Precambrian rocks from southern Ethiopia; petrology, geochemistry and their interaction with the Recent volcanism from the Ethiopian Rift valley

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Authors:Peccerillo, A.; Mandefro, B.; Solomon, G.; Hambisa, G.; Bedru, H.; Tesfaye, K.
Author Affiliations:Primary:
Universita di Perugia, Dipt. Sci. Terra, Perugia, Italy
Volume Title:Neues Jahrbuch für Mineralogie. Abhandlungen
Source:Neues Jahrbuch für Mineralogie. Abhandlungen, 173(3), p.237-262. Publisher: E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Federal Republic of Germany. ISSN: 0077-7757
Publication Date:1998
Note:In English. 33 refs.; illus., incl. 1 table, geol. sketch map
Summary:The Precambrian basement rocks from S Ethiopia are medium- to high-grade metamorphic rocks with pre-, syn- and post-metamorphic granitic rocks. They show a wide range of major and trace element abundances and present-day Sr isotope signature, in agreement with their variable petrological nature. The metavolcanic rocks have compositions akin to those of island arc magmas, testifying to an emplacement along an active converging plate boundary. The granitic rocks appear to have been emplaced both during plate convergence and in a post-collisional environment. The two classes of granitic rocks have different petrological and geochemical characteristics reflecting different mechanisms of genesis in the two distinct tectonic environments. The geochemical data suggest that the basement rocks were derived from mafic or intermediate parents by fractional crystallization processes with a moderate amount of crustal assimilation. The data are also interpreted as indicating an interaction between basaltic magmas and the Precambrian basement rocks, generating important modifications in the LILE/HFSE ratios. The composition of basaltic magmas was also modified by mixing with associated acid liquids. [R.A.H.]
Sections:Petrology
Subsections:General
Subjects:Alkaline earth metals; Basement; Cenozoic; Chemical composition; Continental crust; Correlation; Crust; Holocene; Igneous rocks; Incompatible elements; Isotopes; Major elements; Metals; Metamorphic rocks; Precambrian; Quaternary; Rare earths; Rift zones; Strontium; Trace elements; Volcanic rocks; Volcanism; Africa; East Africa; East African Rift; Ethiopia; Ethiopian Rift; Southern Ethiopia
Coordinates:N032500 N110000 E0480000 E0330000
Abstract Numbers:99M/806
Record ID:2005040198
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe
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