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To investigate the origin of compositional zonation in the Bishop Tuff magma body, we have analyzed trace elements in the matrix glass of pumice clasts and in quartz-hosted melt inclusions. Our results show contrasting patterns for quartz in different parts of the Bishop Tuff. In all samples from the early part of the eruption, trace element compositions of matrix glasses are similar to but slightly more evolved than quartz-hosted melt inclusions. This indicates a cogenetic relationship between quartz crystals and their surrounding matrix glass, consistent with in situ crystallization. The range of incompatible element concentrations in melt inclusions and matrix glass from single pumice clasts requires 16-20 wt% in situ crystallization. This is greater than the actual crystal content of the pumices (<15 % crystals). In contrast to the pattern for the early pumices, pyroclastic flow samples from the middle part of the eruption show contrasting trends: In some clasts, the matrix is more evolved than the inclusions, whereas in other clasts, the matrix is less evolved. In the late Bishop Tuff, all crystal-rich samples have matrix glasses that are less evolved than the melt inclusions. Trace element abundances indicate that the cores of quartz in the late Bishop Tuff crystallized from more differentiated rhyolitic magma that was similar in many ways, yet distinct from the early-erupted Bishop Tuff. Our results are compatible with a model of secular incremental zoning (Hildreth and Wilson in Compositional zoning of the Bishop Tuff. J Petrol 48(5):951-999, ), in which melt batches from underlying crystal mush rise to various levels in a growing magma body according to their buoyancy. Early- and middle-erupted quartz crystallized from highly evolved rhyolitic melt, but then some parts of the middle-erupted magma were invaded by less differentiated rhyolite such that the matrix melt at the time of eruption was less evolved than the melt inclusions. A similar process occurred but to a greater extent in magma that erupted to form the late Bishop Tuff. In addition, there was a final, major magma mixing event in the late magma that formed Ti-rich rims on quartz and Ba-rich rims on sanidine, trapped less evolved rhyolitic melt inclusions, and resulted in dark and swirly crystal-poor pumice that is a rare type throughout much of the Bishop Tuff. [ABSTRACT FROM AUTHOR]

In recent years, the popularity of metal hydrides has increased considerably for hydrogen storage and their applications in hydrogen fuel cells. Their potential applications for clean energy are promissory. However, the temperatures required for adsorption and desorption are extremely high, which range between 500 and 700 K, making their use impractical. To overcome these difficulties, the following work considers using three hydride alloys: magnesium-aluminum (MgAl), magnesium-nickel (MgNi), and magnesium-zinc (MgZn). The Mg concentrations were set to be between 80 and 100 wt% in order to reduce the temperatures of adsorption and desorption in contrast with the temperatures of pure magnesium. The chemisorption and repulsion energies of the hydrogen molecule on the surface (110) of the different metallic alloys were studied at 0, 200, 400, 600, and 700 K, respectively. The study was based on the density functional theory (DFT), with the module DMol3 of the molecular simulation program Materials Studio, which was used to obtain these energy values. The results confirm that adding aluminum, nickel, or zinc into magnesium matrix increases the chemisorption and decreases the energy repulsion values on surfaces of the metallic alloys, improving the effectiveness of the hydrogen storage. [ABSTRACT FROM AUTHOR]

Pelado volcano is a typical example of an andesitic Mexican shield with a summital scoria cone. It erupted ca. 10 ka in the central part of an elevated plateau in what is today the southern part of Mexico City. The volcano forms a roughly circular, 10-km wide lava shield with two summital cones, surrounded by up to 2.7-m thick tephra deposits preserved up to a distance of 3 km beyond the shield. New cartographic, stratigraphic, granulometric, and componentry data indicate that Pelado volcano was the product of a single, continuous eruption marked by three stages. In the early stage, a > 1.5-km long fissure opened and was active with mild explosive activity. Intermediate and late stages were mostly effusive and associated with the formation of a 250-m high lava shield. Nevertheless, during these stages, the emission of lava alternated and/or coexisted with highly explosive events that deposited a widespread tephra blanket. In the intermediate stage, multiple vents were active along the fissure, but activity was centered at the main cone during the late stage. The final activity was purely effusive. The volcano emitted > 0.9 km3 dense-rock equivalent (DRE) of tephra and up to 5.6 km3 DRE of lavas. Pelado shares various features with documented “violent Strombolian” eruptions, including a high fragmentation index, large dispersal area, occurrence of plate tephra, high eruptive column, and simultaneous explosive and effusive activity. Our results suggest that the associated hazards (mostly tephra fallout and emplacement of lava) would seriously affect areas located up to 25 km from the vent for fallout and 5 km from the vent for lava, an important issue for large cities built near or on potentially active zones, such as Mexico City. [ABSTRACT FROM AUTHOR]