Zircon Trace Element Geochemistry and Ti-in-Zircon Thermometry of the Ngazi-Tina Pan-African Post-Collisional Granitoids, Adamawa Cameroon

In\r\nCameroon, the Ngazi-Tina region belongs to the Adamawa-Yade domain of the\r\nPan-African Central African Fold Belt (CAFB). It is composed of two\r\npetrographic types: quartz-monzonites (majority) and nepheline syenites. Two\r\nmorphological types, prismatic and pyramidal, were recognized in the zircon\r\ngrains samples. These zircon types display internal structures typical of magmatic\r\nzircons. Zircons separated from the Ngazi-Tina samples contain higher\r\nabundances of Hf (close to 8000 ppm) and moderate trace elements (Y, Th, U, Nb,\r\nTa) and REE contents, suggesting a variable degree of magmatic evolution. The\r\nchondrite-normalized REE patterns of zircons are characterized by LREE\r\ndepletion relative to HREE with positive Ce and negative Eu anomalies, typical\r\nof magmatic zircons. The high Hf content together with high Ce/Ce*, Th/U, Zr/Hf\r\nratios suggest magma crystallization under variable oxidation and oxygen\r\nfugacity. The application of Ti-in-zircon thermometer reveals crystallization\r\ntemperatures ranging from 678°C to 811°C and 658°C to 768°C for quartz\r\nmonzonites and nepheline syenites respectively. These features indicate\r\nprobably a partial melting of continental crust as the source of these zircons\r\ngrains and emplacement in the magmatic-arc setting.