Origin of Massive Iron Oxide Deposits in Silicic Igneous Rocks

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9405050 Kesler This is a preliminary study of the Vergenoeg iron-fluorite deposit in South Africa. Vergenoeg consists if fluorite and iron oxides and is closely associated with silicic extrusive rocks. Research a Vergenoeg will attempt to answer two questions. The first question involves the nature of fluid phases present during formation of the deposits, which should clarify the relation between silicate and iron oxide magmas and the possible role of volatile phases(s) in causing the heavy iron oxide phase to extrude. The second question is why the immiscible iron oxide phase separated from the silicate magma, if indeed it did. We plan to map these rocks, verify the stratigraphic position of iron ore in the sequence and then look for any changes in the oxygen isotope composition of the silicic rocks, which might relate to introduction of ground (e.g. meteoric) water.