Late Cenozoic magmatism of the Bolivian Altiplano

Small basalt to dacite volcanic centers are distributed sparsely over the Bolivian Altiplano, behind the Andean volcanic front. Most are Pliocene to Recent in age, and are characterized by textural and mineralogical disequilibrium with abundant xenoliths and xenocrysts. True phenocrysts are rare in the more mafic samples. Compared with Recent volcanic rocks from Andean stratovolcanoes, the Bolivian centers overlap in major element trends. Incompatible element contents tend to be higher, particularly in the eastern Altiplano. The ranges of isotopic compositions reflect ubiquitous crustal contamination. Pb isotope compositions are dominated by Pb from isotopically heterogeneous basement, resulting in a wide scatter of data lying between inferred crustal compositions and showing little overlap with possible mantle sources in the region. Rocks sampled from the Bolivian Altiplano were probably derived from asthenospheric mantle and subjected to extensive open system differentiation during ascent through the 70 km thick crust of the region. Major element trends are largely controlled by the fractionating phase assemblage (olivine, clinopyroxene and amphibole). Trace element and isotope systematics, however, defy realistic attempts at modeling due to the geographic scatter of samples, the uniformity of compositions at a given center, and the heterogeneity of the contaminant. Nevertheless, there are first order systematic trace element variations that appear to relate to the geometry of the subduction zone. In particular, LIFE/HFSE (exemplified by Ba/Nb), and Zr/Nb ratios decrease from the arc front eastward into the Altiplano. These variations are not easily reconciled with control by crustal contamination alone. A model is proposed in which the asthenospheric source is fluxed by high Ba/Nb slab-derived fluid to induce melting. Beneath the arc, high fluid flux increases the Ba/Nb ratio of the asthenosphre and leads to high degrees of partial melting (high Zr/Nb). To the east, lower or no fluid flux leads to low Ba/Nb and low degrees of partial melting (low Zr/Nb). Melting in the back arc region of the Altiplano may be facilitated by lithospheric delamination that leads to decompression melting of counter-flowing asthenosphere. There is no unequivocal evidence that requires a significant role for the lithospheric mantle.     

Some properties of decorrelation techniques in the ambiguity space

The most recent contributions to ambiguity resolution techniques have mainly focused on resolution in the ambiguity domain. Two techniques utilizing a decorrelation approach are compared. These techniques are the least-squares ambiguity decorrelation adjustment method and the lattice basis reduction. The latter is also known as the LLL method. The main focus in this article is on the decorrelation performance of these state-of-the-art techniques, which are aiming at ambiguity space decorrelation through unimodular transformations. The performances of the two-decorrelation techniques are compared through their ability in making the ambiguity space as orthogonal as possible.     

Priorities, policies and (time)scales: the delivery of emissions reductions in the UK transport sector

The transport sector is consistently responsible for around 30 per cent of carbon dioxide emissions in developed countries and is one of few sectors where emissions continue to increase as a result of apparently insatiable demand for road and air travel. This paper examines how the formulation of transport policy fits into the exposition of UK climate policy, focusing on three principal areas of tension: policy priority (congestion and carbon reduction); strategies to reduce emissions (technological and behavioural solutions) and timescale (short- and long-term vision). We suggest that in overcoming such tensions government ministers will need to devolve significant policy formulation and implementation powers to an appropriate scale of governance – in this case the city-region – to fashion a 'convergence space' capable of promoting meaningful action with regard to transport's climate impact.     

The origin and evolution of magmas from the San Pedro-Pellado volcanic complex,S. Chile: multicomponent sources and open system evolution

The San Pedro-Pellado volcanic complex is located at 36° S in the Chilean Andes. The eruptive rocks of the complex record the development and collapse of a caldera, followed by voluminous, largely basaltic andesite, volcanism. At each stage of evolution, crystal fractionation was accompanied by variable degrees of contamination and mixing. Large variations in incompatible element ratios cannot be produced by closed system evolution. Correlations between indices of differentiation and incompatible element ratios, together with high ¹⁸O values, indicate that basaltic andesites have assimilated crust to generate the evolved volcanic rocks at San Pedro-Pellado. Even in the most mafic rocks, however, incompatible element characteristics are variable as a result of source heterogeneity and deep level processes. The restricted ranges in isotope ratios of Sr, Nd and Pb among San Pedro-Pellado rocks are due to the small contrast in isotopic compositions between magma and wallrock. Three source components are recognized as contributing to parental magmas at San Pedro-Pellado. Although the relative contributions of each cannot be quantified, the volumetrically dominant source component is the sub-arc asthenospheric mantle (MORB source). The major source of LILE is thought to be slab-derived fluids which modified the sub-arc mantle. Other incompatible elements may also have been enriched by interaction with the continental lithosphere (mantle and/or lower crust) during ascent.     

Spatial discovery and the research library

Academic libraries have always supported research across disciplines by integrating access to diverse contents and resources. They now have the opportunity to reinvent their role in facilitating interdisciplinary work by offering researchers new ways of sharing, curating, discovering, and linking research data. Spatial data and metadata support this process because location often integrates disciplinary perspectives, enabling researchers to make their own research data more discoverable, to discover data of other researchers, and to integrate data from multiple sources. The Center for Spatial Studies at the University of California, Santa Barbara (UCSB) and the UCSB Library are undertaking joint research to better enable the discovery of research data and publications. The research addresses the question of how to spatially enable data discovery in a setting that allows for mapping and analysis in a GIS while connecting the data to publications about them. It suggests a framework for an integrated data discovery mechanism and shows how publications may be linked to associated data sets exposed either directly or through metadata on Esri's Open Data platform. The results demonstrate a simple form of linking data to publications through spatially referenced metadata and persistent identifiers. This linking adds value to research products and increases their discoverability across disciplinary boundaries.     

Polycyclic aromatic hydrocarbons in sediments of the Great Barrier Reef region,Australia

At present the concentrations of polycyclic aromatic hydrocarbons in sediments from the Great Barrier Reef are remarkably low. The baseline levels range from <0.01 μg kg^?1 dry wt. for benzo(k)fluoranthene and benzo(a)pyrene to <0.82 μg kg^?1 for chrysene. Measurable levels of polycyclic aromatic hydrocarbons have only been found in small areas close to sites frequently visited by power boats. Sediments from Townsville and Gladstone Harbours on the coast adjacent to the reef are polluted with polycyclic aromatic hydrocarbons to a similar degree to that reported for coastal sediments in similar locations in other parts of the world.     

Design and routing of storm flows in an urbanized watershed without surface streams

In the karst geologic setting of Greenbrier County, West Virginia, USA, the drainage network in the watersheds do not support surface streams, but depend entirely on sinkholes, solution cavities, or injection wells as discharge points for accumulated storm water. By providing a systematic framework for designing and routing storms in this geologic setting, functioning retention and attenuation structures have been developed which are protective of water quality while still safely discharging storm water in a controlled manner to the subsurface. This article provides a rationale for the design methodology and then examines the successful implementation of an attenuation and storm water retention design to manage the surface discharges for an entire watershed. By examining the pre-development flows and evaluating future land use patterns (i.e., installation of impermeable surfaces over large areas), as well as sinkhole conveyance capabilities, it was necessary to examine alternative disposal options for collected storm water as well as devise a basin-wide management strategy to coordinate future development of the watershed. Additionally, innovative water quality measures were implemented to help prevent contamination from preferentially infiltrating into the subsurface as a result of these land development activities.     

The Wilson–Burg method of spectral factorization with application to helical filtering

Spectral factorization is a computational procedure for constructing minimum-phase (stable inverse) filters required for recursive inverse filtering. We present a novel method of spectral factorization. The method iteratively constructs an approximation of the minimum-phase filter with the given autocorrelation by repeated forward and inverse filtering and rearranging of the terms. This procedure is especially efficient in the multidimensional case, where the inverse recursive filtering is enabled by the helix transform. To exemplify a practical application of the proposed method, we consider the problem of smooth two-dimensional data regularization. Splines in tension are smooth interpolation surfaces whose behaviour in unconstrained regions is controlled by the tension parameter. We show that such surfaces can be efficiently constructed with recursive filter preconditioning and we introduce a family of corresponding two-dimensional minimum-phase filters. The filters are created by spectral factorization on a helix.