ALBERT

Description: Multibeam bathymetry raw data was recorded in the Pacific during cruise SO249/2 that took place between 2016-07-17 and 2016-08-13. The data was collected using the ship's own Kongsberg EM 122. Sound velocity profiles (SVP) were applied on the data for calibration. SVP data are part of this dataset publication.

Description: Multibeam bathymetry raw data was recorded in the Pacific during cruise SO201-1b that took place between 2009-06-09 and 2009-07-06. The data was collected using the ship's own Kongsberg EM 120.

Description: Multibeam bathymetry raw data was recorded in the Pacific during cruise SO249/1 that took place between 2016-06-06 and 2016-07-14. The data was collected using the ship's own Kongsberg EM 122. Sound velocity profiles (SVP) were applied on the data for calibration. SVP data are part of this dataset publication. Please see environmental data (zip file) and the cruise report for details.

Description: The formation of the Pannonian basin by major lithospheric extension during the early to mid-Miocene was accompanied by intensive volcanic activity. Among it, explosive volcanism fed by silicic (dacite to rhyolite) magmas is considered to have been the largest (accumulated tephra volume exceeded 4000 km3) in Europe in the last 20 Myr. Zircon U-Pb geochronology indicates that this occurred between 18.2 and 14.4 Ma (Bükkalja volcanic field; BVF) and involved at least four major eruption episodes. Distal ash materials related to these volcanic eruptions are recognized around the Pannonian basin and even farther, over thousand kilometre away, based on zircon and glass shard data. Another major silicic volcanic activity developed eastward (Tokaj Mts., TM) from 13.2 to 11.5 Ma. In this case, explosive and effusive volcanic products were equally preserved. Explosive events in the TM are also clearly distinguished by zircon geochronology as well as zircon and glass shard trace element compositions. The diverse zircon and glass geochemical data from these two areas suggest that reservoirs with distinct silicic magmas developed in the shallow continental crust for about 7 Myr. The epsilon-Hf values of zircon crystals are in a similar range from -10 to +2 and show a temporal increase, implying increasing role of mantle-derived magmas. In the BVF, an abrupt change in the epsilon-Hf values occurred after 16.2 Ma, suggesting that by this time the crust, and the lithospheric mantle was considerably thinned, while in the TM, this occurred later and in two smaller steps. MELTS modelling results, zircon and glass trace element data suggest different magma evolution in the BVF and TM as shown particularly by the Eu and Ce anomalies. In the TM, silicic magmas evolved under more reduced and drier magmatic environments. In contrast, wetter, and more oxidised conditions, with the presence of amphibole in the mineral assemblage, dominated in some of the BVF silicic magmas. The silicic magmatism had a major influence on the state of the continental crust due to the contemporaneous presence of large volume silicic magma reservoirs in the crust, and could have contributed to the crustal stretching beneath the Pannonian basin.

Description: The Mid-Miocene volcanism in the northern Pannonian basin has a peculiar nature. The first volcanic products (metaluminous andesite to peraluminous dacite-rhyodacite) are unique since the dacites and rhyodacites contain almandine garnet, which rarely occurs in volcanic rocks. The primary almandine crystals have a moderate Ca content (CaO=4.5–8.1 wt%), although low-Ca (CaO〈3 wt%) almandine derived from lower crustal metapelites is also found. Trace element variations in garnet are consistent with progressive crystal fractionation at high-pressure (〉700 MPa). Zircon U-Pb geochronology results suggest eruption ages between 15.6 and 15.0 Ma. Remarkably, this volcanism has no relationship with coeval subduction, but it occurred in response to continental rifting. The nature of these magmas was further explored with the help of trace element and Hf-isotope composition of zircon. Zircon in the peraluminous rhyodacites has a unique compositional feature, an elevated Al content (Al=10–15 ppm) not found in other silicic volcanic rocks in this region. Notably, zircon in the coeval metaluminous volcanic rocks has also relatively high Al-content (5–10 ppm). Zircon crystals in the peraluminous rocks have relatively high Dy/Yb and low Th/U ratios consistent with early garnet crystallization. Strong depletion of heavy rare earth elements is observed also in the glass shards. The epsilon Hf values of zircon crystals show a variation from -4 to +2, transitional values compared to the Miocene volcanic rocks of the region and suggest mixing of mantle-derived and crustal-derived magmas. This is consistent with petrogenetic modelling calculations based on bulk rock isotope and trace element data, implying interaction between mafic magmas derived from enriched lithospheric mantle and metasedimentary lower crust. Thus, the peraluminous garnet-bearing magmas in the northern Pannonian basin are hybrids, and are not of pure anatectic origin, as being proposed for compositionally similar magmas, such as in SE Spain. Preservation of high-pressure garnet can be explained by fast magma ascent enhanced by crustal extension. In contrast, some magmas stalled at shallow crust. They also contain Al-bearing zircon crystals suggesting peraluminous character of their parental magmas, whereas garnet phenocrysts were likely dissolved at low pressure (as also reflected in the glass composition).

Description: Carbon dioxide (CO2) is one of the main volatile components of natural magmas, but estimation of its initial contents remains a challenge. Study of melt inclusions in minerals permits a direct estimation of the content of CO2 in the melts. For the precise determination of its content in melt inclusions, it is necessary to analyze the contents of CO2 both in glass and in the fluid daughter phase of the inclusions. In this work we constructed a calibration dependence of the density of CO2 in the range 0.01-0.22 g/cm3 on the distance between its characteristic peaks in Raman spectra (Fermi diads). The accuracy of density determination is ±0.03 g/cm3. The calibration was used to estimate the density of CO2 in the gas phase of melt inclusions in magnesian olivine (Fo84.8-88.5) from basalts of the Karymsky Volcano, eastern Kamchatka. The estimated density was 0.03-0.21 g/cm3. Using these values, we evaluated the minimum initial content of CO2 in the parental magmas of the Karymsky Volcano, 0.45 wt.%. These data, along with the known initial content of water (~4.5 wt.%), indicate that the parental magmas began to crystallize at a pressure of at least 7 kbar (depth of 〉25 km). To increase the reliability of the above method of estimation of the CO2 content in olivine-hosted melt inclusions, we propose to carry out preliminary experimental reheating of inclusions for complete homogenization of the fluid phase and determination of the 3D size of melt inclusions. The performed study provides a reliable evaluation of the content of CO2 in parental magmas, the depth of crystallization, and the degree of magma degassing and permits a comparison of the compositions of magmatic fluids and high-temperature volcanic gases.

Description: 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.

Description: Highlights • 14C-based Holocene chronology of explosive eruptions from Avachinsky group volcanoes. • Bulk rock and glass chemistry (single-shard microprobe and LA-ICP-MS data). • Two stages of Avachinsky volcano activity. • Volcanic glasses reflect temporal evolution of Avachinsky magma plumbing system〉 • Slab temperature increasing with depth causes difference between neighboring Kamchatka volcanoes. Abstract Avachinsky, Kozelsky, and Koryaksky volcanoes form one of the most volcanically active clusters in the Kamchatka volcanic arc and are located in close proximity of the cities of Petropavlovsk-Kamchatsky and Elizovo – the most populated area in Kamchatka. In this paper, we report a compilation of new and revised previously published data on the eruptive history of these volcanoes during the past 13.5 kyrs. We identify 217 explosive eruptions of these volcanoes, determine their ages using 207 radiocarbon dates and Bayesian statistical modeling, and characterize their tephra geochemically using major and trace element compositions of bulk samples (40 samples) and volcanic glass (75 samples). Avachinsky has been the most active during the Holocene time and had 〉150 explosive eruptions; Koryaksky produced ~60 eruptions; and Kozelsky had only two final eruptions in the early Holocene. Our new data confirm the onset of the Avachinsky postglacial activity at 11.3 cal ka BP and previously distinguished two major stages of Avachinsky Holocene eruptive history: stage I (8–3.8 cal ka BP) and stage II (3.8 cal ka BP – present). During stage I, eruptions were relatively rare, but they included at least six large pumice eruptions with tephra volumes exceeding 0.5 km3. Stage I tephras had low-K andesitic bulk compositions and low-K rhyolitic matrix glasses. The andesites likely sampled volatile-rich crystal mush from a long-lived magma chamber under Avachinsky volcano. The stage II started at ~3.8 cal ka BP with a powerful eruption and was related to the construction of the Young Cone inside the Avachinsky somma. The subsequent late Holocene eruptions were frequent, but most of them did not exceed the volume of 0.3 km3. The stage II tephras are mostly cindery basaltic andesites containing well-crystallized groundmasses of andesitic composition. These tephras originate from smaller, perhaps more shallow magmatic reservoirs, and their matrix glasses are likely products of in-situ crystallization of relatively mafic magmas on their ascent to the surface. Koryaksky volcano was mostly active in the early Holocene when Avachinsky was quiet. Koryaksky tephras had a relatively constant bulk medium-K andesitic composition during the Holocene. Thanks to characteristic compositions, high frequency, and well-constrained ages, tephras of Avachinsky and Koryaksky volcanoes can be used for high resolution dating of local sediments. Some eruptions of Avachinsky volcano reached volcanic explosivity index (VEI) 5 and produced widely dispersed tephras. These eruptions could have had global environmental effects, and their tephras can be used for the correlation of disparate sedimentary archives. Some Avachinsky and Koryaksky eruptions were closely spaced in time. However, their tephras are easily distinguished by respective low-K and medium-K compositions and by different trace element patterns, which imply compositionally different sources in the mantle wedge. We interpret these differences to reflect the increasing slab surface temperature and transition of slab component from a relatively low-temperature fluid-like phase under Avachinsky to more high-temperature and solute-rich supercritical fluid or melt under Koryaksky. The transition appears to be very sharp in Kamchatka, causing a large compositional shift in magmas just behind the volcanic front.

Description: This paper presents the first detailed study of a late Pleistocene marine tephra sequence from the NW Pacific, downwind from the Kamchatka volcanic arc. Sediment core SO201-2-40, located on the Meiji Rise similar to 400 km offshore the peninsula, includes 25 tephras deposited within the last 215 ka. Volcanic glass from the tephras was characterized using single-shard electron microprobe analysis and laser ablation inductively coupled mass spectrometry. The age of tephras was derived from a new age model based on paleomagnetic and paleoclimate studies. Geochemical correlation of distal tephras to Kamchatkan pyroclastic deposits allowed the identification of tephras from the Karymsky, Gorely, Opala and Shiveluch eruptive centers. Three of these tephras were also correlated to other marine and terrestrial sites and hence are identified as the best markers for the north-west Pacific region. These are an early Holocene tephra from the Karymsky caldera (similar to 8.7 ka) and two tephras falling into the Marine Isotope Stage (MIS) 6 glacial time: an MIS 6.4 tephra from Shiveluch (similar to 141 ka) and the MIS 6.5 Rauchua tephra (similar to 175 ka) from Karymsky. The data presented in this study can be used in paleovolcanological and paleoceanographic reconstructions.