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Titolo:
Ar-40/Ar-39 thermochronology of the Ethiopian and Yemeni basements: reheating related to the Afar plume?
Autore:
Mock, C; Arnaud, NO; Cantagrel, JM; Yirgu, G;
Indirizzi:
Univ Blaise Pascal, CNRS, UMR 6524, F-63038 Clermont Ferrand, France Univ Blaise Pascal Clermont Ferrand France F-63038 rmont Ferrand, France Univ Addis Ababa, Dept Geol & Geophys, Addis Ababa, Ethiopia Univ Addis Ababa Addis Ababa Ethiopia & Geophys, Addis Ababa, Ethiopia
Titolo Testata:
TECTONOPHYSICS
fascicolo: 4, volume: 314, anno: 1999,
pagine: 351 - 372
SICI:
0040-1951(199912)314:4<351:ATOTEA>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
RED-SEA RIFT; GEOLOGICAL EVOLUTION; ZIRCON AGES; DIFFUSION; VOLCANISM; ARGON; GEOCHRONOLOGY; TEMPERATURE; SOUTHERN; ERITREA;
Keywords:
Ar-40/Ar-39 thermochronology; crustal thermal anomaly; crystalline basement; Ethiopia; mantle plume; Yemen;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
48
Recensione:
Indirizzi per estratti:
Indirizzo: Mock, C Univ London Imperial Coll Sci Technol & Med, TH Huxley Sch Environm Earth Sci & Engn, London SW7 2AZ, England Univ London Imperial Coll Sci Technol & Med London England SW7 2AZ
Citazione:
C. Mock et al., "Ar-40/Ar-39 thermochronology of the Ethiopian and Yemeni basements: reheating related to the Afar plume?", TECTONOPHYS, 314(4), 1999, pp. 351-372

Abstract

In order to constrain the timing of mantle plume-related basement uplift and to discuss the active or passive mechanisms of the continental rifting in the Afar triple junction area, a Ar-40/Ar-39 thermochronological study has been carried out on the Panafrican basement in Ethiopia and Yemen. Muscovites, biotites and K-feldspars from granitoids and high-grade metamorphic samples have been analysed using the Furnace step heating procedure. R-feldspar thermal histories have been numerically modelled, according to the multi-domain Ar diffusion theory. The cooling ages range from 462 Ma to 679 Ma for granitoids and from 495 Ma to 796 Ma for high-grade metamorphic rocks, which suggests that magmatic and metamorphic episodes belong to the same thermotectonic event. A gradual younging of cooling ages from north to south is consistent with the assumption that Panafrican continental collision began in Southern Ethiopia. Age gradients recorded by K-feldspars reflect Ar loss and are most likely related to the Cenozoic reheating of the basement. The estimated mean temperature over the last 50 Ma is between 138 degrees C and 177 degrees C at 2 km below the surface, which suggests a minimum mean thermal gradient of 69-88 degrees C/km. The thermal anomaly is expected to reflect heat conductionfrom the mantle plume, magma underplating and melting of the lower crust, and heat advection related to the magma transfer through the crust. However, due to limited exhumation, it was not possible to constrain the timing ofany mantle plume-related basement uplift. This study suggests that the Ar-40/Ar-39 thermochronology is generally unsuited to monitor denudation of a continental crust in an extensional setting. Furthermore, it highlights some of the thermal effects that continental flood basalts may have on the crust, which can lead to inconsistencies between K-feldspar and mica age data. (C) 1999 Elsevier Science B.V. All rights reserved.

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Documento generato il 16/07/20 alle ore 19:56:34