Kwankam Florence Njinto, Ekoko Eric Bokanda, Adama Amaya, Salomon Bertrant Bisse, Njeck Rexon Junior Anyeku, Shannon Ngwakfu Nfor, Fidelis Esue Mokake, Hewett Ekumeli Matombo, Maureen Ntube Ngwane, Agyingi M Christopher
National Higher Polytechnic Institute, University of Bamenda, P.O.BOX 039, Bambili, Cameroon.
Department of Geology, University of Buea, Cameroon.
Heliyon. 2023 May 12;9(5):e16034. doi: 10.1016/j.heliyon.2023.e16034. eCollection 2023 May.
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 and ALO TiO, 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), DF1&2(Arc-Rift-Col) 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 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) 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.
对科姆皮纳（西非杜阿拉盆地西北部的恩卡帕组）的碎屑沉积岩进行了化学分析，以揭示其源岩的成分，确定其构造域特征，利用主要氧化物、稀土元素和微量元素的浓度来解读过去的风化强度、沉积旋回和成熟度。根据La/Co、La/Sc、Th/Sc、Cr/Th比值以及Zr与TiO和ALO TiO的二元图构建的物源区图解，揭示了长英质岩石成分是科姆皮纳碎屑岩的源岩。在球粒陨石计算和图解中，轻稀土元素相对于重稀土元素的富集以及负铕异常也支持了为所研究的碎屑物质指定的长英质源岩成分。用于区分活动和被动构造域的新判别函数图，如DF 1&2(弧-裂谷-大陆)、DF1&2(弧-裂谷-大陆)与DF(A-P)M、DF(A-P)MT图相结合，表明在所研究的碎屑物质分选的源岩具有被动构造背景特征。CIA和PIA指数揭示的风化强度和斜长石淋滤表明，化学风化和斜长石长石的淋滤强度从弱到强，而CIX和PIX在其公式中消除了CaO，表明斜长石长石的风化和淋滤强度极高。大多数样品的ICV值>1，显示出不成熟的性质，但在本研究中引入ICV，将铁和方解石的氧化物视为胶结物并从公式中去除后，表明所有研究样品的值<1，表明它们是成熟的。Th/Sc和(Gd/Yb)比值的图解，以及Zr与(La/Yb)N的关系表明，所研究的碎屑物质是成熟的、经历了锆石矿物添加的二次循环沉积物。
