Late Cretaceous intraplate silicic volcanic rocks from the Lake Chad region: An extension of the Cameroon volcanic line?

J.g  Shellnutt, T. Y. Lee, P. K. Torng, C. C. Yang, Y. H. Lee

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Silicic volcanic rocks at Hadjer el Khamis, near Lake Chad, are considered to be an extension of the Cameroon volcanic line (CVL) but their petrogenetic association is uncertain. The silicic rocks are divided into peraluminous and peralkaline groups with both rock types chemically similar to within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma indicating the magmas erupted ∼10 million years before the next oldest CVL rocks (i.e., ∼66 Ma). The Sr isotopes (i.e., ISr = 0.7021–0.7037) show a relatively wide range but the Nd isotopes (i.e., 143Nd/144Ndi = 0.51268–0.51271) are uniform and indicate that the rocks were derived from a moderately depleted mantle source. Thermodynamic modeling shows that the silicic rocks likely formed by fractional crystallization of a mafic parental magma but that the peraluminous rocks were affected by low temperature alteration processes. The silicic rocks are more isotopically similar to Late Cretaceous basalts identified within the Late Cretaceous basins (i.e., 143Nd/144Ndi = 0.51245–0.51285) of Chad than the uncontaminated CVL rocks (i.e., 143Nd/144Ndi = 0.51270–0.51300). The age and isotopic compositions suggest the silicic volcanic rocks of the Lake Chad region are related to Late Cretaceous extensional volcanism in the Termit basin. It is unlikely that the silicic volcanic rocks are petrogenetically related to the CVL but it is possible that magmatism was structurally controlled by suture zones that formed during the opening of the Central Atlantic Ocean and/or the Pan-African Orogeny.

Original languageEnglish
Pages (from-to)2803-2824
Number of pages22
JournalGeochemistry, Geophysics, Geosystems
Volume17
Issue number7
DOIs
Publication statusPublished - 2016 Jul 1

Fingerprint

Chad
Cameroon
Volcanic rocks
lakes
Lakes
volcanology
volcanic rock
Rocks
rocks
Cretaceous
lake
rock
Isotopes
isotope
Pan African orogeny
isotopes
suture zone
Crystallization
fractional crystallization
basin

Keywords

  • Cameroon volcanic line
  • Chad
  • Late Cretaceous
  • continental rifting
  • geochronology
  • silicic volcanism

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

Late Cretaceous intraplate silicic volcanic rocks from the Lake Chad region : An extension of the Cameroon volcanic line? /  Shellnutt, J.g; Lee, T. Y.; Torng, P. K.; Yang, C. C.; Lee, Y. H.

In: Geochemistry, Geophysics, Geosystems, Vol. 17, No. 7, 01.07.2016, p. 2803-2824.

Research output: Contribution to journalArticle

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