Trace-Element Composition of Titanium Phases of Leucoxene–Quartz Ores from the Yarega Oil–Titanium Deposit, South Timan

Abstract

The distribution of trace elements (secondary ion mass spectrometry method) in rutile from the Yarega oil–titanium deposit was studied for the first time. A significant difference in the composition in the series leucoxene–rutile leucoxene (rutile with microscopic quartz inclusions)–rutile (recrystallized crystals) was established. Leucoxene is characterized by increased contents of the following elements (average values): Al (20 650 ppm), Fe (4833 ppm), Nb (2229 ppm), Zr (1273 ppm), Cr (436 ppm), V (1191 ppm), Sn (230 ppm), W (130 ppm), and Th (125 ppm). As leucoxene is converted to rutile leucoxene, represented by rutile with numerous quartz inclusions, a decrease in the contents of almost all trace elements, with the exception of V, was recorded. The Fe content decreases to 1892 ppm, that of Al to 1468 ppm, of Nb to 605 ppm, of Zr to 409 ppm, of Sn to 46 ppm, and of Cr to 181 ppm. A separate group is represented by rutile grains, in which one can observe a combination of rutile with numerous inclusions of quartz and “pure” rutile (recrystallized rutile with inclusions). The main trend in the change in the composition of rutile is a significant decrease in contents of a number of trace elements, compared with leucoxene and rutile leucoxene: the average V content is 71 ppm in rutile, 2.5 ppm in Sn, 144 ppm in Zr, 2.4 ppm in Hf, 52 ppm in Cr, and 677 ppm in Fe. There is also a decrease in Sb, Th, and U contents to about 1 ppm. There is a tendency toward accumulation of Nb when comparing rutile leucoxene and “pure” rutile. One can assume that the purification of rutile from admixtures as rutile leucoxene is transformed into sites of “pure” rutile (anatase?), up to the formation of single idiomorphic rutile crystals is a consequence of the hydrothermal process previously recorded in the geochemical characteristics of zircons from the Yarega deposit.