Insights into shallow magmatic processes in large silicic magma bodies: the trace element record in the Fish Canyon magma body, Colorado

Highly evolved rhyolite glass plus near-solidus mineral assemblages in voluminous, dacitic, crystal-rich ignimbrites provide an opportunity to evaluate the late magmatic evolution of granodiorite batholiths. This study reports laser-ablation ICP-MS analyses of trace element concentrations in feldspars, hornblende, biotite, titanite, zircon, magnetite, and interstitial glass of the crystal-rich Fish Canyon Tuff. The high-silica rhyolite glass is characterized by relatively high concentrations of feldspar-compatible elements (e.g., 100ppm Sr and 500ppm Ba) and low concentrations of Y (40) compared to many well-studied high-silica rhyolite glasses and whole-rock compositions. Most minerals record some trace element heterogeneities, with, in particular, one large hornblende phenocryst showing four- to six-fold core-to-rim increases in Sr and Ba coupled with a decrease in Sc. The depletions of Y and HREE in the Fish Canyon glass relative to the whole-rock composition (concentrations in glass ~30% of those in whole rocks) reflect late crystallization of phases wherein these elements were compatible. As garnet is not stable at the low-P conditions at which the Fish Canyon magma crystallized, we show that a combination of modally abundant hornblende (~4%) + titanite (~0.5-1%) and the highly polymerized nature of the rhyolitic liquid led to Y and HREE depletions in melt. Relatively high Sr and Ba contents in glass and rimward Sr and Ba increases in euhedral, concentrically zoned hornblende suggest partial feldspar dissolution and a late release of these elements to the melt as hornblende was crystallizing, in agreement with textural evidence for feldspar (and quartz) resorption. Both observations are consistent with thermal rejuvenation of the magma body prior to eruption, during which the proportion of melt increased via feldspar and quartz dissolution, even as hydrous and accessory phases were crystallizing. Sr/Y in Fish Canyon glass (13-18) is lower than the typical "adakitic” value (>40), confirming that high Sr/Y is a reliable indicator of high-pressure magma generation and/or differentiation wherein garnet is implicate

Compositional and Dynamic Controls on Mafic—Silicic Magma Interactions at Continental Arc Volcanoes: Evidence from Cordón El Guadal, Tatara-San Pedro Complex, Chile

Heterogeneous andesitic and dacitic lavas on Cordón El Guadal bear on the general problem of how magmas of differing compositions and physical properties interact in shallow reservoirs beneath continental arc volcanoes. Some of the lavas contain an exceptionally large proportion (<40%) of undercooled basaltic andesitic magma in various states of disaggregation. Under-cooled mafic magma occurs in the silicic lavas as large (<40 cm) basaltic andesitic magmatic inclusions, as millimeter-sized crystal-clots of Mg-rich olivine phenocrysts plus adhering Carich plagioclase microphenocrysts (An50-70), and as uniformly distributed, isolated phenocrysts and microphenocrysts. Compositions and textures of plagioclase phenocrysts indicate that inclusion-forming magmas are hybrids formed by mixing basaltic and dacitic melts, whereas textural features and compositions of groundmass phases indicate that the andesitic and dacitic lavas are largely mechanical mixtures of dacitic magma and crystallized basaltic andesitic magma. This latter observation is significant because it indicates that mechanical blending of undercooled mafic magma and partially crystallized silicic magma is a possible mechanism for producing the common porphyritic texture of many calc-alkaline volcanic rocks. The style of mafic-silicic magma interaction at Cordon El Guadal was strongly dependent upon the relative proportions of the endmembers. Equally important in the Guadal system, however, was the manner in which the contrasting magmas were juxtaposed. Textural evidence preserved in the plagioclase phenocrysts indicates that the transition from liquid-liquid to solid-liquid mixing was not continuous, but was partitioned into periods of magma chamber recharge and eruption, respectively. Evidently, during periods of recharge, basaltic magmas rapidly entrained small amounts of dacitic magma along the margins of a turbulent injection fountain. Conversely, during periods of eruption, dacitic magma gradually incorporated small parcels of basaltic andesitic magma. Thus, the coupled physical-chemical transition from mixed inclusions to commingled lavas is presumably not coincidental. More likely, it probably provides a partial record of the dynamic processes occurring in shallow magma chambers beneath continental are volcanoe

NBP 2.0: Updated Next Bar Predictor, an Improved Algorithmic Music Generator

Deep neural network advancements have enabled machines to produce melodies emulating human-composed music. However, the implementation of such machines is costly in terms of resources. In this paper, we present NBP 2.0, a refinement of the previous model next bar predictor (NBP) with two notable improvements: first, transforming each training instance to anchor all the notes to its musical scale, and second, changing the model architecture itself. NBP 2.0 maintained its straightforward and lightweight implementation, which is an advantage over the baseline models. Improvements were assessed using quantitative and qualitative metrics and, based on the results, the improvements from these changes made are notable

Approaches to Improving School Attendance: Insights From Australian Principals

School absenteeism has been concerning educators in the Global North (including Australia) as research suggests a relationship between school attendance, academic achievement and subsequent life chances. This paper focuses on the perspectives of 50 school leaders in Queensland, Australia about approaches to improving attendance. Strategies reflected the cultural, economic and social diversity of their school communities. In general, quality curricula and pedagogies were considered important, but were not explicitly linked to attendance. This suggests the need for schools to develop strategies to enhance student engagement in meaningful learning through quality curricula and pedagogies within a positive school environment

REDD1 Knockout Reduces Whole Body Glucose And Insulin Tolerance, And Impairs Skeletal Muscle Insulin Signaling

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Species Specific Microcalcification in Reef Building Caribbean Corals in Ocean Acidification Conditions

Coral reefs are one of the most economically important ecosystems on the planet. Despite their great contribution to the world economy, anthropogenic influence via carbon dioxide emissions is leading to unprecedented changes with concerns about subsequent negative impacts on reefs. Surface ocean pH has dropped 0.1 units in the past century; in spite of this rapid shift in oceanic chemistry, it is unclear if individual species or life stages of Caribbean stony corals will be more sensitive to ocean acidification (OA). Examined is the relationship between CO2-induced seawater acidification, net calcification, photosynthesis, and respiration in three model Caribbean coral species: Orbicella faveolata, Montastraea cavernosa, and Dichocoenia stokesi, under near ambient (465 ± 5.52 ppm), and high (1451 ± 6.51 ppm) CO2 conditions. A species specific response was observed for net calcification; D. stokesi and M. cavernosa displayed a significant reduction in CaCO3 secreted under OA conditions, while O. faveolata fragments showed no significant difference. At the cellular level, transmission electron micrographs verified that all species and treatments were actively calcifying. Skeletal crystals nucleated by O. faveolata in the high CO2 treatments were statistically longer relative to controls. These results suggest that the addition of CO2 may shift the overall energy budget, causing a modification of skeletal aragonite crystal structures, rather than inhibiting skeletal crystal formation. Consequential to this energy shift, Orbicella faveolata belongs in the category of Scleractinian corals that exhibit a lower sensitivity to ocean acidification