TITLE:
Zircon Trace Element Geochemistry and Ti-in-Zircon Thermometry of the Ngazi-Tina Pan-African Post-Collisional Granitoids, Adamawa Cameroon
AUTHORS:
Alexis Hamdja Ngoniri, Habib Dadjo Djomo, Timoleon Ngnotue, Patrick Ayonta Kenne, Ghislain Ngassam Mbianya, Sylvestre Ganno, Jean Paul Nzenti
KEYWORDS:
Granitoids, Zircon Geochemistry, Ti-in-Zircon Thermometer, Continental Crust, Ngazi-Tina, Adamawa-Yade Cameroun
JOURNAL NAME:
International Journal of Geosciences,
Vol.12 No.4,
April
15,
2021
ABSTRACT: In
Cameroon, the Ngazi-Tina region belongs to the Adamawa-Yade domain of the
Pan-African Central African Fold Belt (CAFB). It is composed of two
petrographic types: quartz-monzonites (majority) and nepheline syenites. Two
morphological types, prismatic and pyramidal, were recognized in the zircon
grains samples. These zircon types display internal structures typical of magmatic
zircons. Zircons separated from the Ngazi-Tina samples contain higher
abundances of Hf (close to 8000 ppm) and moderate trace elements (Y, Th, U, Nb,
Ta) and REE contents, suggesting a variable degree of magmatic evolution. The
chondrite-normalized REE patterns of zircons are characterized by LREE
depletion relative to HREE with positive Ce and negative Eu anomalies, typical
of magmatic zircons. The high Hf content together with high Ce/Ce*, Th/U, Zr/Hf
ratios suggest magma crystallization under variable oxidation and oxygen
fugacity. The application of Ti-in-zircon thermometer reveals crystallization
temperatures ranging from 678°C to 811°C and 658°C to 768°C for quartz
monzonites and nepheline syenites respectively. These features indicate
probably a partial melting of continental crust as the source of these zircons
grains and emplacement in the magmatic-arc setting.