Factors useful for predicting future mineral-commodity supply trends

The analysis of various factors influencing mineral availability documents future short-and long-term mineral-commodity supply trends. The lifetime of reserves, the development of the relative importance of production centres and the forecasting of the depletion of a resource base are mainly geological factors, although the category “reserves”, in contrast to “resources”, is determined by technical and economical aspects. These three factors govern the short-and long-term supply of mineral commodities. The intensity-of-use factors and the growth rate of consumption are variables related to the demand of mineral commodities. They influence the decision of companies for certain commodities as targets for exploration and investment in production centres. Both factors control the short-to medium-term mineral supply. Finally, the lead time to production is a technical variable, although influenced by ore deposit type, and controls short-term mineral availability.     

Compartmented flow at the Bátaapáti site in Hungary

Integration of hydrogeological and geological data into a conceptual model is critical for site investigation programs, since this model is the basis for hydrogeological modeling and for engineering. In the Hungarian Radioactive Waste Disposal Investigation Program, several methods have been used to characterize the potential host rock (granite) at the Bátaapáti site for a repository for low and intermediate level radioactive waste. Hydrogeological data acquisition revealed some characteristic aspects of the site. One of the most important is the presence of extensive rock deformation zones (faults) with low hydraulic conductivity, which strongly reduce the direct hydraulic communication between adjacent blocks of rock (compartmentalization). This characteristic of the rock mass results in a mosaic-like distribution of rock compartments, each with an almost constant hydraulic head. Within the compartments, hydraulic tests have shown that transmissivity is strongly scale dependent: the larger the scale, the higher the measured transmissivity. The extensive highly transmissive zones cause very low hydraulic gradients within each block, thus the transport processes are strongly influenced by the low or average transmissivity zones and the rock matrix.     

Applying size segregation to relate the surrounding aerosol pollution to its source

Size segregated sampling of aerosol particles at the coal-fired power station Šoštanj, Slovenia was performed by a newly developed system. In addition, simultaneous sampling of particles was performed at two locations, Velenje and Veliki vrh, chosen on the basis of long term monitoring of SO₂ in the influential area of power plant. The signature of the power plant (e.g. characteristic size distributions of some typical trace elements) was identified. For elements, like As, Mo, Cd and Ga, which are typical for coal combustion, the highest concentrations were observed in the size range between 1 and 4 μm. For Se and sometimes for Ga two modes were identified, first between 0.1 and 0.5 μm and second between 1 and 4 μm. Ratios between the average concentrations of selected elements in fine and coarse particles collected at Veliki vrh (the most influenced location) and Velenje (usually not influenced by the thermo power station) were significantly higher than 1 in the case of Mo and Se for coarse and fine size range, while for As the ratio was higher than 1 for the coarse fraction. Consequently, Mo, Se and As were found as the most important tracers for the emissions from the investigated source. On the basis of the ratios between the concentrations of elements measured in particles at low and high SO₂ concentrations at Veliki vrh, Cd was shown to be a typical tracer as well. Our results definitely showed that size segregated measurements of particles at the source and in the influenced area give more precise information on the influence of source to the surrounding region. It was found that patterns of size distributions for typical trace elements observed at the source are found also in the influenced area, i.e. Veliki vrh.     

Aragonite dissolution on the Bermuda pedestal: Its depth and geochemical significance

The depth distribution of pteropod and planktonic foram tests, and fine-grained (<62 μm) aragonite, high-Mg calcite (12 mode mol.% MgCO₃), and low-Mg calcite has been determined for surface sediments of an area of the eastern slope of the Bermuda pedestal. Over the range 1800–3000 m, fine-grained aragonite and fine-grained high-Mg calcite gradually disappear relative to fine-grained low-Mg calcite, and pteropods gradually disappear relative to planktonic forams. This is interpreted as preferential dissolution of aragonite (and high-Mg calcite) relative to low-Mg calcite over this depth range. Coarse aragonitic debris derived from shallow-water organisms living on the Bermuda platform does not show consistent disappearance over the same depth zone. Chemical analyses of bottom water samples taken at the same time as some of the sediment samples indicate that the degree of saturation with respect to aragonite Ω_A over the zone of aragonite disappearance ranges from 0.55 to 0.85; i.e. major dissolution occurs only at Ω_A values distinctly less than one. These results lend credence to the hypothesis that CaCO₃ dissolution in the oceans, both as aragonite and as calcite, takes place mainly as a response to complex chemical kinetic phenomena and not as a result of the simple attainment of undersaturation (thermodynamic hypothesis) or the resuspension of bottom sediment (hydrodynamic hypothesis).     

Long-term summer temperature reconstruction inferred from tree-ring records from the Eastern Carpathians

The first 1,000 year long Carpathian tree-ring width chronology was established based on living and subfossil stone pine (Pinus cembra L.) samples from an upper timberline forest located in Calimani Mts. (Romania). Tree-ring data were standardized using the regional curve standardization method in order to preserve the low and medium frequency climate signals. The de-trended index strongly correlates with summer mean temperature both at annual and decadal scales. The Calimani summer mean temperature anomalies were reconstructed for the period ad 1163-2005 applying the rescaling method. This new climate proxy from the Carpathians shows similar fluctuations to other North Hemispheric temperature reconstructions, but with periods of distinct differences. The fingerprint of Little Ice Age in the Calimani area is visible between ad 1370 and 1630 followed by lagged cold decades in ad 1820 and 1840. The recent warming is evident only after the 1980s in our reconstruction.     

High stress late Maastrichtian – early Danian palaeoenvironment in the Neuquén Basin, Argentina

During the late Maastrichtian to early Danian the Neuquén Basin of Argentina was adjacent to an active volcanic arc to the west and an extensive land area to the northeast. Mineralogical and geochemical studies of the Bajada del Jagüel in the Neuquén Basin indicate a generally warm climate with seasonal changes in humidity and an open seaway to the South Atlantic that maintained marine conditions. Biostratigraphic and quantitative foraminiferal and nannofossil analyses indicate that sediment deposition during the late Maastrichtian (zones CF4-CF2, N. frequens) occurred in relatively shallow middle neritic (100 m) depths with largely dysaerobic bottom waters (abundant low O₂ tolerant benthics) and fluctuating sea level. Calcareous nannofossils indicate a high stress marine environment dominated by Micula decussata. Planktic foraminifera mimic the post-K/T high stress environment with alternating blooms of the disaster opportunists Guembelitria and low oxygen tolerant Heterohelix groups, indicating nutrient-rich surface waters and an oxygen depleted water column. The high stress conditions were probably driven by high nutrient influx due to upwelling and terrestrial and volcanic influx. The K/T boundary is marked by an erosional surface that marks a hiatus at the base of a 15-25 cm thick volcaniclastic sandstone, which contains diverse planktic foraminiferal zone P1c assemblages and nannofossils of zone NP1b immediately above it. This indicates deposition of the sandstone occurred 500 ky after the K/T hiatus. No evidence of the Chicxulub impact or related tsunami deposition was detected.     

Barremian–Danian chemostratigraphic sequences of the Cauvery Basin,India: Implications on scales of stratigraphic correlation

Chemostratigraphic concepts postulate that distinct chemozones could be recognized from rock records to help correlate geographically separated strata. Many studies have upheld this view, but were limited to classic boundaries such as Cenomanian–Turonian or Cretaceous–Tertiary. Only a few elements and isotopic compositions were made use in such studies. An attempt to recognize chemozones of Barremian–Danian strata of the Cauvery Basin, South India through whole-rock chemistry had revealed many complex signals and depositional events as expressed by bulk geochemical profiles. The signals indicate major shift in sedimentation pattern from dynamic depocenter to stable depositional conditions during Santonian. Varying sensitivities of different elements towards prevalent depositional conditions are also inferred. Trends of geochemical composition indicated domination of single depositional control all through the depositional history, basinal configuration that limited terrestrial sediment source and episodic influx of detrital materials. Presence of distinct change in whole-rock geochemistry across geochronological and lithostratigraphic boundaries is deciphered through a statistical tool ANOVA. These results demonstrate that visual delineation of chemozones in a long ranging rock record would be tenuous and has to be exercised with caution.     

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco

With a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct δ¹³C_org isotope excursion of +2.5‰ occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40–60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from 2.5% to 10%). This is interpreted as the consequence of a long-term eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed ‘detrital index’ can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of P_reactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The C_org/P_total and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.