Abstract
Chemical analyses were carried out on clastic sedimentary rocks in Kompina (N'kapa Formation of the NW, Douala Basin, West Africa) to disclosed the composition of their source rock, characterised their tectonic domains, decipher the intensity of the past weathering, sedimentary cycles and maturity using concentrations of major oxides, REES and trace elements. Provenance diagram constructed from ratios of La/Co, La/Sc, Th/Sc, Cr/Th and from binary diagrams of Zr vs TiO(2) and AL(2)O(3)vs TiO(2), disclosed a felsic rock composition as the source rock of the Kompina clastic rocks. The felsic source rock composition designated for the studied clastic materials is also supported by LREE enrichment over HREE and a negative europium anomaly on chondrite calculation and diagram. New discriminant functions diagrams to delineate between active and passive domains such as DF 1&2(Arc-Rift-Col)(M1), DF1&2(Arc-Rift-Col)(M2) combined with diagrams of DF(A-P)M, DF(A-P)MT label a passive tectonic setting characteristics for the source rock where there studied clastic materials were sorted. The weathering intensity and plagioclase lixiviation revealed by the CIA and PIA indexes advocate a weak to intense strength of chemical weathering and lixiviation of plagioclase felspars while the CIX and PIX with elimination of CaO in their formulars show extreme intensity of weathering and lixiviation of plagioclase felspars. Most of the samples show immature nature from their ICV values > 1 but with the introduction of ICV(new) in this work, where oxides of iron and calcite are considered as cement and eliminated from the formular show that all the studied samples have values < 1 indicating they are mature. Plotted diagrams of Th/Sc, and (Gd/Yb)(N) ratios, with relationship of Zr and (La/Yb)N shows that the studied clastic materials are mature, second cycle sediments, which have experience zircon mineral addition.