Tectonic evolution of the Lachlan Fold Belt, southeastern Australia: constraints from coupled numerical models of crustal deformation and surface erosion driven by subduction of the underlying mantle

We have used a coupled thermo-mechanical finite-element (FE) model of crustal deformation driven by mantle/oceanic subduction to demonstrate that the tectonic evolution of the Lachlan Fold Belt (LFB) during the Mid-Palaeozoic (Late Ordovician to Early Carboniferous) can be linked to continuous subduction along a single subduction zone. This contrasts with most models proposed to date which assume that separate subduction zones were active beneath the western, central and eastern sections of the Lachlan Orogen. We demonstrate how the existing data on the structural, volcanic and erosional evolution of the Lachlan Fold Belt can be accounted for by our model. We focus particularly on the timing of fault movement in the various sectors of the orogen. We demonstrate that the presence of the weak basal decollement on which most of the Lachlan Fold Belt is constructed effectively decouples crustal structures from those in the underlying mantle. The patterns of faulting in the upper crust appears therefore to be controlled by lateral strength contrasts inherited from previous orogenic events rather than the location of one or several subduction zones. The model also predicts that the uplift and deep exhumation of the Wagga-Omeo Metamorphic Belt (WOMB) is associated with the advection of this terrane above the subduction point and is the only tectonic event that gives us direct constraints on the location of the subduction zone. We also discuss the implications of our model for the nature of the basement underlying the present-day orogen.     

Kamafugitic diatremes: their textures and field relationships with examples from the Goiás alkaline province, Brazil

Kamafugitic rocks intruded the Precambrian basement and Phanerozoic sediments at the northeast border of the Paraná basin as part of the Late Cretaceous Goiás alkaline province (GAP). Plutonic complexes dominate the north of the province, whereas lavas and pyroclastic rocks prevail in the south. The central GAP is characterized by kamafugitic diatremes, which may crop out continuously for up to 850 m and consist of a central breccia body, surrounded and overlain by lava flows and crosscut by dykes. The breccias contain some special spheroidal juvenile fragments—namely, accretionary and armored lapilli, frozen droplets, spinning droplets, and wrapped fragments—whose textural and mineralogical aspects are described in detail. Irregularly shaped tuff pockets that occur within the breccias contain textures and structures similar to those of subaerial surge deposits and formed in confined, high gas to solid+liquid ratio domains in the conduit. Diatreme emplacement affected the country rock through thermal metamorphism, development of columnar jointing, and formation of peperite-like mixtures. There is no evidence of phreatomagmatic activity in the diatremes, and CO₂, rather than H₂O, seems to have been the major volatile component of the kamafugitic magmas. This finding implies that features such as accretionary lapilli and peperites are not exclusively associated with H₂O-dominated processes.     

Impact of the past mining activity in Roşia Montană (Romania) on soil and vegetation

The paper presents the results of a combined soil and vegetation survey in Ro?ia Montan? mining area (western Romania), famous for its gold and silver deposits, extensively exploited over the last 2,000 years. As the ore extraction has ceased in 2006 and new operations could be initiated in the future, the study contributes to the definition of the environmental baseline. Samples of topsoil and leaves of the tree species Betula pendula and Carpinus betulus have been collected from the inside and outside of the mining area, on a total surface of more than 60 km². The pH and heavy metal concentrations (Cd, Cr, Cu, Ni, Pb, and Zn) have been measured on 262 soils/sediments samples, revealing the predominantly acidic character of soils and the generally low contents of heavy metals. Stronger acidity and higher contents of heavy metals have been noticed in the proximity of the mining site, on the tailings and waste rock dumps, and along the streams with acid water. More than 100 leaf samples have been analysed for the same heavy metals as soils and also for chlorophyll fluorescence and pigment concentrations. B. pendula has shown a particular ability to concentrate Zn in leaves, at levels that may greatly exceed the Zn content in the corresponding soil samples. The correlation between the heavy metal contents in leaves and in soils, in most of the cases, is not very strong, presumably in relation to the low concentrations in soils. The chlorophyll concentration in leaves of B. pendula slightly diminishes on soils with low pH.     

Witnessing North Atlantic westerlies variability from ships’ logbooks (1685–2008)

A monthly index based on the persistence of the westerly winds over the English Chanel is constructed for 1685–2008 using daily data from ships’ logbooks and comprehensive marine meteorological datasets. The so-called Westerly Index (WI) provides the longest instrumental record of atmospheric circulation currently available. Anomalous WI values are associated with spatially coherent climatic signals in temperature and precipitation over large areas of Europe, which are stronger for precipitation than for temperature and in winter and summer than in transitional seasons. Overall, the WI series accord with the known European climatic history, and reveal that the frequency of the westerlies in the eastern Atlantic during the twentieth century and the Late Maunder Minimum was not exceptional in the context of the last three centuries. It is shown that the WI provides additional and complementary information to the North Atlantic Oscillation (NAO) indices. The analysis of WI series during the industrial era indicates an overall good agreement with the winter and high-summer NAO, with the exception of several multidecadal periods of weakened correlation. These decoupled periods between the frequency and the intensity of the zonal flow are interpreted on the basis of several sources of non-stationarity affecting the centres of the variability of the North Atlantic and their teleconnections. Comparisons with NAO reconstructions and long instrumental indices extending back to the seventeenth century suggest that similar situations have occurred in the past, which call for caution when reconstructing the past atmospheric circulation from climatic proxies. The robustness and extension of its climatic signal, the length of the series and its instrumental nature make the WI an excellent benchmark for proxy calibration in Europe and Greenland.     

Advances and Practices on the Research,Prevention and Control of Land Subsidence in Coastal Cities

Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructures and exacerbates the effect of the sea-level rise at regional scale. Although it is a well-known process, there is still much more to be improved on the monitoring, mapping and modeling of ground movements, as well as the understanding of controlling mechanisms. The International G...     

The supergene origin of ruthenian hexaferrum in Ni‐laterites

For two decades, the nature of Fe‐rich, oxygen‐bearing, Ru–Os compounds found in the supergene environment has been debated. Ru–Os–Fe‐oxides and nano‐intergrowths of ruthenium with magnetite have been proposed. We applied FE‐SEM, EMPA, μ‐Raman spectroscopy and synchrotron tts‐μXRD to Ru–Os–Fe compounds recovered from Ni‐laterites from the Dominican Republic. The results demonstrate that a significant portion of Fe exists in a common structure with the Ru–Os alloy, that is, ruthenian hexaferrum. This mineral occurs both as nanoparticles and as micrometric patches within a matrix of Fe‐oxide(s). Our data suggest that supergene ruthenian hexaferrum with a (Ru_0.4(Os,Ir)_0.1Fe_0.5)_?1.0 stoichiometry represents the most advanced weathering product of primary laurite within Ni‐laterites from the Dominican Republic.     

Provenance of Holocene beach sand in the Western Iberian margin: the use of the Kolmogorov–Smirnov test for the deciphering of sediment recycling in a modern coastal system

Detrital zircons from Holocene beach sand and igneous zircons from the Cretaceous syenite forming Cape Sines (Western Iberian margin) were dated using laser ablation – inductively coupled plasma – mass spectrometry. The U–Pb ages obtained were used for comparison with previous radiometric data from Carboniferous greywacke, Pliocene–Pleistocene sand and Cretaceous syenite forming the sea cliff at Cape Sines and the contiguous coast. New U–Pb dating of igneous morphologically simple and complex zircons from the syenite of the Sines pluton suggests that the history of zircon crystallization was more extensive (ca 87 to 74 Ma), in contrast to the findings of previous geochronology studies (ca 76 to 74 Ma). The U–Pb ages obtained in Holocene sand revealed a wide interval, ranging from the Cretaceous to the Archean, with predominance of Cretaceous (37%), Palaeozoic (35%) and Neoproterozoic (19%) detrital‐zircon ages. The paucity of round to sub‐rounded grains seems to indicate a short transportation history for most of the Cretaceous zircons (ca 95 to 73 Ma) which are more abundant in the beach sand that was sampled south of Cape Sines. Comparative analysis using the Kolmogorov–Smirnov statistical method, analysing sub‐populations separately, suggests that the zircon populations of the Carboniferous and Cretaceous rocks forming the sea cliff were reproduced faithfully in Quaternary sand, indicating sediment recycling. The similarity of the pre‐Cretaceous ages (>ca 280 Ma) of detrital zircons found in Holocene sand, as compared with Carboniferous greywacke and Pliocene–Pleistocene sand, provides support for the hypothesis that detritus was reworked into the beach from older sedimentary rocks exposed along the sea cliff. The largest percentage of Cretaceous zircons (<ca 95 Ma) found in Holocene sand, as compared with Pliocene–Pleistocene sand (secondary recycled source), suggests that the Sines pluton was the one of the primary sources that became progressively more exposed to erosion during Quaternary uplift. This work highlights the application of the Kolmogorov–Smirnov method in comparison of zircon age populations used to identify provenance and sediment recycling in modern and ancient detrital sedimentary sequences.     

Biosorption with autochthonous and allochthonous fungal biomasses for bioremediation and detoxification of landfill leachate

Landfill leachates are not adequately treated in traditional wastewater treatment plants, on account of their problematic peculiarities: i.e., dark colour, high concentration of recalcitrant pollutants and COD, and high toxicity. In this work, 19 biomasses (15 autochthonous and 4 allochthonous) were exploited in biosorption treatment for the remediation of a leachate (influent) and the effluent coming from the biological oxidation with activated sludge and nitrification–denitrification treatment. The effects of the initial pH, the biomass amount, and the medium for the biomass pre-culture were considered. The best configuration was: pH 5, 5 g L^??1 biomass cultivated on STY medium. Eventually, the two most effective biomasses, Cunninghamella bertholletiae MUT 2861 and Aspergillus fumigatus MUT 4050, were used in consecutive 2 h cycles in a batch biosorption experiment. The effectiveness of the treatment decreased in subsequent cycles in terms of decolourisation (31–15%). COD, Cl^?, SO₄^2?, total N, and toxicity were removed mainly in the second cycle of treatment (up to ??36, ??12, ??15, ??17 and ??49%, respectively). The results suggest that the effluent toxicity was basically due to uncoloured substances, which were mainly removed after coloured molecules.