Iron ore mining promotes iron enrichment in sediments of the Gualaxo do Norte River basin,Minas Gerais State,Brazil

The objective of the present study is to assess the influence of iron ore mining on Fe concentrations in fluvial sediments of the Gualaxo do Norte River basin (Minas Gerais State, Brazil). Initially background values were determined for Fe by means of the boxplot representation, the iterative 2σ technique and the calculated distribution function, using geochemical data obtained for alluvial terraces. Geochronologic analyses in carbonaceous materials attested for the proposed background values. After that, chemical analyses of active drainage sediments collected along the entire basin were carried out and a geochemical map of the study area was prepared. The mean background value for Fe is relatively high (8.2 wt %), when compared to the Fe concentration in the Earth’s crust (5.6 wt %). Such background value is strongly associated with the geological characteristics of the region. It was observed that most of the high Fe concentrations were detected in active sediments collected in the main river of the basin and not in its tributaries. This suggests that Fe enrichment is not only linked to the local geology but also to possible increase resulting from accidental leakage of iron ore mining tailings from containment dams and lakes upstream. It is suggested that measures that help stop or minimize such impact be adopted. The large capacity of Fe to adsorb and form complexes with toxic metals implicates in environmental hazards that may not be restricted only to the Gualaxo do Norte river basin, but may affect the other basins downstream.     

A Lost Realm in the Internal Domains of the Betic-Rif Orogen (Spain and Morocco): Evidence from Conglomerates and Consequences for Alpine Geodynamic Evolution

The Malaguide-Ghomaride Complex is capped by Upper Oligocene-Aquitanian clastic deposits postdating early Alpine orogenesis but predating the main tectonic-metamorphic evolution, end of nappe emplacement, unroofing, and exhumation of the metamorphic units of the Betic-Rif Orogen. Two conglomerate intervals within these deposits are characterized by clasts of sedimentary, epimetamorphic, and mafic volcanic rocks derived from Malaguide-Ghomaride units and by clasts of acidic magmatic and orthogneissic rocks of unknown provenance, here studied. Magmatic rocks originated from late-Variscan two-mica cordierite-bearing granitoids and, subordinately, from aplitic dikes. Orthogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist (T=510&j0;-530 degrees C and P=5-6 kbar) to low-temperature amphibolite facies (T>550&j0;C and P<3 kbar). Such a plutonic rock suite is unknown in any Betic-Rif unit or in the basement of the Alboran Sea, and the metamorphic evolution in the orthogneisses is different from (and older than) that of Alpujarride-Sebtide rocks to which they were formerly ascribed. Magmatic and metamorphic rocks very similar to those studied characterize the basements of some Kabylia and Calabria-Peloritani units. Therefore, the source area is a currently lost continental-crust realm of Calabria-Peloritani-Kabylia type, located to the ESE of the Malaguide-Ghomaride Domain and affected by a pre-latest Oligocene Alpine metamorphism. Increasingly active tectonics transformed this realm into rising areas from which erosion fed small subsiding synorogenic basins formed on the Malaguide-Ghomaride Complex. This provenance analysis demonstrates that all these domains constituted a single continental-crust block until Aquitanian-Burdigalian times, before its dispersal around nascent western Mediterranean basins.     

Influence of the sediment delivery ratio index on the analysis of silting and break risk in the Plasencia reservoir (Central System,Spain)

The random forest method was used to generate susceptibility maps for debris flows, rock slides, and active layer detachment slides in the Donjek River area within the Yukon Alaska Highway Corridor, based on an inventory of landslides compiled by the Geological Survey of Canada in collaboration with the Yukon Geological Survey. The aim of this study is to develop data-driven landslide susceptibility models which can provide information on risk assessment to existing and planned infrastructure. The factors contributing to slope failure used in the models include slope angle, slope aspect, plan and profile curvatures, bedrock geology, surficial geology, proximity to faults, permafrost distribution, vegetation distribution, wetness index, and proximity to drainage system. A total of 83 debris flow deposits, 181 active layer detachment slides, and 104 rock slides were compiled in the landslide inventory. The samples representing the landslide free zones were randomly selected. The ratio of landslide/landslide free zones was set to 1:1 and 1:2 to examine the results of different sample ratios on the classification. Two-thirds of the samples for each landslide type were used in the classification, and the remaining 1/3 were used to evaluate the results. In addition to the classification maps, probability maps were also created, which served as the susceptibility maps for debris flows, rock slides, and active layer detachment slides. Success and prediction rate curves created to evaluate the performance of the resulting models indicate a high performance of the random forest in landslide susceptibility modelling.     

Hydrocarbon generation potential of the uppermost Jurassic—basal Cretaceous Sulaiy formation, South Iraq

Organic geochemical analysis, palynology, and PetroMod software for the organic matters of subsurface Tithonian to Valanginian Sulaiy formation of six wells in Basrah Region, South Iraq showed evidences for hydrocarbon generation potential. These analyses include quantitative studies such as pyrolysis, fluorescence spectroscopy, and total organic carbon (TOC), while the qualitative studies are the textural microscopy used in evaluating amorphous organic matter for palynofacies analysis leading to hydrocarbon assessments. High TOC content of up to 7.3 wt.%, kerogen type II of mesoliptinic type with hydrogen index of up to 466 mg HC/g TOC, and mature organic matter along with dysoxic–anoxic environment and stratigraphic framework have rated the succession as a source rock for oil with ordinate gas, not only in Iraq but also in neighboring Kuwait and Saudi Arabia. This case study is also inferred for hydrocarbon generation and expulsion by PetroMod software which confirmed the source potential.     

Levels of tributyltin in sediments from Tagus estuary nature reserve

Concentrations of tributyltin in sediments from 9 selected stations located in the upper Tagus River estuary nature reserve, Portugal, were determined. Tributyltin (TBT) concentrations in the sediments ranged from 5 to 35 ng g⁻¹ on a dry weight basis. The persistent TBT contamination observed in the sediments from this important European ecosystem is primarily related to shipping activities as well as the naval industrial complexes located downstream. This exploratory survey suggests that both dumping and dredging, or the effects of tidal transport of resuspended sediments, are likely the main sources for the TBT contamination observed in the upper estuary. Although the TBT contents found in the sediments studied are low relative to concentrations reported from other parts of the world, they appear to represent a potential risk for some resident marine populations.