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
Tephra layers are widely used for correlation and dating of various deposits and landforms, for the synchronization of disparate paleoenvironmental archives, and for reconstruction of magma origin and temporal evolution. These applications are in high demand in paleoclimatology, paleoseismology, archaeology, and other Quaternary science disciplines (e.g., Lowe, 2011), as well as in petrology and geochemistry (e.g., Cashman and Edmonds, 2019; Ponomareva et al., 2015a; Straub et al., 2015). Tephra is composed of minerals, volcanic glass (melt rapidly quenched upon eruption), and rock fragments in different proportions. A major modern approach for correlation of tephra layers between different locations is using major and trace element composition of volcanic glass (e.g., Cashman and Edmonds, 2019; Lowe, 2011; Ponomareva et al., 2015a). The composition of volcanic glasses has been shown to vary significantly on spatial scales ranging from volcanic region to a single volcano, reflecting a large variability of thermodynamic conditions of magma storage and fractionation and the composition of crustal and mantle sources of magmas (e.g., Bachmann and Bergantz, 2008; Cashman and Edmonds, 2019; Frost et al., 2001; Pearce, 1996; Pearce et al., 1984; Schattel et al., 2014).
Tephra often dominates the erupted products in terms of volume, eruption frequency, and variety of compositions, some of which may never occur in lava. It is particularly true for highly explosive volcanic arcs where the vast majority of the magma is erupted as tephra (e.g., Kutterolf et al., 2008). Therefore, tephra studies have a large, still only partly explored, potential to trace temporal and spatial variations in magma compositions in volcanic arcs (e.g., Clift et al., 2005; Kimura et al., 2015; Straub et al., 2004, 2015).
The Kamchatka Peninsula (Fig. 1) hosts more than 30 recently active large volcanic centers and a few hundred monogenetic vents, comprising the northwestern segment of the Pacific Ring of Fire. Kamchatka volcanism is highly explosive. According to some estimates, Kamchatka has the largest number of Quaternary calderas per unit of arc length in the world (Hughes and Mahood, 2008). Kamchatka tephra layers provide chronological control for deposits and events over large areas, both in Kamchatka and farther afield, up to Greenland and North America, which is critical for many studies (e.g., Cook et al., 2018; Hulse et al., 2011; Kozhurin et al., 2014; Mackay et al., 2016; Pendea et al., 2016; Pinegina et al., 2013, 2014, 2012; Plunkett et al., 2015; van der Bilt et al., 2017). However, geochemical characterization of Kamchatka volcanic glasses is still in a developing phase. In the Kamchatka volcanic arc, the Holocene tephrochronological framework (until recently) has been based mainly on direct tracing of tephra layers, bulk composition of tephra, and bracketing radiocarbon dates (e.g., Bazanova et al., 2005; Braitseva et al., 1998, 1996, 1995, 1997; Pevzner, 2010; Pevzner et al., 1998, 2006). Significant progress towards creating geochemical database of Kamchatka tephras has been achieved in the past 10 years (Dirksen et al., 2011; Kyle et al., 2011; Plunkett et al., 2015; Ponomareva et al., 2013a, b, 2017, 2015b). However, the published geochemical data are mostly restricted to the Holocene and do not include data on trace element composition of volcanic glasses.
Volcanoes and samples presented in TephraKam. Large red circles with labels are volcanic centers, and yellow circles are sample locations. Note that Kamchatka hosts more presently inactive volcanic centers than shown on the map, but tephra samples from these extinct volcanoes were not available for this study. The background image was drawn by the authors using public-domain datasets: SRTM for landmass (Farr et al., 2007) and GEBCO for ocean floor (Smith and Sandwell, 1997).
In this paper, we present TephraKam – our original, internally consistent
and, so far, most complete database of single-shard glass composition
from tephras and welded tuffs of Kamchatka volcanoes, covering the period
from the Miocene until the present (Portnyagin et al., 2019). The data have been
collected during the past 10 years and include major element compositions
obtained by electron microprobe and trace element compositions of
representative samples by laser ablation inductively coupled plasma
mass spectrometry (LA-ICP-MS). Ages based on published radiocarbon and
The Kamchatka Peninsula overlies the northwestern margin of the subducting
Pacific plate and is one of the most volcanically and tectonically active
regions in the world (e.g., Gorbatov et al., 1997). Kamchatka hosts more than
30 large active volcanoes, 40 calderas, and hundreds of monogenetic vents
grouped into two major volcanic belts running northeast–southwest along the peninsula, which are
the Eastern Volcanic Belt and the Sredinny Range (SR) (Fig. 1). The Eastern Volcanic
Belt includes the volcanic front (VF) and rear arc (RA) in the southern
(51–53
The products of the continuous explosive volcanism in Kamchatka during the last 2.5 Ma are not equally represented in the depositional record. Holocene tephra layers mantle the topography and, being interlayered with paleosol or peat horizons, form a sequence that provides a nearly continuous record of the Holocene explosive activity (e.g., Bazanova and Pevzner, 2001; Braitseva et al., 1998, 1996, 1995, 1997; Kyle et al., 2011; Pevzner, 2010; Pevzner et al., 1998; Ponomareva et al., 2015a, b, 2017). Earlier pre-Holocene pyroclastic products are mostly ignimbrite (pumiceous or welded tuffs), which survived through glacial stages better than loose pyroclastics and in many cases experienced alteration (Bindeman et al., 2019, 2010; Ponomareva et al., 2018; Seligman et al., 2014). These deposits are partly eroded by glacial processes, buried by younger deposits, and/or covered with dense vegetation, which hampers their identification.
TephraKam database provides data on volcanic glass composition from 65
volcanic centers in Kamchatka. Of these centers, 43 were active in the
Holocene and the remaining 22 centers ceased their activity prior to
the Holocene. Some volcanic centers are individual volcanic cones (e.g.,
Iliinsky), calderas (e.g., Kurile Lake caldera), monogenetic lava fields
(e.g., Tolbachik lava field), or monogenetic vents (cinder cones and craters),
while other centers combine several volcanoes and/or calderas (e.g., Karymsky
center). The latter approach was used in cases when thick local pyroclastic
deposits could not be unambiguously assigned to a certain volcano within the
volcanic cluster. We define the source vent within the volcanic center where
possible (e.g., Karymsky/Polovinka caldera). Eight ignimbrite units come
from unknown sources so we use coordinates of their samples instead of vent
coordinates.
We have analyzed glass from 487 samples, including 11 replicate samples
marked as “–rep” in the database. Overall, our samples characterize about
300 individual explosive eruptions. A total of 298 samples come from tephra fall
deposits, 187 are from ignimbrite units (42 of them welded), and 2 are from
lava. Our sampling covers all the Quaternary volcanic belts: 25 % of the
samples are from VF, 27 % are from RA, 40 % are from CKD, and 8 % are from
the Sredinny Range. The coverage among the volcanic centers is not uniform: some
volcanoes are characterized by only one sample while others are densely
sampled and analyzed. The sampling density partly reflects the amount of
large explosive eruptions from a certain volcano. The analyzed samples span
an age interval from the Miocene (ca. 6 Ma) to recent times (Fig. 2). About
60 % of samples and data presented in this database are from the Holocene
and characterize all large explosive eruptions in Kamchatka during this time
(Braitseva et al., 1995, 1997; Ponomareva et al., 2013b, 2015b), as well as many moderate-size eruptions. Ages, tephra
dispersal areas, and volumes for most of the Holocene eruptions have already been
published (Braitseva et al., 1998, 1996, 1997; Kyle et al., 2011; Ponomareva et al., 2017;
Zaretskaya et al.,
2007). The pre-Holocene record of explosive eruptions is spotty, and its
representativeness decreases with increasing rock age (Fig. 2). Most of the
pre-Holocene samples characterize ignimbrites associated with large
(diameter 5–40 km) collapsed calderas. A total of 69 of the
Number of single-spot major and trace element analyses of glass from tephra and welded tuffs of different age groups included in the TephraKam database. Note the logarithmic vertical scale.
Tephra samples have been prepared using our original technique, developed in
the past 20 years at GEOMAR (Kiel) and the Vernadsky Institute (Moscow). The
technique aims for uncomplicated, time- and material-effective preparation of
many tephra samples for microanalytical work. The technique applies no
strong heating (
The samples have been cleaned in water to wash out clay and the finest
(
In this study, EPMA data have been obtained following published recommendations for the analytical conditions, primary and secondary reference materials, the number of analyses, and other factors and procedures, which may influence the quality of EPMA data for tephra glasses and their interpretation (Froggatt, 1992; Morgan and London, 1996, 2005; Hunt and Hill, 2001; Turney et al., 2004; Kuehn et al., 2011; Lowe et al., 2017). A particularly influential study was an intercomparison of electron microprobe data for volcanic glasses between different labs (Kuehn et al., 2011), which confirmed a high quality of our data (GEOMAR lab is no. 12 in Kuehn et al., 2011) and allowed us to further improve our EPMA protocol.
The glasses were analyzed at GEOMAR (Kiel, Germany) using a JEOL JXA 8200
electron microprobe equipped with five wavelength dispersive spectrometers,
including three high-sensitivity instruments (two PETH and a TAPH). The analytical
conditions were 15 kV accelerating voltage, 6 nA current, and 5
Basaltic glass (USNM 113498/1 VG-A99) for Ti, Fe, Mg, Ca, and P; rhyolitic glass (USNM 72854 VG568) for Si, Al, Na, and K; scapolite (USNM R6600-1) for S and Cl (all from the Smithsonian collection of natural reference materials; Jarosewich et al., 1980); comendite obsidian KN-18 (Nielsen and Sigurdsson, 1981; Mosbah et al., 1991) for F; and synthetic rhodonite for Mn were used for calibration and monitoring of routine measurements. Two to three analyses of all standard glasses and scapolite were performed at the beginning of analytical session, after every 50–60 analyses and at the end. The data reduction included online CITZAF correction and small drift correction for systematic deviations (if any) from the reference values obtained on standard materials. The latter correction has not exceeded a few relative percent for all elements and allowed us to achieve the best possible accuracy and precision. The correction resulted in a very minor change of the mean concentrations but allowed 20 %–40 % improvement of the analytical precision (2 SD; SD is sample standard deviation) and the shape of data distribution, making it closer to Gaussian distribution (see the Supplement to Ponomareva et al., 2017).
The glass analyses used in this study were obtained in the period from 2009
to 2019. The summary of data for reference materials collected over this
period of time is presented in TephraKam Table 1b (Portnyagin et al., 2019).
The data include results obtained on major reference glasses and minerals,
which were used in calibration of quantitative microprobe measurements (USNM
72854 VG568, USNM 113498/1 VG-A99, USNM R6600-1, KN18), and also results
obtained for other reference materials analyzed as unknown in the course of
our study. The latter include natural glasses USNM 111240/52 VG-2
(Jarosewich et al., 1980); Lipari obsidian (Hunt and Hill, 1996); Mt. Ediza
Sheep Track tephra; Laki 1783 AD tephra; Old Crow tephra (Kuehn et al.,
2011); and glasses made of natural rock powders ATHO-G, BM90/21-G, GOR128-G,
KL2-G, StHs60/8-G, ML3B-G (Jochum et al., 2006), and artificial glass
NIST SRM 612 (Jochum et al., 2011). The data demonstrate remarkable agreement
with recommended concentrations for all elements and thus excellent accuracy
of our data, which reproduces reference concentrations within the reported 2
SD in nearly all cases. The latter is also true for concentrations, which
significantly exceed the concentrations in reference glasses used for
calibration. This is illustrated, for example, by analyses of
Precision of single-point analyses depends on the element concentration and analytical conditions for every element. Assuming that the reference materials used in this study were perfectly homogeneous (which may be not true for natural glasses containing microlites of minerals), the precision of single-point analysis of typical rhyolite can be assessed from 2 SD of the long-term mean concentrations obtained for glass USNM 72854 VG568 or Lipari obsidian. Precision of single-point basaltic glass analysis can be evaluated from the data on glasses USNM 113498/1 VG-A99 or USNM 111240/52 VG-2. For more precise determination of a single-point analytical precision, we provide TephraKam Table 1c (Portnyagin et al., 2019), where the precision for every element is calculated based on element concentration in glass, taking into account long-term reproducibility of reference materials. Correlation of the oxide concentrations in reference materials plotted against long-term relative standard deviation (2 RSD, %) allows for estimating analytical detection limits and finding element concentrations at which 2 RSD approaches 100 % (TephraKam Table 1c).
During the subsequent data reduction, we excluded analyses with the totals
lower than 90 wt %, which resulted from possible unevenness of sample
surface, entrapment of voids, or epoxy during analysis of very small glass
fragments. The latter has been also identified by unusually high measured
chlorine concentrations, resulting from entrapment of epoxy resin during
analysis (see Sect. 3.1). Analyses contaminated by occasional entrapment
of crystal phases, usually microlites of plagioclase, pyroxene, or Fe-Ti
oxides, were mostly identified and excluded on the basis of excessive
concentrations of
In the past 25 years LA-ICP-MS became a common technique to quantify concentrations of a wide range of trace elements in tephra glasses (e.g., Westgate et al., 1994; Pearce et al., 1996, 2007, 2014; Tomlinson et al., 2010; Kimura and Chang, 2012; Maruyama et al., 2016; Lowe et al., 2017). The LA-ICP-MS technique adopted for this study and its development were based on the principal results and recommendations from the previous works and our own experimental results. All the trace element analyses were obtained at the Institute of Geosciences, CAU Kiel, Germany. Conditions of analysis are summarized in TephraKam Table 1d (Portnyagin et al., 2019).
Before 2017, analyses were performed using a quadrupole-based ICP-MS
(Agilent 7500s) and a Coherent GeoLas ArF 193 nm Excimer LA system. In situ
microsampling was done with 24–50
Beginning from January 2017, the analyses were obtained using a new ICP-MS
Agilent 7900s and a Coherent GeoLas ArF 193 nm Excimer LA system operated
with a fluence of 5 J cm
During all periods of data collection from 2011 to 2019, BCR2-G, KL2-G, and
STHS60/8-G glasses (Jochum et al., 2006) were analyzed as unknown in one
series with the samples (TephraKam Table 1e). The data confirms good
consistency of the entire dataset and no bias related to periodic
instrumental upgrades. Based on these data, the analytical precision and
accuracy are typically between
Overall, the data obtained since 2017 using the very sensitive modern
instrument Agilent 7900 and after implementation of additional improvements
(modified cell, addition of
Knowledge of tephra ages (or at least approximate age ranges) is crucial for
their use as marker horizons. For many tephras in our database, the age
estimates are available from published data (Auer et al., 2009; Bazanova and
Pevzner, 2001; Bazanova et al., 2019; Bindeman et al., 2019, 2010; Braitseva et al., 1998, 1991,
1995; Churikova et al., 2015; Cook et al., 2018; Dirksen, 2009; Dirksen and
Bazanova, 2009; Dirksen and Melekestsev, 1999; Florensky, 1984; Kozhurin et
al., 2006; Masurenkov, 1980; Melekestsev et al., 1992,
1995; Pevzner, 2015; Plechova et al., 2011; Ponomareva et al., 2018, 2013b, 2017, 2015b, 2006;
Ponomareva, 1990; Seligman et al., 2014; Volynets
et al., 1998; Zaretskaia et al., 2001; Zaretskaya et al., 2007; Zelenin et
al., 2020). In this case, we report bibliographical references and details
on the age estimates and dating techniques. The majority of previously
reported tephra ages were obtained by radiocarbon dating of host sediments.
The ages are usually published as uncalibrated
The TephraKam database is provided in Excel 2016 file (.xlsx) and consists
of six folders (TephraKam Tables 2a–f, Portnyagin et al., 2019): (a) comments,
(b) volcanoes, (c) sample description, (d) major elements, (e) trace elements,
and (f) discrimination diagrams. Table 2a, comments, explains
abbreviations of columns in the data tables. Table 2b, volcanoes,
contains information about volcanic centers of Kamchatka, from which
volcanic glass data exist and are presented in the database. Table 2c,
sample description, includes coordinates, information of sample age,
outcrop, type of material (ash, pumice, and welded tuff), collector's name,
and other information including data for source volcano via link to Table 2b. Table 2d, major elements, contains EPMA data on individual glass shards
from samples studied and related information. Table 2e, trace elements,
contains LA-ICP-MS major and trace element data on single glass shards,
information about the dates and conditions of LA-ICP-MS analysis, trace element
concentrations normalized to mantle composition, and some element ratios for
plotting the data. The tables are linked to each other so that any changes
in volcano or sample description will be seen in geochemical data tables.
Table 1f, discrimination diagrams, contains sample plots and coordinates
of corner points to draw compositional fields of the modern volcanic zones
in Kamchatka using coordinates
Major element data are available for all samples and are comprised of 7049 individual analyses. Trace elements are available for 114 samples and include 738 individual analyses. About 30 % of the major element data have already been published, e.g., for the Shiveluch eruptions (Ponomareva et al., 2015b); the Ushkovsky eruptions (Ponomareva et al., 2013b); and a part of the Bezymianny and Tolbachik eruptions (Ponomareva et al., 2017). The majority of the trace element data are presented here for the first time.
An overview of the available major element data is shown in Fig. 3, a common
classification diagram for island arc rocks in coordinates
The compositions of glasses are grouped in Fig. 3 according to their source
volcano location in Kamchatka (Fig. 3a), age (Fig. 3b), type of volcano
(Fig. 3c), and type of sample (Fig. 3d). Figure 3a–c show glasses taken only from
tephra; Fig. 3d compares glasses taken from tephra and welded tuffs. Glasses from
VF are represented by a full range of compositions from basaltic andesites to
rhyolites and belong to low-
Trace element variations in Holocene and late Pleistocene tephra
glasses south to north (left) and across (right) the Kamchatka volcanic
belts. Trace element ratios are normalized to primitive mantle values
(McDonough and Sun, 1995).
Data on concentrations of trace elements in glasses add significant information, which are highly valuable for precise identification of volcanic sources, as well as for petrological and geochemical applications of this database. The data for Ti, Mn, and P obtained by LA-ICP-MS are generally of higher precision in comparison to EPMA data, particularly for glasses with concentrations of these elements below 500 ppm (0.05 wt %), approaching the detection limit of EPMA.
Trace elements provided in this database belong to different groups with contrasting geochemical properties in magmatic systems and therefore provide different geochemical information. Behavior of Sr, Ti, V, Sc, P, Zr, Hf, and heavy rare earth elements (heavy REEs: Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) is strongly controlled by solid crystalline phases. When plagioclase (Sr, Eu), Fe-Ti oxides (Ti, V), pyroxene (Sc), apatite (P), zircon (Zr, Hf), and amphibole (heavy REEs) crystallize from magmas, these elements behave as “compatible elements”, and their concentrations decrease in residual melts. In contrast, elements Rb, Ba, Th, Nb, Ta, Pb, and light REEs (La, Ce, Pr, Nd, Sm) behave as “incompatible elements” in most magmas of Kamchatka because they are not concentrated in solid phases and enrich in residual melt. Systematics of incompatible elements can be informative of the magma source composition and subduction-related parameters, such as, for example, the distance from volcano to subducting plate (e.g., Volynets et al., 1994; Churikova et al., 2001; Duggen et al., 2007). The ratios between incompatible elements do not change as magma fractionates and are instructive for identifying the source volcano of variably fractionated melts. This information is quite unique in comparison to the systematics of major elements, which, in contrast to incompatible trace elements is largely related to the conditions of magma storage and also to syneruptive crystallization and magma mixing (Cashman and Edmonds, 2019; Ponomareva et al., 2015a).
Although detailed evaluation of trace element systematics in Kamchatka glasses is beyond the scope of this work, in Fig. 4 we illustrate some regularity in trace element composition of tephra glasses from different volcanic zones in Kamchatka, which can help identify source volcano or at least volcanic zone for tephra of unknown provenance. In this diagram, we show only Holocene and Late Pleistocene samples as their source volcanoes are reliably constrained, and the available data are the most representative compared to older volcanic rocks.
(
(
To sum up the overview of geochemical data, compositions of glass in Kamchatka tephra are very variable, enabling robust correlation of tephra layers as well as identification of source volcano and volcanic zone, from which unknown tephra could come from.
TephraKam was initially created for tephrochronological needs to enable
reliable identification and dating of tephra layers in Kamchatka and
neighboring areas and for identification of their sources. The data have
been used in a number of publications (Cook et al., 2018; Derkachev et al.,
2019; Plunkett et al., 2015; Ponomareva et al., 2018,
2013a, b, 2017,
2015b; Zelenin et al., 2020). Our experience showed that ash layers produced
by the largest explosive eruptions in Kamchatka can be recognized using
major element systematics of tephra glasses. A diagram of
In rare cases, tephra glasses from different volcanoes have hardly
distinguishable major element composition. In this case minor elements
determined by EPMA (P, Cl) and trace elements by LA-ICP-MS are useful to
identify source volcanoes. In Fig. 5, we illustrate this case using
compositions of tephra glasses from the Baranii Amphitheater Crater at the
foot of Opala volcano (eruption OP 1356 BP) and Khangar volcano (eruption
KHG6600 7490 BP). Although these tephras have very different ages, this
comparison is instructive to illustrate the value of minor and trace element
data to distinguish compositionally similar tephras. The difference in major
elements is very subtle and mostly within long-term analytical uncertainty:
Khangar glass has about 0.5 wt % lower
Example of using minor and trace element data to precisely identify
source volcanoes for glasses with very similar major element composition:
the case of tephras from Opala (eruption OP) and Khangar (KHG6600) volcanic
centers. Uncertainty of single EPM points
Backscattered electron images of glass devitrification in welded
tuffs:
Distinguishing tephra layers from the same volcano is a more difficult task. However, there is a number of examples from Kamchatkan volcanoes where tephra compositions are different even over short intervals of time (e.g., Kyle et al., 2011; Ponomareva et al., 2013b, 2017, 2015b). For example, Ponomareva et al. (2015b) showed that even compositionally similar tephra layers of the frequently erupting Shiveluch volcano can be distinguished using major element systematics in tephra glasses, particularly when the time period of eruption can be narrowed using marker layers from other volcanoes. The cases of compositionally identical products of different eruptions from the same volcanic center are also known. For example, Derkachev et al. (2020) reported two late Pleistocene layers produced by large eruptions from Gorely caldera, which have barely distinguishable major and trace element composition of glass. On a longer timescale of 100 000 years, the products of the Gorely caldera eruptions are more variable (Seligman et al., 2014), enabling their identification using glass composition in tephra and welded tuffs.
TephraKam contains abundant data for glasses in welded tuffs of the Miocene to
Pleistocene from different parts of Kamchatka. These rocks clearly
represent products of large caldera-forming eruptions during the history of Kamchatka. Identification of their sources, age, and ash distribution is of
great interest. However, some welded tuff glasses in the database have signs
of secondary alteration that hamper their direct interpretation as
compositions representative for native glass, i.e., quenched melt. Typically,
the alteration results in characteristic “spaghetti”-like textures,
precipitates of tiny magnetite crystals in glassy matrix followed by
complete glass replacement by microcrystalline aggregate, and development of
concentric perlite texture (Fig. 6). The process of devitrification is also
associated with chemical modification of welded tuffs. Spot analyses usually
reveal a large and correlated variability of alkalis and alkali earth
elements within single samples, which typically is not observed in volcanic
glasses from pumice fragments or ash layers. Representative trace element
composition of variably altered glasses from the same unit of Karymsky/Stena-Sobolinaya caldera welded tuffs is shown in Fig. 7. A major feature of
the glass alteration is enrichment in
Illustration of chemical effects of secondary alteration on major
and trace element composition of glass from welded tuffs:
Discrimination diagrams for different volcanic zones in Kamchatka.
The fields are drawn based on Holocene and late Pleistocene compositions.
Colored symbols show compositions of glasses according to their estimated
ages and present-day location: Holocene and late Pleistocene
In comparison with major elements, concentrations of some trace elements in
Kamchatka glasses are more variable and exhibit characteristic regional
distribution (Fig. 4). This makes it possible to use trace elements for
identification of volcanic zones, i.e., sources of distal tephra. Ideally, these
criteria should use immobile elements, which are unaffected by alteration of
glasses in welded tuffs and ancient tephras buried in marine sediments and
other deposits. We performed a search for the most effective criteria based
on trace element concentrations in glasses from this database. Based on this
search, diagrams using trace element ratios
The archive .zip file containing tables of this database is available on
ResearchGate:
TephraKam is the largest and most comprehensive collection of internally consistent high-quality chemical analyses of major and trace elements in glasses of pyroclastic rocks of Kamchatka volcanoes. Precise or estimated ages are provided for every sample. Use of this database opens the possibility for reliable identification and correlation of tephra layers in Kamchatka and neighboring areas, enables dating of sedimentary archives onshore and offshore of Kamchatka and allows the multicomponent petrological and geochemical analysis of composition and origin of magmatic melts, preserved as quenched glass in tephra. The latter application is straightforward for rhyolite glasses, which have been shown to preserve the composition of magmas at depth (except for volatiles) and thus are informative of magma composition and its storage conditions at depth in Kamchatka (Ponomareva et al., 2015a). The amount of presented data is comparable and exceeds that available from published sources on the composition of volcanic rocks in Kamchatka (e.g., GEOROC database). For silicic compositions, this database is a major source of information.
MVP and VVP designed the study and wrote the paper. MVP, VVP, LIB, MMP, and ANR conducted the fieldwork and collected most of the samples. MVP developed protocols of the EPM and LA-ICP-MS analyses and designed the database structure. MVP, VVP, AAP, and ANR produced the EPM and LA-ICP-MS data. EAZ compiled all the age data. DGS managed the LA-ICP-MS analyses. All authors discussed the results and participated in preparation of the paper.
The authors declare that they have no conflict of interest.
The authors cordially thank all colleagues who donated their samples for this research. The field efforts of Ilya N. Bindeman, Tatiana G. Churikova, Oleg V. Dirksen, Natalia V. Gorbach, Boris N. Gordeichik, Sergei A. Khubunaya, Natalia A. Kim, Stepan P. Krasheninnikov, Philip R. Kyle, Ivan V. Melekestsev, Nikita L. Mironov, Alexander B. Perepelov, Peter Rinkleff, and Oleg B. Seliangin are highly appreciated. We are deeply grateful to the late Olga A. Braitseva and Vladimir L. Leonov for providing their samples and for their long-term support of our research. We appreciate the help of Kronotsky Reserve in acquiring the samples from Uzon caldera and Kronotsky Lake. We thank Mario Thöner and Ulrike Westernströer for all their efforts in managing laboratory work and many years of excellent assistance with the electron probe and LA-ICP-MS. Constructive comments from Bärbel Sarbas and an anonymous referee helped us to improve the quality of this paper.
This research was supported by the Russian Science Foundation (grant no. 16-17-10035, partial funding of fieldwork, data processing, and work on the database and manuscript). All laboratory costs related to electron microprobe and LA-ICP-MS analyses were covered by the GEOMAR Helmholtz Centre for Ocean Research (Kiel, Germany).
This paper was edited by Attila Demény and reviewed by Bärbel Sarbas and one anonymous referee.