Pumice Samples Research Articles

Effect of physical, chemical and electro-kinetic properties of pumice on strength development of pumice blended cements

In the present study, the potential effects of physical, chemical and electro-kinetic properties of pumice on the strength development of pumice blended cements (PBC) were examined and documented. A significant relationship between zeta potential of pumice samples, setting time and water demand of PBC was found. A relationship between the chemical content of pumice samples and compressive strength of PBC was also observed. However, zeta potential of the pumice samples was found to be less effective in strength development. Despite the lower clinker content, the setting time of the PBC samples was shorter than control specimen. 30 % pumice replacement by clinker resulted in 5–28 % reduction in 28-day strength depending on the characteristics of the pumice samples and grinding time.

The dynamics of a pumice granular soil in dry state under isotropic resonant column testing

The response of soils under vibrations strongly depends on the type of particles which reflects the behavior at particle contacts and the micro-mechanisms that dominate granular assemblies. In this paper the dynamic properties of a pumice soil of low bulk density and high porosity were investigated. As a reference soil, a quartzitic crushed rock with hard particles was used. The experiments were performed on dry samples of sand to gravel size under isotropic conditions of confinement in a fixed-free resonant column apparatus. In the range of small strains, the Vs–σm′ and GO–σm′ relationships are dominated by particle type in terms of mineralogy and morphology; plastic response at particle contacts of the pumice samples led to higher nV and nG exponents in comparison to the quartz ones. The small-strain damping ratio values were fairly similar for pumice and quartz soils, while the values of the exponent nD were more scattered. At higher shear strain amplitudes, the pumice soils showed higher linearity in comparison to the quartz ones. This is attributed partially to micro-crushing at particle contacts that occurs during the dynamic loading of the pumice soils which shifts the elastic and volumetric thresholds to higher strains and plays an important role in the energy dissipation in granular assemblies.

Geochemical fingerprints of volcanic materials: Identification of a pumice trade route from Pompeii to Rome

Geochemical investigations on samples of pumice and lava extracted from the mortars and concretes of the Forum of Caesar and the Forum and Markets of Trajan are pre- sented and integrated with previous analyses of lava samples from Rome and Pompeii, and of pumices from the Colosseum and the Dioclethian's Bath, with the aim to identify the lithological provenance of these materi- als. Discrimination diagrams based on ratios of selected trace elements (i.e., Zr/Y, Nb/Y, Th/Ta, Nb/Zr) allow us to recognize the geo- chemical signature of the different volcanic regions of central Italy. These diagrams in- dicate that in the mortars of the Forum of Caesar and Forum of Trajan, the Roman builders integrated the scanty pumices from deposits of the Monti Sabatini Volcanic Dis- trict near Rome with others coming from the Vesuvius and Phlegrean Fields. Some of the pumices employed in the vaulted ceil- ings of these monuments display a peculiar geochemistry that has a unique correspon- dence with a pyroclastic deposit recovered in a borehole drilled on the southern fl anks of Vesuvius. Similarly, lava fl ows from this borehole display a different trace-element signature with respect to that of other coeval lava fl ows of the northern fl anks of Vesuvius, and it has a closer correspondence to that of the archaeological lava samples. These observations, integrated with historical and archaeological data, indicate that the Roman builders had a profound empirical knowl- edge of the physical properties of the volcanic rocks from different regions, and suggest that a systematic cultivation of lightweight volca- nic material occurred in the area of Pompeii for exportation to Rome and, likely, to other regions of the Mediterranean.

Study of acoustic radiation during air stream filtration through a porous medium

The paper presents results of laboratory experiments on studying the characteristics of acoustic emission generated by a flow of compressed air, which is filtered by porous pumice samples with and without partial fluid saturation. The construction features of the laboratory setup and details of the experiments are described. Porous samples with dry and partially fluid-filled pores are used. The visual patterns of the acoustic emission spectrum, which occurs under stationary filtration of the compressed air, are presented, and its amplitude-frequency distribution characteristic for different sample porosities and different degrees of their fluid saturation is shown. It is demonstrated that the relaxation times of the emission noise level differ. This is revealed during the sharp elimination of the drop in pressure from such samples, i.e., in the nonstationary filtration mode.

Estimation of the Bond Grindability Index From the Sink-Float Test Data of Two Different Particulate Pumices

In this study, equations for estimating the Bond grindability index by the sink-float test data of pumice were developed. Primarily, the cumulative weight and porosity content of the floating fraction were determined for two different pumice samples in all relative densities. Then, grindability of the pumice samples was determined for its constituent specific gravity fractions. Though the grindability of the constituent specific gravity fractions of both the pumices varies in a systematic manner, certain differences, it can be observed in the variation pattern between the two pumices. These differences included easy washability and moderate difficult washability characteristic pumices. The relationships between the Bond grindability and relative densities and between the Bond grindability and porosity were stated as simple equations, and the calculated values from equations were compared with the experimental results. Finally, the float–sink test results can be stated by simple equations relating to the Bond grindability value. The Bond grindability (Gbg) was easily measured by carrying out sink-float tests, and by measuring the constituent relative density fractions and porosity content.

Structure and distribution of allophanes, imogolite and proto-imogolite in volcanic soils

Despite half a century of intensive research, the structure and presence of short-range ordered aluminosilicates in volcanic soils is still the focus of debate. Imogolite is easily distinguishable because of its tubular structure, whereas allophane compounds—usually described as spheres—are harder to identify, especially because of their variable structure and occurrence patterns. In addition, the local structure of allophanes can be very similar to that of proto-imogolite (imogolite precursor). Strangely, this similarity is seldom considered in most characterization studies. In this context, our study focuses on the structure of two Al-rich short range-ordered aluminosilicates of two different origins, from: (i) an Andosol B horizon (Andosol sample); and (ii) a weathered pumice grain (pumice sample). These natural samples were compared to a synthetic proto-imogolite. The three samples were analyzed using experimental tools that are commonly used for the identification of these nanophases (chemical composition, X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy and transmission electron microscopy). The three samples exhibited the same local structure, but significant differences were observed at a larger scale. The pumice sample clearly showed ring-shaped particles, while the Andosol sample and the synthetic proto-imogolite were amorphous. Our results suggest that poorly ordered proto-imogolite, rather than Al-rich allophones and imogolites, is present in Andosol horizons. We believe that the mineralogy of these phases needs to be reassessed along with their growth mechanisms.

Decompression rate of magma at fragmentation: Inference from broken crystals in pumice of vulcanian eruption

Decompression rate of magma at fragmentation (immediately before or after fragmentation) was determined using broken crystals found in the pumices ejected during the vulcanian explosion of Sakurajima volcano, Japan. The combined analysis of textural data obtained from the natural pumice samples and a simple model for the crystal fracturing in vesiculating viscous magma indicated a decompression rate 7.0×103–7.8×104Pa/s for the ejecta produced during the later phase of vulcanian explosion. This result suggests that the short duration of the vulcanian explosion is controlled by the rapid decrease of the magma ascent rate to a vent. An understanding of the control mechanism of the termination of an eruption by precise prediction of the eruption process is essential for both volcanology and hazard mitigation.

Investigation of Acoustic Emission Caused by Filtration of an Air Flow through a Porous Medium

We study characteristics of acoustic emission caused by an air flow filtered through samples of solid porous pumice either partially filled with glycerin or dry. Some peculiarities of the laboratory setup and the performed experiments are described. Samples of different porosity and several values of the air pressure drop are tested. Physical reasons for the difference in acoustical emission spectra of samples of different porosity and in the relaxation times of the acoustic emission level caused by different porosity and fluid saturation are discussed. It is proposed to use the phenomenon of acoustic emission for detecting the fluid trapped in the pores of cores. The existing results based on the borehole field experiments are rough. The frequency range of signals recorded in these experiments is less than 5 kHz (up to 10 kHz). It is shown by our laboratory measurements that the required frequency band should be up to 50 - 60 kHz to reflect the features of the spectral composition of the acoustic emission in predicting the fluid content. The level of acoustic noise under field conditions is much higher, i.e., by 10 - 15 dB, than the noise achieved under laboratory conditions. Since the sensitivity of the recorders and the frequency range are considerably higher in our experiments, they are unique when applied to the solved problem.

Trace element and Pb–B–Li isotope systematics of olivine-hosted melt inclusions: insights into source metasomatism beneath Stromboli (southern Italy)

We studied the elemental and isotopic (Pb, B and Li isotopes) composition of melt inclusions hosted in highly forsteritic (Fo83–91) olivines that were collected from San Bartolo lava and pumice (ST79p, ST82p and ST531p) samples erupted by Stromboli in historical times. The studied melt inclusions have primitive calcalkaline to shoshonitic basaltic compositions. They cover a compositional range far wider than that exhibited by the whole-rocks and differ in key trace element ratios. San Bartolo melt inclusions are characterized by lower incompatible trace element abundances, higher ratios between fluid-mobile (B, Pb, U and LILE) and less fluid-mobile (REE, Th, HFSE) elements and lower La/Yb ratios relative to the pumice-hosted melt inclusions and pumiceous melts erupted during paroxysmal events. Trace elements, along with different Pb, B and Li isotopic signatures, attest to source heterogeneity on the small scale and provide new insights into subducted components beneath Stromboli. Results of a mixing model suggest that metasomatism of the mantle source of pumice-hosted melt inclusions was driven by solute-rich high-pressure fluids (<20%) expelled from the deep portion of the slab. Heterogeneous Pb isotopic composition together with light δ11B (−8.6 to −13.7‰) and δ7Li (+2.3 to −1.7‰) indicates that high-pressure liquids were released in variable proportions from highly dehydrated metabasalts and metasediments. On the other hand, the elemental and isotopic (δ11B ~ −1.9 to −5.9‰) composition of San Bartolo melt inclusions is better explained by the addition of a prevalent aqueous component (~2 to 4%) escaped at shallower depths from sediments and altered basaltic crust in almost equivalent proportions, with a smaller contribution by high-pressure fluids. Owing to the high-angle dip of the subducted cold Ionian slab, aqueous fluids and high-pressure fluids would rise through the mantle wedge and locally superimpose on each other, thus giving origin to variously metasomatized mantle domains.

Physical Properties, Morphology and Petrological Characteristics of Pumices from the Central Indian Ocean Basin

Abstract:About 400 pumice clasts collected from the Central Indian Ocean Basin (CIOB) were studied for their morphology and were classified based on their shape and size. A majority of the samples range between &lt;1 cm and 36 cm and in the Zinggs shape diagram plot in the equant and oblate fields. The Corey Shape Factor for most of the samples is close to 0.7, which is common for volcaniclastic material. The physical properties such as density, specific gravity, void ratio, porosity, moisture content and degree of saturation, were determined for 30 pumice samples. Density varies from 0.21 to 0.74 g/cm3 specific gravity 1.84 to 3.27, void ratio 2.21 to 10.67, porosity 67% to 91%, moisture content during sinking 0.44 to 2.35 and degree of saturation varies from 26.5% to 86%. Binocular and electron microscopy studies reveal that 60% of the vesicles are elongated, 30% are spherical and 10% are fibrous. Petrography of the pumices exhibits vitrophyric texture with phenocrysts of feldspars and clinopyroxenes. X‐ray diffractrogram and mineral analyses confirm plagioclase to be a major phase, while quartz and orthoclase are not uncommon. Todorokite is commonly present in the ferromanganese oxide coating present over some of the pumices. This paper also delves into some details concerning the controversial origin of the pumices and glass shards in the CIOB.

Petrography, mineralogy and geochemistry of a primitive pumice from Stromboli: implications for the deep feeding system

We describe the field relations, petrographic, mineralogical and geochemical characteristics of an exceptional “ golden ” pumice belonging to a tephra layer exposed on the summit area of Stromboli volcano, Italy. Pumice sample PST-9 comes from a fallout deposit older than a spatter agglutinate sequence emplaced during the twentieth century. The eruption that produced it had a size exceeding that of intermediate paroxysms but was smaller than large-scale, spatter-forming, paroxysms from the sixteenth century and 1930 A.D. Lapilli are strongly vesicular and crystal-poor, similar to other “ golden ” pumices. Modal proportions include 89 vol% glass, 8 vol% clinopyroxene, 1–2 vol% olivine and 1–2 vol% plagioclase. Plagioclase is represented by reacted crystals coming from the shallow resident magma and incorporated in the pumice during eruption. A total of 74 and 44 crystals of olivine and clinopyroxene, respectively, were examined and 187 and 99 electron microprobe analyses obtained. Fo in olivine ranges between 70 and 92 mol% and Fs in clinopyroxene between 3 and 13 mol%. PST-9 hosts a higher proportion of Fo-rich olivine and Fs-poor clinopyroxene than the other “ golden ” pumices. Groundmass glasses are basaltic (Mg# = 66–69), as are most rim glasses around olivine and clinopyroxene, and glass inclusions in clinopyroxene. They are more primitive than in the other “ golden ” pumices. A few rim glasses and glass inclusions are shoshonitic (Mg# = 45–50). Most glass inclusions in olivine have CaO/Al 2 O 3 higher than the other glasses and the whole-rock. PST-9 has the highest bulk MgO, CaO, Mg# and CaO/Al 2 O 3 and the lowest FeO t of all “ golden ” pumices analysed to date. Analysis of Fe-Mg partitioning between olivine, clinopyroxene and melt allows three crystallization stages to be recognized. The first involves primitive mantle-derived melts (Mg# = 74–80), the second basaltic melts represented by groundmass glasses and the third is associated with more evolved melts represented by the shoshonitic glasses. The population of crystals in “ golden ” pumices is heterogeneous not only because of crystal incorporation from the shallow resident magma, but also because of pre-eruptive recharge of the deep reservoir with primitive melts. Differences between PST-9 and the other “ golden ” pumices in terms of groundmass glass composition and distribution of olivine and clinopyroxene compositions reflect contrasted replenishment rates of the deep reservoir with primitive liquids. Gabbroic inclusions in a clinopyroxene crystal provide a direct illustration of melt wall-rock interaction and stress the variability of the deep reservoir in terms of temperature, crystallinity and phase assemblages. Deep crystallization of plagioclase should be considered as a possibility at Stromboli. PST-9 is exceptionally well representative of the early magmatic evolution of “ golden ” pumices.

Investigation of breakage behavior of different mineralogical and morphological characteristic pumices

Theobjectiveofthisstudyistoanalyzedrygrind- ing behavior of four different pumices in terms of Bond grindabilityvalue,selectionandbreakageparametersvalues. Forthispurpose,firstly,Bondgrindabilitytestweremadefor four pumices. Then, eight different mono-size fractions for each of pumices were carried out between 1.7 and 0.106mm formed by a √ 2 sieve series, and ground batch wise in a laboratory ball mill for determination of breakage parame- ters. Finally, Si and Bi, j equations were determined from the size distributions at different grinding times, and the model parameters (Si , aT ,α , γ , βand φ j) were compared for four different pumice samples.

Texture analysis of volcanic rock samples: Quantitative study of crystals and vesicles shape preferred orientation from X-ray microtomography data

In the texture analysis of volcanic rocks, the preferred orientation of the constituents can provide useful information for the interpretation of the processes involved in the rock formation. We present here a new data analysis technique, based on X-ray microtomography measurements and on shape preferred orientation analysis, to obtain the orientation distribution functions of the constituents of volcanic rocks. This procedure proved to be very suitable for volcanic samples, where diffraction-based techniques, developed for crystallographic preferred orientation studies, are of limited utilization, in addition to the fact that they cannot provide any information about vesicles or bubbles. Moreover the analysis performed directly in three dimensions (3D) overcomes the problems that usually occur when employing stereological methods for the analysis of the images obtained via microscopy-based techniques. In this study, two scoriae (from Stromboli and Etna) and a tube pumice (from Campi Flegrei) were measured via X-ray microtomography and then the resulting volumes were analyzed following the proposed procedure. Results highlight little preferred orientation for the vesicles in the two scoria samples, whereas the pumice shows a marked preferred orientation. Crystals (also divided by mineral species) were taken into account as well and in the two scoria samples there is no crystal preferred orientation, in contrast with the pumice, where crystal preferred orientation features are very similar to the ones found for the vesicles. Overall we found strong differences in preferred orientation: weak for vesicles in scoriae, showing an axial symmetry with the axis parallel to the elongation axis of the sample, and a stronger and more complex orientation texture in the pumice sample for both crystals and vesicles. The promising results obtained suggest that this procedure is potentially very useful for the analysis of preferred orientation in volcanic rocks and geomaterials in general.

Magma degassing process during Plinian eruptions

To assess magma degassing processes during Plinian eruption, noble gas abundances and isotopic ratios have been determined in pumices by crushing under vacuum. Samples come from Plinian eruptions, which occur along different subduction zones. In addition, two pumice samples come from the Azores hotspot. All samples are characterized by a systematic enrichment in neon over argon, a depletion of krypton relative to argon and an isotopically fractioned 38Ar/ 36Ar ratio. These features do not depend on geological setting, or on pumice age, or eruption intensity. However, they are similar for pumices from the same eruption. A correlation is observed between 84Kr/ 36Ar and the 38Ar/ 36Ar ratio. This illustrates that only one physical process is at the origin of the fractionation. We propose here a model of kinetic magma degassing before fragmentation to explain the elemental and isotopic fractionation. Noble gases diffuse in a magma shell surrounding a preexisting bubble. The model put forward an alternative to the model of Pinti et al. (1999), in which diffusion occurs after pumice quenching in Plinian plume. The model explains measurements and shows the rapidity of the magma degassing process in the conduit (few hundreds of seconds).

Linking experimental and natural vesicle textures in Vesuvius 79AD white pumice

Vesicle populations in volcanic pumice provide a partial record of shallow magma ascent and degassing. Here we compare pumice textures from the well-characterized 79AD Vesuvius eruption to those generated during isothermal decompression experiments. Three series of experiments were conducted using starting material from the first two phases of the eruption (eruptive units EU1 and EU2). Samples were decompressed from 100 or 150 MPa to final pressures of 10–25 MPa using conditions appropriate for simulating eruption conditions ( T = 850 °C, d P/d T = 0.25 MPa/s). The experiments differed not only in starting material but also in temperature at which samples were annealed prior to decompression, which determined the initial number of crystals present in the melt. Results show that experiments approach the vesicle number densities and sizes of pumice samples, but show narrower size distributions. The wider size range of pumice samples suggests continuous, rather than instantaneous nucleation, which may reflect non-linear rates of decompression. All experiments exhibited equilibrium degassing, a process that was probably aided by heterogeneous bubble nucleation on oxide microlites. We conclude that delayed bubble nucleation cannot explain the explosivity of the Vesuvius eruption, which instead appears to require high rates of magma decompression.

Provenancing of archeological pumice finds from North Sinai

Seven pumice samples from excavations in North Sinai have been investigated with respect to their geochemical composition. This type of volcanic rock has been used as an abrasive and thus has been an object of trade since antiquity. With the help of Instrumental Neutron Activation Analysis, six of these Bronze Age samples could be correlated to their volcanic sources on the islands of Santorini, Nisyros and Giali (Greece) using the typical element concentrations ("chemical fingerprint"). The source of one pumice sample remains unidentified excluding, however, the Santorini eruption as a possible source. The concluding section of this article discusses the possible contribution, however indirect, of the pumice from Sinai and elsewhere in the Eastern Mediterranean to the controversial issue of the accurate date of the "Minoan" eruption of Santorini.

Eyewitness, stratigraphy, chemistry, and eruptive dynamics of the 1913 Plinian eruption of Volcán de Colima, México

Based on the stratigraphic record of the deposits, analysis of previous works, historic archives, and eyewitness accounts the 1913 eruption of Volcán de Colima was reconstructed. The eruption started in 17 January and peaked in 20 January, 1913. It occurred in three main phases: 1) An opening phase with the generation of Merapi-type pyroclastic flows (units F 1, F 2, F 3) and a pyroclastic surge (S 1), 2) A vent-clearing phase with strong explosions that produced Vulcanian-Soufriere-type pyroclastic flows (F 4) and a pyroclastic surge (S 2) which destroyed the summit dome decompressing the magma system, and 3) a Plinian phase with the establishment of a ∼ 23 km high column dispersing a fallout (C 1) to the NE followed by the collapse of the column that generated a pyroclastic surge (S 3) and 15-km long pumice-rich pyroclastic flows (F 5). After the eruption, remobilization of the pyroclastic material generated lahars in main gullies around the crater. Fallout C 1 blanketed an area of ∼ 191,318 km 2 covering the cities of Guzman, Guadalajara, and Saltillo (Coahuila) located at 725 km from the source. It had a volume of 1.4 km 3 (0.57 km 3 DRE = Dense Rock Equivalent). The total volume of pyroclastic flow and surge deposits was 0.26 km 3 (0.07 km 3 DRE) giving a total volume of the eruption of 1.66 km 3 (0.64 km 3 DRE). The Plinian column lasted 4.6 h with a total mass of 1.5 × 10 12 kg and a mass eruption rate of 9.02 × 10 7 kg/s. The column height and the ejected magma volume indicate that the 1913 eruption had a VEI = 5 being the largest event in the historical record of Colima Volcano. Juvenile scoria and pumice consisted of Pl > Opx > Cpx > Hbl + accessory titanomagnetite + Ap and Ol with reaction rims. Chemistry of juvenile scoria and pumice samples is andesitic very homogeneous (58.3 ± 0.5 wt.% SiO 2) and similar to the 1818 juvenile products (58.9 ± 0.2 wt.% SiO 2). The presence of banded scoria, olivine phenocrysts with reaction rims, and trace element variations strongly suggest that the 1913 eruption was caused by a magma mixing event.

トカラ列島における中期更新世の酸性海底火山活動

To understand the submarine volcanism surrounding the Tokara Islands, a submarine topographic analysis and 67 dredge samplings were carried out. Prior to the submarine investigations, we reviewed comprehensively geological and geophysical data on this region and confirmed the complexity of both volcanic activity and tectonic setting of the Tokara Islands. In contrast to the homogeneous subaerial volcanic rocks comprising predominantly two-pyroxene andesite lava flows, the dredged samples vary from basaltic andesite to rhyolite in composition. Furthermore, we reveal that dacitic and rhyolitic pumices are abundant and broadly distributed throughout the submarine area. The recovered volcanic rocks were mainly subangular to angular cobble-boulder fragments of lava, scoria, and variably vesiculated pumice. Volcanic rocks with hornblende phenocrysts occur only north of the Tokara strike-slip fault, which is a major tectonic element of volcanism. The pumices can be classified into three categories based on the size and abundance of the phenocrysts: aphyric pumice, fine-grained porphyritic pumice, and coarse-grained porphyritic pumice. Occurrences, such as amount in a dredge, shape without extensive abrasion, large fragment size, and bulk rock chemical compositions of the major pumice fragments suggest that they are in situ, rather than originating as drifted pumice or air fall, exotic pyroclastic fragments derived from the four super-eruptions of Kyushu Island. Because dredged samples contained fresh volcanic glass in the groundmass, and are not covered by iron-manganese oxide crust, they appear to have originated from the Quaternary eruptions. Indeed volcanic islands have developed above the submarine erosional terraces (indicated as knick points at approximately 110 m in depth), which is assumed to have formed during the last glacial age. K-Ar age dating on the representative pumice samples resulted in ages of 0.60 ± 0.20 Ma and < 0.2 Ma, respectively. These newly obtained submarine data support that acidic volcanisms occurred around the submarine calderas during the Mid-Pleistocene age.

Sr, Nd and Pb isotopic and geochemical constraints for the origin of magmas in Popocatépetl volcano (central Mexico) and their relationship with the adjacent volcanic fields

We present new geochemical data (major- and trace-elements, as well as Sr and Nd isotopic compositions) of volcanic rocks erupted from Popocatépetl volcano during the volcanic event from December 2000 to January 2001. These data along with an exhaustive compilation of geochemical and Sr, Nd, and Pb isotope data reported for Popocatépetl rocks and nearby volcanic areas are used to examine the origin and geochemical evolution of the magmas in the central Mexican volcanic belt (CMVB). During this period of volcanic eruptions Popocatépetl produced ash columns as high as 7 km. Pyroclastic flows and lahars were observed after the completion of the activity. Samples of banded pumice and a bomb fragment transported by the lahar were chemically analysed for this work. Rocks show an andesitic composition with 58.5–61.7 wt.% SiO2 and 5.9–4.0 wt.% MgO. Contents of large ion lithophile elements (LILE), rare-earth elements (REE) and Zr are nearly constant through the compositional range. No significant Eu anomaly is present, but the samples show Nb-anomaly relative to LILE and high-field strength elements (HFSE). Nd- and Sr-isotopic compositions of these samples range from 143Nd/144Nd = 0.51291 to 0.51287 and 87Sr/86Sr = 0.70399 to 0.70422. Comparison of Popocatépetl products with volcanic rocks from the nearby areas shows that the magmas in CMVB were generated in a heterogeneously veined-mantle source enriched in LILE, HFSE, and REE. Additional crustal assimilation as well as fractional crystallization could account for the great chemical variability of rocks in the CMVB. Statistical comparison of the geochemical compositions of the volcanic products ejected from 1994 to 2000 to those ejected during the 2001 event shows that most geochemical parameters (major- and trace-elements, normative minerals, Sr and Nd isotopic composition, as well some elemental ratios) present no statistically significant differences. Statistically significant differences in the mean only were computed for the major-elements SiO2, FeO, MgO, CaO, and K2O, as well as for the rare-earth elements Nd, Sm, Eu, Gd, Dy, Ho, Tm, and Yb.

The natural radioactivity levels and radiation hazard of pumice from the East Mediterranean Region of Turkey

The concentrations of natural radionuclides in 20 pumice samples from the Toprakkale-Osmaniye area were studied using γ-ray spectrometry in order to assess the radioactivity levels and health hazard. The activity concentrations of 226Ra, 232Th and 40K in the pumice samples ranged from 9.44 to 27.31, 12.24 to 25.43 and 289.48 to 673.18 Bq kg−1, respectively. The radionuclide concentrations in pumice samples were matched with typical world values and the radium equivalent activity (Raeq), external (Hex) and internal (Hin) hazard index and representative level index (Iγr) determined. All the calculated values were below the internationally accepted limits and indicate that the Toprakkale-Osmaniye pumice can safely be used in construction.