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Monogenetic volcanism produces small-volume volcanoes with a wide range of eruptive styles, lithological features and geomorphic architectures. They are classified as spatter cones, scoria (or cinder) cones, tuff rings, maars (maar–diatremes) and tuff cones based on the magma/water ratio, dominant eruption styles and their typical surface morphotypes. The common interplay between internal, such as the physical–chemical characteristics of magma, and external parameters, such as groundwater flow, substrate characteristics or topography, plays an important role in creating small-volume volcanoes with diverse architectures, which can give the impression of complexity and of similarities to large-volume polygenetic volcanoes. In spite of this volcanic facies complexity, we defend the term “monogenetic volcano” and highlight the term’s value, especially to express volcano morphotypes. This study defines a monogenetic volcano, a volcanic edifice with a small cumulative volume (typically ≤1 km 3 ) that has been built up by one continuous, or many discontinuous, small eruptions fed from one or multiple magma batches. This definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism.

High-silica rhyolites and granites (>75 wt% SiO2, anhydrous basis) are common features of the crust as part of both the volcanic and the plutonic records. While low crystallization pressure (<250 MPa) is typically inferred, it has been suggested that they form via polybaric evolution, with initial crystallization at relatively high pressures (>500 MPa). We use glass compositions derived from the EarthChem portal, selected natural examples from the literature, and rhyolite-MELTS calculations to show that the phase relations in the quartz-albite-orthoclase ternary dictate the silica content of silicic melts. In particular, we show that silica content of melts increases with decreasing pressure as a result of the displacement of the quartz-sanidine cotectic toward the Qz apex with decreasing pressure. It follows from our analysis that (1) the crust is expected to be stratified in terms of the silica content of residing melts; (2) high-silica glasses form at low pressure, requiring shallow-level crystallization, and preclude a polybaric evolution for many systems (e.g., Bishop Tuff); (3) the existence of high-silica pumice requires fractionation (or melting) at low pressure, showing that high-silica rhyolites are intrinsic to the shallow crust; and (4) low-pressure cumulates (or melting residues) must exist in the shallow crust, weighing in favor of the cumulatic nature of many granitoids found in plutons.

The article is devoted to the study of the light concrete shrinkage deformations’ development patterns on porous aggregates of the volcanic tuff Kamensky deposit in Kabardino-Balkaria, prepared on quartz and tuff sands, using an expanding additive of sulfo-aluminate type in the amount of 12.5% Portland cement mass, the composition and amount of which was determined by the DSTU method.

Six tuffaceous beds within the Omo Group of the Omo-Turkana Basin have been dated using the 40Ar/39Ar single crystal total fusion method on anorthoclase, yielding eruption ages. The Omo Group constitutes up to 800 m of subaerially exposed sediments surrounding Lake Turkana within the East African Rift system in northern Kenya and southern Ethiopia. Rhyolitic explosive eruptions produced tuffs and pumice clasts that are considered to have been deposited shortly after eruption. The new age data on feldspars from the pumice clasts range from 4.02 ± 0.04 Ma for the Naibar Tuff of the Koobi Fora Formation to 1.53 ± 0.02 Ma for Tuff K of the Shungura Formation. The Orange Tuff in the KBS Member of the Koobi Fora Formation was dated at 1.76 ± 0.03 Ma, providing good control in this part of the sequence where formerly there was a >200 ka gap. Data are consistent with earlier measurements and significantly improve age resolution within the Omo Group, which has yielded many vertebrate fossils, including hominin fossils comprising a number of species. We suggest new age estimates for a limited number of hominin specimens.

An updated and expanded data set that consists of 214 plagioclase-liquid equilibrium pairs from 40 experimental studies in the literature is used to recalibrate the thermodynamic model for the plagioclase-liquid hygrometer of Lange et al. (2009); the updated model is applicable to metaluminous and alkaline magmas. The model is based on the crystal-liquid exchange reaction between the anorthite (CaAl2Si2O8) and albite (NaAlSi3O8) components, and all available volumetric and calorimetric data for the pure end-member components are used in the revised model. The activities of the crystalline plagioclase components are taken from Holland and Powell (1992). Of the 214 experiments, 107 are hydrous and 107 are anhydrous. Four criteria were applied for inclusion of experiments in the final data set: (1) crystallinities <30%; (2) pure-H2O fluid saturated; (3) compositional totals (including H2O component) of 97-101% for hydrous quenched glasses and 98.5-101 for anhydrous quenched glasses; and (4) melt viscosities ≤5.2 log10 Pa·s. The final data set spans a wide range in liquid composition (45-80 wt% SiO2; 1-10 wt% Na2O+K2O), plagioclase composition (An17-95), temperature (750-1244°C), pressure (0-350 MPa), and H2O content (0-8.3 wt%). The water solubility model of Zhang et al. (2007) was applied to all hydrous experiments. The standard error estimate on the hygrometer model is 0.35 wt% H2O, and all liquid compositions are fitted equally well. Application of the model as a thermometer recovers temperatures to within ±12°, on average. Tests of the hygrometer on anhydrous piston-cylinder experiments in the literature, not included in the regression, show that the model is accurate at all pressures where plagioclase is stable. Applications of the hygrometer are made to natural rhyolites (Bishop Tuff, Katmai, and TobaTuff) with reported H2O analyses in quartz-hosted melt inclusions from the literature; the results show agreement. Applications of the hygrometer/thermometer are additionally made to natural rhyolites from Iceland and Glass Mountain, California. The updated model can be downloaded either as a program in Excel format or as a MatLab script from the Data Repository.

This article presents the results of numerical modeling for a hypothetical CO[sub.2]-EGS system in the volcanic rocks of the Gorzów Block, Poland. Modeling was carried out in the following stages: in phase 0, modeling of the fracturing process was performed, as a result of which the permeability distribution for the newly created fractured zone was obtained. Next, the process of saturating the EGS reservoir with CO[sub.2] was modeled until pure CO[sub.2] could enter the production well (phase 1). Then, a multi-variant simulation of heat production was performed (phase 2). The obtained results allowed for drawing interesting conclusions: (1) the duration of phase 1 may take several years unless a sufficiently high injection rate of CO[sub.2] is supplied, (2) the higher the injection rate of CO[sub.2], the lower the cumulative storage ratio of CO[sub.2], and (3) most of the CO[sub.2] storage in the formation takes place in phase 1, while even 92% of the CO[sub.2] injected in phase 2 can be recovered via the production well. Despite the environmental benefits connected with structural trapping of CO[sub.2], the Gorzów Block has probably too low formation temperature (145 °C) and too low stimulated volume (~0.1 km[sup.3]) to deliver satisfactory and stable thermal output.

Hydrovolcanism is a type of volcanism where magma and water interact either explosively or non-explosively. The less frequently used term, hydromagmatism, includes all the processes responsible for magma and water interaction in a magmatic system. Hydrovolcanism is commonly used as a synonym for phreatomagmatism. However, in recent years phreatomagmatism appears more in association with volcanic eruptions that occur in shallow subaqueous or terrestrial settings and commonly involves molten fuel-coolant interaction (MFCI) driven processes. Here a revised and reviewed classification scheme is suggested on the basis of the geo-environment in which the magma-water interaction takes place and the explosivity plus mode of energy transfer required to generate kinetic energy to produce pyroclasts. Over the past decade researchers have focused on the role hydrovolcanism/phreatomagmatism plays in the formation of maar craters, the evolution of diatremes and the signatures of magma—water interaction in the geological record. In the past five years, lithofacies-characterization is the most common approach to studying hydrovolcanism. By far mafic monogenetic volcanic fields generated the greatest number of research results. Significant knowledge gaps are identified, especially in developing tools to identify the textural signatures hydrovolcanism leave behind on eruptive products and exploring the role of hydrovolcanism in the growth of intermediate and silicic small volume volcanoes.

Accurate and precise ages of large silicic eruptions are critical to calibrating the geologic timescale and gauging the tempo of changes in climate, biologic evolution, and magmatic processes throughout Earth history. The conventional approach to dating these eruptive products using the 40Ar/39Ar method is to fuse dozens of individual feldspar crystals. However, dispersion of fusion dates is common and interpretation is complicated by increasingly precise data obtained via multicollector mass spectrometry. Incremental heating of 49 individual Bishop Tuff (BT) sanidine crystals produces 40Ar/39Ar dates with reduced dispersion, yet we find a 16-ky range of plateau dates that is not attributable to excess Ar. We interpret this dispersion to reflect cooling of the magma reservoir margins below ∼475 °C, accumulation of radiogenic Ar, and rapid preeruption remobilization. Accordingly, these data elucidate the recycling of subsolidus material into voluminous rhyolite magma reservoirs and the effect of preeruptive magmatic processes on the 40Ar/39Ar system. The youngest sanidine dates, likely the most representative of the BT eruption age, yield a weighted mean of 764.8 ± 0.3/0.6 ka (2σ analytical/full uncertainty) indicating eruption only ∼7 ky following the Matuyama−Brunhes magnetic polarity reversal. Single-crystal incremental heating provides leverage with which to interpret complex populations of 40Ar/39Ar sanidine and U-Pb zircon dates and a substantially improved capability to resolve the timing and causal relationship of events in the geologic record.