Scientific article
English

Magmatic arc construction within the Kedougou-Kenieba inlier, eastern Senegal: Petrographic, lithogeochemical and radiogenic isotope constraints

Published inJournal of African earth sciences, vol. 208, 105076
Publication date2023-12
Abstract

New petrographic, lithogeochemical and radiogenic isotope results from magmatic intrusions of the southeastern part of the Kedougou-Kenieba Inlier, Senegal document that these intrusions display evidence of a magmatic continuum of medium to high-K composition. A low-K intrusion group consists of andesitic, dioritic and tonalitic compostitions, with moderate (La/Yb)N and low (Dy/Yb)N ratios ranging, respectively, from 7.3 to 21.4 (with an average of 17.3) and 1.0 to 1.5. These intrusions have no obvious Eu anomalies (Eu/Eu* = 0.90–1.17), an average SiO2 concentration of 60.5 wt%, and are enriched in MgO, with an average concentration of 4.1 wt%. Their εNd values are high and range from +5.16 to +8.88, whereas they have low 87Sr/86Sri ratios of 0.701380–0.702552. This geochemical signature is characteristic of a depleted mantle source, which is supported by high Ni concentrations up to 211 ppm and high Mg# up to 85.35. The high-K leucogranite is characterized by high (La/Yb)N and higher (Dy/Yb)N ratios of, respectively, 10.6–48.3 (with an average of 30.5) and 2.0 to 2.4. It displays strong negative Eu anomalies (Eu/Eu* = 0.33–0.52), and has a higher average SiO2 concentration of 74 wt%, lower MgO concentration with an average of 0.21 wt%, as well as lower εNd values below 􀀀 1.95. This geochemical signature suggests a continental crustal source for the magmas. Between these two end-members, there is an intermediate group of medium to high-K intrusions including quartz diorite, tonalite, granodiorite and monzogranite. These rocks are characterized by a wide variation of geochemical compositions and are most likely the result of a mixing of different magmatic sources and extreme fractional crystallization processes. Furthermore, we demonstrate that these magmatic intrusions were formed in a volcanic arc. These new data are evidence for a diversity of the intrusions within the southeastern part of the Kedougou-Kenieba Inlier.

Keywords
  • Senegal
  • Magmatic intrusions
  • Subduction
  • Fractional crystallization
  • Kedougou-Kenieba inlier
Citation (ISO format)
FAYE, Cheikh Ibrahima et al. Magmatic arc construction within the Kedougou-Kenieba inlier, eastern Senegal: Petrographic, lithogeochemical and radiogenic isotope constraints. In: Journal of African earth sciences, 2023, vol. 208, p. 105076. doi: 10.1016/j.jafrearsci.2023.105076
Main files (1)
Article (Published version)
accessLevelRestricted
Identifiers
Journal ISSN1464-343X
80views
0downloads

Technical informations

Creation12/10/2023 09:19:39
First validation18/10/2023 11:38:20
Update18/10/2023 11:38:20
Status update18/10/2023 11:38:20
Last indexation01/11/2024 06:25:57
All rights reserved by Archive ouverte UNIGE and the University of GenevaunigeBlack