Granitoids of the Magba shear zone, West Cameroon, Central Africa: Evidences for emplacement under transpressive tectonic regime

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• 作者：Benjamin Ntieche ; M. Ram Mohan ; Moundi Amidou
• 刊名：Journal of the Geological Society of India
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：89
• 期：1
• 页码：33-46
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Geology; Hydrogeology;
• 出版者：Geological Society of India
• ISSN：0974-6889
• 卷排序：89

文摘

The Magba Shear Zone is made up of granites, migmatites, orthogneiss, metagabbro, mafic dyke and mylonites with coarse grained texture, porphyroblastic, granoblastic, cataclastic and mylonitic texture respectively. Structural features and kinematic indicators testify the syntectonic emplacement of Magba granitoids and also provide detailed information on the relative timing of deformation as follows: (1) D1 of tangential movement immediately followed by (2) the D2 phase which is heterogeneous simple shear in dextral transpressive context with a NW-SE direction (3) D3 tectonic phase is marked by sinistral transpressive tectonic and superposed folding with a NE-SW kinematic direction. Combined ductile NE-SW shear movements and NWSE compressional movements defined a transpressional tectonic regime during the D3 deformation (4) A brittle stage D4 is controlled by transcurrent tectonics and responsible for the emplacement of faults, and joints. The Magba granites would have intruded along sub-vertical mid-crustal feeder channels and were emplaced as a sheet or sheets along the shear zone during the early stage of the C3 shearing, followed by gabbro and mafic dyke at the late stage. Strike-slip dilatancy pumping under transpressive tectonic is suggested as a possible mechanism for the emplacement of the Magba granites.