Pan-African Cratonization (about 800 to 680 Ma)
Nehlig et al. (2002) conducted a study to review the Pan-African evolution of the Arabian Shield on the premise that new perspectives on the geologic history and structural evolution on the Arabian Shield had emerged. These new perspectives were brought by the extensive fieldwork as well as synthesis and review of structural, aeromagnetic, geochemical, geologic, and geochronological data. The geologic evolution of the Arabian Shield took place between 900 to 550 Ma. This period was also characterized by the “formation, amalgamation, and final Pan-African cratonization of several tectonostratigraphic terranes” (Nehlig et al., 2002, p.103). These terranes were separated by key NW-trending faults and various oriented suture zones covered by ophiolites i.e. serpentinized ultramafic rocks.

Pan-African cratonization between 800 and 680 Ma incorporated the final cratonization of the terranes. The final cratonization of the terranes, which took place between 680 and 610 Ma, generated a network of strike-slip, anastomosing faults that comprised of the N-trending Nabitah belt. In addition, the network comprised of key NW striking left-lateral transpressive faults covered by gneiss domes and linked to sedimentary basins. The other component of the subsequent network of the final cratonization of terranes is the N- to NE-trending right-lateral transpressive faults.

Pan-African Cratonization around 800 to 680 Ma relates to the Arabian Plate on the premise of what it produced. This cratonization resulted in the extensive alkaline granitization, which was simultaneous with Jibalah volcanic and sedimentary rocks disposition in transtensional pull-apart basins. However, Nehlig et al. (2002) state that N-trending Nabitah and NW-trending Najd faults zones form part of oblique transpressional accretion instead of being two distinct events as proposed in earlier studies.

Reference

Nehlig et al. (2002). A Review of the Pan-African Evolution of the Arabian Shield. GeoArabia, 7(1), 103-124.

Pan-African Plate Tectonics

An important component of Pan-African Cratonization is the Pan-African plate tectonics, which had significant impacts on the crust of continent and is linked to the Arabian Plate. Through these plate tectonics, Pan-African Cratonization constitute a critical component of the baseline tectonics of the Arabian Plate. Kroner (2000) conducted a study to examine Pan-African plate tectonics and its implications on the crust of the African continent, particularly the crust of northeast Africa. This study was carried out on the premise that Pan-African belts of the African mainland and the Arabian-Nubian Shield have similar evolutionary characteristics. These attributes are either compatible with intracontinental ensialic development or plate margin. They are also considered to be compatible with Wilson cycle tectonics between 1100 and 500 Ma.

The essential subcrustal forces that result in current lithospheric motion are regarded as the causes of the ensialic and plate margin developments. Consequently, Pan-African cratonization is representative of the shift from Precambrian ensialic plate tectonics to Wilson cycle tectonics. Pan-African cratonization, especially North African craton, comprises widespread Pan-African thermal activity. Such activity incorporates voluminous calc-alkaline granitoid intrusions as well as alkaline to peralkaline ring complexes. Moreover, the widespread Pan-African thermal activity is characterized by a general resetting of mineral isotopic systems in mature basement rocks.

Kroner (2000) contends that pre-Pan-African continental crust already existed in northeast Africa and was affected by the intraplate pressures emerging from the closure of the Pharusian ocean and collisional tectonics in the Arabian Shield. Therefore, Pan-African cratonization relates to the Arabian Plate on the premise that intraplate pressures from collisional tectonics in the Arabian Shield affected the Pan-African continental crust.

Reference

Kroner, A. (2000). Pan African Plate Tectonics and It’s Repercussions on the Crust of Northeast Africa. Geologische Rundschau, 68(2), 565-583.

Spread of Pan-African Cratonization on all Terranes

Heikal (2013) examined...…Ma. The south-central Arabian Plate comprises various areas of gneissic granitoid rocks that are akin to pre-Pan-African basement. In essence, a pre-Pan-African sialic basement complex existed in Saudi Arabia through gneissic granitoid rocks.

According to Kroner, Roobol, Ramsay & Jackson (2013), one of the major syntectonic batholith of the Pan-African age and cratonization is the Dahul gneisses. Alongside other rocks, Dahul gneises played a critical role in the Pan-African cratonization and its impacts on all terranes. The period around 600 Ma was regarded as the age of intrusion through which Pan African cratonization of several rocks was widespread on all terranes and played a part in the evolution of the Arabian Shield.

Reference

Kroner, A., Roobol, M.J., Ramsay, C.R. & Jackson, N.J. (2013, February 28). Pan African Ages of Some Gneissic Rocks in the Saudi Arabian Shield. Journal of the Geological Society, London, 136, 455-461.

Rock Sequences

Pan-African cratonization is characterized by various rock sequences and terranes that shape the evolution of the Arabian Plate. Caby (2003) investigated the rock sequences and terrane assembly of central-western Hoggar. The rock sequences and terranes of Hoogar are some of the most important components of Pan-African cratonization. The evolution of the eastern and central terranes of Hoggar included the Pharusian terrane, which is floored in the east by Iskel basement. During the Pan-African cratonization, an arc-shaped Mesoproterozoic terrane cratonized around 840 Ma. This was part of the Pharusian terrane that is also floored by Late Paleoproterozoic rock sequences in the southeast.

The evolution of the eastern and central terranes of Hoggar as part of Pan-African cratonization included volcanosedimentary formations comprising of volcanic greywackes that were deposited in nearby troughs. The volcanic greywackes were deposited in troughs surrounding subduction-related andesitic volcanic ridges between 690 and 650 Ma (Caby, 2003, p.153). In addition, the evolution…