Monatélé Region As in the Bafia and Yaounde Groups Within the Central

Sciences, TechnologiesSciences, Technologies et Développement, & Développement, Volume 15, ISSN pp1-15, 1029 Septembre- 2225 2014 http://www.univ-douala.com/sdt/

Evidence of the ~NE-SW extension in the Sa’a - Monatélé Region as in the Bafia and Yaounde groups within the Central African Fold belt (Cameroon): Implication for the Southern Cameroon Neoproterozoic extension Simon Pierre Mbola Ndzana 1&2 , Joseph Mvondo Ondoa 2* , Sébastien Owona 3, Jean Paul Sep Nlongang 1, Jean Bosco Olinga 1, Paul Bilong 2 1Institute for Geological and Mining Research, Yaoundé, P.O. Box: 4110 Nlongkak, Yaoundé, Cameroon, 2University of Yaoundé I, Faculty of Science, Department of Earth Sciences, P.O. Box: 812 Yaoundé Cameroon, 3University of Douala, Faculty of Science, Department of earth Sciences. P.O. Box. 24157, Cameroon.

Received : April 2013 Révision received: August 2013 Accepted: August 2013 Available online: September 2014

Abstract

The Sa’a -Monatélé Region within the Neoproterozoic North Equatorial Fold Belt located between the Bafia and Yaounde groups, highlights a polyphase D 1- D4 Pan-African deformation that emplaced the Yaounde tectonic nappe transported top-to the SSW onto the Congo Craton and responsible for its actual geometry. D1 is a compression tectonic phase dominated by the simple shear type, represented by S 0/1 foliation and F 1 folds. D 2 is a general flattening under a pure shear regime associated to the exhumation of D 1 nappe due to the NE-SW extension; responsible for L2 lineations, B 2 boudins, F 2 folds, S 0/1/2 and S 2 foliations in metapelites and metagranitoids, respectively and C 2 shear planes. D 3 mainly an ~E-W shortening and a ~NE-SW extension, emplaced F 3 meso- and large-scale folds that form tectonic units of the Yaounde nappe. D 4 was an N-S to NE-SW shortening, perpendicular to the D 3 once and represented by F4 large-scale folds. C 3 shear zones as the NE-SW Central Cameroon shear zone was emplaced under the same r egime. The Sa’a -Monatélé Region may correspond mostly accordingly to a thrusting zone than a real tectonic suture between the Bafia and Yaounde groups. In comparison, D 1-D4 stages show similar geometry and kinematics in Bafia and Yaounde groups. Both groups are composed of similar rock types made of low- to high grade metapelites, amphibolites and metagranitoids with comparable volcano-sedimentary origin for metapelites and amphibolites; Archean to Proterozoic (Nd model ages 3500-2100 Ma) in metapelites, crustal rocks with minor mantle contributions origin for metagranitoids; the Neoproterozoic as the same maximum deposit age fixed at ~1600 Ma (U/Pb-, Pb/Pb-detrital zircons) as well as a comparable syntectonic granitoids emplaced between ~625 – 600 Ma (U/Pb-, Pb/Pb- zircons); an analogous Pan-African orogeny (650-542 Ma) with the retrograde phase from the granulite to amphibolite facies that ranges 616 – 540 Ma (Sm/Nd-garnet, EMP-monazite, Rb/Sr- whole rock - biotite ± muscovite). The admitted Bafia and Yaounde groups that outline the similar litho-chemistry nature and origin, a comparable Pan-African thermotectonic evolution can therefore be considered as a single and a same litho-chrono-thermo-structural unit: the Yaounde Group.

ISSN 1029 –2225©2014 Sciences, Technologies et Développement os Key words : Pan-African tectonics, Sa’a -Monatélé Region, Yaoundé Group, North Equatorial Pan-African Fold Belt, Cameroon. Résumé La région de Sa’a -Monatélé située au cœur de la chaine néoprotérozoïque nord équatoriale située entre les groupes de Bafia et de Yaoundé, met en relief une déformation panafricaine polyphasée D 1-D4, responsable de la mise en place la nappe de Yaoundé transportée vers le SSW sur le Congo Craton et sa géométrie actuelle. D 1 est une phase compressive dominée par un cisaillement simple, représentée par la foliation S 1 et les plis P 1. D 2 est un aplatissement général en régime de cisaillement pure associée à une extension NE-SW provoquant l’exhumation de la nappe mise en place au cours de D 1 ; responsable des linéations L 2, des boudins B 2, des plis P2, les foliations S 0/1/2 et S 2 respectivement dans les metapelites et les métaplutonites et des plan de cisaillement C2. D 3 dominée par un raccourcissement ~E-W et une extension ~NE-SW, a mis en place des plis P 3 méso- et cartographiques formant les unités tectoniques de la nappe de Yaoundé. D 4 un raccourcissement N-S à NE-SW perpendiculaire à celui de D 3, représentée par des plis P 4 cartographiques. Les cisaillements C 3 à l’instar du Cisaillement Centre Camerounais ont été mis en place sous le même régime. La région de Sa’a -Monatélé correspondrait donc beaucoup plus à une zone de chevauchement qu’à une zone de suture entre les groupes de Bafia et de Yaoundé. En comparaison, D 1-D4 sont des déformations similaires dans les groupes de Bafia et de Yaoundé. Les deux groupes possèdent des types lithologiques identiques que sont de métapelites de faible à haut degrés métamorphiques et des amphibolites, d’origine volcano -sedimentaire ainsi que des métagranitoïdes d’origine crustale archéenne à protérozoïque (âges Nd 3500-2100 Ma) avec des contributions mantelliques ; une même période maximale de dépôts, le Néoprotérozoïque, fixée à ~1600 Ma (U/Pb-, Pb/Pb-zircons détritiques) ainsi qu’une période comparable de mise en place des granitoïdes syntectoniques fixée entre ~625 – 600 Ma (U/Pb-, Pb/Pb-zircons); une orogénèse panafricaine analogue (650-542 Ma) dont la phase rétrograde du faciès des granulites à celui des amphibolites est fixée entre 616 – 540 Ma (Sm/Nd-grenat, EMP-monazite, Rb/Sr-roche totale - biotite ± muscovite). Les groupes de Bafia et de Yaounde qui admettent une origine et une nature litho-géochimique similaires, une évolution thermotectonique panafricaine semblable peuvent être considérées en une seule et même unité litho- chrono-thermo-structurale: Le groupe de Yaoundé.

1. Introduction such as pertrographical, structural, mineralogical, geothermo- 1The world is comprised of cratons, mobile zones and barometrical, geochemical and geochronological. Phanerozoic covers differentiated into lithostructural units (Fig. Lithostructural units such as Bafia, Yaounde, Mbalmayo 1a, b). These lithostructural units have been unfortunately, Mbengbis, Ayos, Lower Nyong in South Cameroon were mainly defined by pioneers without a maximum of criterion typified as “ series ” (e.g. Lasser e et Soba, 1979; Noizet, 1982, Nédélec et al., 1986), term dedicated for chronostructural Corresponding author: [email protected] ones.

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Figure 1. (a) Geological sketch of the West-Central Africa and South America connection with cratonic masses, Paleo- and Neoproterozoic provinces of Pan-Gondwana belt in a Pangea reconstruction modified from Castaing et al. (1994) and Ngako et al. (2003). CC: Congo Craton; KC: Kalahari craton; SFC: Sao-Francisco Craton; TK: Tanganyika Craton; WAC: West African Craton; CMR: Cameroon; CAR: Central African Republic; EG: Equatorial Guinea. CCSZ: Central Cameroon Shear Zone; SF: Sanaga Fault. Dashed lines mark the country boundaries. (b) The southern Cameroon geological map (modified after Ngako et al. , 2003; Ngnotue et al. , 2000; Njonfang et al. , 2008; Nzenti et al. , 2006; Toteu et al. , 2006): SCSG: Southern Cameroon Super group; NC: Ntem complex; NyC: Nyong Complex; YG: Yaounde Group, DG: Dja Group, YoG: Yokadouma Group, SOG: Sembe-Ouesso Group; SF: Sanaga fault. Black arrows indicate Nyong nappe transport toward the East onto to NC. White arrows indicate Yaounde nappe transport toward the SSW onto to NC and NyC. The location of study area is shown (c). 11 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

Figure 2. Geological sketch of the Yaounde Group modified from Champetier de Ribes and Aubague, 1956; Weecksteen, 1957, Owona et al. (2011a, 2013). NEFB: North Equatorial Fold belt; SCSG: Southern Cameroon Supergroup; WCAFB: West Central African Fold Belt; CC: Congo Craton.

When talking of lithostructural units, these denominations Bafia and Yaounde as groups. These have been previously have to be replaced by “Complex”, “Group”, “Formation” typified as two Precambrian units without a clear identified or according to the international union of the geologist society mapped suture zone in the Sa’a -Monatélé Region (SMR), (IUGS) classification (Neville, 1976). In this work, we consider between both groups (Fig. 1c; Noizet, 1982). Recent

3 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225 geochemical and geochronological data show that the Bafia a sub- to horizontal pure shear regime, is characterised by the and Yaounde groups derived from Neoproterozoic volcano- S0/1/2 foliation in metapelites and S 2 foliation in metaplutonites, sedimentary protoliths and experienced the Pan-African the L 2 lineations, the B 2 boudins, the F 2 asymmetric, isoclinal pressure-temperature-deformation-time (P-T-d-t) evolution folds and C2 shear planes. The D 3 deformation phase is a ~E- (Nzenti et al. 1988; Mvondo et al., 2003; Mvondo et al., 2007; W transcurent tectonics regime that induced F 3 meso- and Tchakounté et al. 2007; Ganwa et al., 2008; Owona et al., megafolds that form structural units of the Yaounde nappe 2011b). The SMR, poorly known, is located at 4°10’ - 4°35’’ N (Mvondo et al. 2003; 2007; Mvondo Ondoa, 2009; Owona et and 11°10’ - 11°35’ E, between the above Bafia and Yaounde al. 2011a). This nappe is dissected by C 3 shear zones as the groups (Fig. 2). Both are parts of the Oubanguide complex or CCSZ. D4 phase is a ~N-S transcurent tectonics regime, the Central African Fold Belt (CAFB) that extends until NE responsible for F 4 large-scale folds (Mvondo Ondoa, 2009). Brazil and has experienced the Pan-African tectonothermal Faults as the Sanaga Fault (Ngako et al. 1991; Njonfang et al. event (Fig. 1; Castaing et al. 1994; Abdelsalam et al. 2002; 2008) represents the post-Pan-African D 5 brittle deformation OIiviera et al. 2006). The SMR geodynamic evolution remains phase. under discussion. To study this area means to (1) look for a 3. Material and methods suture zone. The present paper also aims (2) to bring out new Bedding (S 0), foliation (S n), lineation (L n), axial planes of folds petrostructural data of the SMR, (3) to determine whether this (F n), fold axes (B n), S-C foliation-shear fabrics and faults were SMR belongs to Bafia or Yaounde groups, (4) to compare the identified and measured in outcrops. The foliations were Bafia and Yaounde geodynamic evolution, (5) to discuss on classified by the metamorphic minerals that define them. We the Yaounde tectonic nappe and the CAFB extension. discriminate stretching and crenulation lineations. Kinematic Available litho-geochemical and P-T-d-t data from the Bafia or shear criteria, used to estimate the sense of ductile flow, and Yaounde groups will also be used to (6) constrain the comprise shear zones, S-C fabrics, offset markers, northern extension of the Yaounde nappe or the asymmetric boudinage, and rotated porphyroclasts or Neoproterozoic domain. porphyroblasts; these fabrics were typified in the field and in 2. Geological setting thin sections. We refer the readers to compilation papers for a The SMR is located between the Yaounde Group (YG) and compressive description (William et al. 1994; Passchier and Bafia Group (BG). Both groups belong to the Southern Druguet, 2002; Passchier and Trouw, 2005). Bedding (S 0), Cameroon supergroup, (Toteu et al., 2006a; Tchakounté et al. foliation (S n), lineation (L n), axial planes of folds (F n), fold axes 2007). They are meta-volcano-sedimentary sequence (Nzenti (B n) were treated with the aid of an available commercial et al., 1988; Nkoumbou et al., 2006, Owona et al. 2012b). program Spheristat. See the Stesky R.M., Sperhistat User's They consist of low- to high-grade metapelites, amphibolites, Manual, Pangaea Scientific, Brockville, Ontaria, Canada. metaplutonites and quartzites (Fig. 2). Pelites have the Planar structures are in the Dip-Dip-direction e.g. 45 273 and average sandy-clay composition of post-Archean shales while linear structures, in the plunge-plunge direction e.g. 45 273 granitoids derived from differentiation of within plate basalts forms. (Nédélec et al. 1986; Nzenti et al., 1988; Mvondo et al., 2003; 4. Results Owona et al. 2012). Metagranidoids are reworked Archean to 4.1. The SMR Petrography Neoproterozoic materials (SHRIMP U/Pb, Pb/Pb detrital The SMR consists of metapelites, quartzites defining ~NE-SW zircon; Toteu et al. 2006b; Tchakounté et al. 2007; Ganwa et lengthened massives, amphibolites and metaplutonites (Fig. al., 2008). Amphibolites display typical MORB and ITA 3). Metapelites include two micas ± garnet ± kyanite- bearing characteristics defining old oceanic crust within the gneisses, mica schists, garnet-bearing amphibolites and Oubanguide complex (Nkoumbou et al. 2006; Owona et al. quartzites, foliated from the outcrops to the microscope where 2013). YG and BG have been affected by the Pan-African they display blastic textures. In metapelites, quartz (25-30 %) tectonothermal event under granulitic to amphibolitic appears as inclusions in garnet and forms either felsic layers conditions (Bessole et Trompette, 1980; Nzenti et al. 1988; corresponding to the S 0/1/2 composite foliation. Biotites (15-20 Mvondo et al. 2003; Owona et al. 2011b). Noizet (1982) %) define mafic layers, parallel to previous ones and are proposed the first tectonic sketch integrating the SMR. The associated to garnet and sillimanite. Garnets (10-15 %) Pan-African deformation is a polyphase type (D 1-D4) ranges in surrounded by biotite, quartz and plagioclase characterize the the YG between 630 Ma (Sm/Nd-WR-Grt in kyanite gneisses; S0/1/2 foliation. Some blasts in atoll contain inclusions of rutile, Toteu et al. 1994), 613±33 Ma to 586±15 Ma (U/Th/Pb-Mnz, graphite and garnet which form a Si internal schistosity while Owona et al. 2011b); 598 – 540 Ma in metapelites and rims show quartz-biotite-sillimanite mineral transformations. metadiorites (Rb/Sr-WR-Bt/-Ms, Owona, 2008; Owona et al. Plagioclases (5-10 %) are either in crystals associated with 2012). The D 1 compressive and thrust tectonic phase under a biotite, garnet, kyanite and opaque, or in elongated prisms simple shear regime emplaced sub-horizontal S 1 foliation and following the foliation. Muscovite (5-7 %) occurs as flakes F1 isoclinal folds preserved in quartzites and amphibolites parallel to biotite. Green hornblendes (4-6 %) form prisms (Mvondo et al. 2007). During the D 2, deformation assigned as 4 Mbola et al., Sciences, Technologies et Développement (Septembre 2014), Volume 16, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225 belonging to mafic layers. Rutile, graphite, zircon, sphene, Metaplutonites include augen orthogneisses that show the S 2 sericite and epidote are accessories. Quartzites are a NE-SW foliation in outcrops. They are well foliated in hand sample massif band. They debit in plates of thickness of 1-2 cm used scale, meso- to melanocratic under the microscope where by populations as building materials. Microscopically, they are they display blastic textures. Augen orthogneisses that leuco- to mesocrate and consist of quartz ( 50-55%), outcrop in Bégny consist of quartz (25-30 %), orthoclase (10- muscovite (15-20 %), biotite (5-10 %), hornblende (3-5 %), 15 %), microcline (5-10 %), plagioclase An25-40 (5-10 %), graphite, magnetite and garnet (3-5 %), plagioclase (< 3 %), biotite (5-10 %), amphibole (5-10 %), garnet (5-10 %) and sphene, epidote and zircon. Garnet-bearing amphibolites accidentally; tourmaline, titanite, calcite, zircon, and apatite. occur as discrete boudins in metapelites and are foliated from These blasts define felsic and mafic layers representing the outcrops to the microscopic scale where they display above S 2 foliation. nematoblastic texture. They consist of green hornblende (50- Leptynites are leucocratic and present a granoblastic texture. 60 %), garnet (15-25 %), diopside (10 %), quartz (3-5 %) and They consist of quartz (15-30 %), plagioclase (15-25 %), plagioclase An15-30% (5 %). Biotite, zircon, calcite and garnet (15-20 %), amphibole (5-10 %), clinopyroxene (5-10 chlorite are accessories. %), biotite (10 %) and accidentally sphene and sericite.

Figure 3. The SMR geological map. 1: Augen orthogneisses; 2: Metasyenite; 3: Quartzites; 4: Garnet ± kyanite bearing micas schists; 5: Biotite ± muscovite bearing gneisses; 6: Fined grained orthogneisses; 7: Garnet bearing amphibolites; 8: Faults; 9: Foliation and plane dip angle; 10: Lineation.

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most popular is the Sanaga fault oriented NE-SW guiding the Sanaga River (Figs. 3, 8a).

Figure 4. F3 meso-folds with ~vertical S 0/1/2 foliations in Monatélé quartzites and paragneisses. Note the ~N-S and ~vertical character of axial planes and the southern transport of material.

4.21. The SMR deformation The SMR is affected by a polyphase deformation that can be segmented in D 1, D2, D3 and D 4. D 1 is underlined by the flat S 0/1 foliation and F 1 folds represented by quartzites and amphibolite layers. It was a pure shear deformation. It has been strongly overprinted by D 2 deformation represented by the flat S 0/1/2 composite foliation in metapelites and S 2 foliation in metaplutonites with N or S vergences, F 2 intrafolial folds, L 2 subhorizontal and submeridian lineation and B 2 boudins. D 3 emplaced in mesoscopic scale, F 3 isoclinal, meso- and megafolds that affect S 0/1/2 and S 2 foliations with N or S vergences, ~N-S axial planes, either S or N plunges as well as B 2 boudins, and B 2 fold axes. S 0/1/2 as well as S 2 doesn’t show particular reorientation in the SMR. They display a sub-vertical dip (>60 °) such as in the locality of Nkomesse at Monatélé suggesting the existence a thrust zone (Fig. 4). The distribution of poles of foliation and lineation suggest a NNE- SSW to NE-SW extension (Fig. 5). F 3 meso-scale folds represented by quartzites and amphibolites metamorphic layers as B 2 boudins show the ~NE-SW extension parallel to Figure 5. Synthetic stereograms of the S 0/1/2 and S 2 foliations, and L 2 B3 fold axes (Fig. 5). Large scale folds are defined by great lineation in the SMR. (a) represent S 2 foliation and L 2 lineation in circles foliations (Figs. 4, 6a). They define a tectonic nappe Begny metaplutonites; (b) for S 0/1/2 and L 2 lineation in Balamba two dissected by C 3 dextral shear zones mostly oriented NE-SW, micas bearing gneisses; (c) in Mbangassina two micas bearing parallel to the CCSZ. D 4 is represented by F 4 large-scale folds gneisses; (d) in the Monatélé micas schists; (e) in Sa’a quartzites. (Fig. 7c). The SMR is affected by the post-Pan-African D 5 Bold and with arrows indicate the s1 and s3 main stress directions. brittle deformation that emplaced NE-SW and NW-SE faults suggesting at least existence of two generation of faults. The 5 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

5. Yaounde and Bafia Groups relationships 5.1. Litho-chemistry The Bafia and Yaounde groups display similar metapelites and metaplutonites or syntectonic granitoids compositions (Figs. 2, 3, 9). The Bafia metapelites are made up of gneisses of various composition (garnet-biotite-, garnet-amphibole and biotite-muscovite gneisses), micas schists, quartzites, and amphibolites whereas synkinematic granitoids are metamonzodiorite and metagranites (Ngnotué et al., 2000; Toteu et al., 2006b;Tchakounté et al., 2007 ; Ganwa et al., 2008).The Yaounde group is composed of gneisses of various composition (garnet-biotite-, garnet-amphibole and biotite- muscovite gneisses), micas schists, chlorite schists, quartzites, and amphibolites whereas syntectonic granitoids are metadiorites, metagabbros, metasyenogabbro, metagranites, syenites, norites and dolerites (Nzenti et al., 1988; Mvondo et al., 2003; Toteu et al., 2006b; Owona et al., 2011a). Bafia and Yaounde groups are volcano- metasedimentary units (Ganwa et al., 2008; Owona et al., 2012). Metasediments derived from greywacke and shale sequence deposited in an extensional environment related to the Congo craton (Nzenti et al., 1988; Ngnotue et al., 2000). Amphibolites result from basalts, that derived from subalkaline Figure 6. Mesoscopic kinematics criteria displayed by the S 0/1/2 magmas (high-Fe tholeiites to basaltic andesites) with the foliation, NE-SW F 3 meso-folds in Sa’a micas schists (Gneissic slab, Nkolbogo outcrop) in response of NW-SE shortening that outline the MORB, continental flood basalts and OIB composition regional folding. (Nkoumbou et al., 2006; Ganwa et al., 2008; Owona et al., 2012). The metagranitoids derived mainly from crustal rocks Table 1. The Bafia and Yaounde group lithostructural and chronostratigraphic similarities. with minor contributions from mantle materials (Nzenti et al., Lithostructral units Bafia group Yaounde group 1988; Ngnotue et al., 2000; Toteu et al., 2006b; Owona et al., Lithologies Types Low- to high grade Low- to high grade 2012). metapelites, metapelites, Quartzites, Quartzites, amphibolites, amphibolites, 5.2. P-T evolution metagranitoids metagranitoids The Bafia and Yaounde groups syndeformational P –T path Origin Volcano-sediment Volcano-sediment for for metapelites; metapelites; crustal sections calculated from cores and rims of garnets in crustal and mantellic and mantellic individual samples partly overlap and align along overall contributions for contributions for clockwise P –T trends (Nzenti et al., 1988; Mvondo et al., granitoids granitoids Deformation D1 Compression S0/1 , F 1 S0/1 , F 1 2003; Owona et al., 2011b). To the D 1-D4 deformation stages, ductile phases tectonics we correlated four Pan-African metamorphic stages (M 1-4). M 1 D2 Extensive S0/1/2 , S 2, B 2, F 2 S0/1/2 , S 2, B 2, F 2 tectonics stage that didn’t exceed the amphibolite facies can be related D3 Transcurent S3, F 3, C 3 S3, F 3, C 3 to the burial of sediments and the beginning of basins closure. tectonics M2 stage admitted as granulite facies is associated to the D4 Transcurent F4 F4 tectonics peak of the Pan-African metamorphism while M 3-4 evolved Orogeny Typology Pan-African Pan-African from amphibolite to green schist facies are linked to the Facies Granulite to Granulite to amphibolite amphibolite cooling stage (Owona et al. 2011b). In Bafia gneisses P–T P-T peak 800 –825 °C 9.5 –11 600 –800 °C 11 –12 conditions were 800 –825 °C and 9.5 –11 kbar. Amphibolites kbar kbar Time Protoliths of Archean to Archean to P-T conditions were 500 –540 °C and 5 –7.5 kbar (Ganwa et metapelites Mesoproterozoic Mesoproterozoic al., 2008). In the Yaounde group, the Pan-African event (3400 –1500 Ma) (3400 –1500 Ma) started at 450 °C and 7 kbar peaked at 11 –12 kbar with Metamorphic 650-542 Ma 650-542 Ma event variable temperatures 600 –800 °C and involved a marked Syntectonic Neoprterozoic Neoprterozoic decompression towards 6 –7 kbar at high temperatures 700 – granitoids occurrences (620- occurrences (620-600 600 Ma) Ma) 750 °C (Nzenti et al., 1988; Mvondo et al., 2003; Owona et al., Cooling Neoprterozoic (600- Neoprterozoic (600- 2011b). Yaounde amphibolites encompassed prograde 375- 540 Ma) 540 Ma) 550°C/4-8 kbar, peaked 400-670°C/6-10 kbar and retrograde 675-550°C/7-5 kbar stages (Owona et al., 2011). Both P-T evolutions in the Bafia and Yaounde groups are typical parts 6 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225 of orogens which underwent contractional crustal thickening and ended in the South (Yaounde group) until the Congo by stacking of nappe units during continental collision and/or Craton contact zone (e.g. Ball et al., 1984; Jegouzo, 1984; during subduction-related accretionary processes that can be Nédélec et al., 1986; Mvondo et al. 2007; Owona et al. directly compared to those exemplified in younger collisional 2011b). orogens as the Caledonides and the Variscides (Owona et al., 2011b, 2013).

5.3. Deformation The deformation that affected SMR includes the D 1-D4 Pan- African ductile stages and the D 5 post-Pan-African brittle phase, similar as in the Yaounde and Bafia groups (Table 1; Mvondo et al. 2007; Mvondo Ondoa, 2009; Owona et al. 2011b). D1 was a compressive and thrust tectonic phase under a simple shear regime, strongly overprinted by D 2; accessible only by the S 1 foliation and F 1 isoclinal folds preserved in quartzites and amphibolites (Fig. 7). D 2 coaxial deformation is responsible of the exhumation of the earliest D 1 nappe; emplaced the S 0/1/2 foliation in metapelites and S 2 foliation in metaplutonites, the L 2 lineations, the B 2 boudins, the F 2 asymmetric, isoclinal folds and C 2 shear planes (Fig. 7). D3 ~E-W to NW-SE transcurent tectonics induced F 3 meso- and megafolds that form structural units of the Yaounde nappe and C3 shear zones such as the CCSZ (Fig. 7). D 4 ~N- S to NE-SW transcurent tectonics regime defined F4 large- scale folds (Mvondo Ondoa, 2009).

These D 2-D4 tectonic imprints materialised the geometry of the Yaounde nappe as lithological massives N-S to NE-SW lengthened as well as the above E-W to NW-SE shortening in metapelites and metaplutonites and structural sketches (Figs. 2, 8a, b), synthetic stereographic diagrams from the Bafia region (Ganwa, 1998; Mvondo Ondoa, 2009), the SMR (the present study, Fig. 5), Yaounde (Mondo, 2003; Mvondo et al. 2003; Owona, 2008; Owona et al. 2011b, 2012) equivalent to F3 large-scale folds (Figs. 8a, b). Flanks of F 3 large-scale folds are themselves folded in F 4 megafolds, outlined lithology boundaries and structural sketches (Figs. 2, 8c, d). See details in Ganwa et al. (2007) and Mvondo Ondoa (2009) for the Bafia Region and, Mvondo (2003), Mvondo et al. (2003, 2007), Owona (2008) and Owona et al. (2011a, b) for the Yaounde Region. These F 3-4 megafolds form tectonic “scales” or synclines/anticlines, composing the Yaounde nappe. This regional folding is accompanied by N-S to NE-SW L 2 lineations showing ~N or ~S trending (Figs. 2, 3, 5). L 2 ~E- or W-ward trending is associated to these refolding processes (Mvondo et al. 2007; Owona et al. 2011b). The Yaounde nappe is later dissected by C 3 shear zones as the CCSZ in response of regional E-W to NW-SE shortening and ~N-S extension (Figs. 9). D 5 post-Pan-African faults such as the SF (Figs. 1, 2, 3, 8). Tectonic imprints such as B 2 boudins, F 2 and F3 isoclinal and asymmetric meso-folds as well as F 3 large scale folds and C 3 shear zones, characterized the D 2-D4 kinematics from meso- to mega-scales and look similar from Bafia to Yaounde (Figs. 9). The SSW-ward transport of the Figure 7. Nature of D 1-D4 deformation phases main stress Yaounde nappe may have started in the North (Bafia group) orientations and natures in both in Bafia and Yaounde Groups 7 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

Figure 8. F3-4 regional folding in the Bafia (a, c) and Yaounde (b, d) groups. (a, b) show the F 3 regional folding underlined by the S 0/1/2 and S 2 foliations in metapelites and metagranitoids, respectively. (c, d) display the F 4 regional folding underlined by the S 3 schistosities and B 3 fold axes in metapelites and metagranitoids. Note the major ~NNE-SSW to NE-SW extensions of F 3 due to the E-W to NW-SE D 3 transcurent tectonics; the major ~E-W to NW-SE extensions of F 4 due to the N-S to NE-SW D 4 transcurent tectonics -4 regional folds.

8 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

Figure 9. C3 shear zones that affected Bafia and Yaounde metamorphites. (a) C 3 Reverse slips or the eastern thrust type in the YZ and E-W section in response of a ~horizontal σ1 in the Bafia group. (b) C 3 Reverse slips or the southern thrust type in the XZ and N-S section and parallel to L2 in response of a ~horizontal σ1 observed i n Olembe paragneisses (Yaounde group). (c, d) C 3 normal and southern thrust type in the XZ and N-S parallel to L 2 in (c) Manya paragneisses (Bafia group) and (d) Mbalmayo chlorite schist in response of subvertical σ1

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According to the model of Harris (2003), NNE-SSW to NE-SW F3 mesofolds and C 3 shear zones recorded D 3 earlier stage in Bafia group can be related to regional transpression (Mvondo Ondoa, 2009), corroborated by the constriction model proposed in Yaounde group (Mvondo et al., 2007); due to a ~E-W shortening (σ1) associated to the ~NNE -SSW ~- horizontal extension (σ3) (Fig. 6). F 3-4 mega-folds become sub-N-S in the Yaounde latitude and disappear close to the Congo craton contact zone were S 0/1/2 foliations remained ~E- W, following the northern limit of that craton (Owona et al., 2011a).

If the Bafia and Yaounde groups show similar structural imprints, the SMR located between both groups display ~vertical S 0/1/2 foliation (dip > 60°) than the above groups where S 0/1/2 foliation in metapelites and S 2 foliation in metagranitoids are ~horizontal and dip gently (<45 °). SMR area cannot be considered as a suture zone, rather broadly as a thrust zone as suggested by Noizet (1982) and Toteu et al. (2006a).

5.4. Time The Bafia and Yaounde available ages are summarize in Table 2. The Bafia group zircon morphology and 207 Pb/ 206 Pb evaporation ages (2351 –2289Ma) show that metapelites contain detritus of Archean to Paleoproterozoic plutonic rocks (Figs. 11, 12), confirmed by TIMS-ID detrital zircons 1991 – 1977 Ma for migmatites (Toteu et al., 2001) and, Nd model ages 3400 –2400 Ma (Ganwa et al., 2008). They are associated to younger contribution as obtained in Bafia garnet-amphibole paragneisses, Nd model age at ca. 2400- 1500 Ma for mafic sediment source (Toteu et al., 2006b; Ganwa et al., 2008), attested by TIMS-ID detrital zircons from the Bafia Region that yielded at 1617 ± 16 Ma in granitoids (Tchakounté et al., 2007). TIMS-ID detrital zircons range from 2313-2116 Ma for Sa’a quartzites in the SMR (Toteu et al., 2006b). The Bafia group is intruded by granitoids such as Elon augen metagranite and Ngaa Mbappe metamonzodiorite that yielded ca. 600 Ma (TIMS-ID and SIMS U –Pb dating on zircons, Toteu et al., 2006b). In the Yaounde group, TIMS-ID detrital zircons of Pouma quartzites range between 2501-1880 Ma (Toteu et al., 2001). Metapelites host rocks derived also from the Paleo- to Neoproterozoic time according to detrital U/Pb zircon ~2127 Ma, overprinted by an early Pan-African event 1127-911 Ma (Figs. 11, 12; Gnotué et al., 2012). U-Pb dating of zircons in leucosomes reveal Pan-African ages ranging from 654 to 626 Ma (Gnotué et al., 2012), con- temporaneous with the magmatism responsible for the

emplacement of granitoids in the Yaounde group as displayed Figure 10. The Bafia and Yaounde lithologies. Note similar low- to by Masins metagabbro in the Lomie region at 666 ± 26 Ma; high grade metapelites and granitoids in both groups. Mamb metasyenogabbro and the Yaounde metadiorite at ca. 620 Ma and are broadly coeval with deposition of the Yaounde metapelites (TIMS-ID and SIMS U –Pb dating on

zircons, Penaye et al., 1993; Toteu et al., 2006b; Owona et al., 2012). 11 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

Table 2. Compilation of available radiometric ages from the Southern Cameroun Supergroup Pan-African North Equatorial Fold Belt.

Bafia Group Location Rock type Sample Error U/Th/Pb Mz Rb/Sr WR-Bt/Ms Sm/Nd-Grt Pb/Pb Rt Pb/Pb-Zr U/Pb-Zr Authors Ngaa Mbape Metamonzodiorite IG-41 4 598 Toteu et al., 2006b

Ngaa Mbape Metamonzodiorite IG-41 4 618.1

Ngaa Mbape Metamonzodiorite IG-41 3 603

Kobe II Grt-Bt-gneiss 2KS 4 2289 Ganwa et al., 2008

Kobe II Grt-Bt-gneiss 2KS 4 2351

Bafia Gneiss 68 628 Tcahkounté et al.,

Bafia Gneiss 87 674 2007

Bayomen Gneiss IG-45-IG44 35 1603

Bayomen Gneiss IG-45 16 1917

Bayomen Gneiss IG-45 87 674

Bayomen Gneiss IG-44 68 626

Yaounde Group Yaounde Metasediment 30 570 Lasser et Soba, 1979

Yaounde Metasediment 22 565 Dada et al.,1993

Yaounde Mafic granulite 10 620

Yaounde Mafic granulite 10 620 Penaye et al., 1993

Yaounde Metadiorite 10 620

Yaounde Metasediment 100 2117

Yaounde Metasediment 20 571

Yaounde Granulite 10 620

Rocher du Loup Syenite 20 590 Toteu et al., 1994

Bivouba Mica schist 616

Yaounde Px-Grt metadiorite 10 620

Sa'a Quartzite 93-32 2900 Toteu et al., 2001 Sa'a Quartzite 93-32 2100 Sa'a Quartzite 93-32 600 Pouma Quartzite 93-33 2900

Pouma Quartzite 93-33 2100

Pouma Quartzite 93-33 600

Yaounde Kya-Grt-gneiss 20 611 Stendal et al., 2006

Mamb Metasyeno-gabbro 7 618 Toteu et al, 2006a Yaounde Metasediment Geo-5B

Yaounde Metasediment 89-71

Yaounde Metasediment Geo-3 22 911

Yaounde Metasediment Geo-3 7 626

Mahan Amphibolite G-33 26 824

Mahan Amphibolite G-33 20 1071

Yaounde Metasediement 22 911 Toteu et al., 2006b

Yaounde Mica schist 7 626

Mahan Amphibolite 20 1071

Rocher du Loup Metasyenite 19 591 Lerouge et al., 2006

Odza Paragneiss Ow73 14 594 Owona et al., 2011b

Afaneyoa Paragneiss Ow200 33 613

Afaneyoa Paragneiss Ow200 12 605

Nkong Binguela Paragneiss Ow203 17 591

Nkong Binguela Paragneiss Ow203 27 593

Mbankomo Paragneiss Ow215 19 595

Yaounde Paragneiss Ow254 24 599

Bilik Paragneiss Ow248 15 586

Biwong Mica schist Ow263 11 600

Ottotomo Mica schist Ow264 13 603

Mbankomo Paragneiss Ow215 3 599 Owona et al., 2012b

Yaounde Metadiorite Ow1 4 622.9

Afamba Metadiorite Ow24 4.3 623.6

Binguela Metadiorite Ow197 4.2 624.6

Yaounde Metadiorite Ow1 4 572

Nkoulou Mica schist Ow84 5 554

Ndageng Mica schist Ow159 5 540

Yaounde Leucosome 6.4 626 Ngnotue et al., 2012

Yaounde Metapelite 6.7 654

Yaounde Leucosome-metabasite 150 2127

Yaounde Leucosome-metabasite 56 911

Yaounde Leucosome Metapelite 110 1122

Yaounde Leucosome Metapelite 61 620

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high pressure stages occurred between 613 ± 33 Ma and 586 ± 15 Ma (Fig. 10; EMP-monazite age, Owona et al., 2011b; Gnotué et al., 2012). The 87 Rb/ 86 Sr isochrone ages of metadiorite and metapelites, significantly younger than the obtained intrusion age, from 600-540 Ma, represent the Pan- African cooling period (Fig. 12; Owona et al., 2012).

6. Conclusion The SMR was explored for its transition position between the admitted Bafia and Yaounde groups, its geodynamic evolution and relationship with above groups. According to its petrography, lithology, tectonics, mineralogy, geotheromobarometry and geochronology, the SMR shows similar origin and geodynamic evolution as the Bafia and Yaounde groups. It was affected by the D 1-4 Pan-African deformation. The tectonic evolution shows that the main feature, the Yaounde nappe, made of F 3-4 large-scale folds emplaced under a transpression tectonic regime; is transported top-to the SSW onto the Congo craton and the West Central African Fold Belt. According to its uncommon ~vertical foliation, the SMR constitutes a thrust zone where the northern Bafia part thrust the southern Yaounde part of the Yaounde nappe. Both, the Bafia and Yaounde groups can therefore form a single lithostructural unit: the Yaounde Group.

References Abdelsalam, G. M. Liégeois, L. & Stern, R. J. 2002. The Saharan Metacraton. Journal of African Earth Sciences 34 : 119-136. Ball, E. Bard, J.P. & Soba, D. 1984. Tectonique tangentielle Figure 11. The Bafia and Yaounde similar geochronological dans la catazone panafricaine du Cameroun: les evolution. In both groups, radiogenic U/Pb and Pb/Pb zircon indicate gneiss de Yaoundé. Journal of African Earth Sciences sources and maximum deposits for metapelites and occurring time 2 : 91-95. for granitoids; Pb/Pb rutile and EMP monazite ages for the peak of Bessoles, B. & Trompette, R. 1980 : Géologie de l’Afrique. La the Pan-African orogeny and, Rb/Sr whole rocks, biotite and chaîne panafricaine “zone mobile d’Afrique Centrale muscovite for the Pan-African cooling period. See table 1 for authors, (partie sud) et zone soudanaise. Memoire B.R.G.M. ages and dating methods. 92 : 397p. Castaing, C. Feybesse, J.L. Thieblemont, D. Triboulet, C. & Chevremont, P. 1994. Paleogeographical reconstructions of the Pan-African/Brasiliano orogen: closure of an oceanic domain or intracontinental convergence between major blocks. Precambrian Research 69 : 327-344.

Champetier de Ribes, G. & Aubague, M., 1956. Notice Figure 12. The Bafia and Yaounde Region overall available ages explicative feuille Yaoundé Est. Avec carte géologique (Ma) de reconnaissance au 1/500 000. Imprimerie Rébon, Paris. These ages are corroborated by metamorphic ages in Dada, S.S. Tubosun, I.A. Lancelot, J.R. & Lar, A.U. 1993. Late leucosomes at ca. 658 Ma and 613-540 Ma in metapelites Archaean U –Pb age for the reactivated basement of (EMP Th/U/Pb monazite dating, Owona et al., 2011b, Gnotué northeastern Nigeria. Journal of African Earth et al., 2012). The Pan-African metamorphism with dominant Sciences 16 : 405 –412. 13 Mbola et al., Sciences, Technologies et Développement ( Septembre 2014 ), Volume 1 6, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

Ganwa, A. 1998. Contribution à l’étude géologique de la Rendus Académie des Sciences, Paris 303 (2) : 75- région de Kombé II – Mayabo dans la série 80. panafricaine de Bafia. Géomorphologie structurale, Neville, G. Hollis, H. Pamerol, C. Salvador, A. & Stöcklin, J. tectonique, pétrologie. Thèse de doctorat 3 ème cycle 1976. International stratigraphic guide. Guide to non publiée, Université de Yaoundé I, Cameroun, stratigraphic classification, terminology, and 173p. procedure. By the international Subcommission of Ganwa, A.A. Frisch, W. Siebel, W. Kongyuy Shang, C. Stratigraphy. Classification of IUGS Commission on Mvondo Ondoa, J. Muharrem, S. & Tchakounté, N.J. Stratigraphy. Holis D. Heldberg, Editor : 9-89. 2008. Zircon 207Pb/206Pb evaporation ages of Ngako, V. Affaton, P. Nnange, J.M. & Njanko, Th. 2003. Pan- Panafrican metasedimentary rocks in the Kombe´-II African tectonic evolution in central and southern area (Bafia Group, Cameroon): Constraints on Cameroon: transpression and transtension during protolith age and provenance. Journal of African Earth sinistral shear movements. Journal of African Earth Sciences 51 : 77 –88. Sciences 36 : 207 –214. Haris, L.B. 2003. Folding in high grade rocks due to back- Ngako, V. Jegouzo, P. & Nzenti, J.P. 1991. Le Cisaillement rotation between shear zones. Tectonics Special Centre Camerounais. Rôle structural et géodynamique Research Centre, Dep. Of Geology and Geophysics, dans l‘orogenèse panafricaine. Comptes Rendus The University of Western Australia. Journal of Académie des Sciences, Paris 313 : 457 –463. Structural Geology 25 : 223 240. Ngnotue, T. Ganno, S. Nzenti, J.P. Schulz, B. Tchaptchet Jegouzo, P. 1984. Evolution Structurale du Sud-ouest Tchato, D. & Suh Cheo, E. 2012. Geochemistry and Cameroun Durant l’orogénèse panafricaine. Geochronology of Peraluminous High-K Granitic Association de tectonique cisaillante et chevauchante. Leucosomes of Yaoundé Series (Cameroon): Coll. Chevauchement et déformation, Toulouse, Mai, Evidence for a Unique Pan-African Magmatism and 1984. Melting Event in North Equatorial Fold Belt. Lasserre M. & Soba, D. 1979. Migmatisation d’âge panafricain International Journal of Geosciences 3: 525-548. au sein des formations camerounaises appartenant à Ngnotué, T. Nzenti, J.P. Barbey, P. & Tchoua, M.F. 2000. la zone mobile d’Afrique centrale. Comptes Rendus de “The Ntui -Betamba High Grade Gneisse: A Northward la Société Géologique de France 2 : 64-68. Extension of the Pan-African Yaoundé Gneisses in Mvondo Ondoa, J. 2009. Caractérisation des événements Cameroon”. Journal of African Earth Sciences 31 (2) : tectoniques dans le domaine sud de la Chaîne 369-381. Panafricaine au Cameroun : styles tectoniques et Njonfang, E. Ngako, V. Moreau, Ch. Affaton, P. & Diot, H. 2008. géochronologie des séries de Yaoundé et de Bafia. Restraining bends in high temperature shear zones: The Unpublished PhD thesis, Université de Yaoundé I, 162 ―Central Cameroon Shear Zone ǁ, Central Africa. p. Journal of African Earth Sciences 52 : 9-20. Mvondo, H. Den Brock, S.W.J. & Mvondo Ondoa, J. 2003. Nkoumbou, C. Yonta Goune, C. Villiéras, F. Njopwouo, D. Yvon, Evidence for symmetric extension and exhumation of J. Ekodeck, G.E. & Tchoua, F. 2006. Découverte des the Yaounde nappe (Pan-African fold belt, Cameroon). roches à affinité ophiolitique dans la chaîne panafricaine Journal of African Earth Sciences 36 : 215 –231. au Cameroun: les talcschistes de Ngoung, Lamal Mvondo, H. Owona, S. Mvondo Ondoa, J. & Essono, J. 2007. Pougue et Bibodi Lamal. Comptes Rendu s de l’Académie Tectonic evolution of the Yaoundé segment of the des Sciences 338 : 1167-1175. Neoproterozoic Central African Orogenic Belt in Noizet, G. 1982. Disposition géologique des régions de southern Cameroon. Canadian Journal of Earth Yaoundé et Bafia, Annale de la Faculté des Sciences, Sciences 44 : 433-444. Université de Yaounde. Mvondo, H., 2003. Analyse structurale et pétrogéochimique Numbem Tchakounté, J., Toteu, F.S., Van Schmus, W.R., des roches de la région de Yaoundé nord; arguments Penaye, J., Deloule, E., Mvondo Ondoua, J., Bouyo contribuant à la connaissance de l’évolution Houketchang, M., Ganwa, A.A., White. M.W., 2007. géotectonique de la chaîne panafricaine au Evidence of ca 1.6-Ga detrital zircon in the Bafia Cameroun. Unpublished Ph.D. Université de Yaoundé Group (Cameroon): Implication for the I, 188 p. chronostratigraphy of the Pan-African Belt north of the Nedelec, A. Macaudière, J. Nzenti, J.P. & Barbey, P. 1986. Congo craton. Compte Rendu Geoscience 339 : 132 – Evolution structurale et métamorphisme des schistes 142. de Mbalmayo (Cameroun). Informations pour la Nzenti, J.P. Barbey, P. Macaudiere, J. & Soba, D. 1988. structure de la zone mobile panafricaine d’Afrique Origin and evolution of the late Precambrian high- Centrale au contact du Craton du Congo. Comptes grade Yaounde gneisses (Cameroon). Precambrian Research 38 : 91 –109.

14 Mbola et al., Sciences, Technologies et Développement (Septembre 2014), Volume 16, 1-15 Sciences, Technologies & Développement, ISSN 1029 - 2225

Nzenti, J.P. Kapajika, B. Wörner, G& Lubala, T. 2006. interpretation of granulitic rocks as the suture of a Synkinematic emplacement of granitoids in a Pan- collision in the “Centrafrican belt”. Comptes Rendu de African shear zone in Central Cameroon. Journal of l’Académie des Sciences, Paris 317 (II): 789-794. African Earth Sciences 45 : 74 –86. Tchakounté, N.J. Toteu, S.F. Van Schmus, W.R. Penaye, J. Oliveira, E.P. Toteu, S.F. Araújo, M.N.C. Carvalho, M.J. Deloule, E. Mvondo Ondoa, J. Bouyo Houketchang, Nascimento, R.S. Bueno, J.F. McNaughton, N. & M. Ganwa, A.A. & White, W.M. 2007. Evidence of ca Basilici, G. 2006. Geologic correlation between the 1.6 Ga detrital zircon in the Bafia Group (Cameroon): Neoproterozoic Sergipano belt (NE Brazil) and the Implication for the chronostratigraphy of the Pan- Yaounde belt (Cameroon, Africa). Journal of African African Belt north of the Congo craton. Comptes Earth Sciences 44 (4-5): 470-478. Rendus Géosciences 339 : 132 –142. Owona S., Tichomirowa M. Ratschbacher L. Mvondo Ondoa Toteu, S. F. Penaye, J. Deloule, E. Van Schmus, W.R. & J. Pfänder J. Ekodeck E. Tchoua M. F. & Affaton P. Tchameni, R. 2006a. Dichronous evolution of volcano- 2012. New igneous (zircon Pb/Pb) and metamorphic sedimentsary basins north of the Congo craton: (Rb/Sr) ages in the Neoproterozoic Yaoundé Group Insights from U-Pb ion microprobe dating zircons from (Cameroon, Central Africa): consequences for the Poli, Lom and YGs (Cameroon). Journal of African orogenic evolution north of the Congo Craton. Earth Sciences 44 (4-5) : 428-442. International Journal of Earth Sciences (Geolgische Toteu, S.F. Michard, A. Bertrand, J.M. & Rocci, G. 1987. U– Rundschau). DOI 10.1007/s00531-012-0751-x. Pb dating of Precambrian rocks from northern Owona, S. 2008. Archaean, Eburnean and Pan-African Cameroon, orogenic evolution and chronology of the Features and Relationships in their Junction Zone in Pan-African belt of central Africa. Precambrian the South of Yaoundé (Cameroon). Unpublished PhD. Research 37 : 71 –87. Thesis, Univ., Douala, 232p. Toteu, S.F. Michard, A. Macaudière, J. Bertrand, J.M. & Owona, S. Mbola Ndzana,S.P. Mpesse, J.E. Mvondo Ondoa, Penaye, J. 1986. Données géochronologiques J. Schulz, B. Pfänder, J. Jegouzo, P. Affaton, A. nouvelles (U –Pb et Rb/Sr) sur la zone mobile Ratschbacher, L. & Ekodeck, G.E. 2013. Petrology panafricaine du nord Cameroun. Comptes Rendus de and geothermobarometry of amphibolites from the l’Aca démie des Sciences, Paris 303 : 375 –378. Neoproterozoic Yaounde Group (Cameroon, Central Toteu, S.F. Van chmus, R.W. Michard, A. 2001. New U-Pb Africa): Evidence of MORB and implications on their and Sm-Nd data from north-central Cameroon and its geodynamic evolution. Comunicações Geológicas 100 bearing on the pre-Pan-African history of Central (1): 5-13. Africa. Precambrian Research 108 : 45-73. Owona, S. Mvondo Ondoa, J. Ratschbacher, L. Mbola Toteu, S.F. Van Schmus, W.R. Penaye, J. & Nyobé, J.B. Ndzana, S.P. Tchoua, M.F. & Ekodeck, G.E. 2011a. 1994. U/Pb and Sm/Nd evidence for Eburnean and The geometry of the Archean, Paleo- and Pan-African high-grade metamorphism in cratonic Neoproterozoic tectonics in the Southwest Cameroon. rocks of southern of Cameroon. Precambrian Comptes Rendus Géosciences 343 : 312 –322. Research 67 : 321-347. Owona, S. Schulz B. Ratschbacher, L. Mvondo Ondoa, J. Toteu, S.F. Yongue, F.R. Penaye, J. Tchakounté, J. Seme Ekodeck, G.E. Tchoua, M.F. & Affaton, P. 2011b. Pan- Mouague, A.C. Van Schmus, W.R. Deloule, E. & African metamorphic evolution in the southern Stendal, H. 2006b. U –Pb dating of plutonic rocks Yaounde Group (Oubanguide Complex, Cameroon) involved in the nappe tectonic in southern Cameroon: as revealed by EMP-monazite dating and consequence for the Pan-African orogenic evolution of thermobarometry of garnet metapelites. Journal of the central African fold belt. Journal of African Earth African Earth Sciences 59 : 125-139. Sciences 44 (4-5) : 479-493. Passchier, C.W. & Druguet, E., 2002. Numerical modelling of Weecksteen, G. 1957. Carte géologique de reconnaissance à asymmetric boudinage. Journal of Structural Geology l’échelle du 1:500 000 e, feuille Douala-Est avec notice 24 : 1789-1803. explicative. Publication de la Direction des Mines et de Passchier, C.W. & Trouw, R.A.J. 2005. Microtectonics. la Géologie du Cameroun. Springer, 366 p. William, P.F. Goodwin, B.L. & Ralser, S. 1994. Ductile Pénaye, J. Toteu, S.F. Van Schmus, W.R. & Nzenti, J.P. deformation processes. Continental deformation. Ed. 1993. U/Pb and SM/Nd preliminary geohronologic Paul L. Hancock, Univ. Bristol, UK., Pergamon Press, data on the Yaounde series, Cameroon: Re- 1-27.

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