13 research outputs found
New Nd and Pb isotope data on the ophiolite complexes of the Kronotskii paleoarc, Eastern Kamchatka
The classification of potassium basaltic trachyandesites that were discharged by the 2012ā2013 parasitic eruption on Ploskii Tolbachik Volcano, Kamchatka using geochemical criteria
New evidence for the composition and structure of volcanic complexes on Cape Nalycheva and the Shipunskii Peninsula, Kamchatka
On the eruptions, deformation, and seismicity of Klyuchevskoy Volcano, Kamchatka in 1986ā2005 and the mechanisms of its activity
Tectonostratigraphic complexes of the southern Kronotskii paleoarc (Eastern Kamchatka): Structure, age, and composition
New petrological data on the volcanic rocks of the Chichinautzin region: The sources of the magmatic melts and the origin of the Trans-Mexican volcanic belt
A petrological and geochemical study on time-series samples from Klyuchevskoy volcano, Kamchatka arc
The Origin of Hydrous, high-Ī“18O voluminous volcanism: Diverse Oxygen Isotope Values and High Magmatic Water Contents within the Volcanic Record of Klyuchevskoy Volcano, Kamchatka, Russia
Klyuchevskoy volcano, in Kamchatkaās subduction zone, is one of the most active arc volcanoes in the world and contains some of the highest Ī“18O values for olivines and basalts. We present an oxygen isotope and melt inclusion study of olivine phenocrysts in conjunction with major and trace element analyses of 14C- and tephrochronologically-dated tephra layers and lavas spanning the eruptive history of Klyuchevskoy. Whole-rock and groundmass analyses of tephra layers and lava samples demonstrate that both high-Mg (7ā12.5 wt% MgO) and high-Al (17ā19 wt% Al2O3, 3ā6.5 wt% MgO) basalt and basaltic andesite erupted coevally from the central vent and flank cones. Individual and bulk olivine Ī“18O range from normal MORB values of 5.1ā° to values as high as 7.6ā°. Likewise, tephra and lava matrix glass have high-Ī“18O values of 5.8ā8.1ā°. High-Al basalts dominate volumetrically in Klyuchevskoyās volcanic record and are mostly high in Ī“18O. High-Ī“18O olivines and more normal-Ī“18O olivines occur in both high-Mg and high-Al samples. Most olivines in either high-Al or high-Mg basalts are not in oxygen isotopic equilibrium with their host glasses, and Ī18Oolivineāglass values are out of equilibrium by up to 1.5ā°. Olivines are also out of FeāMg equilibrium with the host glasses, but to a lesser extent. Water concentrations in olivine-hosted melt inclusions from five tephra samples range from 0.4 to 7.1 wt%. Melt inclusion CO2 concentrations vary from below detection (<50 ppm) to 1,900 ppm. These values indicate depths of crystallization up to ~17 km (5 kbar). The variable H2O and CO2 concentrations likely reflect crystallization of olivine and entrapment of inclusions in ascending and degassing magma. Oxygen isotope and FeāMg disequilibria together with melt inclusion data indicate that olivine was mixed and recycled between high-Al and high-Mg basaltic melts and cumulates, and FeāMg and Ī“18O re-equilibration processes were incomplete. Major and trace elements in the variably high-Ī“18O olivines suggest a peridotite source for the parental magmas. Voluminous, highest in the world with respect to Ī“18O, and hydrous basic volcanism in Klyuchevskoy and other Central Kamchatka depression volcanoes is explained by a model in which the ascending primitive melts that resulted from the hydrous melt fluxing of mantle wedge peridotite, interacted with the shallow high-Ī“18O lithospheric mantle that had been extensively hydrated during earlier times when it was part of the Kamchatka forearc. Following accretion of the Eastern Peninsula terrains several million years ago, a trench jump eastward caused the old forearc mantle to be beneath the presently active arc. Variable interaction of ascending flux-melting-derived melts with this older, high-Ī“18O lithospheric mantle has produced mafic parental magmas with a spectrum of Ī“18O values. Differentiation of the higher Ī“18O parental magmas has created the volumetrically dominant high-Al basalt series. Both basalt types incessantly rise and mix between themselves and with variable in Ī“18O cumulates within dynamic Klyuchevskoy magma plumbing system, causing biannual eruptions and heterogeneous magma products