Abstract The Dschang granites, SW Cameroon, are post-Panafrican granitoids, hosted in Paleoproterozoic orthogneiss in the Western domain of the Central African fold belt. They include coarse-grained K-feldspar biotite granite and fine-grained magnetite granite. Magnetite forms nodules surrounded by a quartzo-feldsparthic halo. Major and trace element data of both granites show high SiO 2 , Al 2 O 3 , total alkalis and Ba and low TiO 2 , MgO, P 2 O 5 and Nb contents, conferring a fractionated I-type high-K alkali-calcic and weakly peraluminous character. Both granites are enriched in light rare earth elements and large ion lithophile elements, depleted in high field strength elements, and show a rare earth element pattern with Eu/Eu* = 0.3 to 0.9. Primitive mantle-normalized spidergrams display negative Nb, Ta and Ti anomalies, typical of their derivation from subduction-related post-collisional melt. Laser inductively coupled plasma mass spectrometry U–Pb data on zircons yielded crystallization ages of 578 +7/−11 Ma and 563+8/−3 Ma for the biotite and magnetite granites respectively. Inherited zircon (1991–1442 Ma), whole-rock Nd model ages in the range 2.1–1.9 Ga, highly negative ε Ndt (−16 to −18) and initial 87 Sr/ 86 Sr ratios in the range 0.7075–0.7114, support the remobilization of a Paleoproterozoic crust. The felsic magmas were probably produced by partial melting of Paleoproterozoic orthogneiss host rocks, under oxidizing conditions. Magnetite granite is also known from the Nkambé region. Such granites from both the Dschang and Nkambé regions suggest the presence of a Paleoproterozoic domain rich in iron mineralization. This domain potentially represents a Cu, Pb, Zn and Mo metallogenic province, heavily reworked during the Pan-African orogeny.

Alkaline magmatism along the Cameroon Line has been active for at least 67 m.y. and is currently defined by an almost SW-NE geological lineament (mean value: N30°E). Available petrological, geochemical, and structural data obtained over the last 20 yr lead us to reappraise its mechanism of emplacement. Known as the second most important geological curiosity in Africa, after the East African Rift system, it displays a continental part and an oceanic part, a unique feature in Africa and even in the world. The continental part contains both plutonic and volcanic massifs, and the oceanic part consists only of volcanic massifs. Plutonic rocks as a whole define a complete series of gabbro-diorite-monzonite-syenite-granite type, whereas volcanic rocks display abundant basic (basalt-hawaiite) and felsic (trachyte-phonolite-rhyolite) lavas with very few intermediate ones (mugearite-benmoreite). The formerly entire alkaline nature of these rocks is here ruled out by the discovery of volcanoes with geochemically transitional affinities in some areas of the continental sector. On the other hand, new K-Ar and 40 Ar/ 39 Ar dates confirm the absence of any age migration associated with the SW-NE linear trend. This lack of steady time-space migration and the SW-NE trend have also been observed in the magmatic provinces of Nigeria and Benue Trough, which share similar geochemical features with the Cameroon Line, and along the NE-SW major igneous lineaments in South Africa. The mechanism of such episodic emplacement of alkaline magmatism can be better explained in terms of complex interactions between hotspots and lithospheric fractures during African plate motion.