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

Abstract

Combined 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.

Petrography and geochemistry of the Lower Miocene Moghra sandstones, Qattara Depression, north Western Desert, Egypt

“…The major‐element‐based discrimination diagrams of Bhatia () and Roser and Korsch () for clastic sediments have been traditionally used in various studies to identify the tectonic setting of unknown basins (e.g., Tawfik et al, , ). However, numerous studies have confirmed that the results obtained from such diagrams were inconsistent with the general geology of the investigated areas (Khan & Khan, ).…”

“…Recently, on the basis of the geochemical composition of Miocene to Recent sediments, Verma and Armstrong‐Altrin () proposed two discriminant‐function‐based major‐element diagrams for the tectonic discrimination of siliciclastic sediments from three main tectonic settings; island or continental arc, continental rift, and collision. In fact, these discrimination diagrams were successfully used in recent studies to discriminate the tectonic setting of a source region based on the geochemistry of clastic sediments (e.g., Armstrong‐Altrin & Machain‐Castillo, ; Guadagnin et al, ; Nagarajan et al, ; Tawfik et al, ; Zaid, , , ). On these high silica and low silica multidimensional diagrams, most studied samples plot within the collision field (Figure a,b).…”

Provenance and tectonic setting of the Quemoco sandstones in the North Qiangtang Basin, North Tibet: Evidence from geochemistry and detrital zircon geochronology

“…Three different tectonic settings can be classified on these diagrams including island arc, rift, and collision. These diagrams had been successfully applied to discriminate tectonic setting of clastic sediments in recent studies (Armstrong‐Altrin, Nagarajan, et al, ; Tawfik et al, ; Verma & Armstrong‐Altrin, ; Zaid, ). In the present study, the (SiO 2 ) adj contents of the Quemoco sandstones vary from 55.6% to 68.0% (Table ).…”

“…Numerous studies have certified that the chemical components of terrigenous sediments are closely connected with the tectonic setting of source area (Bhatia & Crook, ; Fatima & Khan, ; Moosavirad, Janardhana, Sethumadhav, Moghadam, & Shankara, ; Sun, Gui, & Chen, ), which have been extensively applied to analyse the provenance (Madhavaraju, ; Sun et al, ; Tawfik, Ghandour, Maejima, Armstrong‐Altrin, & Abdel‐Hameed, ; Zaid, ) and constrain the tectonic setting (Armstrong‐Altrin et al, ; Armstrong‐Altrin, Nagarajan, Balaram, & Natalhy‐Pineda, ; Moosavirad et al, ; Tao, Sun, Wang, Yang, & Jiang, ) of sedimentary basins in the past 20 years. To deduce the tectonic setting, previous studies are continuously using the traditional tectonic identification diagrams put forwarded by Bhatia () Fe 2 O 3 T + MgO vs. TiO 2 , Fe 2 O 3 T + MgO vs. Al 2 O 3 /SiO 2 , Fe 2 O 3 T + MgO vs. K 2 O/Na 2 O) and Bhatia and Crook () La–Th–Sc, Th–Co–Zr/10, Th–Sc–Zr/10).…”

“…In addition, a low success rate (0–30%) in trace elements for Bhatia and Crook () were also estimated by Verma and Armstrong‐Altrin (). Recently, two new discrimination plots according to major elements were put forwarded by Verma and Armstrong‐Altrin () to infer the tectonic setting of clastic sediments, which have been successfully used in provenance and tectonic setting studies (Armstrong‐Altrin, Nagarajan, et al, ; Moradi, Sarı, & Akkaya, ; Tawfik et al, ; Zaid, ). Furthermore, detrital zircon U–Pb age pattern has been applied extensively to analyse the provenance of terrigenous sediments, solving the evolution of sedimentary basin and revealing the tectonic affinity of different blocks in recent years due to the fact that they are not fractionated during the process of weathering, diagenesis and sedimentary recycling (Condie, Belousova, Griffin, & Sircombe, ; Fedo, Sircombe, & Rainbird, ; Lee, Choi, Lim, & Orihashi, ; Squire, Campbell, Allen, & Wilson, ; Wang et al, ; Yao, Li, Li, Su, & Yang, ).…”