Fe oxide minerals

Scheinost, A.C. Chavernas, A. Barron,V. Tor-rent, J. (1998) Use and limitations of second-derivative diffuse reflectance spectroscopy in the visible to near-infrared range to identify and quantify Fe oxide minerals in soils. Clay Min. Soc. 46 528-536... 

Grossman and Millet (1961) found that the free Fe-oxide concentration in noncalcareous soils was unchanged after contact with this buffer for nine weeks. Other researchers have shown that acetic acid at a concentration of 2.5% and pH 2.5 led to a partial attack of Fe and Mn oxides (Nissenbaum, 1972 Mclaren and Crawford, 1973 Tessier et al., 1979). Tessier et al. (1979) also indicated that this buffer solution at pH 5.0 was minimal in the attack of silicate minerals and sulfide. 

Fe-containing minerals Fe203 hematite oxidation number of Fe = +3... 

We might, for example, study the rate at which the ferrous ion Fe++ oxidizes by reaction with O2 to produce the ferric species Fe+++. Since the reaction occurs within a single phase, it is termed homogeneous. Reactions involving more than one phase (including the reactions by which minerals precipitate and dissolve and those involving a catalyst) are called heterogeneous. 

Observations of the same clay sample in a very finer scale (500 nm) by TEM, may help to identify the potential Fe-oxyhydroxide surfaces attached on a sediment grain (Fig.6). Moreover, abundances of wide spread oxides that may have formed oxide minerals after binding with other elements such as Si, Fe and Al can easily be recognized from the right part of the TEM image (Fig. 7). 

The evolved hardpans (Fig. 1b) are composed by rhythmic alternation of submillimetric goethite-rich (ochreous) and hematite-rich (red) layers. This layering is the result of a complex evolution of the pristine authigenic Fe-oxides and -oxyhydroxides during which the mineral phases are cyclically involved in transformation processes including recrystallization, dissolution and reprecipitation (Carbone etal. 2005). 

Alteration-Mineralization Pattern and Geochemical Characteristics of Samli (Balikesir) Fe-Oxide-Cu-(Au) Deposit, Turkey... 

The Samli Fe-oxide deposit (Balikesir, Western Anatolia-Turkey) is one of the iron-oxide producing mines in western Anatolia. This deposit has long known as a skarn-type Fe-oxide deposit. However, our recent research has revealed that the alteration hosting the iron-oxide mineralization also contains some unusual assemblages, and the sulfide mineralogy with abundant gold content, should not be related to skarn systems. 

Fig. 2. Alteration-mineralization pattern of Samli Fe-oxide deposit, Turkey.

The Na-Ca and K-Fe-(Ca) alteration assemblage hosting iron-oxide, copper and gold mineralization and spatial and temporal relationship between mineralization and alteration, as well as the oxide and sulfide mineralogy at amli (Balikesir) suggest that it has characteristics more akin to Fe-oxide-Cu-Au systems. 

The mixed willemite-smithsonite ore has the simplest mineral composition of the three basic ore types. The silicate, goethite and barite are the principal gangue minerals. Will-emite is a major zinc oxide mineral present as free crystals ranging from 50 to 500 pm in size. Smithsonite is usually stained with Fe-hydroxides and sometimes is associated with silicate as inclusion and/or attachments. The barite content of the ore may vary from several percent up to 12%. A few deposits of this ore type are found in Mexico and South America. 

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