Kamaunji, Vandi Dlama, Ahmed, Hafizullah Abba, Wang, Lian-Xun, Sanislav, Ioan, Girei, Musa Bala, Zhu, Yu-Xiang, Liang, Xin-xin, Chen, Xin, and Sami, Mabrouk (2026) Progressive mantle melting and crust–mantle–fluid hybridization in fluorite-bearing Sn–Nb ± Mo-rich alkaline granites of the Jos Plateau, central Nigeria. Ore Geology Reviews, 195. 107405.

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Abstract

Alkaline granites of the Jos Plateau Tin Belt (central Nigeria) host Sn-Nb-Mo mineralization. However, their petrogenesis, metal enrichment, and tectono-geodynamic evolution remain poorly constrained. This study integrates whole-rock geochemistry and Sr-Nd isotopes, amphibole-fluorite chemistry, and zircon U-Pb geochronology from the Buji, Jos-Bukuru (JBK), and Kigom (KGM) complexes. Zircon U-Pb ages reveal a north-to-south younging trend from Buji (∼179 Ma) through JBK (∼168 Ma) to KGM (∼166 Ma). Buji barren granites exhibit the most negative εNd(t) (–4.4 to –4.2), least radiogenic 87Sr/86Sr(i) (0.7065–0.7066), and highest Neodymium Crustal Index (NCI = 0.31), indicating an enriched mantle source with strong crustal input. JBK Sn–Nb biotite-amphibole granites show intermediate εNd(t) (–3.3 to –3.0), NCI (0.25), and moderately radiogenic 87Sr/86Sr(i) (0.7066–0.7173), suggesting an enriched mantle source with moderate crustal input and selective hydrothermal overprint. KGM Mo–Nb arfvedsonite–riebeckite granites exhibit near-chondritic εNd(t) (–1.1 to –0.4), lowest NCI (0.25), and most radiogenic 87Sr/86Sr(i)r (0.7139–0.7206), reflecting extreme fluid-mediated metasomatism on a mantle-dominated magma. Decoupled fO2 distinguishes oxidized JBK Ca-amphiboles from reduced KGM Na-amphiboles hosting oxidized zircons. Mass balance modeling indicates ∼40–50 vol% feldspar-dominated fractional crystallization coupled with ∼30–40 vol% upper crustal assimilation. JBK granites show Sn-Nb enrichment (4–126 ppm; 37–910 ppm), while KGM granites exhibit high Nb with extreme Zn-Pb-Cu (≤1326, 1054, 845 ppm), consistent with Mo-enriched systems. Fluorite compositions (F = 52–56 wt%) record F-rich reducing fluids that promoted HFSE-REE-Sn-Nb-Mo mobility. A four-stage model explains Sn-Nb-Mo enrichment in JBK and KGM: (I) magmatic enrichment; (II) magmatic-hydrothermal transition; (III) hydrothermal veining and stockworks formation; (IV) supergene placer formation. Transtension triggered adiabatic melting of metasomatized mantle, generating alkaline magmas that ascended along shear zones to form shallowly emplaced (2.6–8.7 km) anorogenic alkaline complexes. Fertile global analogues share this convergence of transtensional shearing, crustal assimilation, and F-rich fluid flux.

Item ID:	92546
Item Type:	Article (Research - C1)
ISSN:	1872-7360
Copyright Information:	© 2026 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
Date Deposited:	30 Jun 2026 23:50
FoR Codes:	37 EARTH SCIENCES > 3705 Geology > 370503 Igneous and metamorphic petrology @ 40% 37 EARTH SCIENCES > 3705 Geology > 370508 Resource geoscience @ 40% 37 EARTH SCIENCES > 3703 Geochemistry > 370301 Exploration geochemistry @ 20%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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