Geochemistry of Cretaceous Mudrocks and Sandstones from Douala Sub-Basin, Kumba Area, South West Cameroon: Constraints on Provenance, Source Rock Weathering, Paleo-Oxidation Conditions and Tectonic Environment

Abstract

Geochemical data of fifteen Cretaceous sediment samples from Kumba area in the Douala sub-basin are presented to determine the provenance, source rock weathering, tectonic setting and paleo-oxidation conditions of the depositional setting of these rocks. For this purpose, the whole-rocks were analyzed for their major and trace element, including rare earth elements (REEs), contents by ICP-AES and ICP-MS methods respectively. On the basis of their major element composition, the rocks have been classified mainly as Fe-shale, shale, arkose and Fe-sandstone. For the provenance, the plot of Zr vs. 1.03. This is also confirmed by the values of Ni/Co (less than 7), U/Th (less than 1.25) and Cu/Zn (mostly less than 1). Tectonic discrimination diagrams (e.g., SiO 2 -K 2 O/Na 2 O and Th-Sc-Zr/10) show that these rocks were deposited mainly in an active continental margin setting, and in various tectonic environments. This reflects probably the recycling effect experienced by the samples studied.

Paleoenvironmental significance and provenance of the Cretaceous calcareous deposits from the Djerem sub-basin (Adamawa, Cameroon) during the Gondwana evolution: sedimentary structures and geochemical constraints

“…For source lithotype, many plots have been proposed and widely used such as Th/Co versus La/Sc [Cullers, 2002, Ngueutchoua et al, 2017 and Zr versus TiO 2 [Hayashi et al, 1997. The location of the studied materials on these scattered plots shows that the geochemical signatures of the source lithotype correspond to felsic rocks (Figure 8(A)) and silicic rocks (Figure 8(B)).…”

“…Many ratios have been used to indicate chemical maturity of some deposits such as K 2 O/Na 2 O [Mongelli, 2004, Ngueutchoua et al, 2017. This ratio increases with weathering due to more liable nature of plagioclase relative to K-feldspar [Nesbitt and Young, 1982].…”

“…In addition, other parameters such as chemical index of alteration (CIA) and index of compositional variability (ICV) have been used to characterize the compositional maturity of sediments [e.g., Mongelli et al, 2006, Perri et al, 2011, Tao et al, 2013, Perri, 2014, Absar and Sreenivas, 2015, Ngueutchoua et al, 2017, Tawfik et al, 2017. ICV > 1 indicates immature sediments and ICV < 1 shows mature sediments.…”

Influence of biotic vs abiotic processes on the genesis of non‐marine carbonates along the Cameroon Volcanic Line (Cameroon) and palaeofluid provenance

“…The Palaeogene-Neogene and Lower Cretaceous sandstones (Figure 1C) are mostly sub-arkosic sandstones dominated by feldspars, quartz and micas (biotites and muscovites) with ferruginous and carbonate cements (Ngueutchoua et al, 2017). The Upper Cretaceous shales are mostly made up of quartz, feldspars and calcites.…”

“…The Upper Cretaceous shales are mostly made up of quartz, feldspars and calcites. The alluvium (Palaeogene to Neogene) is mostly quartz-rich sand with minor amounts of feldspars, muscovite and biotite (Ngueutchoua et al, 2017).…”