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Biotite -and amphibole -bearing monzogranite, quartz monzonite, and tonalite intrude into the biotite granitoids and biotite -hornblende gneisses of the Pan -African belt in the Nkambe area, northwestern Cameroon. The common mineral assemblage in these rocks is amphibole + biotite + plagioclase + K -feldspar + quartz + zircon + apatite; however, their modal composition varies in each rock -type. Most amphibole grains are relatively homogeneous and locally have slightly Al -rich rims. They are mostly ferro -edenite or ferropargasite, and in a tonalite sample, there is magnesiohornblende with less aluminous and more magnesian composition. The amphibole + biotite + plagioclase + K -feldspar + quartz assemblage was affected by several pressure -sensitive and H 2 O -free reactions. The ferro -edenite -and/or ferropargasite -bearing samples show similar pressure -temperature (P -T) ranges of 0.46 -0.50 GPa/655 -690 °C and 0.43 -0.69 GPa/675 -705 °C. In contrast, the magnesiohornblendebearing tonalite records lower temperature conditions of 0.77 GPa/610 °C, which is attributed to subsolidus reequilibration during cooling. The P -T estimates for the biotite -amphibole granitoids in this and previous studies suggest that relatively high -pressure granitoids are widespread in the Nkambe area.

Hydroxylian pseudorutile in an adamellite from Cameroon has been identified using EPMA, FT-IR and single-crystal XRD analysis. TiO 2 and Fe 2 O 3 contents range between 60.6 and 67.9 wt.% and 22.2 and 36.5 wt.%, respectively, and totals vary from 90.1 to 98.1 wt.%. The SiO 2 (0.03 -1.40 wt.%), Al 2 O 3 (0.02 -0.68 wt.%) and CaO (0.03 -0.44 wt.%) contents increase systematically and MnO (0.04 -0.69 wt.%) decreases slightly with decreasing Fe 3+ /Ti values. The MgO content is <0.06 wt.%. H 2 O contents (1.3 -7.5 wt.%) are greater in parts of crystals with lower Fe 3+ /Ti, suggesting solid solution between the end-members Fe 3+ 2 Ti 3 O 9 and Fe 3+ Ti 3 O 6 (OH) 3 . The lattice parameters are a = 2.85 A Ê and c = 4.57 A Ê with hexagonal symmetry and point group 6/mmm.

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