Mineralogical-geochemical (SIMS method) study of titanite and geochronological (ID-TIMS method) study of garnets from mineral mines of the Southern Urals has been carried out. The mineral associations containing titanite belong to four contrasting types: epidote-titanite-garnet (Akhmatovskaya mine); garnet-titanite-diopside (Akhmatovskaya mine); epidote-titanite-chlorite (Nikolaje-Maksimilianovskaya mine); chlorite-titanite-garnet (Praskovie-Evgenyevskaya mine). Titanite from mineral aggregates of the Akhmatovskaya mine is enriched with LREE and Th, Nikolaje-Maksimilianovskaya mine – with HREE, Hf and Ta, Praskovie-Evgenyevskaya mine – with V, Cr, and Sr. It was found that the distribution of trace and rare-earth elements in titanite is related both to the composition of paragenetic minerals (garnet and epidote, Akhmatovskaya and Nikolaje-Maksimilianovskaya mines) and to the influence of rock-forming minerals of the parent rock – gabbro (plagioclase and pyroxene, Praskovie-Evgenyevskaya mine). The age of garnets (504.1±4 Ma) determined by ID-TIMS method from silicate-carbonate rocks of the Perovskitovaya mine does not agree with the ideas about the formation of the latter as a result of contact metasomatosis synchronous with the introduction of gabbroids or granitoids of the Kusa-Kopan complex (1,390-1,350 Ma), but does not exclude the influence of superimposed contact metasomatosis associated with late endogenous processes.
A study on the U-Pb age of rutile from the Ichetju polymineral occurrence has been done for the first time by LA-ICP-MS and TIMS methods. It was established that rutile originates from various sources with different ages (presumably, ca. 1000, 1660, 1860 and 1980 Ma), but all the rutile types have undergone a common thermal event at ca . 580 Ma. Obtained results are consistent with U-Pb zircon data for the Ichetju occurrence and the Pizhemskoe deposit. According to modern concepts, the closure temperature for the U-Pb system in rutile is higher than 500 ° С, which suggests fairly high-temperature conditions of the rutile hydrothermal transformation during the formation of the deposits in Riphean. Obviously, a placer hypothesis of formation of titanium deposits of the Middle Timan which is supported by a number of researchers does not explain such temperature of rutile alteration.
Results of isotope-geochemical studies by PbLS step-leaching method of cassiterite from greisens located in Logrosán granite massif (Central Iberian Zone, Spain) and apatite from hydrothermal quartz-apatite vein on its exocontact indicate that in both cases a hydrothermal event is recorded in the interval of 114-126 Ma, which has been accompanied by lead supply. Within the limits of estimation error, the same age around 120 Ma corresponds to crystallization of hydrothermal apatite, formation of sticks and micro-inclusions in cassiterite from greisens and is suggested for Au-As-Sb-Pb ore mineralization, which calls for further confirmation. Xenogenous zircon from quartz-apatite vein does not react to this relatively low-temperature hydrothermal event either with building up new generations (sticks, areas of recrystallization) or with rebalancing of U-Pb isotope system. The age of greisen formation has been confirmed to be around 305 Ma by PbLS method on final phases of cassiterite leaching. Earlier it was estimated with 40 Ar/ 39 Ar method on muscovite.
