Geochemistry of rutile from the Pan-African Yaoundé metamorphic group: Implications for provenance and conditions of formation

Louise Marie Ngo Bidjeck Bondje, Thierry Bineli Betsi, Lionel Nicaise Yannick Mama Nga, Rose Noel Ngo Belnoun, Alexia Corinne Molotouala, Chris McFarlane, Lucien Dieudonné Bitom

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Morphological and geochemical features of both in-rock and alluvial rutile within the Yaoundé Group of the Pan-African Central African Orogenic Belt (CAOB) were assessed, using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in order to assess its provenance and condition of formation. Rutile in gneiss and micaschist is fine grained (<0.2 × 0.8 mm) and occurs as euhedral to subhedral crystals, either within the matrix or included in garnet, biotite, kyanite and plagioclase. The alluvial rutile is coarse-grained and ranges in size from several millimetres to 5 x 2 cm. The alluvial rutile shapes (angular to sub-blunt) indicate local sedimentation or more or less important hydromechanical transport. Alluvial rutile is Al, Fe and Sb-rich compared to in-rock rutile. The Cr and Nb abundances and the ≤0.02 232Th/238U ratios suggest a common origin (metapelitic and metamafic) for both alluvial and in-rock rutile. The Zr-in-rutile thermometer indicates that coarse-grained alluvial rutile formed under blueschist and greenschist facies temperature conditions (514–561 °C), while the in-rock rutile was formed under amphibolite to granulite facies temperature conditions (614–726 °C). Alluvial rutile temperatures are symptomatic of pegmatites and high-grade hydrothermal bodies formed during late-stage tectono-metamorphic episodes of the Pan-African Orogeny. The temperature evolution depicted from in-rock rutiles indicates a regional metamorphism dominated by retrogression from granulite to amphibolite facies from central to coastal Cameroon.

Original languageEnglish
Article number103912
Number of pages10
JournalJournal of African Earth Sciences
Publication statusPublished - Oct 2020

All Science Journal Classification (ASJC) codes

  • Geology
  • Earth-Surface Processes


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