Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

The petrogenesis of the Edough amphibolites, Annabar, NE Algeria; two unrelated basic magmas and the lherzolite-harzburgite residue of a possible magma source.

Ahmed-Said, Y. and Leake, B. E. 1997. The petrogenesis of the Edough amphibolites, Annabar, NE Algeria; two unrelated basic magmas and the lherzolite-harzburgite residue of a possible magma source. Mineralogy and Petrology 59 , pp. 207-237. 10.1007/BF01161860

Full text not available from this repository.

Abstract

The conditions of metamorphism and petrogenesis of Kef Lakhal amphibolites and associated amphibolite and olivine-rich lenses are discussed. The Kef Lakhal amphibolites contain plagioclase ranging from An85 and An12 and Ca-poor normally zoned garnet (< 9 wt% CaO) and were last metamorphosed to upper amphibolite facies. The amphibolite lenses invariably contain calcic plagioclase (An97-78) and Ca-rich (up to 14 wt% CaO) doubly zoned garnets. Based on garnet zoning, it is found that the lenses experienced the three metamorphisms recorded elsewhere in the massif whereas the main amphibolites suffered only the last two metamorphisms, the last of which reached conditions of about T= 700 ± 80 °C and P= 8–10 Kb. This agrees with two unrelated igneous suites and is supported by the chemistry of the rocks and quantitative modelling. The Kef Lakhal amphibolites were formed by olivine-dominated fractional crystallisation processes from melts derived by partial melting of a homogeneous source and preserve MORB affinities. The amphibolite lenses were also evolved by fractional processes dominated by olivine but from a less homogeneous source and have island arc characteristics. The associated olivine-rich lenses are lherzolite-harzburgite mantle residua which suffered up to 35% melting. Bearing in mind the lack of isotopic and structural information, the data presented in this study indicate that fractional crystallisation of liquids produced through non model melting of these residua does not reproduce the composition of either of the amphibolites. Fractionation of melts similar to those derived from the Ronda peridotites yield compositions similar to the Edough amphibolites.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Publisher: Springer Verlag (Germany)
ISSN: 0930-0708
Date of Acceptance: 2 October 1996
Last Modified: 08 Jul 2020 14:15
URI: http://orca-mwe.cf.ac.uk/id/eprint/133065

Actions (repository staff only)

Edit Item Edit Item