Late Neoproterozoic volcanics and associated granitoids at Wadi Ranga, south Eastern Desert, Egypt: A transition from subduction related to intra-arc magmatism

Gharib, Moustafa E.; Ahmed, Ahmed H.

doi:10.1016/j.lithos.2012.09.004

Cited by 23 publications

(3 citation statements)

References 97 publications

(120 reference statements)

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“…They are dark greenish-gray and suffer from low-grade metamorphism. On the other hand, the felsic to intermediate metavolcanics are light green to buff colors and consist of slightly metamorphosed porphyritic rhyolites and dacites with subordinate dacitic andesites [45,46]. The investigated metavolcanics are associated with metapyroclastics and lapilli metatuffs, mostly of felsic composition (Figure 1b).…”

Section: Geologic Settingmentioning

confidence: 99%

Mineralogy and Geochemistry of Jasperoid Veins in Neoproterozoic Metavolcanics: Evidence of Silicification, Pyritization and Hematization

Khedr,

Sayed,

Ali

et al. 2024

Minerals

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The Wadi Ranga sulfidic jasperoids in the Southern Eastern Desert (SED) of Egypt are hosted within the Neoproterozoic Shadli metavolcanics as an important juvenile crustal section of the Arabian Nubian Shield (ANS). This study deals with remote sensing and geochemical data to understand the mechanism and source of pyritization, silicification, and hematization in the host metavolcanics and to shed light on the genesis of their jasperoids. The host rocks are mainly dacitic to rhyolitic metatuffs, which are proximal to volcanic vents. They show peraluminous calc-alkaline affinity. These felsic metatuffs also exhibit a nearly flat REE pattern with slight LREE enrichment (La/Yb = 1.19–1.25) that has a nearly negative Eu anomaly (Eu/Eu* = 0.708–0.776), while their spider patterns display enrichment in Ba, K, and Pb and depletion in Nb, Ta, P, and Ti, reflecting the role of slab-derived fluid metasomatism during their formation in the island arc setting. The ratios of La/Yb (1.19–1.25) and La/Gd (1.0–1.17) of the studied felsic metatuffs are similar to those of the primitive mantle, suggesting their generation from fractionated melts that were derived from a depleted mantle source. Their Nb and Ti negative anomalies, along with the positive anomalies at Pb, K, Rb, and Ba, are attributed to the influence of fluids/melt derived from the subducted slab. The Wadi Ranga jasperoids are mainly composed of SiO2 (89.73–90.35 wt.%) and show wide ranges of Fe2O3t (2.73–6.63 wt.%) attributed to the significant amount of pyrite (up to 10 vol.%), hematite, goethite, and magnetite. They are also rich in some base metals (Cu + Pb + Zn = 58.32–240.68 ppm), leading to sulfidic jasperoids. Pyrite crystals with a minor concentration of Ag (up to 0.32 wt.%) are partially to completely converted to secondary hematite and goethite, giving the red ochre and forming hematization. Euhedral cubic pyrite is of magmatic origin and was formed in the early stages and accumulated in jasperoid by epigenetic Si-rich magmatic-derived hydrothermal fluids; pyritization is considered a magmatic–hydrothermal stage, followed by silicification and then hematization as post-magmatic stages. The euhedral apatite crystals in jasperoid are used to estimate the saturation temperature of their crystallization from the melt at about 850 °C. The chondrite (C1)-normalized REE pattern of the jasperoids shows slightly U–shaped patterns with a slightly negative Eu anomaly (Eu/Eu* = 0.43–0.98) due to slab-derived fluid metasomatism during their origin; these jasperoids are also rich in LILEs (e.g., K, Pb, and Sr) and depleted in HFSEs (e.g., Nb and Ta), reflecting their hydrothermal origin in the island arc tectonic setting. The source of silica in the studied jasperoids is likely derived from the felsic dyke and a nearby volcanic vent, where the resultant Si-rich fluids may circulate along the NW–SE, NE–SW, and E–W major faults and shear zones in the surrounding metavolcanics to leach Fe, S, and Si to form hydrothermal jasperoid lenses and veins.

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Section: Geologic Settingmentioning

confidence: 99%

Mineralogy and Geochemistry of Jasperoid Veins in Neoproterozoic Metavolcanics: Evidence of Silicification, Pyritization and Hematization

Khedr,

Sayed,

Ali

et al. 2024

Minerals

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“…They are composed of a series of volcanic rocks ranging from basalts to andesites and rhyolites, formed towards the end of the Precambrian era in the Egyptian basement complex, where the best type of locality is recognized as the Gabal Dokhan region in the northern part of the Eastern Desert. Dokhan volcanics have been studied by several authors [11][12][13][14][15][16][17][18][19][20][21][22].…”

Section: Geological Settingmentioning

confidence: 99%

The Geology, Petrography, and Geochemistry of Egyptian Dokhan Volcanics: A Potential Source for Construction Aggregate

El-Desoky

El-Hafez

Kettab³

et al. 2023

Minerals

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The present paper focuses on the geology, petrography, and geochemistry of the well-known Dokhan volcanics encountered in the northern part of the Eastern Desert of Egypt. The basalts, andesites, rhyolites, and agglomerates exposed at the Makhar Seal (flood plain) as well as Wadi Abu Zoghot, Wadi El-Ghafiryia, Wadi Al-Radah Luman, Wadi Al-Ushsh, Wadi Umm Sidrah, and Gabal Ghuwayrib are herein examined as sources of coarse aggregate in concrete mixes. A representative total of 28 samples—collected from different Dokhan volcanics—was studied in terms of field geology, petrography, and geochemistry wherein a variety of experiments related to construction material validation apply. The petrographic examination revealed that the studied Dokhan volcanics consist of basic, intermediate, and acidic volcanic igneous rocks. These rocks are represented through basalts, andesites, imperial porphyry, dacites, rhyodacites, rhyolites, and their pyroclastics. Furthermore, the applied geochemical analysis indicated that the studied Dokhan volcanics are alkaline to sub-alkaline, calc-alkaline and classified as basalts, basaltic andesites, andesites, trachyandesites, trachydacites, trachytes, and rhyolites, indicating an initial potential as aggregate for concrete mixes. Finally, the results obtained from incorporating Dokhan volcanics as aggregates in concrete mixes demonstrated a significant improvement in regard to the properties of the comprising concrete mixes. Herein, a higher compressive strength was witnessed after 28 days for Dokhan volcanic concrete, when compared to concrete comprising dolomite aggregate, amounting to an average increase that exceeded 36%.

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“…Compiled data of whole-rock major, trace and REE of representative granitic samples from different occurrences are presented [24,[41][42][43][44]. The OG are metaluminous to slightly peraluminous, and have calc-alkaline affinity, whereas most of YG have a peraluminous character and slightly metaluminous and peralkaline [24,45].…”

Section: Geochemical Characteristicsmentioning

confidence: 99%

An Overview on the Classification and Tectonic Setting of Neoproterozoic Granites of the Nubian Shield, Eastern Desert, Egypt

Bahariya¹

2021

Geochemistry

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Granites constitute the main rock components of the Earth’s continental crust, which suggested to be formed in variable geodynamics environments. The different types of granitic rocks, their compositional characteristics, tectonic settings and magma sources are outlined. Mineralogical classification of granites includes four rock types: tonalites, granodiorites, granite (monzogranite and syenogranites) and alkali-feldspar granites. Alphabetical classification subdivided granites into: I-type, S-type, A-type and M-type granites. Moreover, formation of granitic magmas requires distinctive geodynamic settings such as: volcanic arc granite (Cordilleran); collision-related granites (leucogranites); intra-plate and ocean ridge granites. The Eastern Desert of Egypt (ED) forms the northern part of Nubian Shield. Both older and younger granites are widely exposed in the ED. Old granites (OG) comprise tonalites and granodiorites of syn- to late-orogenic granitoid assemblages. They are calcalkaline, I-type, metaluminous and display island arc tectonic setting. Younger granites (YG) on the other hand, include granites, alkali-feldspar granites and minor granodiorites. They are of I- and A-type granites and of post-orogenic to anorogenic tectonic settings. The majority of the YG are alkaline, A-type granite and of within-plate tectonic setting (WPG). The A-type granites are subdivided into: A2-type postorogenic granites and A1-type anorogenic granites. Granite magma genesis involves: (a) fractional crystallization of mafic mantle-derived magmas; (b) anatexis or assimilation of old, upper crustal rocks (c) re - melting of juvenile mafic mantle – derived rocks underplating the continental crust. Generally, older I-type granitoids were interpreted to result from melting of mafic crust and dated at approximately 760–650 Ma, whereas younger granites suggested to be formed as a result of partial melting of a juvenile Neoproterozoic mantle source. Moreover, they formed from anatectic melts of various crustal sources that emplaced between 600 and 475 Ma.

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Late Neoproterozoic volcanics and associated granitoids at Wadi Ranga, south Eastern Desert, Egypt: A transition from subduction related to intra-arc magmatism

Cited by 23 publications

References 97 publications

Mineralogy and Geochemistry of Jasperoid Veins in Neoproterozoic Metavolcanics: Evidence of Silicification, Pyritization and Hematization

Mineralogy and Geochemistry of Jasperoid Veins in Neoproterozoic Metavolcanics: Evidence of Silicification, Pyritization and Hematization

The Geology, Petrography, and Geochemistry of Egyptian Dokhan Volcanics: A Potential Source for Construction Aggregate

An Overview on the Classification and Tectonic Setting of Neoproterozoic Granites of the Nubian Shield, Eastern Desert, Egypt

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