PALEOMAGNETISM OF PRECAMBRIAN ROCKS FROM GABON, CONGO CRATON, AFRICA

Palaeomagnetic results for 75 orientated hand samples (25 sampling sit es) from the Ogooue Series amphibolites (27), Archean basement amphibo lites and granulites (14) and Precambrian dolerite dykes (34) are pres ented. Magnetization of many amphibolites showed unstable directions d uring alternating field (AF) and thermal demagnetization experiments a nd no directions of magnetization could be isolated. However, a charac teristic direction could be isolated in a few amphibolite sites and fo r the granulites studied. The best group of site mean directions Dm=54 degrees, Im=69 degrees (kappa=27, alpha(95)=18 degrees, N=4) yielded a palaeomagnetic pole located at 44 degrees E, 19 degrees N (K=10, A(9 5)=30 degrees). This pole is close to a palaeomagnetic pole obtained f or granulites from the Jequie complex (Sao Francisco craton) dated by the Ar-40/Ar-39 method as 2.0 Ga, suggesting that both areas belonged to the same tectonic unit at that time. The unmetamorphosed dolerite d ykes (5) displayed multi-component behavior, but a common characterist ic direction could be isolated for four dykes, Dm=262 degrees, Im=-49 degrees (kappa=13, alpha(95)=27 degrees, N=4), which yielded a palaeom agnetic pole located at 72 degrees E, 8 degrees N (K=9; A(95)=33 degre es). However, this pole is different from those obtained for dyke swar ms in Brazil, which are supposedly of comparable age.