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Titolo:
MAGMATISM IN THE GREGORY RIFT, EAST-AFRICA - EVIDENCE FOR MELT GENERATION BY A PLUME
Autore:
LATIN D; NORRY MJ; TARZEY RJE;
Indirizzi:
BP EXPLORAT CO,4-5 LONG WALK,STOCKLEY PK UXBRIDGE UB11 1BP ENGLAND UNIV CAMBRIDGE,BULLARD LABS CAMBRIDGE CB3 0EZ ENGLAND UNIV LEICESTER,DEPT EARTH SCI LEICESTER LE1 7RH ENGLAND
Titolo Testata:
Journal of Petrology
fascicolo: 5, volume: 34, anno: 1993,
pagine: 1007 - 1027
SICI:
0022-3530(1993)34:5<1007:MITGRE>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
KENYA RIFT; UPPER MANTLE; FLOOD BASALTS; THICKNESS; GEOCHEMISTRY; VOLCANICS; EVOLUTION; BENEATH; ICELAND; CRUST;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
68
Recensione:
Indirizzi per estratti:
Citazione:
D. Latin et al., "MAGMATISM IN THE GREGORY RIFT, EAST-AFRICA - EVIDENCE FOR MELT GENERATION BY A PLUME", Journal of Petrology, 34(5), 1993, pp. 1007-1027

Abstract

The volume and composition of volcanic rocks associated with the Gregory rift are interpreted in the light of inversions performed on the REE concentrations of the most magnesian basalts. When the estimated volume of salic rock (approximately 88 000 km3) is converted into basalt(approximately 792 000 km3) the total volume of basaltic melt generated over the last 30 My is at least 924 000 km3, corresponding to an average rate of melt production of approximately 0.03 km3/yr and an average melt thickness of between 7 and 26 km everywhere beneath the rift. The mean compositions of the basaltic magmas erupted within the rift and on the rift flanks during the Upper Oligocene and Miocene, the Pliocene, and the Quaternary are taken to be representative of the average compositions of melts produced by fractional melting in the asthenospheric mantle. When the REE concentrations of the observed average compositions are inverted they suggest that much of the melt was producedin the depth and temperature range of the transition from garnet to spinel peridotite. For a mantle potential temperature of approximately 1500-degrees-C the top of the melting region predicted from the inversions is at approximately 70 km beneath the rift axis and approximately80 km beneath the rift flanks. Within the rift zone the predicted thickness of melt increases from the Upper Oligocene and Miocene to the Pliocene and is always greater than that predicted for the rift flanks,and the time-averaged thickness of melt predicted is 0.5 km. To generate the observed volume of melt the asthenospheric mantle must continually upwell through the melting region (extending from 70 to 150 km) with a vertical velocity of between 40 and 140 mm/yr. The results suggest that, volumetrically and compositionally, magmatic activity associated with the Gregory rift is quantitatively consistent with a model ofa mantle plume upwelling beneath thinned continental lithosphere. Predictions made by such a model are in broad agreement with geophysical observations.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 21/09/20 alle ore 07:57:35