60 m. There is a strong linear correlation between dolines areas and volumes with a determination coefficient (R 2 ) of 0.88. When 65 collapse dolines in China are added to the dataset for comparison, the correlation becomes R 2 = 0.83. This geometric similarity may suggest an analogous mechanism of their development. This research reveals that these dolines developed from the enlargement of fractures and bedding planes, forming various sizes of cavities in the sub-surface through chemical weathering. The subsequent collapse of the roof of these enlarged voids was most likely influenced by local stress fields around them, leading to extensive extension and shear fractures. Numerical models suggest that the local stress field favoured rupture and fracture propagation, once tensile and shear stresses exceed the tensile and shear strengths of the host rocks, thus causing the breakdown and the formation of collapsed dolines.

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Volcano-tectonics of the Al Haruj Volcanic Province, Central Libya

Cited by 25 publications

References 39 publications

Quantifying Asthenospheric and Lithospheric Controls on Mafic Magmatism Across North Africa

Quantifying Asthenospheric and Lithospheric Controls on Mafic Magmatism Across North Africa

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

Development of collapse dolines in Al Jabal Al Akhdar, NE Libya: geomorphic analysis and numerical modeling-based approach

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