Mineralogical and Technological Features of the Titanium-Bearing Sandstones of the Pizhemskoye Deposit

Unique titanium Deposits of Timan: genesis and age issues

“…There are no other similar deposits in the world. In the classification of titanium ore deposits, one should distinguish a new genetic subtype, pseudorutile-leucoxene-quartz, among metamorphogenic deposits [1,6].…”

“…In the 1950-60 ies, V.A.Kalyuzhny put forward a hypothesis [6][7][8][9]: the source of titanium accumulations in the discovered Yarega deposit of Timan could be the strata of the metamorphosed Riphean shale containing ilmenite and leucoxene, along which weathering crusts were formed. Destruction, rewashing, and redeposition of weathering crust material along shales led to the formation of the Yarega commercial titanium placer.…”

“…The analysis of the mineral composition features of the Timan placers and their bedrock, the comparison of the Yarega placer structure with the Pizhemskoye and Ichetyu placers shows their qualitative analogy [12,17]. They are considered products of a single Devonian crust-and placerforming process in Timan [2,6,7,18]. The age of the Pizhemskoye placer is considered to be Early Devonian (Emsian), which is comparable with the age of Devonian lateritic bauxites of Timan, formed on the weathering crusts of carbonate-argillaceous rocks of the Late Proterozoic basement [12].…”

“…The age of the Pizhemskoye deposit was determined by the Rb-Sr method at 685±30 Ma [23] Ilmenite transforms into leucoxene in shales under supergene conditions This hypothesis has not been proven. Hydrothermal conditions are required for iron removal from ilmenite and impregnation of pores in a sagenite rutile or anatase lattice with quartz with leucoxene formation: the presence of carbon dioxide in the fluid and a relatively high temperature (150-250 С) for the transport of iron bicarbonate and silicic acid (SiO2) in dissolved form [6] Polymorphic transformations of TiO2 occur under supergene conditions: metastable anatase transforms into rutile Researchers of the Timan Riphean shales note that predominantly anatase leucoxene develops after ilmenite in them [8,11,14,16]. In the Yarega and Pizhemskoye deposits, rutile-leucoxene is the most widespread.…”

“…Leucoxene is formed during the hydrothermal alteration of ilmenite in a multi-stage sequential chemical process. The replacement of ilmenite by leucoxene proceeds with the removal of iron due to its interaction with carbon dioxide fluid and the formation of siderite (FeCO3) through the phases: ferruginous rutile (nigrin), pseudorutile, then into leucoxene [3,6].…”