Abstract. Tephra layers produced by volcanic eruptions are widely used for correlation and dating of various deposits and landforms, for synchronization of disparate paleoenvironmental archives, and for reconstruction of magma origin. Here we present our original database TephraKam, which includes chemical compositions of volcanic glass in tephra and welded tuffs from the Kamchatka volcanic arc. The database contains 7049 single-shard major element analyses obtained by electron microprobe and 738 trace element analyses obtained by laser ablation inductively coupled plasma mass spectrometry on 487 samples collected in close proximity to their volcanic sources in all volcanic zones in Kamchatka. The samples characterize about 300 explosive eruptions, which occurred in Kamchatka from the Miocene up to recent times. Precise or estimated ages for all samples are based on published 39Ar∕40Ar dates of rocks and 14C dates of host sediments, statistical age modeling and geologic relationships with dated units. All data in TephraKam are supported by information about source volcanoes and analytical details. Using the data, we present an overview of geochemical variations in Kamchatka volcanic glasses and discuss applications of these data for precise identification of tephra layers, their source volcanoes, and temporal and spatial geochemical variations in pyroclastic rocks in Kamchatka. The data files described in this paper are available on ResearchGate at https://doi.org/10.13140/RG.2.2.23627.13606 (Portnyagin et al., 2019).

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The Kamchatka Peninsula of eastern Russia is currently one of the most volcanically active areas on Earth where a combination of >8 cm/yr subduction convergence rate and thick continental crust generates large silicic magma chambers, reflected by abundant large calderas and caldera complexes. This study examines the largest center of silicic 4-0.5 Ma Karymshina Volcanic Complex, which includes the 25 × 15 km Karymshina caldera, the largest in Kamchatka. A series of rhyolitic tuff eruptions at 4 Ma were followed by the main eruption at 1.78 Ma and produced an estimated 800 km 3 of rhyolitic ignimbrites followed by high-silica rhyolitic post-caldera extrusions. The postcaldera domes trace the 1.78 Ma right fracture and form a continuous compositional series with ignimbrites. We here present results of a geologic, petrologic, and isotopic study of the Karymshina eruptive complex, and present new Ar-Ar ages, and isotopic values of rocks for the oldest pre-1.78 Ma caldera ignimbrites and intrusions, which include a diversity of compositions from basalts to rhyolites. Temporal trends in δ 18 O, 87 Sr/ 86 Sr, and 144 Nd/ 143 Nd indicate values comparable to neighboring volcanoes, increase in homogeneity, and temporal increase in mantle-derived Sr and Nd with increasing differentiation over the last 4 million years. Data are consistent with a batholithic scale magma chamber formed by primarily fractional crystallization of mantle derived composition and assimilation of Cretaceous and younger crust, driven by basaltic volcanism and mantle delaminations. All rocks have 35-45% quartz, plagioclase, biotite, and amphibole phenocrysts. Rhyolite-MELTS crystallization models favor shallow (2 kbar) differentiation conditions and varying quantities of assimilated amphibolite partial melt and hydrothermally-altered silicic rock. Thermomechanical modeling with a typical 0.001 km 3 /yr eruption rate of hydrous basalt into a 38 km Kamchatkan arc crust produces two magma bodies, one near the Moho and the other engulfing the entire section of upper crust. Rising basalts are trapped in the lower portion of an upper crustal magma body, which exists in a partially molten to solid state. Differentiation products of basalt periodically mix with the resident magma diluting its crustal isotopic signatures. Bindeman et al. Isotopic and Thermomechanical Model of Karymshina Caldera At the end of the magmatism crust is thickened by 8 km. Thermomechanical modeling show that the most likely way to generate large spikes of rhyolitic magmatism is through delamination of cumulates and mantle lithosphere after many millions of years of crustal thickening. The paper also presents a chemical dataset for Pacific ashes from ODDP 882 and 883 and compares them to Karymshina ignimbrites and two other Pleistocene calderas studied by us in earlier works.

We describe a new caldera-volcano in the volcanic front of Kamchatka named Verkhneavachinskaya caldera (VC). According to geological mapping, the VC is interpreted as an eroded shield volcano with a summit caldera exposing 1 km-thick lava-like ignimbrites. It is one of the largest (10 × 12 km diameter) and oldest (c. 5.78-5.58 Ma, Ar-Ar dating) morphologically preserved paleovolcano in Kamchatka. The welded ignimbrites with fiammes are andesites-basaltic andesites in composition, they are more mafic than most ignimbrites worldwide and than other post-Pliocene calderas in Kamchatka. The deposits of VC are interbedded layers of welded ignimbrites and volcanoclastic material, which we interpret as result of long-lived volcanic center activity with hot pyroclastic flows and subsequent accumulations of volcanoclastic suites (e.g. lahars). The most trace element ratios in VC rocks (e.g. La/Yb, Nb/La, Ba/Th) show similarity with post-accretion magmatism at Kamchatka and especially with Late Pleistocene-Holocene Bakening volcano located in the same area. The VC provides new insights into the early stages of Kamchatka frontal zone development after the Kronotsky Arc Terrane accretion. This potentially explains the origin of voluminous basaltic-andesitic ignimbrites formed on thin crust during the initial stage of the arc formation.

Abstract. Tephra layers produced by volcanic eruptions are widely used for correlation and dating of various deposits and landforms, for synchronization of disparate paleoenvironmental archives, and for reconstruction of magma origin. Here we present our original database TephraKam, which includes chemical compositions of volcanic glass in tephra and welded tuffs from the Kamchatka volcanic arc. The database contains 7049 major element analyses obtained by electron microprobe and 738 trace element analyses obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on 487 samples collected in proximity of their volcanic sources in all volcanic zones in Kamchatka. The samples characterize about 300 explosive eruptions, which occurred in Kamchatka from the Pliocene until historic times. Precise or estimated ages for all samples are based on published 39Ar/40Ar dates of rocks and 14C dates of host sediments, statistical age modelling and geologic relationships with dated units. All data in TephraKam is supported by information about source volcanoes and analytical details. Using the data, we present an overview of geochemical variations of Kamchatka volcanic glasses and discuss application of this data for precise identification of tephra layers, their source volcanoes, temporal and spatial geochemical variations of pyroclastic rocks in Kamchatka. The data files described in this paper are available on ResearchGate at https://doi.org/10.13140/RG.2.2.23627.13606 (Portnyagin et al., 2019).

Based on the statistical data of the Global Volcanism Program of the Smithsonian Institution and published materials, we present a comparative analysis of caldera-forming eruptions on global scale. The geodynamic settings and genesis of the caldera-forming eruptions with basaltic-andesitic magma compositions are described. The origin of the majority of mafic ignimbrites was related with external water. Such ignimbrites were generated in a submarine environment or with a contact with water. The newly obtained data, paleogeodynamic reconstruction and geological mapping of Miocene mafic ignimbrites of the Eastern volcanic belt (EVB) of Kamchatka confirm their genesis in costalmarine environment. These new data show significance of paleoreconstructions in studies of paleo-volcanoes and relief-forming pyroclastic rocks.

The monograph is devoted to the politics of memory of the Second Polish Republic concerning national uprisings and armed struggles of the years 1794–1864 and the figures involved in them. The author argues that it was set in a larger political, social and cultural context and shows the dependence of interpreting history by the elites of the state on the political situation in the country and abroad.