Rutile From the Zelenyi Yar Titanium-Zirconium Placer and Its Possible Primary Sources

Abstract

Rutile of the Neogene-aged Zelenyi Yar titanium-zirconium placer was studied. The average size of the rutile grains is 0.25 mm that are elliptical, rounded, short-prismatic, isometric, and elongated-prismatic crystals in shape. On the surface of the crystals, elements of physical abrasion of varying degrees, as well as chemical dissolution, are observed. The color of the rutile crystals ranges from black to yellow with black and brown being the most common. A relationship between the concentration of various impurity elements and their variations with the color of the crystals is present. The highest average content of impurity elements is recorded in green rutiles and the lowest in light brown crystals. About 61% of the rutiles contain V2O5 (30% of all crystals; average content 1.28%), Nb2O5 (25%; 1.38%), FeO (24%; 1.10%), WO3 (9%; 0.91%), ZrO2 (9%; 0.85%), Al2O3 (2%; 0.70%), Cr2O3 (5%; 0.60%), SiO2 (7%; 0.57%). The temperature of primary rutile crystallization was calculated using Zr-in-rutile thermometry and corresponds to granulite and eclogite metamorphic conditions. Cluster analysis of 284 microprobe analyses of rutile allows at least five groups of crystals to be identified. According to the chemical composition of various rutiles, it can be concluded that they originated from metapelitic rocks, enderbites, and eclogite-like rocks located in the Dniester-Bug megablock of the Ukrainian Shield.