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Research practices and support needs of Language and Literature faculty at the University of Utah

ReportThis report investigates the research practices and support needs of Language and Literature scholars at the University of Utah

LA-MC-ICPMS and SHRIMP U-Pb dating of complex zircons from Quarternary tephras from the French Massif Central: Magma residence time and geochemical implications

Analyses of zircon grains from the Queureuilh Quaternary tephras (pumice) provide new information about their pre-eruptive history. U-Pb dating was performed in situ using two methods: SHRIMP and LA-MC-ICPMS equipped with a multi-ion counting system. Both methods provided reliable 207Pb/206Pb and 206Pb/238U ratios as well as U and Th abundances required for U-Pb Concordia intercept age determination, after initial 230Th disequilibrium correction. The new LA-MC-ICPMS method was validated by dating a reference zircon (61.308B) and zircons from a phonolitic lava dated independently with the two techniques. A time resolution of about 20 kyr for 1 Ma zircon crystals was achieved for both methods. The clear euhedral zircon population from Queureuilh tephras is quite complex from several points of view: (1) some grains are reddish or yellowish while others are colorless; (2) the U and Th composition changes by more than an order of magnitude and Th/U is generally high (∼1-2); (3) there are three discrete ages recorded at 2.35 ± 0.04, 1.017 ± 0.008 and 0.640 ± 0.010 Ma. From the previously determined 40Ar/39Ar age at 0.571 ± 0.060 Ma [Duffell H. (1999) Contribution géochronologique à la stratigraphie volcanique du Massif des Monts Dore par la méthode 40Ar/39Ar. D.E.A. Univ. Clermont-Ferrand, 56 p.], the discontinuous zircon age populations, the color of the grains and their composition, we favor the following model as explanation: The oldest, less numerous group of reddish zircons represents xenocrystic grains resulting from assimilation of the local material during magma ascent. A primitive magma chamber, perhaps deep in crustal level, was formed at 1.0 Ma. The related magma, previously characterized by high Th/U ratio (2.2 ± 1.1), underwent rejuvenation during ascent to a new chamber at shallow depth and/or during injection of more mafic magmas. During this stage, at 0.64 Ma, the colorless zircon grains of lower Th/U ratio (1.3 ± 0.5) crystallized. This last stage defined the magma residence time of 70 kyr prior to eruption dated by the 40Ar/39Ar method. However, if the primitive magma is considered, the magma residence time as a whole from this first stage reached 446 kyr. In the light of the complex history of such magmas, which commonly involves recycling of zircon grains that precipitated tens to hundreds of kyr earlier than eruptions, the use of Zr concentration in geochemical modeling of whole rock compositional data can be problematic

Ultramafic rocks in the North Patagonian Andes: is their emplacement associated with the Neogene tectonics of the Liquiñe–Ofqui Fault Zone?

Serpentinites and fresh or partially serpentinized harzburgite crop out in the western slope of the North Patagonian Andes of continental Chiloé (41°44’-42°12’S). These rocks are spatially associated with low-grade metamorphic rocks containing Cenozoic detrital zircons. The metamorphic rocks, together with Devonian metasediments, have been mapped previously as Late Paleozoic-Triassic metamorfic complex, an age no longer tenable for at least part of the complex. Transpressional tectonic emplacement of the ultramafic body or bodies is thought to have been related to activity on the Liquiñe-Ofqui Fault Zone, following a late Oligocene-Early Miocene extensional phase in the forearc region of the present Andes. This fault zone occurs immediately east of the outcrops of the ultramafic rocks and has been interpreted previously as generating a hemi-flower or flower structure

Assessing Integrated Pest Management Implementation and Knowledge Gaps in South Dakota

A survey of commercial pesticide applicator training participants was carried out during 2015 winter pesticide certification meetings to assess integrated pest management (IPM) knowledge gaps. Overall, the majority of the respondents reported that they have adequate access to IPM information and that they apply IPM principles in their pest management programs. Preventive fungicide use was identified as a regular practice by half the respondents and was dependent on the region of the state. Participants identified basic pest identification as an area in which more resources are needed. Online information and field days were the preferred options for accessing outreach and Extension

Concrete beams with externally bonded flexural FRP-reinforcement: analytical investigation of debonding failure

This paper studies the problem of early concrete cover delamination and plate-end failure of reinforced concrete beams strengthened with externally bonded FRP-reinforcement. The accuracy of analytical models and finite element (FE) methods for predicting this type of failure is assessed against published experimental data. Two design approaches based on the maximum concrete tensile strength and the shear capacity of concrete beams were examined first and it was found that linear elastic analysis cannot accurately predict the brittle plate-end concrete failure. It was also found that the extent of strengthening that can be achieved is limited by the shear capacity of concrete beams. The FE analysis is used to examine the effects of internal tensile reinforcement on the magnitude of principal tensile stresses in the critical region. The non-linear behaviour of FRP-strengthened beams is also examined in the FE analysis using the smeared crack model for concrete which is shown to adequately display the inelastic deformation of the beam. Finally, the mixed mode of failure due to the combined shear and concrete cover delamination is addressed through modelling plate-end and shear crack discontinuities using the discrete crack approach

Las rocas huésped del magmatismo devónico en el macizo norpatagónico y Chaitenia

Trabajos anteriores han demostrado que el magmatismo devónico en los Andes meridionales se produjo en dos cinturones contemporáneos: uno emplazado en la corteza continental del Macizo Norpatagónico y el otro , hacia el oeste, en un arco de islas oceánico, Chaitenia, que más tarde se acrecionó a Gondwana. Las rocas hospedantes de las rocas plutónicas consisten en complejos metasedimentarios que aparecen esporádicamente en los Andes a ambos lados de la frontera entre Argentina y Chile, y adicionalmente de metabasaltos de almohadilla en Chaitenia. Las determinaciones de la edad de U-Pb de circones detríticos en 13 muestras de estas rocas metasedimentarias indican edades deposicionales máximas posibles de ca. 370 a 900 Ma, y se argumenta que la sedimentación es principalmente del Devónico similar a las pizarras fosilíferas de Buill. Procedencia del Ordovícico, del Cámbrico-tardío a Neoproterozoico y “Grenville” se ve en todas las rocas, a excepción de los afloramientos más occidentales donde predominan los zircones detríticos del Devónico. Además de una diferencia en los granos de zircón precámbricos, 76% versus 25% respectivamente, no hay variación sistemática en la procedencia del antepaís patagónico a Chaitenia, por lo que el arco de islas debe haber sido proximal al continente: su corteza más profunda no está expuesta pero se conocen varios afloramientos de rocas ultramáficas. Los bordes metamórficos desarrollados durante el Devónico en circones de las rocas del Macizo Norpatagónico no tienen su equivalente en los circones de las rocas metamórficas de bajo grado del sector chileno. Estas rocas metasedimentarias paleozoicas también fueron intruidas por granitoides del Pennsylvaniano y Jurásico.Previous work has shown that Devonian magmatism in the southern Andes occurred in two contemporaneous belts: one emplaced in the continental crust of the North Patagonian Massif and the other in an oceanic island arc terrane to the west, Chaitenia, which was later accreted to Patagonia. The country rocks of the plutonic rocks consist of metasedimentary complexes which crop out sporadically in the Andes on both sides of the Argentina-Chile border, and additionally of pillow metabasalts for Chaitenia. Detrital zircon SHRIMP U-Pb age determinations in 13 samples of these rocks indicate maximum possible depositional ages from ca. 370 to 900 Ma, and the case is argued for mostly Devonian sedimentation as for the fossiliferous Buill slates. Ordovician, Cambrian-late Neoproterozoic and “Grenville-age” provenance is seen throughout, except for the most westerly outcrops where Devonian detrital zircons predominate. Besides a difference in the Precambrian zircon grains, 76% versus 25% respectively, there is no systematic variation in provenance from the Patagonian foreland to Chaitenia, so that the island arc terrane must have been proximal to the continent: its deeper crust is not exposed but several outcrops of ultramafic rocks are known. Zircons with devonian metamorphic rims in rocks from the North Patagonian Massif have no counterpart in the low metamorphic grade Chilean rocks. These Paleozoic metasedimentary rocks were also intruded by Pennsylvanian and Jurassic granitoids.Centro de Investigaciones Geológica