Raman and SEM analysis of a biocolonised hot spring travertine terrace in Svalbard,Norway

Background  

A profile across 8 layers from a fossil travertine terrace from a low temperature geothermal spring located in Svalbard, Norway has been studied using both Raman spectroscopy and SEM (Scanning Electron Microscopy) techniques to identify minerals and organic life signals.     

Petrological and Sr-Nd evidence bearing on Early Proterozoic magmatic events of the subcontinental mantle: Sao Francisco craton (Uaua,NE-Brazil)

: Early Proterozoic (2.0–2.4 Ga), unmetamorphosed mafic dykes intrude Archean (3.1–2.7 Ga) terrains of the northern Sao Francisco craton (Uaua, NE-Brazil). The dykes are composed of evolved [atomic Mg/(Mg+Fe²)<0.6] two-pyroxene quartz tholeiites, the compositional variations of which are compatible with gabbro fractionation from different parental melts. The incompatible trace-element patterns indicate that the parental melts derived from partial melting of chemically heterogeneous garnet peridotite sources. Geochemistry and Sr-Nd isotopes imply some contamination of the Uaua dyke magma by continental crustal components during emplacement. Sr-isotopes suggest that the “uncontaminated” dykes may be related to time-integrated depleted mantle materials, while Nd-isotopes suggest mantle sources similar to the bulk Earth composition. The “uncontaminated” dykes have a positive Nb-anomaly and incompatible element contents which do not support appreciable enrichment of large ion lithophile and light rare earth elements in the source(s) throughmantle metasomatism and/or crustal components related to dehydration of a subducting slab, and an anorogenic ensialic emplacement is inferred. The Uaua dykes are chemically and isotopically distinct from the Early–Middle Proterozoic (1.9–1.7 Ga) unmetamorphosed dykes from W-Uruguay (Rio de La Plata craton) which are believed to have originated from different garnet peridotite sources. This suggests that Uaua–Uruguay compositional differences may reflect different Archean mantle differentiation and evolution of the cratonization processes. If this possibility proves to be correct, then magma genesis from various South American cratons would be by independent cratonic processes and their imprints on the subcratonic mantle. Received: 22 November 1994/Accepted: 24 July 1995     

Assessing interpolation error for space–time monitoring data

In Europe, since 1990, a survey on environmental monitoring has been taking place every 5 years, using moss samples to study the distribution of heavy metal concentration and assess contamination sources, resulting on the identification of statistical association of several heavy metal concentrations in mosses. With this work, we propose an extension of an existing spatio-temporal model, introduced in Høst et al. (JASA 90(431):853–861, 1995), allowing for prediction at unsampled locations of pollution data in the presence of covariates related to each country specificities, when separately modelling the spatial mean field, the spatial variance field and the space–time residual field. Moreover, this model allows to estimate an interpolation error, as an accuracy measure, derived dependently on the case study. For a validation purpose, a simulation study is conducted, showing that the use of the proposed model leads to more accurate prediction values. Results obtained by the proposed methodology for the most recent available survey, are compared with results obtained with no temporal information, namely when Ordinary Kriging, according to the definition in Cressie (Statistics for spatial data, Wiley, New York, 1993), is used to derive illustrative prediction maps based only on the most recent data. An exercise of cross-validation is performed relative to each of the scenarios considered and the average interpolation errors are presented. While assessing interpolation errors, we conclude that the monitoring specificities of each country and the information of preceding surveys allow for more accurate prediction results.