Diverse Lavas of the Tigilsky Dol and Mount Oxi Massif (Sredinny Range, Kamchatka): a Perspective from the New Sr–Nd Isotope Data

Unique compositional diversity of volcanic rocks was recently discovered in an active fault zone of the Sredinny Range (Kamchatka) located in the zone of monogenetic volcanism near the Tigil and Oxi volcanoes. The lavas in the zone represent common for SR medium-K, high-K and high-Ti, and also unique for Kamchatka high-LREE and high-Mg varieties. In this contribution, we present new Sr-Nd isotope data for a representative set of lava samples from this area. The isotopic and geochemical characteristics of the majority of selected samples can be explained by the differences in the amount of fluid, fluid sources and melting conditions, proposed earlier for the SR. The high-LREE picritic basalts, however, differ significantly from the other Kamchatka volcanic rocks—their highly unusual high-LREE, high-Li and low-LILE geochemical characteristics combine with the highest 87Sr/86Sr (0.70365) and second-highest εNd (9.9) values ever reported for lavas from the SR. We suggest that they represent the product of melting of the specific SR lithosphere domain that has been metasomatized by melts derived from a strongly degassed slab.