Generation of early Archaean felsic greenstone volcanic rocks through crustal melting in the Kaapvaal, craton, southern Africa

摘要: Abstract High-potassium felsic volcanic rocks interlayered with basalt and komatiite in early Archaean greenstone sequences the Barberton Greenstone Belt of South Africa Swaziland, previously considered to be derived from melting mafic precursors, are shown result significantly older crust. This is documented by a combination SHRIMP zircon dating Hf-in-zircon whole-rock Lu–Hf Sm–Nd isotopic data. Zircons oldest unit, 3.53 Ga Theespruit Formation, yielded predominantly negative e Hf ( t ) -values, whereas - Nd -data slightly positive. Similar results were obtained for ca. 3.45 Hoeggenoog Noisy Formations higher up stratigraphy. These data rule out derivation units basaltic precursors favor crustal source, most likely TTG composition. The not compatible an entirely oceanic origin pre-greenstone basement beneath rocks. Crustal Eo- Paleoarchaean lower crust probably generated have been responsible gradual stabilization Kaapvaal craton.