Airborne particles, such as dust and volcanic ash, pose a serious hazard to aircraft in flight due to their potential to cause erosion damage to engine components. It is crucial to anticipate and address the impact of erosion wear on engine performance and safety. This study aims to enhance our understanding of how volcanic ash particles behave when ingested through a high bypass turbofan engine (HBTFE) and assess the development of erosion wear in the front components. The effects of four different ash samples are assessed in various scenarios of encountering volcanic ash during cruise flight conditions. First, the flow solution is obtained for all front components, including the Pitot intake, spinner, fan, inlet guide vanes (IGVs), outlet guide vanes (OGVs), and connecting ducts. Based on the flow data, the particle motion equations are solved step by step using an in-house trajectory and erosion code. This latter adopts the Lagrangian approach, which incorporates a particle-eddy interaction model and includes probabilistic descriptions for the release positions of particles, sizes, and restitution factors. The finite element method (FEM) is used to track particles through the computational cells and determine impact positions and conditions. As a result, the Pitot intake design seems to prevent many ash particles from reaching the fan blade beyond 80% of the span. The fan blade leading edge (LE) exhibits extreme erosion on both sides. The blade’s pressure side (PS) displays erosion spreading practically on the entirety of the surface, especially near the trailing edge (TE). In contrast, the suction side (SS) has scattered erosion at lower rates. Furthermore, the rotor’s hub presents almost uniform erosion patterns, whereas the shroud depicts scattered erosion. This large fan appears to function as a separator, expelling a significant amount of ash particles through the secondary duct, thereby reducing the engine core’s susceptibility to erosion. Out of the four volcanic ash samples, those from the Kelud and Etna volcanoes appear to cause the highest hourly eroded mass, about twice as much as the samples from the Chaiten and Eyjafjallajokull volcanoes.

Two diagenetic stages of zeolitic alteration were recognized in a study of a thin bed of rhyolitic ash that was deposited in Eocene Lake Gosiute (Laney Member of the Green River Formation). The ash bed can be traced for 30 km along strike and represents a single volcanic event. The bed was not buried deeply (<100°C), and originally it was compositionally homogeneous. Initially, the bed altered to clino-ptilolite, heulandite, an intermediate phase between these two zeolites, and mordenite. These early reactions involved the hydration and solution of glass by saline, alkaline solutions and the subsequent precipitation of zeolites. The variation in zeolite mineralogy is due to differences in interstitial fluid chemistry that resulted from either fluctuations in lake-water chemistry or the proximity of spring discharge. These reactions, exclusive of the addition of H2O, involved only minor amounts of mass transfer over very small distances. Later, after burial, the early-formed zeolites reacted with upward moving sodium carbonate brines that were produced by dewatering of underlying evaporite deposits. The sodium carbonate brines, in equilibrium with trona and nahcolite, elevated the activity of Na+ and produced analcime. These later dehydration reactions involved significant mass transfer.

Allophane samples from soils, pumice, and stream beds have been studied by electron optical, infrared absorption, X-ray fluorescence, gas chromatography, and phosphate adsorption methods. The allophane particles were hollow spherules or polyhedra 35 and 50 Å in diameter with molar Al/Si ratios close to 2.0. The thickness of the wall of the spherules was estimated to be 7 Å. For the pumice allophanes, the wall was largely composed of imogolite structural units (OH)3Al2O3SiOH. Defects or pores were present in the wall and probably were the sites where phosphate was adsorbed. It is suggested that these allophanes with molar Al/Si ratios close to 2.0 should be called “proto-imogolite” allophane.

Two soil allophanes had a similar structure to the allophane from Stratford pumice, but small amounts of layer silicates, including halloysite, were also present in the soil samples, as indicated by infrared bands at 470, 1030, and 1100 cm−1. The allophane from the stream bed at Silica Springs had an infrared spectrum similar to feldspathoids, and it did not have the imogolite structure.

The most prominent authigenic reaction in Holocene tuffaceous sediments at Teels Marsh, Nevada, is the hydration of rhyolitic glass by interstitial brines and the subsequent formation of phillipsite. This reaction has the form: rhyolitic glass + H2O → hydrous alkali alumninosilicate gel → phillipsite. Phillipsite is the most abundant authigenic phase in the tuffaceous sediments (>95%), analcime is the next most abundant phase, and clinoptilolite occurs as a trace mineral in the <2-mm fraction. Analcime forms by the reaction of phillipsite and Na+. Gaylussite and searlesite also are common authigenic phases at Teels Marsh. The concentration of silica in the interstitial brines is controlled by one or more of the authigenic reactions at less than 100 ppm. A stoichiometric equation for the reaction of phillipsite to analcime at Teels Marsh is:

$$0.43N{a + }\, + {K_{0.43}}N{a_{0.57}}AlS{i_{3.1}}{O_{8.2}}\, \cdot \,3.2{H_2}O\, \to \,NaAlS{i_2}{O_6}\, \cdot \,{H_2}O\, + \,1.1{H_4}Si{O_4}\, + \,0.43{K + }.$$

Sodium and potassium activities of brines associated with both phillipsite and analcime were used to estimate the equilibrium constant for this reaction as 3.04 × 10−5. The ΔG0 value for the reaction is +6.2 kcal/mole at 25°C and 1 atm pressure. The estimated ΔG0 value of phillipsite, using this reaction, is −1072.8 kcal/mole at 25°C and 1 atm.

The effects of NaOAc removal of carbonates, H2O2 removal of organic materials, and sodium citrate-bicarbonate-dithionite (SCBD) removal of iron oxides upon the X-ray powder diffraction (XRD) characteristics of clay minerals present within weathered volcanic ash deposits were examined. All pretreatments of samples derived from the Ae and Bhf horizons containing volcanic ash resulted in dramatic increases in XRD peak intensities, while the treatment of IIC-horizon samples resulted in subdued XRD peak intensities. Also, the chemical treatments produced an apparent increase in the amount of expandable clay minerals within the Ae horizon, due probably to the hydrolysis and removal of interlayer Al3+ when H2O2 and SCBD were used. Hence, poorly ordered and pedogenically modified vermiculite or vermiculite/montmorillonite interstratifications became “weathered” by H+ attack and Al3+ removal in a manner similar to the natural processes which take place in the acid and eluvial A horizon. In addition, possible XRD peak modification due to the dilution of crystalline clay concentrations by amorphous clay-size material appeared to be subordinate to the laboratory-induced chemical alteration of the weathered clay minerals.

Mordenite occurs in hydrothermally altered rhyolitic volcanic rocks at the margin of a Late Miocene lake basin on the island of Samos, Greece. The mordenite was identified by its X-ray powder diffraction pattern and appearance in scanning electron micrographs. Electron microprobe analyses show high Si, Ca, and K, low Na, and high balance errors. The b cell dimension is consistent with a high Si/(Al + Si) ratio, and the balance errors are apparently due to Na deficiency. The missing Na was estimated from the amount required to give (Si + Al) = 48 and yielded analyses comparable with X-ray fluorescence analyses of samples predominantly of mordenite. Even after this correction, the mordenite had a low Na:K ratio compared with most analyses reported in the literature. The peculiar chemistry of the mordenite may have resulted from a high-temperature metasomatic origin as a result of basaltic volcanism at the basin margin and characterized by hydrothermal circulation of alkaline lake water rich in K.

Volcanic and non-volcanic partings are exposed in coal beds of the Tertiary Beluga and Sterling Formations along the shores of the Kenai lowland, Alaska. About two-thirds of the partings originated as air-fall tephra which fell in coal-forming swamps. The tephra partings in the Pliocene strata are unaltered or slightly altered and have a characteristic mineral assemblage of volcanic glass ± montmoriUonite ± kaolinite ± opal-CT. Miocene strata are slightly altered to totally altered, and a typical mineral assemblage consists of feldspar ± kaolinite ± montmorillonite ± quartz ± crandallite ± altered volcanic glass. Crandallite appears to have formed early in diagenesis by the replacement of volcanic glass prior to the formation of montmorillonite and kaolinite.

About one-third of the partings originated primarily as detrital sediments derived from surrounding metamorphic and sedimentary terranes and were deposited by periodic floods. Mixtures of tephra and detrital sediments were also noted and were difficult to distinguish from tephra partings in the field. Detrital partings are characterized by detrital chlorite + illite + smectite + quartz ± feldspar ± siderite ± kaolinite. The chlorite in these strata is allogenic. Smectite is less common in the detrital partings.

Ash layers from Searles Lake, California, were sampled in core of drill hole KM-3, which penetrated 693 m of lacustrine sediment deposited in a playa-lake complex over the past 3.2 my. Lake water changed from moderately saline and slightly alkaline (pH ~7.5) to highly saline 2.04 my ago and to highly saline and alkaline (pH ~9.5) 1.28 my ago. As a result of brines flushing downward, the upper 291 m of sediment, spanning the past 1.28 my, contain highly saline, alkaline pore fluid. Silicic ash layers in contact with highly saline, alkaline pore fluid were first altered to phillipsite and meriinoite and then to K-feldspar and searlesite. The transformation of phillipsite and/or meriinoite to K-feldspar required more than 45,000 years and was largely completed in 140,000 years. Tephra layers in contact with moderately saline, slightly alkaline pore fluid vary from uncemented vitric ash containing minor smectite to bentonites in which glass is wholly altered to smectite, clinoptilolite, analcime, and opal. Layers with much fine tephra are more altered than the coarser, better-sorted layers. Alteration is attributed to hydrolysis in essentially a closed hydrologic system, in which the alteration of glass to smectite raised the pH, aSiO2, and (Na+ + K+)/H+ activity ratio to the level where clinoptilolite formed. Some diffusion and/ or fluid flow is, however, indicated by the loss of SiO2 during the alteration of ash layers to smectite and by anhydrite deposited during and after clinoptilolite in some tuffaceous sandstones.

A hydrated alumino-phosphate mineral was identified in thin, kaolinitic clay beds of the Cretaceous Dakota Group and the overlying Mowry Shale in the Dakota hogback west of Denver, Colorado. It occurs as 1–3-μm size euhedral crystals and makes up as much as 15% of the rock. Sr is by far the dominent divalent cation present, ranging from 9.4 to 13.1%, confirming the X-ray powder diffraction identification of this mineral as goyazite, the Sr member of the plumbogummite group. The characteristic pseudo-cubic, rhombohedral morphology of this mineral is plainly visible in scanning electron micrographs. On the basis of its euhedral morphology and its occurrence in volcanic ash-derived kaolin beds, the goyazite probably formed during early diagenesis, before or during the alteration of the ash, and before much compaction of the beds.

Low-angle X-ray powder diffraction (XRD) measurements of soil samples, made at controlled relative humidities, showed the presence of major reflections at 20–33, 10–27, and 7–8 Å. The first reflection, which increased in intensity but did not shift in spacing with decreasing relative humidity, represents curved smectite layers. This spacing was also observed by high-resolution transmission electron microscopy. The value of 10–27 Å for the second reflection, the 001 reflection of smetite, is unusually high, probably due to poorly stacked, irregularly curved layers. The 7–8-Å reflection originates from kaolinite or dehydrated halloysite, which also contain curved layers. The more curved the layer structure of the smectite, the more difficult it is to detect this phase; therefore the XRD relative peak heights are not directly proportional to the percentages of the smectite.

Phyllosilicates are major components of the <2-μm fraction (1–3 wt. % of most bulk specimens) in more than 50 samples of air-fall tephra from several 1980 eruptions of Mount St. Helens. In all samples, trioctahedral smectite is the major clay mineral. The integral series of 00ℓ reflections in ethylene glycol-treated samples indicates a lack of interstratification; absence of a peak near 5 Å after heat treatment, the 060 peak at 1.54 Å, and energy dispersive chemical analyses indicate that the smectite is a Mg- and Fe- rich, trioctahedral saponite. Minor mica and chlorite are present in the <2-μm fraction of most samples, and some samples show a peak near 12 Å after heating to 550°C which is probably due to the presence of an interstratifled chlorite/collapsed smectite or chlorite/collapsed vermiculite. The tephra contains glass and crystals originating from new magma and lithic fragments incorporated from the pre-existing cone. The clay minerals in the tephra are lithic components stripped from older, hydrothermally altered rocks during explosive ejection. Cleaned pumice fragments, which are new magmatic components, lack smectite, but contain rare biotite in xenoliths. Old, hydrothermally altered rocks from the volcano's summit and from the debris-avalanche (former north flank) contain saponite together with chlorite and chlorite/smectite which may have formed from it. Saponite and zeolites that precipitated from neutral to alkaline hydrothermal solutions line cavities in some of these rocks. The saponite was probably not subjected to magmatic temperatures because heating this material for 5 min at 750°C collapses it irreversibly to 10 Å. Kaolinite, alunite, and opal, indicative of acid-sulfate alteration, were found only in the pre-1980 summit crater and the southwest thermal area, but were not evident in the lithic components of the 1980 deposits.

The oxygen and hydrogen isotope compositions of volcanic ash layers from coastal outcrops of the Miocene Monterey Formation elucidate the progressive burial diagenesis of glass to bentonite and metabentonite. Volcanic glass that texturally appears unaltered is found to have δl8O and δD values that are significantly higher than fresh volcanic glasses. The positive shift in δ18O and δD values is proportional to the amount of hydration and chemical alteration of the glass samples. Initial hydration of the glass results in the exchange of Na for H; later hydration results in the loss of K and Fe in exchange for H and Na. The δ18O values of the most hydrated glass, and clay minerals from bentonite and metabentonite layers are approximately in equilibrium with slightly modified seawater. The δD values of the hydrated glass, and clay minerals from bentonite and metabentonite layers, are significantly depleted in D relative to seawater and suggest meteoric exchange associated with tectonic uplift and erosion in the Pliocene and Pleistocene. Smectite from bentonite layers has δ18O and δD values similar to the most hydrated glass samples, suggesting similar glass-water and smectite-water fractionation factors. Kaolinite and mixed-layered illite-smectite (I-S) altered from smectite have lower δ18O and higher δD values than their precursor. The δ18O and δD of nonvolcanic siliceous mudstones from the Pt. Arguello oil field show an unusual decrease in δD with increasing burial depth that probably reflects the presence of organic hydrogen in the analyzed samples as well as possible D-depleted formation waters from detrital illite-water and hydrocarbon-water exchange.

Smectite and fine-grained quartz were separated from 6 volcanic ash samples collected in Japan from Shinmoe-dake Volcano, southern Kyushu, and Mt. Usu Volcano, southern Hokkaido. Oxygen isotope ratios of smectite in the volcanic ash range from +6.9 to +12.9 per mill (‰), which are comparable to the values of smectite (δ18O = +6.5 and +9.4‰) from currently active geothermal fields. Evaluation of the oxygen isotope data from smectite (δ18O = +6.9 and +8.4‰) and quartz (δ18O = +6.6 to +11.2‰) in volcanic ash erupted from Shinmoe-dake in 1959 indicates a hydrothermal origin at elevated temperatures (150 to 270 °C) from waters that have calculated 8180 values (8180 = -3 to +5%o) that are enriched relative to local meteoric water (δ18O = -7 to -8‰). This precludes an authigenic formation of the smectites under ambient temperatures in crater lakes and/or somma-atrios which had been previously proposed as a plausible mechanism. A peculiar clay flow was extruded on the somma-atrio of Mt. Usu Volcano. The isotopic composition of the clay (<0.5 μm, δ18O = + 12.2‰) and evidence from geophysical exploration over volcanic vents of Shinmoe-dake support the concept that extensive hydrothermal alteration is taking place within volcanic vents.

The chemical composition of the source magma along with the physiochemical conditions of the depositional environment are the main controlling factors in determining the behavior and mobility of trace elements and rare earth elements (REEs) during the transformation of volcanic ash to bentonite. The purpose of the present study was to determine the distribution pattern and mobility of trace elements and REEs in several bentonite deposits formed by diagenetic alteration of volcanic ash in shallow alkaline water in eastern Iran. Using geochemical and statistical data, the degree of weathering in the parent rocks and the distribution and mobility of trace elements and REEs during the alteration process at seven deposits (Chah-Taleb, Chah-Keshmir, Chah-Golestan, Chah-Pirouz, Gholeh-Gelia, Kharman-Sar, and Khal-Kooh) were studied. None of the parent rocks showed an advanced degree of depositional reworking and, therefore, their chemical composition is representative of the volcanic ash from which the bentonites were formed. In the chondrite-normalized REE patterns of both parent rocks and bentonites, the light rare earth elements (LREEs) were found to be enriched relative to the heavy rare earth elements (HREEs). The variation in δEu and δCe values suggested a high-temperature (<200°C), suboxic, aquatic environment in which the conversion of volcanic ash to bentonite occurred. In the bivariate correlation analysis, Si showed a strong inverse relationship with Al and LREEs, while large ion lithophile elements (LILEs), high field strength elements (HFSEs), HREEs, and LREEs displayed a positive correlation between the elements of their respective groups. The R2 values in the binary diagram of potential immobile elements against Al suggest a qualitative classification in which Ti, Gd, Ga, Pr, Tb, Nd, Sm, Ce, and Nb are considered immobile, and U, Dy, In, Sc, Hf, Zr, La, and Eu are considered to have had poor mobility during formation of the Eastern Iranian bentonite deposits.

Layers of volcanic ash and Andosol soils derived from the ash may play an important role in preserving snow and ice as well as in the development of permafrost conditions in (a) the immediate vicinity of volcanoes at high elevations or at high latitudes and (b) land areas that are often distant from volcanic activity and are either prone to permafrost or covered by snow and ice, but have been affected by subaerial ash deposition. The special properties of volcanic ash are critically reviewed, particularly in relation to recent research in Kamchatka in the Far East of Russia. Of special importance are the thermal properties, the unfrozen water contents of ash layers, and the rate of volcanic glass weathering.Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite), but occurs at a much slower rate under cold compared to warm climate conditions. Existing data reveal (1) a strong correlation between the thermal conductivity, the water/ice content, and the mineralogy of the weathered part of the volcanic ash, (2) that an increase in the amounts of amorphous clay minerals (allophane, palagonite) increases the proportion of unfrozen water and decreases the thermal conductivity, and (3) that amorphous silica does not alter to halloysite or other clay minerals, even in the Early Pleistocene age (Kamchatka) volcanic ashes or in the Miocene and Pliocene deposits of Antarctica due to the cold temperatures. The significance of these findings are discussed in relation to past climate reconstruction and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.

Minerals such as quartz, present widely in various volcanic ashes, remain unaltered throughout the low-temperature hydrothermal process currently used in industry to obtain zeolites, causing an incomplete hydrothermal transformation of the starting solid. This study presents a novel and cost-effective procedure which improves the reactivity of ash toward the generation of zeolite by increasing the availability of silica and alumina components. This method leads to a final product with a large zeolite content. The transformation consisted of an ash-activation step followed by hydrothermal zeolitization. The influence of the structural, chemical, and morphological characteristics of the volcanic ash as well as the effect of the activation procedure on the ash reactivity were studied. A collected sample (VA) and an amorphous fraction obtained after VA sieving (VA40, retained on #40 mesh) were used for zeolite production. These solids were alkaline-treated separately, aged, and reacted under controlled conditions of temperature at autogenous pressure. Throughout the process, the solid phases were characterized by X-ray diffraction, energy dispersive X-ray microanalysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2adsorption-desorption porosimetry measurements. After activation and alkaline aging, the presence of quartz and plagioclase minerals in the natural ash seemed to improve the growth of NaAlSiO4 polymorphs, which in turn were transformed easily to zeolite structures. Even under adequate pretreatment and suitable synthesis conditions, the coarse non-crystalline fraction led to low conversion, while the highest conversions to zeolites A and X were obtained from the natural ash. The outcomes of the present study could be used to improve the conversion levels of other non-conventional aluminosiliceous minerals into zeolites.

The composition of altered volcanic ash of the Late Ordovician Kinnekulle bed was studied in geological sections of the Baltic Paleobasin. The composition of altered ash varies with paleosea depth from northern Estonia to Lithuania. The ash bed in shallow shelf limestones contains an association of illite-smectite (I-S) and K-feldspar, with the K2O content ranging from 7.5 to 15.3%. The limestone in the transition zone between shallow- and deep-shelf environments contains I-S-dominated ash with K2O content from 6.0 to 7.5%. In the deep-shelf marlstone and shale, the volcanic ash bed consists of I-S and kaolinite with a K2O content ranging from 4.1 to 6.0%. This shows that authigenic silicates from volcanic ash were formed during the early sedimentary-diagenetic processes. The composition of the altered volcanic ash can be used as a paleoenvironmental indicator showing the pH of the seawater or porewater in sediments as well as the sedimentation rate.

Production and consumption of pottery tempered with fresh volcanic ash peaked in the Late to Terminal Classic periods in the Maya lowlands. Differences in the type of volcanic inclusion and vessel form indicate that the pottery was produced in multiple locations by different groups of potters. In this article, we characterize pottery from household contexts at Baking Pot, Belize, using thin-section petrography and neutron activation analysis (NAA) to document mineralogical and chemical variability and determine provenance. The pottery was produced by adding fresh volcanic ash to a micritic clay. The petrographic and chemical data indicate that this paste recipe was produced locally in the Belize Valley. Variation in the paste recipes used is likely due to both production differences and postdepositional alteration. We argue that it is critical to use both petrography and NAA to understand pottery production and provenance in the Maya region.