Structural and Chemical Characteristic of Tourmaline, and Mineralogy of Associated Micas from Tourmaline Bearing Quartzite of Kombé II (Bafia Group, Central Africa Fold Belt); Implication on the Metamorphic Conditions

Author(s): Alembert Alexandre Ganwa, Urs Klötzli, Nubem J. Tchakounté, Eva Kloetzli-Chowanetz, Andreas Ertl, B. Djom
Abstract: Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had been recognized among accessory minerals. In the present study, attention is focus on the tourmaline bearing quartzite to the southeast of Kombé II. Structure refinement shows that tourmaline is a Fe-dravite with the formula X(Na0.95[]0.05)Y(Mg2.39Fe0.61)Z(Al5.10Mg0.90)(BO3)3T[Si6O18](OH)3[(O,OH)0.88F0.12]. The Fe-dravite is hosted in a Ca-poor quartzite, which is made up, in addition to quartz and tourmaline, of biotite and muscovite. The structure of the dravites shows a low vacancy at the X site, which militates for a crystallization of the tourmaline at a high temperature > 750℃. This is in agreement with previous work which shows that the metamorphic peak in the associated biotite gneiss reaches 825℃. The R1 value of 1.24% means that the crystal structure of the tourmalines is of high quality. The genetical link between gold mineralization and tourmaline should stimulate exploration interest in the study area.
Organisation(s): Department of Lithospheric Research, Department of Mineralogy and Crystallography
External organisation(s): Université de Ngaoundéré, University of Vienna, Université de Yaoundé I, Naturhistorisches Museum Wien (NHM)
Journal: International Journal of Geosciences
Volume: 13
Pages: 882-904
ISSN: 2156-8359
DOI: https://doi.org/10.4236/ijg.2022.1310044
Publication date: 2022
Peer reviewed: Yes
Austrian Fields of Science 2012: 105105 Geochemistry
Portal url: https://ucrisportal.univie.ac.at/en/publications/25c46aac-7088-4d96-a622-b72b33dcb2b5

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