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

Amadou Diguim Kepnamou,Hauzenberger Christoph,Naïmou Seguem,Klötzli Urs,Ngounouno Ismaïla,Ganwa Alembert Alexandre

doi:10.12691/jgg-5-3-3

Amadou Diguim Kepnamou, Hauzenberger Christoph + Show 4 more

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https://doi.org/10.12691/jgg-5-3-3

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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 â¦) 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.

Highlights

The Central African Fold Belt (CAFB, Figure 1) is classicaly subdivided into three main lithostructural domains [16,18,32]
We present petrography, zircon feature and Th-U-Pb data of biotite-muscovite granite and associated amphibole-biotite granite
The amphibole-biotite granite is characterized by granular texture made up of amphibole, biotite, feldspar, quartz, sphene, apatite and secondary mineral

Summary

Introduction

The Central African Fold Belt (CAFB, Figure 1) is classicaly subdivided into three main lithostructural domains [16,18,32]. The AYD is characterized by the abundance of syn to late tectonic granitoidic rocks [1,9] and the regional transcurent shear zone among which the Tcholliré Banyo Shear Zone (TBSZ), the Central Cameroon Shear. Petrological, geochemical, tectonical and geochronological investigation have been carry out in granitoids of central Cameroon, part of the Adamawa Yade domain [4,17,19,30]. Despite these numerous works, many areas still unexplored and it is difficult in the present state of knowledge to decipher the number of successive generation of granitoids during the Pan-African orogeny in central Cameroon.

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