Provenance, tectonic setting, and source area palaeoweathering of the Lower Cretaceous Nubian sandstones at Gebel Duwi, Eastern Desert, Egypt: inferences from mineralogy and whole-rock geochemistry

Redbeds with a large thickness in the lower Cretaceous record abundant geologic information in the Minle Basin. We have conducted the paleoweathering conditions, provenance, and tectonic settings based on mineralogy and geochemistry. Our results indicate that mudstone samples are characterized by abundant illite with negligible amounts of K-feldspars and analcime. The lower part of the lower Cretaceous is rich in quartz, whereas the upper part is dominated by dolomite and analcime. We suggest that this is caused by the decreasing input of the clastic influx during the middle-late early Cretaceous. High index of compositional variation values (average 1.33) indicate first-cycle sediment supply, suggesting an overall compositional immaturity and short-distance transportation. These characteristics are consistent with an active regional extension tectonic setting. The [Formula: see text] system ([Formula: see text];[Formula: see text];[Formula: see text]) and Th/U versus Th consistently reveal that the lower Cretaceous experienced a positive gradient in chemical weathering from young to old formations. Although the patterns of trace elements in three formations of the lower Cretaceous are different, those of the rare earth elements (REEs) tend to be consistent. The significant enrichment of light REEs, heavy REEs fractionation, and distinctive negative Eu anomalies suggest derivation from an old, upper continental crust composed of predominantly felsic sediments. This interpretation is supported by several discrimination diagrams such as titanium dioxide-nickel ([Formula: see text]), which shows the characteristics of immature recycled sediments. A few sensitive elements, ratios, and normalized REE patterns indicate a provenance of an active continental margin and a continental island arc (CIA). The La-Th-Sc, Th-Co-Zr/10, and Th-Sc-Zr/10 discrimination plots further confirm the CIA signature. Thus, we conclude that the early Cretaceous redbeds in the Minle Basin, Hexi Corridor, were deposited in a dustpan-shaped half-graben basin in a CIA setting when northwest China was influenced by intense regional extension.

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Provenance Studies of Sandstone Facies Exposed Near Igbile Southwestern Nigeria: Petrographic and Geochemical Approach

Journal of Geography and Geology ◽

10.5539/jgg.v6n2p47 ◽

2014 ◽

Vol 6 (2) ◽

pp. 47 ◽

Cited By ~ 4

Author(s):

Ikhane P. R. ◽

Akintola A. I. ◽

Bankole S. I. ◽

Oyinboade Y. T.

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Inductively Coupled Plasma ◽

Tectonic Setting ◽

Source Area ◽

Rock Fragment ◽

Petrographic Analysis ◽

Humid Climate ◽

Southwestern Nigeria ◽

Plagioclase Feldspar

The petrography, as well as the major, trace and rare earth element compositions of ten (10) sandstone samples of Maastrichtian Afowo Formation exposed near Igbile, Southwestern Nigeria, have been investigated to determine their provenance, source area weathering conditions, paleoclimate and tectonic setting using petrographic analysis and Inductively Coupled Plasma - Mass Spectrometry (ICP-MS). Results of the petrographic analysis revealed that quartz is the most dominant detrital mineral with (86%) followed by weathered plagioclase feldspar (5.10%) and rock fragments (10.9%). The quartz grain is sub-angular to sub-rounded in shape and the sandstones were classified as quartz arenites, sublitharenites and subarkoses based on framework composition of quartz, feldspar and rock fragment plots. This suggests a recycled orogen source for the sandstones and deposition in a humid climate, evidenced by the weathered feldspars. Eleven (11) major, seventeen (17) trace and fourteen (14) rare earth elements were obtained from the geochemical analysis. The major elements values range in concentration from 0.01%–81.39% with SiO2 being the dominant oxide followed by Al2O3 and Fe2O3 constituting over 95% of the major oxides; K2O, TiO2, Na2O, CaO, MgO and P2O5 made up the remaining 5%. The average ratio of SiO2/Al2O3 valued 4.31 for the sandstone is appreciably high indicating that it has been heavily weathered. The trace elements range in concentration from 0.2 ppm–1651.2 ppm with Zr being the most dominant element an indication of orogenic recycling. The rare earth elements range in concentration from 0.01 ppm–163.7 ppm with Ce having the highest concentration, depicting that the sandstones were deposited in an oxidizing environment. Also, the trace element relationship illustrated from the spider plot shows chemical coherence and uniformity of the sandstones. The chondrite normalized rare earth elements (REE) plot shows enrichment in the Light REE over the heavy REE for the sediment with strong negative Eu anomaly values between (0.57–0.69) suggesting a felsic provenance derived from upper continental crust for the sandstones.

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Petrography and geochemistry of the siliciclastic Araba Formation (Cambrian), east Sinai, Egypt: implications for provenance, tectonic setting and source weathering

Geological Magazine ◽

10.1017/s0016756815000771 ◽

2015 ◽

Vol 154 (1) ◽

pp. 1-23 ◽

Cited By ~ 34

Author(s):

HOSSAM A. TAWFIK ◽

IBRAHIM M. GHANDOUR ◽

WATARU MAEJIMA ◽

JOHN S. ARMSTRONG-ALTRIN ◽

ABDEL-MONEM T. ABDEL-HAMEED

Keyword(s):

Tectonic Setting ◽

Source Area ◽

Xrd Analysis ◽

Climatic Conditions ◽

Source Rocks ◽

Northern Margin ◽

Rock Fragments ◽

Geochemical Parameters ◽

Clastic Sediments ◽

Chemical Index

AbstractCombined petrographic and geochemical methods are utilized to investigate the provenance, tectonic setting, palaeo-weathering and climatic conditions of the Cambrian Araba clastic sediments of NE Egypt. The ~ 60 m thick Araba Formation consists predominantly of sandstone and mudstone interbedded with conglomerate. Petrographically the Araba sandstones are mostly sub-mature and classified as subarkoses with an average framework composition of Q80F14L6. The framework components are dominated by monocrystalline quartz with subordinate K-feldspar, together with volcanic and granitic rock fragments. XRD analysis demonstrated that clay minerals comprise mixed-layer illite/smectite (I/S), illite and smectite, with minor kaolinite. Diagenetic features of the sandstone include mechanical infiltration of clay, mechanical and chemical compaction, cementation, dissolution and replacement of feldspars by carbonate cements and clays. The modal composition and geochemical parameters (e.g. Cr/V, Y/Ni, Th/Co and Cr/Th ratios) of the sandstones and mudstones indicate that they were derived from felsic source rocks, probably from the crystalline basement of the northern fringe of the Arabian–Nubian Shield. The study reveals a collisional tectonic setting for the sediments of the Araba Formation. Palaeo-weathering indices such as the chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of the clastic sediments suggest that the source area was moderately chemically weathered. On the northern margin of Gondwana, early Palaeozoic weathering occurred under fluctuating climatic conditions.

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Geochemistry and Tectonic Setting of Neoproterozoic Rocks from the Arabian-Nubian Shield: Emphasis on the Eastern Desert of Egypt

Applied Geochemistry with Case Studies on Geological Formations, Exploration Techniques and Environmental Issues ◽

10.5772/intechopen.82519 ◽

2020 ◽

Cited By ~ 1

Author(s):

Gaafar A. El Bahariya

Keyword(s):

Tectonic Setting ◽

Eastern Desert ◽

Nubian Shield ◽

Arabian Nubian Shield

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Geochemistry of the Um Had Plutonites, Central Eastern Desert, Egypt: Implications for Magma Evolution, and Tectonic Setting

Journal of Geography and Geology ◽

10.5539/jgg.v6n2p36 ◽

2014 ◽

Vol 6 (2) ◽

pp. 36 ◽

Cited By ~ 1

Author(s):

Nedal Qaoud

Keyword(s):

Tectonic Setting ◽

Active Continental Margin ◽

Eastern Desert ◽

Island Arc ◽

Water Vapour Pressure ◽

Calc Alkaline ◽

Magma Evolution ◽

Basement Complex ◽

Central Eastern Desert ◽

Pan African

Geochemistry of gabbroid and granitoid plutonites from the Um Had area indicates island arc subalkaline basic magma with tholeiitic affinity and calc-alkaline, metaluminous and slightly peraluminous magma, respectively. Although different in age both plutonite types were emplaced under compressional regime, where subduction-related environment was dominant. They were formed under relatively low to moderate water-vapour pressure (1–5 k-bars) at moderate depths (20–30 km). Biotite granites were formed at a relatively high temperature range (800–840 °C), while biotite-muscovite granites were formed under relatively moderate temperature conditions (760–800 °C). These two units may represent evolution from island arc to active continental margin. It is suggested that island arc gabbros might have sourced the late subduction-related calc-alkaline granitoids during the waning stages of the pan-African orogeny. The I-type nature of the investigated plutonites in the study area and elsewhere suggests the juvenile character of the basement complex of the Eastern Desert of Egypt.

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Age and tectonic setting of granitoid gneisses in the Eastern Desert of Egypt and south-west Sinai

Geologische Rundschau ◽

10.1007/bf01083223 ◽

1994 ◽

Vol 83 (3) ◽

pp. 502-513 ◽

Cited By ~ 124

Author(s):

A. Kr�ner ◽

J. Kr�ger ◽

A. A. A. Rashwan

Keyword(s):

Tectonic Setting ◽

Eastern Desert ◽

South West ◽

Granitoid Gneisses

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