Geochemistry of Precambrian sedimentary rocks used to solve stratigraphical problems: An example from the Neoproterozoic Volta basin,Ghana |
| |
| Authors: | Feiko Kalsbeek Robert Frei |
| |
| Affiliation: | 1. Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark;2. Institute of Geography and Geology, Geology Section, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark;1. Facultad de Ciencias Naturales, Universidad Nacional de Tucumán, Miguel Lillo 205, 4000, Tucumán, Argentina;2. Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina;3. Institute of Earth and Environmental Science, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476, Potsdam-Golm, Germany;1. Department of Earth Science, University of Ghana, Legon, Accra, Ghana;2. Council for Scientific and Industrial Research -Water Research Institute - (CSIR-WRI), Accra, Ghana;1. Federal University Lokoja, Lokoja, Nigeria;2. University of Ilorin, Ilorin, Nigeria;1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China;2. School of Earth Science, East China University of Technology, Nanchang 330013, China;3. State Key Laboratory Breeding Base of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China;1. INSUGEO (CONICET), Facultad de Ciencias Naturales, Universidad Nacional de Tucumán, Miguel Lillo 205, 4000, San Miguel, Tucumán, Argentina;2. Institute of Earth and Environmental Science of the University of Potsdam, Germany |
| |
| Abstract: | The Neoproterozoic Volta basin of Ghana (～115,000 km2; depth up to 5–7 km) consists of flat-lying sedimentary rocks, mainly sandstones that unconformably overlie the crystalline basement of the West-African craton. The stratigraphical column has been subdivided into three main units, in upward succession the Bombouaka, Oti and Obosum Groups, but poor exposure has resulted in major disagreements on stratigraphical correlations and on the areal extents of these units. Geochemical data (major and trace element concentrations as well as Rb–Sr, Pb and Sm–Nd isotope data) on siltstones and mudstones, intercalated with the sandstones from the different units, were used in an attempt to solve some of these problems. Siltstones and mudstones from the Bombouaka Group can be unequivocally distinguished from similar rocks from the Oti and Obosum Groups by higher K2O and Rb, larger Eu anamalies, higher 87Sr/86Sr, and more negative ?Nd values. Geochemical distinction between samples from the Oti and Obosum Groups is ambiguous because published geological maps differ with respect to the relative extents of the Oti and Obosum Groups. Rb–Sr isotope data, combined with high degrees of correlation between the concentrations of K and Rb, and Ca and Sr, indicate that mobility of these elements did not significantly change their concentrations during surface weathering. The clear geochemical distinction between mudstones and siltstones from the Bombouaka Group and similar rocks from the Oti and Obosum Groups is used to solve one of the outstanding controversies regarding the stratigraphy of the Volta basin. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
