The Geology and Geochemistry of the Banded Iron Formation in Chago-werekalu, Wellega Province
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Date
1985-10
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Addis Ababa University
Abstract
The r ocks of the stulied area form nart of the ~ o llepa Birbir
proup of the uppe r c08plex and consist of a series of me t ased i me ntary
and plutonic proterozoic rocks. The winiera lo~ical assembl age
indicate tha t t he metamorphism is of the r r eenshist facies.
The variation diagram cons tructed for the va rious plut onic
re e ks stronpl y supvest coma pmatic oripin by crysta l f rac ti ona ti on .
Major and trace element ana lyses of re ore sentative samples of
the Chago iron formation ? t he plutonic ann. YOllnp:er e f f us i ve rocks
are presented . The Chago iron f ormation can be c las s i f i ed as
nre cambrian banded iron for mation and is in J11any r espects siJrii l ar
to the oxide fa cies iron format i on of Lake Superior t ype. The
Cha go iron fo r mation consis t s only of Iron oxides and mi nor amoun t
of sil i ca with total absence of iron silica t e, s ulfide and carbonate
minerals.
Trace element pe ochemis try sUPRests that t he iron f orma ti on
was chemic ally prec i pitated as ox ida t e s ediments in which the
principal i ron mineral, ma gne tite 1 was formed at low te mpera ture
in a s ~lallow nea r shore environment .
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Geology