Abstract
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.
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Basseka, C.A., Shandini, Y., and Tadjou, J.M. (2011) Sub-surface structural mapping using gravity data of the northern edge of the Congo Craton, South Cameroon: Geofizika, v.28(2), pp.229–245.
Bell, T.H. (1981) Foliation development—the contribution, geometry and significance of progressive, bulk, inhomogeneous shortening. Tectonophys., v.75, pp.263–296.
Blenkinsop, T.G. (1989) Deformation Microstructures and Mechanisms in Minerals and Rocks. Kluwer Academic Publishers
Blumenfeld, P. (1983) Le “tuilage des mégacristaux”, un critére d’écoulement rotationnel pour les fluidalités des roches magmatiques. Application au granite de Barbey-Séroux (Vosges, France). Bull. Soc. géol. Fr. 7 Ser. XXV, pp.309–318.
Blumenfeld, P. and Bouchez, J.-L. (1988) Shear criteria in granite and migmatite deformed in the magmatic and solid states. Jour. Struct. Geol., v.10, pp.361–372.
Brown, M. (1994) The generation, segregation, ascent and emplacement of granite magma: the migmatite-to-crustally-derived granite connection in thickened orogens. Earth Sci. Rev. v.36, pp.83–130.
Burg, J.P., Corsini, M., Diop, C., Maurin, J.C. (1993) Structure et cinématique du Sud de la chaîne des Mauritanides: un système de nappe tégumentaire varisque. C. R. Acad. Sci., v.317, pp.697–703.
Cobbold, P.R., Gapais, D., Rossello, E.A. (1991) Partitioning of transpressive motions within a sigmoidal fold belt: the Variscan Sierras Australes, Argentina. Jour. Struct. Geol., v.13, pp.743–758.
Dabo, M., Gueye, M., Ngom, P.M., Diagne, M. (2008) Orogen-parallel tectonic transport: transpression and strain partitioning in the Mauritanides of NE Senegal. In: Ennih, N & Liégeois, JP. (eds) The Boundaries of West African Craton. Geol. Soc. London, Spec. Publ., v.297, pp.483–497.
Den Tex, E. (1969) Origin of ultramafic rocks, their tectonic setting and history. Tectonophys., v.7, pp.457–488.
D’Lemos, R.S., Brown, M. & Strachan, R.A. (1992) Granite magma generation, ascent and emplacement within a transpressional orogen. Jour. Geol. Soc. London, v.149, pp.287–490.
Ferré, E., Gleizes, G., Caby, R. (2002) Obliques convergent tectonics and granite emplacement in the Trans-Saharian belt of Eastern Nigeria: a Synthesis. Precambrian Res., v.114, pp.199–219.
Feybesse, J.L., Johan, V., Triboulet, C., Guerrot, C., Mayaga-Mikolo, F., Bouchot, V., and Eko N’dong, J. (1998) The West Central African belt: A model of 2.5–2.0 Ga accretion and two-phase orogenic evolution: Precambrian Res., v.87, pp.161–216.
Ganno, S., Nzenti, J., Ngnotue, T., Kankeu, B., Kouankap, N. G. D. (2010) Polyphase deformation and evidence for transpressive tectonics in the Kimbi area, Northwestern Cameroon Pan-African fold belt. Jour. Geol. Min. Res., v.2(1), pp.1–015.
Goldstein, G.A. (1988) Factors affecting kinematic interpretation of asymmetric boudinage in shear zones. Jour. Struct. Geol., v.10, pp.707–715.
Ghosh, S.K. and Sengupta, S. (1987). Progressive evolution of structures in a ductile shear zone. Jour. Struct. Geol., v. 9, pp.277–288.
Hancock, S. L., and Rutland, W. R. (1984) Tectonics of the early Proterozoic geosuture: The Halls Creek Orogenic Sub-Province, Northern Australia. Jour. Geodynamics, v.1, pp.387–432.
Hanmer, S. (1986) Asymmetrical pull-aparts and foliation fish as kinematic indicadors. Jour. Struct. Geol., v.8, pp.111–122.
Ildefonse, B., Sokoutis, D. and Mancktelow, N.S. (1992a) Mechanical interactions between rigid particles in a deforming ductile matrix. Analogue experiments in simple shear flow. Jour. Struct. Geol., v.14, pp.1253–1266.
Ildefonse, B., Launeau, P., Bouchez, J.-L. and Fernandez, A. (1992b) Effect of mechanical interactions on the development of shape preferred orientations: a two-dimensional experimental approach. Jour. Struct. Geol., v.14, pp.73–83.
Imber, J., Holdsworth, R.E., Butler, C.A., Strachan, R.A. (2001) A reappraisal of the Sibson-Scholz fault zone model: the nature of frictional to viscous (“brittle-ductile”) transition along a long-lived crustal scale fault, Outer Hebrides Scotland. Tectonics, v.20, pp.601–624.
Jones, R.R. and Tanner, P.W.G. (1995) Strain partitioning in transpression zones. Jour. Struct. Geol., v.17, pp.793–802.
Kankeu, B., Greiling, R.O., Nzenti, J.P. (2009) Pan-African strike-slip tectonics in eastern Cameroon-Magnetic fabrics (AMS) and structure in the Lom basin and its gneissic basement (Bétare-Oya area). Precambrian Res., v.17(3-4), pp.258–272.
Lerouge, C., Cocherie, A., Toteu, S.F., Penaye, J., Milési, J.P., Tchameni, R., Nsifa, E.N., Mark Fanning, C., and Deloule, E. (2006) Shrimp U–Pb zircon age evidence for Paleoproterozoic sedimentation and 2.05 Ga syntectonic plutonismin the Nyong Group, South-Western Cameroon: Consequences for the Eburnean-Transamazonian belt of NE Brazil and Central Africa. Jour. African Earth Sci., v.44, pp.413–427.
Lister, G. S. & Snoke, A. W. (1984) S-C Mylonites. Jour. Struct. Geol., v.6, pp.617–638.
Miller, R. B. & Paterson, S. R. (1994) The transition from magmatic to hightemperature solid-state deformation: implications from the Mount Stuart batholith, Washington. Jour. Struct. Geol., v.16, pp.853–866.
Mohamed, G., Abdelsalam, Robert, J., Stern, P. C., Elfadil, M., Elfaki, B.E., Fathelrahman, M. and Ibrahim (1998) The Neoproterozoic Keraf Suture in NE Sudan: Sinistral Transpression along the Eastern Margin of West Gondwana. Jour. Geol., v.106, pp.133-147.
Moreau, C., Regnoult, J.M., Deruelle, B., Robineau, B. (1987) A new tectonic model for the Cameroon Line, Central Africa. Tectonophys. v.139, pp.317–334.
Mvondo, H., Owona, S., Mvondo, O.J., Essono, J. (2007) Tectonic evolution of the Yaoundé segment of the Neoproterozoic Central African Orogenic Belt in Southern Cameroon. Can. Jour. Earth Sci., v.44, pp.433–444.
Nédélec, A., Nsifa, E.N., and Martin, H. (1990) Major and trace element geochemistry of the Archaean Ntem plutonic complex (south Cameroon): Petrogenesis and crustal evolution: Precambrian Res., v.47, pp.35–50.
Ngako, V., Affaton, P., Nnange, J.M., Njanko, T. (2003) Pan-African tectonic evolution in central and southern Cameroon: transpression and transtention during sinsistral shear movements. Jour. African Earth Sci., v.36, pp.207–214.
Ngako, V., Affaton, P., Njonfang, E.(2008) Pan-African tectonics in northwestern Cameroon: Implication for the history of western Gondwana. Gondwana Res., v.14, pp.509–522.
Nguiessi, T.C., Nzenti, J.P., Nsifa, E.N., Tempier, P., Tchoua, F.M. (1997) Les granitoïdes calco-alcalins, syn-cisaillement de Bandja dans la Chaîne Panafricaine Nord-Equatoriale au Cameroun. C. R. Acad. Sci., v.325, pp.95–101.
Njonfang, E., Ngako, V., Kwekam, M., Affaton, P. (2006) Les orthogneiss calcoal-calins de Foumban-Bankim: témoins d’une zone interne de marge activepanafricaine en cisaillement. Comptes Rendus Géosciences, v.338, pp.606–616
Njonfang, E., Ngako, V., Moreau, C., Affaton, P., Diot, E. (2008) Restraining bends in high temperature shear zones: the “Central Cameroon Shear Zone”, Central Africa. Jour. African Earth Sci. v.52, pp.9–20.
Ntiéche, B. (2009) Etude pétrographique et géo-environnementale des granitoïdes de la zone de Magba Ouest Cameroun. DEA Univ.Yaoundé I. p.53.
Nzenti, J.P., Barbey, P., Macaudiere, J., Soba, D. (1988) Origin and evolution of the late Precambrian high-grade Yaoundé gneisses (Cameroon). Precambrian Res., v.38, pp.91–109.
Olavi, S., Ehlers, C., and Lindroos, A. (1996) Structural features and emplacement of the late Svecofennian Perniö granite sheet in southern Finland. Bull. Geol. Soc. Finland, no.68, Part 2, pp.5–17.
Passchier, C.W., Ten Brink, C.E., Bons, P.D., Sokoutis, D. (1993) Delta objects as a gauge for stress sensitivity of strain rate in mylonites. Earth Planet. Sci. Lett., v.120, pp.239–245.
Passchier, C.W. and Trouw, R.A.J. (1996) Microtectonics. Springer-Verlag, Berlin Heidelberg New York.
Passchier, C.W. and Trouw, R.A.J. (1998) Microtectonics. Springer, Berlin, pp.1–289.
Passchier, C.W. and Trouw, R.A.J. (2005) Micro-tectonics, 2nd Ed, Springer, Germany.
Paterson, S.R., Vernon, R.H. and Tobisch, O.T. (1989) A review of criteria for the identification of magmatic and tectonic foliations in granitoids. Jour. Struct. Geol. v.11, pp.349–363.
Penaye, J., Toteu, S.F., Tchameni, R., Van Schmus, W.R., Tchakounté, J., Ganwa, A., Minyem, D., and Nsifa, E.N. (2004) The 2.1 Ga West Central African Belt in Cameroon: Extension and evolution: Jour. African Earth Sci., v.39, pp.159–164.
Ragan, D.M. (1973) Structural geology: an introduction to geometrical techniques. 2nd edition, John Wiley and Sons, New York, pp.1–208.
Rutter, E.H. and Neumann, D.H.K. (1995) Experimental deformation of partially molten Westerly granite under fluid-absent conditions, with implications for the extraction of granitic magmas. Jour. Geophys. Res., v.100, pp.15697–15715.
Shang, C.K., Satir, M., Siebel, W., Nsifa, E.N., Taubald, H., Liégeois, J.P., and Tchoua, F.M. (2004) TTG magmatism in the Congo craton; a view from major and trace element geochemistry, Rb–Sr and Sm–Nd systematics: Case of the Sangmelima region, Ntem complex, southern Cameroon: Jour. African Earth Sci., v.40, pp.61–79.
Shang, C., Satir, M., Nsifa, E., Liégeois, J.P., Siebel, W. and Taubald, H. (2007) Archaean high-K granitoids produced by remelting of earlier TonaliteTrondhjemite–Granodiorite (TTG) in the Sangmelima region of the Ntem complex of the Congo craton, southern Cameroon: Internat. Jour. Earth Sci., v.96, pp.817–841.
Suh, C.E., Dada, S.S. (1997) Fault rocks and differential reactivity of minerals in the Kanawa Violaine uraniferous vein, NE Nigeria. Jour. Struct. Geol., v.19, pp.1037–1044.
Suh, C.E., Cabral, A.R., Shemang, E.M., Mbinkar, L., and Mboudou, G.G.M. (2008) Two contrasting iron deposits in the Precambrian mineral belt of Cameroon, West Africa: Exploration and Mining Geol., v.17, pp.197–207.
Tanko, N.E.L., Nzenti, J.P., Njanko, T., Kapajika, B., and Nédélec, A. (2005) New U–Pb zircon ages from Tonga (Cameroon): Coexisting Eburnean-Transamazonian (2.1 Ga) and Pan-African (0.6 Ga) imprints: Comptes Rendus Geosciences, v.337, pp.551–562.
Tchameni, R., Mezger, K., Nsifa, N.E., and Pouclet, A. (2001) Crustal origin of Early Proterozoic syenites in the Congo Craton (Ntem Complex), South Cameroon: Lithos, v.57, pp.23–42.
Tcheumenak, K.J., Njanko, T., Kwekam, M., Naba, S., Bella Nke, B.E., Yakeu Sandjo, A.F., Fozing, E.M., Njonfang, E. (2014) Kinematic evolution of the Fodjomekwet-Fotouni Shear Zone (West-Cameroon): Implications for emplacement of the Fomopea and Bandja plutons: Jour. African Earth Sci., v.99, pp.261–275.
Tikoff, B., De Saint Blanquatt, M. (1997) Transpressional shearing and strikeslip partitioning in the late Cretaceous Sierra Nevada magmatic arc, California. Tectonics, v.16, pp.442–459.
Toteu, S.F., Van Schmus, W.R., Penaye, J., and Nyobé, J.B.(1994) U-Pb and Sm-N edvidence for Eburnian and Pan-African high-grade metamorphism in cratonic rocks of southernCameroon: Precambrian Res., v.67, pp.321–347.
Toteu, S.F., Van Schmus, W.R., Penaye, J. and Michard, A. (2001) New U–Pb and Sm–Nd data from north-central Cameroon and its bearing on the pre-Pan African history of central Africa: Precambrian Res., v.108, pp.45–73.
Toteu, S.F., Penaye, J., and Djomani, Y.P. (2004) Geodynamic evolution of the Pan-African belt in central Africa with special reference to Cameroon: Canadian Jour. Earth Sci., v.41, p.73-85.
Toteu, S.F., Penaye, J., Deloule, E., Van Schmus, W.R., and Tchameni, R. (2006a) Diachronous evolution of volcanosedimentary basins north of the Congo craton: Insights from U–Pb ion microprobe dating of zircons from the Poli, Lom and Yaoundé Groups (Cameroon): Jour. African Earth Sci., v.44, pp.428–442.
Toteu, S.F., Van Schmus, W.R., and Penaye, J. (2006b) The Precambrian of CentralAfrica: Summary and perspectives: Jour. African Earth Sci., v.44, pp.vii–x.
Van Schmus, W.R., Oliveira, E.P., Da Silva Filho, A.F., Toteu, S.F., Penaye, J., and Guimaraes, I.P. (2008) Proterozoic links between the Borborema Province, NE Brazil, and the Central African Fold Belt: Geol. Soc. London, Spec. Publ., v.294(1), pp.69–99.
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Ntieche, B., Ram Mohan, M. & Amidou, M. Granitoids of the Magba shear zone, West Cameroon, Central Africa: Evidences for emplacement under transpressive tectonic regime. J Geol Soc India 89, 33–46 (2017). https://doi.org/10.1007/s12594-017-0556-4
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DOI: https://doi.org/10.1007/s12594-017-0556-4