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 stuJied area form nart of the ~ ol lera Birbir
group of the upper complex and cons ist of a s eries of metasedimentary
and plutonic proterozoic rocks. The l1'inieralo£"ical assemblage
indicate th a t the metamorphism is of the rreenshist facies.
The variation diagram constructed for the various plutonic
rocks strongly suppest comagmatic origin by crystal f ractionation.
Ma jor and trace element analyses of reDresentative samples of
the Chago iron for mation, t he plutonic an~ YOllnper effusive rocks
are present ed. TIle Chago iron formation can be classified as
nrecambrian banded iron formation and is in l1'any r espects similar
to the oxide facies iron formation of Lake Superior t ype. The
Cha go iron formation consists only of iron oxides and mi nor aIT'ount
of si l ica with total absence of iron silicate, sulfide and carbon ate
minerals.
Trace element peochemistry suppests that the iron f ormation
was chemically precipitated as oxidate sediments in wh i ch the
principal iron mineral, ma gne tite, was formed at low temperature
in a shal low near shore environment .
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Keywords
Banded ,Geology ,Geochemistry