Complex investigations of the mineral composition and petromagnetic properties of the rock samples constituting the Minami-Khiosi submarine volcano which is located in the Mariana island arc were carried out for the first time. The Minami-Khiosi submarine volcano is part of the Khiosi volcanic complex in the alkaline province of the Izu-Bonin and Mariana island arcs. The rocks analyzed are enriched in К2О (1.34-3.30 %), Ва - 370-806 ppm, and Sr - 204-748 ppm. Basalts exhibit a porphyric structure. Impregnations are mostly olivine, its single crystals or their concretions. In some samples olivine is very large in size (about 2 cm), but at the same time the grain-size of the main bulk is fine-crystalline. The studied samples include no less than 3 Fe-bearing oxide minerals. Among them are dominant titanomagnetite, and ilmenite and Fe hydroxides are less abundant. It has been established that the studied samples are mainly magnetically isotropic, have high values of natural remanent magnetization and Königsberger factor. As in other Late Cenozoic island arc submarine volcanoes of the Western Pacific the studied samples are highly differentiated by the amount of natural remanent magnetization and magnetic susceptibility. The main carriers of magnetization are low coercive magnetic minerals (titanomagnetite and magnetite) pseudosingle-domain structure and high coercivity (hematite). High values of natural remanent magnetization are due to psevdosingle-domain structure of titanomagnetite grains and high values of magnetic susceptibility are explained by a high concentration of ferromagnetic grains.

A multidisciplinary study of samples that were dredged during cruises of the R/V Vulkanolog was continued in order to interpret results from a survey of the anomalous magnetic field on the Pacific seafloor. We acquired data on the main ferromagnetic carrier and the nature of magnetization. The naturally occurring magnetic parameters and petromagnetic properties of the rocks that make up the edifices of the Sofu underwater volcanic cluster at the Izu-Bonin island arc have been studied. We provide the results of thermomagnetic, petrologic, and microprobe studies of the dredged samples. It is shown that the main magnetic mineral carriers of natural remanent magnetization are unaltered titanomagnetite and oxidized titanomagnetite. The differentiation of rocks over values of natural remanent magnetization was due to different crystallization conditions for titanomagnetite, while that over magnetic susceptibility was controlled by the magnetic grain size. The structural, mineralogic, and petrographic features of the samples show that they were taken from rocks that were discharged during different phases of eruptions.

Получены новые палеомагнитные определения по лавовым потокам и вулканическим пеплам Северной группы вулканов Камчатки, удовлетворяющие современным методическим и аппаратурным требованиям к проведению палеомагнитных исследований. В интервале последних 4000 лет исследовано 12 стратиграфических уровней, датированных тефрохронологическим методом. Полученные направления геомагнитного поля восполняют недостаток данных по вековым вариациям для северо-востока Азии и могут быть использованы при разработке глобальных моделей геомагнитного поля. Кроме того, показана перспективность использования вариаций геомагнитного поля для региональной корреляции вулканических событий.

Рассматриваются геологическая история и петрология крупного полигенного вулканического сооружения верхнеплейстоцен-голоценового времени. Этот долгоживущий вулканический центр знаменателен совместным проявлением магм базальтового и трахибазальтового составов, представленных базальт-андезитовой и трахибазальт-трахиандезитовой сериями. Делается вывод о генетической автономности сосуществующих родительских магм, генерированных в разных глубинных источниках области верхней мантии. Разнообразие составов вулканитов обязано многостадийной пространственно-временной кристаллизационной дифференциации магм и смешению последних в промежуточных очагах.

This paper is concerned with the geological history and petrology of a major polygenic volcanic edifice dating back to Upper Pleistocene to Holocene time. This long-lived volcanic center is remarkable in that it combines basaltic and trachybasaltic magmas which are found in basaltic andesite and trachybasaltic– trachyandesite series. The inference is that the coexisting parent magmas are genetically independent and are generated at different sources at depth in an upper mantle volume. The associated volcanic rocks have diverse compositions, stemming from a multi-stage spatio–temporal crystallization differentiation of the magmas and mixing of these in intermediate chas.

Fieldworks at Alaid Volcano in 2017, Atlasov Island, the Kuriles