Iron-oxide ores in the Takab region, North Western Iran
Résumé
The siliceous iron ore deposits in the NW part of Iran (Takab region) are hosted within parametamorphic rocks, and are attributed to Late Proterozoic age..They comprise massive, banded, nodular and disseminated ore types, which are mainly composed of magnetite. Magnetite contains traces of Al. It is variously hematized. Hematite shows higher Al, Si and Ca contents than the magnetite. The iron oxides contain inclusions of zircon, apatite, uraninite, Mncarbonate and euhedral monazite. Later hydrothermal solutions precipitated goethite surrounding the magnetite-hematite-maghemite grains and replacing hematite. Barite occurs in fractures of iron oxides, Mn-Ba-Pb oxy-hydroxides and scheelite occur interstitial to iron oxides. The ∂ 56 Fe values observed for magnetite decrease from disseminated to nodular iron ore (averages: +1.3, +0.4 and-0.4 ‰ (± 0.2 ‰), respectively). Iron isotopes of hematite in disseminated and layered ore show higher ∂ 56 Fe values than those of magnetite, in the range of +2 to +4 ‰ (± 0.2 ‰). Volcano sedimentary primary processes are thus superposed by a secondary (magmatic?) hydrothermal process.
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