Figure 9 - uploaded by Moujahed Al-Husseini
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Simplified geological map of the Shaghab Quadrangle (reproduced from the 1:1,000,000-scale Structural Sketch Map relating to the 1:250,000-scale map of the Shaghab Quadrangle, Grainger and Hanif, 1989). The Naghr ( " n " ) and Farra'ah ( " f " ) formations are equivalent to the Jibalah and Shammar groups, respectively.
Source publication
This paper starts with a bibliographic review of the lithostratigraphy and radiometric dating of the Ediacaran Thalbah Group in the northwestern Arabian Shield, Saudi Arabia. It seeks to establish the spatio-temporal position of the group in the ongoing compilation and correlation of Ediacaran-Cambrian sedimentary time-rock units in the Middle East...
Citations
... These dykes intersect Neoproterozoic Qaraqir alkali granite of the Midyan suite, close to the tectonic contact with the Atiyah monzogranite (Grainger and Hanif 1989). The age of the Qaraqir formation lies between 630 Ma and 609 Ma (Al-Husseini 2015). Sample AP-14 is from Wadi al Hayil, which corresponds to a dextral fault. ...
The Red Sea rifting nucleated within the Neoproterozoic Arabian-Nubian shield, which formed during the Pan-African orogeny over a time period of about 300 million years. The Red Sea rifting started about at 30 Ma and was assisted by much diffused magmatism that lasted until recent times. The majority of magmatic rocks consist of basalts that constitute volcanic plateaux (harrats), which represent one of the largest Cenozoic volcanic provinces in the world. Volcanic rocks are distributed all along the Arabian plate margin of the Red Sea, from Yemen to Jordan. Some of the oldest magmatic rocks are acidic in composition, especially along the southern part of the Arabian margin. In this chapter microstructure and geochemistry of acidic, intermediate, and basic dykes sampled along the Arabian margin are described. Acidic dykes consist of granitoids and porphyritic rhyolites. Intermediate and basic dykes consist of andesite and basanite/basalt, respectively. Granitoid dykes show equal-granular coarse-grained texture and mostly consist of euhedral crystals. Other than local displays of crystal-plastic deformation in quartz, these dykes have primary magmatic textures. Dykes consisting of rhyolites contain euhedral K-feldspar phenocrysts with frequent perthitic intergrowth of albite. The rock matrix consists of quartz, K-feldspar, and albite. Basanite/basaltic dykes consist of plagioclase, pyroxene, and amphibole phenocrysts. Plagioclase is also abundant in the groundmass where glass is also preserved. Andesite dykes are characterised by a pervasive alteration that in some instances prevents the identification of original phenocrysts. Where identifiable, phenocrysts consist of plagioclase, amphibole, and pyroxene. Locally, in the groundmass interstitial quartz shows crystal-plastic deformation. Fluidal magmatic structures are recorded locally in basanitic and basaltic dykes and only weakly in rhyolitic dykes. The fine-grained texture of the rock groundmass and vesicular structures indicate that dyke emplacement is quite shallow (hypabyssal conditions). However, the Al-content in amphibole phenocrysts of basanite/basalt dykes is consistent with phenocryst crystallisation depths of 15–20 km. The first U-Pb tests on granitoids reveal that they contain zircon grains from Cryogenian to Ediacaran (middle to late Neoproterozoic) age. Geochemical results indicate that basanite/basaltic dykes are compatible with a divergent environment such as the Red Sea rifting, whereas andesite dykes are compatible with a convergent setting. The rhyolitic dykes are interpreted as related to the Red Sea rifting as they show geochemical signatures compatible with divergent tectonics and are from a region where rhyolitic dykes were dated around 20 Ma.
Abstract: The Feinan Granite of the Wadi Feinan type area revealed late Cryogenian (Neoproterozoic) to early Terreneuvian
(Cambrian) magmatic ages with a maximum (94 %) of ages ranging from 550 Ma to 627 Ma (Ediacaran, Neoproterozoic).
The few youngest zircon grains, however, provided a Concordia Age of 535 ± 12 Ma, interpreted here as the intrusion
age of the Feinan Granite. This age spectrum contradicts hitherto assumptions of an absence of ages older than 600 Ma in
the Feinan Granite and re-establishes a former model of a unified igneous complex together with the Timna unit of southern
Israel of which the Feinan Granite is the eastern continuation (Timna-Feinan Igneous Complex). A Neoproterozoic age
(about 600 Ma) was previously indicated for the conglomeratic Saramuj Formation by previous studies, but the present work
provides additional detrital zircon ages that also indicate younger Neoproterozoic zircons (566–718 Ma). This indicates
deposition over an extended time period and, consequently, a shorter stratigraphical gap between this formation and the
overlying Cambrian strata.
Age data of detrital zircons from upper lower and lower middle Cambrian siliciclastic formations (Salib Formation, Burj
Formation, Umm Ishrin Formation) and from Middle to Upper Ordovician formations (Hiswah Formation, Dubaydib Formation,
Tubayliyat Formation) are presented and reveal similar detrital zircon ages. Three of these formations are geochronologically
investigated for the first time. There is a general predominance of Neoproterozoic ages (ranging from 552–
1000 Ma, locally with sporadic early Cambrian zircons from the Umm Ishrin Formation and Hiswah Formation) and a conspicuous
stratigraphic gap in the middle and lower Mesoproterozoic. The youngest of the investigated units (Tubayliyat
Formation) documents an obvious depletion in the number of Neoproterozoic zircons and an increase in older zircons which
we interpret as being eroded from a lower (earlier) stratigraphical level.
The sources of the Neoproterozoic to late Mesoproterozoic detrital zircons are represented by the proximate Arabian-
Nubian Shield, and some more distant areas. Sources of older zircons are proposed – probably after multiple resedimentation
– with greater distance, as for example the southern regions of the East African Orogen, in the Saharan Metacraton, or others
such as European peri-Gondwanan sources, East-Asia or Australia (East African-Arabian Zircon Province).
The data presented fill large gaps in the geochronological record of the Neoproterozoic–Ordovician succession of this
region and contribute to our knowledge of the geological development and architecture at the northern edge of the Arabian-
Nubian Shield.
Based on the present study and published data we introduce a revised lithostratigraphic classification for the Ordovician
to Silurian rocks in southern Jordan.
The Rub' Al-Khali basin lies below a Quaternary sand sea and the structural evolution from the late Precambrian to Neogene is known only from reflection seismic, gravity and magnetic data, and wells. Gravity and magnetic data show north-south and northwest-southeast trends, matching mapped Precambrian faults. The deepest structures imaged on reflection seismic data are undrilled Precambrian rifts filled with layered strata at depths up to 13 km. The distribution of Ediacaran ? Cambrian Ara/Hormuz mobile salt is restricted to an embayment in the eastern Rub' Al-Khali. The Precambrian rifts show local inversion and were peneplained at base Phanerozoic. A broad crustal-scale fold (Qatar Arch) developed in the Carboniferous and amplified in the late Triassic, separating sub-basins in the west and east Rub' Al-Khali. A phase of kilometer-scale folding occurred in the late Cretaceous, coeval with thrusting and ophiolite obduction in eastern Oman. These folds trend predominantly north-south, oblique to the northwesterly shortening direction, and occasionally have steep fault zones close to their axial surfaces. The trend and location of these folds closely matches the Precambrian lineaments identified in this study, demonstrating preferential reactivation of basement structures. Compression along the Zagros suture reactivated these folds in the Neogene, this time the result of highly oblique, north-northeast to south-southwest shortening. Cretaceous-Tertiary fold style is interpreted as transpression with minor strain partitioning. Permian, Jurassic and Eocene evaporite horizons played no role in the structural evolution of the basin but the Eocene evaporites caused widespread kilometer-scale dissolution collapse structures in the basin center.
