Geochemical and palaeoenvironmental characteristics of Missole I iron duricrusts of the Douala sub-basin (Western Cameroon)

详细信息    查看全文

• 作者：Gilbert Franç ; ois Ngon Ngon^a ; ^{gngonngon@yahoo.fr" class="auth_mail" title="E-mail the corresponding author} ; Jacques Etame^a ; Marie Joseph Ntamak-Nida^a ; Cé ; cile Olive Mbesse^a ; Joë ; l Simon Mbai^a ; É ; lie Constantin Bayiga^a ; Martine Gerard^b
• 关键词：Douala sub-basin ; Geochemistry ; Iron duricrust ; Palaeoenvironment ; Western Cameroon
• 刊名：Comptes Rendus Geoscience
• 出版年：2016
• 出版时间：February-March 2016
• 年：2016
• 卷：348
• 期：2
• 页码：127-137
• 全文大小：2231 K

文摘

Major and trace element composition of iron duricrusts including clayey material samples and biostratigraphy of the Missole I outcrop from the Paleocene–Eocene N’Kapa Formation in the Douala sub-basin of Cameroon were used to infer the palaeoenvironment and relative age of the iron duricrusts. Iron duricrusts and clayey materials are essentially kaolinitic and smectitic and are generally siliceous and ferruginous (iron duricrusts) or siliceous and aluminous (clayey materials). These materials have high Chemical Indices of Alteration (CIA = 86.6–99.33%). The negative Eu anomalies with high (La/Yb)_N shown by iron duricrusts and clayey sediments are essentially derived from silicic or felsic parent rocks when fractionated chondrite-normalized REE patterns also indicate felsic or silicic parent rocks. The Missole I iron duricrusts have a post-Thanetian age according to the relative age of claystones (Thanetian) and were formed after the deposition of sedimentary materials in an anoxic low-depth marine environment with eutrophication of surface water, and may have been exhumed and oxidized under arid climate.