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Titolo:
The Cameroon Volcanic Line revisited: Petrogenesis of continental basalticmagmas from lithospheric and asthenospheric mantle sources
Autore:
Marzoli, A; Piccirillo, EM; Renne, PR; Bellieni, G; Iacumin, M; Nyobe, JB; Tongwa, AT;
Indirizzi:
Univ Trieste, Dipartimento Sci Terra, I-34127 Trieste, Italy Univ TriesteTrieste Italy I-34127 nto Sci Terra, I-34127 Trieste, Italy Berkeley Geochronol Ctr, Berkeley, CA 94709 USA Berkeley Geochronol Ctr Berkeley CA USA 94709 Ctr, Berkeley, CA 94709 USA Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 USA Univ Calif Berkeley Berkeley CA USA 94720 Geophys, Berkeley, CA 94720 USA Univ Padua, Dipartimento Mineral & Petrol, I-35137 Padua, Italy Univ Padua Padua Italy I-35137 to Mineral & Petrol, I-35137 Padua, Italy Minist Rech Sci Technol, Yaounde, Cameroon Minist Rech Sci Technol Yaounde Cameroon Sci Technol, Yaounde, Cameroon Univ Tokyo, Earthquake Chem Lab, Bunkyo Ku, Tokyo 113, Japan Univ Tokyo Tokyo Japan 113 thquake Chem Lab, Bunkyo Ku, Tokyo 113, Japan
Titolo Testata:
JOURNAL OF PETROLOGY
fascicolo: 1, volume: 41, anno: 2000,
pagine: 87 - 109
SICI:
0022-3530(200001)41:1<87:TCVLRP>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
EARLY CENOZOIC MAGMATISM; AFRICAN RIFT SYSTEM; TRACE-ELEMENT; BENUE TROUGH; WEST-AFRICA; ORIGIN; SR; GRAVITY; SERIES; PLUME;
Keywords:
Cameroon Line basalts; Ar-40/Ar-39 geochronology; lithospheric and asthenospheric mantle source; hotspot;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
71
Recensione:
Indirizzi per estratti:
Indirizzo: Marzoli, A Univ Geneva, Sect Sci Terre, 13 Rue Maraichers, CH-1211 Geneva 4, Switzerland Univ Geneva 13 Rue Maraichers Geneva Switzerland 4 Switzerland
Citazione:
A. Marzoli et al., "The Cameroon Volcanic Line revisited: Petrogenesis of continental basalticmagmas from lithospheric and asthenospheric mantle sources", J PETROLOGY, 41(1), 2000, pp. 87-109

Abstract

The volcanic activity of Mts Bambouto and Oku (Western Highlands) and of the Ngaoundere Plateau, in the continental sector of the Cameroon Volcanic Line, Equatorial West Africa, ranges in age from Oligocene to Recent. It is characterized by basaltic, alkali basaltic mid transitional basaltic series. Mineral chemistry, major and trace element bulk-rock compositions, and geochemical modelling suggest that the magmatic series evolved mainly at lore, pressure (2-4 kbar) through fractional crystallization of clinopyroxene and olivine +/- magnetite, at moderately hydrated (H2O = 0.5-1 wt %) and QFM(quartz-fayalite-magnetite) to QFM + 1 fO(2) conditions. Basalts from Ngaoundere (Miocene to Quaternary) and from the early activity (31-14 Ma) of the Western Highlands have incompatible trace element and Sr-Nd isotopic compositions similar to those of oceanic Cameroon Line basalts, pointing to a similar asthenospheric mantle source. By contrast, the late (15-4 Ma) Western Highlands basanites and alkali basalts have anomalously high concentrations of Sr, Ba and P, and low concentrations of Zr; which are exclusive features of continental Cameroon basalts.;The genesis of these latter magmas is consistent with derivation from an incompatible element enriched, amphibole-bearing lithosheric mantle source. Western Highlands basalts show a continuous spectrum from high to low Sr-Ba-P compositions, and may result from variable amounts of mixing between melts derived from an anhydrous lherzolitesource (asthenospheric component) and melts from an amphibole-bearing peridotite source (lithospheric HSr component). New Ar-40/Ar-39 ages for Mts Oku and Bambouto basalts, combined with previous Ar-40/Ar-39 and K/Ar ages ofbasaltic and silicic volcanics and with volcanics, and with volcanic stratigraphy, suggest a NE-SW younging of the Peak magmatic activity in the Western Highlands. This SW younging trend extending from the Oligocene volcanism in northern Cameroon (e.g, Mt Oku) to the still active Mt Cameroon, suggests that the African plate is moving above a deep-seated mantle thermal anomaly. However the age and location of the Ngaoundere volcanism does not conform to the NE-SW younging trend, implying that the continental sector of the Cameroon Volcanic Line cannot be easily interpreted as the surface expression of a single hotspot system.

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Documento generato il 06/04/20 alle ore 20:11:35