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The Pan-African Biotite-Muscovite Granite and Amphibole-Biotite Granite of Doua (Central Cameroon): Zircon Features, LA-MC-ICP-MS U-Pb Dating and Implication on Their Tectonic Setting

1Department of Earth Sciences, Faculty of Sciences, University of Ngaoundere, PoBox 454 Ngaoundere, Cameroon

2Labor für Geochronologie, Department für Lithosphärenforschung, Universität Wien, Althanstrasse 14, 1090 Wien, Austria

3Institut für Erdwissenschaften, Bereich Mineralogie & Petrologie, A-8010 Graz, Universitätsplaz 2/2.Stock, Austria

4Department of Geology, Faculty of Sciences and Techniques, University Adam Barka of Abeche, Abeche, Chad


Journal of Geosciences and Geomatics. 2017, Vol. 5 No. 3, 119-129
DOI: 10.12691/jgg-5-3-3
Copyright © 2017 Science and Education Publishing

Cite this paper:
Amadou Diguim Kepnamou, Ganwa Alembert Alexandre, Klötzli Urs, Hauzenberger Christoph, Ngounouno Ismaïla, Naïmou Seguem. The Pan-African Biotite-Muscovite Granite and Amphibole-Biotite Granite of Doua (Central Cameroon): Zircon Features, LA-MC-ICP-MS U-Pb Dating and Implication on Their Tectonic Setting. Journal of Geosciences and Geomatics. 2017; 5(3):119-129. doi: 10.12691/jgg-5-3-3.

Correspondence to: Ganwa  Alembert Alexandre, Department of Earth Sciences, Faculty of Sciences, University of Ngaoundere, PoBox 454 Ngaoundere, Cameroon. Email: ganwa1@yahoo.fr, alembert.alexandre.ganwa@univie.ac.at

Abstract

The Doua area belongs to the Adamawa-Yadé domain (AYD) of the Central African Fold Belt (CAFB) in Cameroon. It is crossed by the Central Cameroonian Shear Zone (CCSZ). The purpose of this research is to determine the tectonic setting of granites of the studied area, based on their petrography, zircons feature and their ages. Petrographicaly, the Doua area is made up of plutonic rocks hosted in an ortho or paraderivative metamorphic basement. Amphibole-biotite granite (ABG) and biotite-muscovite granite form hills and crop out on the hill side, as flagstones in the valley or river bed, and as huge blocks. Amphibole-biotite granite is granular in texture and made up of amphibole, biotite, feldspar, accessory minerals (Sphene, zircon, and apatite) and secondary minerals (sericite). Biotite-muscovite granite (BMG) is granular to granular porphyritic in texture, made up of biotite, muscovite, plagioclase, K-feldspar, quartz, accessory minerals (zircon, opaques minerals) and secondary minerals (chlorite, sericite). ABG show elongated zircon grains with well-developed magmatic oscillatory zonation. LA-ICP-MS U-Pb data from these zircons define a concordia age of 607 ± 3 Ma and considered as crystallization age of the granite. BMG shows zircon with various shape and various internal structures (oscillatory zonation, sector zonation, blurred oscillatory zonation …) which are divided into two sets. The first set regarded as xenocryst from Paleoproterozoic granitoids emplaced at 2126 ±36 Ma or from sediments which detritus comes from such granitoids. The second set of zircons shows effects of recent lead lost and a subconcordant U-Pb age of 646 ± 39 Ma . ABG was emplaced during the D3 deformational phase, date at 607 ± 3 Ma , while BMG was trigger because of syn-D1 activity of the CCSZ at 647 ±46 Ma in association with the collisional process.

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