New LA-ICP-MS U-Pb Ages, Lu-Hf Systematics and REE Characterization of Zircons from a Granitic Pluton in the Betare Oya Gold District, SE Cameroon

Kevin I. Ateh^1, , Cheo E. Suh^{1, 2}, Elisha M. Shemang³, A. Vishiti^{4, 2}, Enerst Tata¹ and Nelson N. Chombong¹

¹Economic Geology Unit, Department of Geology, University of Buea, P.O. Box 63 Buea, South West Region, Cameroon

²Department of Geology, Mining and Environmental Science, University of Bamenda, P.O. Box 39, Bamenda, North‐West Region, Cameroon

³Department of Earth and Environmental Sciences, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana

⁴Higher Institute of Science, Engineering and Technology, Cameroon Christian University Institute, P.O. Box 5, Bali, North West

Cite this paper:
Kevin I. Ateh, Cheo E. Suh, Elisha M. Shemang, A. Vishiti, Enerst Tata and Nelson N. Chombong. New LA-ICP-MS U-Pb Ages, Lu-Hf Systematics and REE Characterization of Zircons from a Granitic Pluton in the Betare Oya Gold District, SE Cameroon. Journal of Geosciences and Geomatics. 2017; 5(6):267-283. doi: 10.12691/jgg-5-6-2

Abstract

A combination of whole rock geochemistry, Ti-in-zircon thermometry, geochronology and Lu-Hf isotope composition of zircon is employed in this study to depict the source of a granitoid from the Bétaré Oya Gold District, its formation temperature, age of emplacement and evaluate the role of petrogenesis and magmatic evolution of the granitic melt in hydrothermal fluid circulation and primary gold precipitation. In this contribution, zircon grains from a granitic pluton were analyzed for their internal structures using cathodoluminescence imagery and dated by U-Pb technique using LA-ICP-MS. Based on the zircon internal structure, magmatic and metamorphic zircons are distinguished. The granitoid reveal a mean age of 635 Ma similar to those obtained from granitic intrusions along the Central African Shear Zone (CASZ) in Cameroon. This age defines a narrow Pan African emplacement age for the pluton and a unique melting event synchronous with magmatism and deformation. It also depicts a new and older mineralization along the CCSZ at 620-635 Ma for the Bétaré Oya Gold District, SE Cameroon. Ti-in-zircon thermometry indicates their emplacement at a modal temperature range between 625°C and 775°C. Based on whole rock geochemistry alongside trace and REE composition of zircon, the pluton shows a granodioritic to tonalitic affinity. The granitoid is sub alkaline with a high K calc-alkaline affinity, peraluminous and of I-type. REE in zircon patterns display high Ce concentrations, negative Eu anomalies, HREE enrichment, ¹⁷⁶Lu/¹⁷⁷Hf ratio < 0.022 and negative ε_Hf values that range from -5.29 to -0.12. Positive ε_Hf values suggest a mafic crustal contribution. Across the Atlantic into NE Brazil, mineralization is often associated to late Pan African event. We disclose an early mineralization event at 635-620Ma in the region.

Keywords:
Granitoid geochemistry Ti-in-zircon thermometry zircon chemistry geochronology

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