Gamal-Adeen, I., Shahien, M.G., Zayed, A.M., Bakhit, B.R., Sanislav, I.V., and Sharib, A.S.A.A. Abu (2026) Petrogenesis of tonalite-trondhjemite and potassic granite, Geita Greenstone Belt, Tanzania Craton: Implication for crustal evolution during Neoarchean plate tectonic initiation. Geoscience Frontiers, 17. 102279.

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Abstract

Geochemical and zircon isotope data reveal a complex petrogenetic history of the Neoarchean granitoids of the Geita Greenstone Belt (GGB), northern Tanzania Craton. Geochemically, the granitoids are categorized into: (1) tonalite-low-silica trondhjemite; (2) high-silica trondhjemite; (3) transitional granitoids; and (4) potassic granite. Compared to tonalite-low-silica trondhjemite, the high-silica trondhjemite displays significant depletion in HREE and HFSE, and have an exceptional high Sr/Y and LaN/YbN ratios. Both categories display similar LREE and LILE patterns. Transitional granitoids comprise dykes and dyke-like bodies of low-silica trondhjemite and quartz monzonite. Characteristically, they have low LaN/YbN and Sr/Y ratios, and are strongly-enriched in LREE and LILE and less depleted in HREE and HFSE. Potassic granite is represented by small intrusions and dykes that exhibit low LaN/YbN and low to moderate Sr/Y ratios, and are moderately-enriched in LREE, strongly-enriched in LILE, and moderately-depleted in HREE and HFSE. The tonalite and low-silica trondhjemite generated (∼2699–2714 Ma) by partial melting of basaltic rock at amphibolite facies metamorphic condition. The high-silica trondhjemite evolved from fractionation of the tonalitic melt. Lithospheric delamination produced high-K mafic magma that fractionated into the transitional granitoids (∼2660–2683 Ma), and caused partial melting of the tonalite-trondhjemites to generate the potassic granite (∼2646–2685 Ma). Geochemical signature of the tonalite-trondhjemites and potassic granite, as indicated by the negative Nb-Ta-Ti anomalies, and strongly-fractionated REEs, supported with the structural style near and at the contact between the felsic gneisses and the greenstone belt infer generation of the gneisses at a convergent plate boundary. Partial melting at the base of an oceanic plateau or a flat subducting slab has been suggested to interpret the evolution of the northern Tanzania Craton (2700–2650 Ma). A metasomatized mantle was introduced by lower crustal delamination/break-off of the down-going slab.

Item ID:	90967
Item Type:	Article (Research - C1)
ISSN:	2588-9192
Copyright Information:	© 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Date Deposited:	25 Mar 2026 02:02
FoR Codes:	37 EARTH SCIENCES > 3705 Geology > 370503 Igneous and metamorphic petrology @ 45% 37 EARTH SCIENCES > 3705 Geology > 370511 Structural geology and tectonics @ 35% 37 EARTH SCIENCES > 3703 Geochemistry > 370303 Isotope geochemistry @ 20%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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