As a result, the feldspar may be cloudy and/or replaced locally by white mica, the biotite may be chloritized and the opaque oxide partially replaced by leucoxene
. In rare cases (Fig.
"Titanium dioxide" is the generic term for ilmenite, leucoxene
, natural and synthetic rutile, as well as titanium slag.
Essence of the liquid-phase process consists in performance of electrochemical decomposition of mixed titanium oxides, such as molten titanium slag, ilmenite, perovskite, leucoxene
, titanite, natural and synthetic rutile, which are in liquid state.
Titanite and other Ti-phases: Titanite, ilmenite, and rutile form large aggregates (leucoxene
) demonstrating that these aggregates are alteration products of former magmatic minerals probably ilmenite.
The replacement of ilmenite by leucoxene
during diagenesis has been known for a long time, but is often ascribed to different stages from early diagenesis in mildly reducing and neutral-acid tropical conditions (Weibel 2003) to late diagenesis (Al-Juboury et al.
Hydrothermal alteration of biotite is associated with the formation of hydrated titanium oxides (leucoxene
?), resulting from the liberation of titanium bounded in the original magmatic biotite.
Ilmenite, variably altered to leucoxene
, is the sole oxide phase in all samples (SEM data not shown).
Apatite Augite Biotite Calcite Chlorite Chromite Fluorite Galena Hematite Ilmenite Leucoxene
Limonite Magnetite Muscovite Olivine Orthopyroxene Pervoskite Phlogopite Pyrite Quartz Serpentine Sphalerite Titanite
These minerals are accompanied by plenty of secondary amphibole chlorite epidote (one or more of the three phases abundant in some rocks) titanite and leucoxene
. Primary amphibole is brown and altered to chlorite with or without epidote a nd secondary amphibole that is bluish green actinolite.
The combined contiguous Cyclone deposit is of global significance containing 2.4 mT of Zircon and 1mT of Rutile and Leucoxene
(0.75% HM cut-off).
Different kinds of mineral alterations taking place in the Devonian sequence during post-sedimentary processes have been studied: formation of authigenic leucoxene
, anatase, apatite, pyrite, and goethite, dissolution of garnet, staurolite and kyanite, replacement of magnetite, amphiboles, titanium-bearing minerals and feldspar, formation of authigenic overgrowths of detrital feldspar grains (Kleesment & Paap 1978; Kleesment 1984, 1998).