Age of lamprophyres of the Middle Timan: First Rb-Sr data

Unique titanium Deposits of Timan: genesis and age issues

“…The bowl-shaped structures of the titaniferous strata occurrence are also visible in the geological sections [1]. It is assumed that the bedrock source of titanium and many other indicator minerals were dikes of lamprophyres (spessartites and comptonites), whose fields are widespread in the neighbouring ridge (Chetlassky Kamen) [16,34] and, presumably, lie in depth the Volsk-Vym ridge as well. The evidence is provided by the typomorphic features of indicator minerals in the Pizhemskoye titanium deposit [3] and the Ichetyu polymineral ore occurrence (Mg, Mn, V, Nb, Cr-ilmenite, Zn-chromium spinel [33], rare garnet with a majorite component, a indicator mineral of diamond [16], biotite, amphiboles, etc.…”

“…The driving factor of the fluidization process could be metamorphic waters, which met with intruding hot magmas or lamprophyres, which intruded at the age boundary of 600-800 Ma (this is exactly the age of the Chetlassky Kamen lamprophyres) [34]. The superheated fluid destroyed and disintegrated lamprophyres with the formation of quartz, kaolinite, hydromica, titanium ore minerals, etc.…”

“…It remains to assume only a deep source of ore material for the sites under consideration. In terms of typomorphic features, many minerals are close to the rock-forming and accessory minerals of lamprophyres [3,16]; therefore, it is assumed that one of the bedrock sources of both sites was precisely lamprophyres, which form large dike fields with an area of several tens of square km in the Chetlassky Kamen ridge [16,34]. It is likely that similar large dike fields of lamprophyres are deep under the Pizhemskoye deposit, and they could be the bedrock source of these sites.…”

“…The most famous and studied in the Chetlassky Kamen are the Kosyu, Bobrovskoe, and Oktyabrskoe dike fields of lamprophyres. According to Rb-Sr isotopic data, a large set of lamprophyre samples forms an isochronewith Neoproterozoic age of 819 ± 19 Ma [34]. There are also lamprophyre dikes about 606 ± 10 Ma in age, coeval with the Chetlassky carbonatites.…”

Novobobrovsky ore field (Chetlass Stone, Middle Thyman): Ar-Ar data

“…Возраст магматических образований оценивается K-Ar (вал) и Ar-Ar (по флогопиту) методами на уровне 600 млн лет [Андреичев, Степаненко, 1983;Степаненко, 2015]. Есть точка зрения, что возраст магматических образований древнее и составляет 820 ± 9 млн лет (Rb-Sr метод по валу [Makeev et al, 2009]).…”