Arc Magmas from Slab to Eruption: The Case of Kliuchevskoy Volcano

Arc magmas are generated by a number of mantle and crustal processes. Our multidisciplinary, long-term research is aimed at deciphering these processes for a single arc volcano, Kliuchevskoy volcano in Kamchatka. Some key results of the study follow: 1) Modeling of trace element and H2O contents in melt inclusions suggests that the primary magmas originate via hydrous flux-melting of the mantle wedge at temperatures close to the dry peridotite solidus. The role of decompression melting is minor or absent at Kliuchevskoy and other arc volcanoes built on relatively thick crust. 2) Geochemistry of high-Mg olivine suggests that primary Kliuchevskoy magmas have substantial contribution from olivine-free pyroxenite (up to 30 %), which could be formed by reaction of slab melts (or supercritical fluids) with mantle wedge peridotite. 3) Parental Kliuchevskoy melts start to crystallize as deep as the Moho boundary, and the erupted magmas reflect multistage and complex processes of crystallization, magma mixing and crustal assimilation. None of the Kliuchevskoy rocks analyzed thus far represent true primary melt compositions. 4) The Kliuchevskoy Holocene eruptive history is not steady-state in terms of eruption rate and geochemistry. There are two millenial cycles with major and trace element and OSr- Nd-Pb and U-series isotope compositions of the magmas changing gradually from more to less affected by crustal (?) assimilation. The onset of the cycles correlates with periods of enhanced volcanic activity in Kamchatka, suggesting that the extent of magma-crust interaction is inversely related to magma production rate and thus magma flux from the mantle

I Didn\u27t Know How All This Works : A Case Study Examining The Transition Experiences of Student-Athletes from High School to a Mid-Major DI Program

The transition period from high school to college includes a myriad of issues specific to student-athletes (Bernhard & Bell, 2015; Bjornsen & Dinkel, 2017; Comeaux, 2015). The present study sought to illuminate the specific transition issues faced by mid-major, DI student-athletes by providing them the platform to describe them in their own words, and provide their own recommendations for improvement. Utilizing a semi-structured interview guide which addressed transition issues, the qualitative study included 23 student-athletes in focus group settings. Analysis of interview data led to the emergence of two themes, with accompanying subthemes: 1) Encounters with academic support, with subthemes of transitioning to campus and perceived responsibilities of athletic academic advisors; and 2) Skewed perceptions and expectations of student-athlete life, with subthemes of expectations regarding the coach-athlete relationship, lifestyle modifications, and high stress practice environments. The findings suggest a notable trend – student-athletes lack the support they need to successfully deal with the transition. The transition process itself also appears to involve three specific periods: 1) Prior to arrival on campus; 2) Initial arrival on campus; and 3) Following the initial transition to campus. The findings will help to better design standards for helping student-athletes navigate the transition process

A Textured Silicon Calorimetric Light Detector

We apply the standard photovoltaic technique of texturing to reduce the reflectivity of silicon cryogenic calorimetric light detectors. In the case of photons with random incidence angles, absorption is compatible with the increase in surface area. For the geometrically thin detectors studied, energy resolution from athermal phonons, dominated by position dependence, is proportional to the surface-to-volume ratio. With the CaWO4 scintillating crystal used as light source, the time constants of the calorimeter should be adapted to the relatively slow light-emission times.Comment: Submitted to Journal of Applied Physic

238U-230Th-226Ra Disequilibria Constraints on the Magmatic Evolution of the Cumbre Vieja Volcanics on La Palma, Canary Islands

A suite of 48 samples, including both historical and prehistoric lavas and some plutonic rocks, have been analysed from the Cumbre Vieja rift, La Palma, Canary Islands. Additionally, mineral–melt partition coefficients have been measured for clinopyroxene, plagioclase, amphibole, titanite and apatite in selected rocks. The lavas range from basanite to phonolite (SiO2 = 41·2–57·5 wt % and MgO = 10–0·8 wt %) in composition and form coherent, curvilinear major and trace element arrays in variation diagrams, irrespective of eruption age. The mafic lavas have typical ocean island incompatible trace element patterns and Sr, Nd and Pb isotope compositions show little variation but have a HIMU-type character. Generation of the parental magmas is inferred to have involved ∼4% dynamic melting of a garnet lherzolite source that may have previously been metasomatized by melts derived from a recycled mafic component containing residual phlogopite. The major process of differentiation to phonotephrite involved fractional crystallization of basanitic magmas that evolved along the same liquid line of descent under similar pressure–temperature conditions. Numerical simulations using the MELTS algorithm suggest that this occurred across a temperature interval from c. 1320 to 950°C at 400 MPa and an oxygen fugacity equivalent to quartz–fayalite–magnetite (QFM), with an initial H2O content of 0·3 wt %. The later stages of differentiation (<5 wt % MgO) were dominated by mixing with partial melts of young syenites formed from earlier magma batches. All of the lavas are characterized by 230Th and 226Ra excesses and (230Th/238U) decreases with decreasing Nb/U and increasing SiO2, with no accompanying change in (226Ra/230Th). To explain the observations, we propose a model in which there was a significant role for amphibole, and more importantly accessory titanite, in decre'asing Nb/U, Ce/Pb and Th/U ratios and increasing or buffering (226Ra/230Th) ratios during the later stages of differentiation and magma mixing. These processes all occurred over a few millennia in small magma batches that were repeatedly emplaced within the mid-crust of the Cumbre Vieja rift system prior to rapid transport to the surface

The CRESST Experiment: Recent Results and Prospects

The CRESST experiment seeks hypothetical WIMP particles that could account for the bulk of dark matter in the Universe. The detectors are cryogenic calorimeters in which WIMPs would scatter elastically on nuclei, releasing phonons. The first phase of the experiment has successfully deployed several 262 g sapphire devices in the Gran Sasso underground laboratories. A main source of background has been identified as microscopic mechanical fracturing of the crystals, and has been eliminated, improving the background rate by up to three orders of magnitude at low energies, leaving a rate close to one count per day per kg and per keV above 10 keV recoil energy. This background now appears to be dominated by radioactivity, and future CRESST scintillating calorimeters which simultaneously measure light and phonons will allow rejection of a great part of it.Comment: To appear in the proceedings of the CAPP2000 Conference, Verbier, Switzerland, July, 2000 (eds J. Garcia-Bellido, R. Durrer, and M. Shaposhnikov

Exploring CEvNS with NUCLEUS at the Chooz Nuclear Power Plant

Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. Nuclear reactors are promising sources to explore this process at low energies since they deliver large fluxes of (anti-)neutrinos with typical energies of a few MeV. In this paper, a new-generation experiment to study CE$\nu$NS is described. The NUCLEUS experiment will use cryogenic detectors which feature an unprecedentedly low energy threshold and a time response fast enough to be operated in above-ground conditions. Both sensitivity to low-energy nuclear recoils and a high event rate tolerance are stringent requirements to measure CE$\nu$NS of reactor antineutrinos. A new experimental site, denoted the Very-Near-Site (VNS) at the Chooz nuclear power plant in France is described. The VNS is located between the two 4.25 GW$_{\mathrm{th}}$ reactor cores and matches the requirements of NUCLEUS. First results of on-site measurements of neutron and muon backgrounds, the expected dominant background contributions, are given. In this paper a preliminary experimental setup with dedicated active and passive background reduction techniques is presented. Furthermore, the feasibility to operate the NUCLEUS detectors in coincidence with an active muon-veto at shallow overburden is studied. The paper concludes with a sensitivity study pointing out the promising physics potential of NUCLEUS at the Chooz nuclear power plant