In this paper, we present a comprehensive review of literature data (~2600 analyses), including major and trace elements and Sr-Nd isotopes, on continental fl ood basalts from the Ethiopia-Yemen, Deccan (India), and Karoo (southern Africa) volcanic provinces in order to evaluate whether they can be attributable to similar tectonomagmatic processes that occurred during the past 200 m.y. in central Gondwana. Results indicate that the three investigated provinces share fundamental features, such as the following: (1) Major and trace element compositions are closely comparable, in terms of parental magmas and fractionation trends, for the various continental flood basalt suites recognized in the provinces, namely, low Ti (LT, TiO2 0.5–3 wt%), high Ti (HT1, TiO2 1–4 wt%), and very high Ti (HT2, TiO2 2.5–7 wt%). (2) There is a clear zonal arrangement of continental fl ood basalts, with the hottest (potential temperature Tp up to ~1600 °C) and deepest (up to 5 GPa) HT picrite-basalt magmas in the central area and cooler and shallower LT basalts (Tp down to 1450 °C, pressure [P] = 2–3 GPa) at the periphery, corresponding to a maximum thermal difference of 60–110 °C from the inner to the outer zones in each province. This conforms to continental fl ood basalt generation from a lenticular melting region, plausibly refl ecting thermo-compositionally zoned plume heads, with maximum excess temperature Tex = 250–300 °C with respect to the notional mid-ocean-ridge basalt (MORB) ambient mantle. (3) The central area of all provinces is characterized by the nearly exclusive occurrence of superheated HT picrite-basalt (and nearly coeval alkaline- carbonatite complexes) at the intersection of multiple extensional lineaments (faulting, rifting, and dike swarms), refl ecting the focus of the tectonomagmatic activities. (4) The common occurrence of rhyolitic differentiates at the top of picrite-basalt lavas (e.g., Lalibela suite, northern Ethiopia; Pavagadh suite, Deccan; Lebombo suite, African Karoo) has to be considered an effect of the inversion of the stress regime, from generalized regional extension (continental fl ood basalt eruption) to localized continental rifting accompanying magma differentiation to rhyolites; activity at some of these rift and dike systems, e.g., the Western Afar Escarpment, the coastal dikes of Western Deccan, and the Rooi Rand dikes, was protracted until continental breakup and the opening of new oceanic branches of the Red Sea, the central Indian Ocean, and southwestern Indian Ocean, respectively. (5) The Sr-Nd isotope distributions of continental fl ood basalts show HT picrite-basalt magmas mostly recording mantle values unaffected by continental lithospheric signatures, and LT basalts mainly refl ecting either mixed source components located at the lithosphere-asthenosphere transition or continental crust contamination, particularly in the Karoo and Deccan provinces. Overall, results from this review provide compelling evidence that hot mantle plumes impinged diachronously on the central Gondwana lithosphere, causing similar tectonomagmatic events and continental fl ood basalt zonal arrangements that refl ect a common thermocompositional zonation of the plume head in the three investigated provinces.
Scheda prodotto non validato
Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo
|Titolo:||Comparison among Ethiopia-Yemen, Deccan, and Karoo continental flood basalts of central Gondwana: Insights on lithosphere versus asthenosphere contributions in compositionally zoned magmatic provinces|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||02.1 Contributo in volume (Capitolo, articolo)|