Browsing by Author "Getahun, Aberra"

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    The Geology and Geochemistry of the Banded Iron Formation in Chago-Werekalu, Wellega Province
    (Addis Ababa University, 1985-10) Getahun, Aberra; Valera, R. (Prof.)
    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 .