Late Alpine brittle faulting in the Rotondo granite (Switzerland): deformation mechanisms and fault evolution

The unlined Bedretto tunnel in the Central Swiss Alps has been used to investigate in detail the fault architecture and late Alpine brittle faulting processes in the Rotondo granite on macroscopic and microscopic scales. Brittle faults in the late Variscan Rotondo granite preferentially are situated within the extent of preexisting ductile shear zones. Only in relatively few cases the damage zone extends into or develops in the previously undeformed granite. Slickensides suggest a predominant (dextral) strike-slip movement along these steeply dipping and NE–SW-striking faults. Microstructures of these fault rocks illustrate a multi-stage retrograde deformation history from ductile to brittle conditions up to the cessation of fault activity. In addition these fabrics allow identifying cataclastic flow, fluid-assisted brecciation and chemical corrosive wear as important deformation mechanisms during this retrogressive deformation path. Based on the analysis of zeolite microfabrics (laumontite and stilbite; hydrated Ca–Al- and Na–Ca–Al–silicate, respectively) in fault breccias, cataclasites and open fractures we conclude, that the main phase of active brittle faulting started below 280°C and ceased ca. 14 Ma ago at temperatures slightly above 200°C. This corresponds to a depth of approx. 7 km.     

Climate policies can help resolve energy security and air pollution challenges

This paper assesses three key energy sustainability objectives: energy security improvement, climate change mitigation, and the reduction of air pollution and its human health impacts. We explain how the common practice of narrowly focusing on singular issues ignores potentially enormous synergies, highlighting the need for a paradigm shift toward more holistic policy approaches. Our analysis of a large ensemble of alternate energy-climate futures, developed using MESSAGE, an integrated assessment model, shows that stringent climate change policy offers a strategic entry point along the path to energy sustainability in several dimensions. Concerted decarbonization efforts can lead to improved air quality, thereby reducing energy-related health impacts worldwide: upwards of 2–32 million fewer disability-adjusted life years in 2030, depending on the aggressiveness of the air pollution policies foreseen in the baseline. At the same time, low-carbon technologies and energy-efficiency improvements can help to further the energy security goals of individual countries and regions by promoting a more dependable, resilient, and diversified energy portfolio. The cost savings of these climate policy synergies are potentially enormous: $100–600 billion annually by 2030 in reduced pollution control and energy security expenditures (0.1–0.7 % of GDP). Novel aspects of this paper include an explicit quantification of the health-related co-benefits of present and future air pollution control policies; an analysis of how future constraints on regional trade could influence energy security; a detailed assessment of energy expenditures showing where financing needs to flow in order to achieve the multiple energy sustainability objectives; and a quantification of the relationships between different fulfillment levels for energy security and air pollution goals and the probability of reaching the 2 °C climate target.     

The potential effects of climate change on malaria transmission in Africa using bias-corrected regionalised climate projections and a simple malaria seasonality model

Climatic conditions such as relatively cold temperatures and dryness are able to limit malaria transmission. Climate change is therefore expected to alter malaria spread. A previous assessment of the potential impacts of climate change on the seasonality of malaria in Africa is revisited. Bias-corrected regional climate projections with a horizontal resolution of 0.5° are used from the Regional Model (REMO), which include land use and land cover changes. The malaria model employed is the climate-driven seasonality model (MSM) from the Mapping Malaria Risk in Africa project for which a comparison with data from the Malaria Atlas Project (MAP) and the Liverpool Malaria Model (LMM), and a novel validation procedure lends more credence to results. For climate scenarios A1B and B1 and for 2001–2050, REMO projects an overall drying and warming trend in the African malaria belt, that is largely imposed by the man-made degradation of vegetation. As a result, the malaria projections of the MSM show a decreased length of the malaria season in West Africa. The northern Sahel is no more longer suitable for malaria in the projections and shorter malaria seasons are expected for various areas farther south. In East Africa, higher temperatures and nearly unchanged precipitation patterns lead to longer transmission seasons and an increase in highland malaria. Assuming constant population numbers, an overall increase in person-months of exposure of up to 6 % is found. The results of this simple seasonality model are similar to previous projections from the more complex LMM. However, a different response to the warming of highlands is found for the two models. It is concluded that the MSM is an efficient tool to assess the climate-driven malaria seasonality and that an uncertainty analysis of future malaria spread would benefit from a multi-model approach.     

New insights into volcanic processes from deep mining of the southern diatreme within the Argyle lamproite pipe,Western Australia

Underground mining and deep drilling of the richly diamondiferous ~1.2 Ga Argyle lamproite in Western Australia has prompted a re-evaluation of the geology of the pipe. Argyle is considered to be a composite pipe that formed by the coalescence of several diatremes and has been offset and elongated by post-emplacement faulting. Recent geological studies have recognised at least five distinct volcaniclastic lamproite lithofacies with differing diamond grades. The new data suggest that the centre of the southern (main) diatreme is occupied by well-bedded, olivine lamproite lapilli tuff with very high diamond grades (>10 ct/t). Characteristic features include a clast-supported fabric and high modal abundance of densely packed lamproite lapilli and coarse-grained, likely mantle-derived olivine now replaced by serpentine and/or talc. The persistence of small-scale graded and cross-bedding in this lithofacies to depths of ~1.5 km below the original surface prior to erosion suggests phreatomagmatic volcanism forming the diatreme was syn-eruptively accompanied by subsidence of the tephra, maintaining a steep-walled diatreme in the water-saturated country rock sediments.

     

First investigations on the quaternary system Na2O-K2O-CaO-SiO2: synthesis and crystal structure of the mixed alkali calcium silicate K1.08Na0.92Ca6Si4O15

Mineralogy and Petrology - In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been...     

Single-crystal structure and Raman spectroscopy of synthetic titanite analog CaAlSiO<Subscript>4</Subscript>F

Synthetic CaAlSiO₄F, the Al-F analog of titanite, has been investigated using single-crystal synchrotron diffraction experiments at Beamline X06DA (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland) and Raman spectroscopy. The presented structural model with 40 parameters was refined against 506 unique reflections to a final R _{o b s} of 0.026 (space group A2/a, a = 6.9120(11), b = 8.5010(10), c = 6.435(2) Å, β = 114.670(11)°, and Z = 4) and exhibits less distorted coordination polyhedra than earlier models from powder data. Vibrational spectra were calculated in harmonic approximation at the Γ point from fully relaxed energy optimisations of the crystal structure, using 3D-periodic density functional theory with Gaussian basis sets and the software CRYSTAL06. The lattice parameters of the fully relaxed structure were in good agreement with the experimental values, with the calculated values 0.8 ± 0.4 % too large; the monoclinic angle was calculated 0.4° too large. The agreement of the calculated Raman frequencies with the observed ones was very good, with standard deviation ±3 cm^?1 and maximum deviations of ±7 cm^?1. Furthermore, a detailed discussion of the atomic displacements associated with each Raman mode is given.     

Formation of carbonate concretions in surface sediments of two mud mounds,offshore Costa Rica: a stable isotope study

The surface sediments of two mud mounds (“Mound 11” and “Mound 12”) offshore southwest Costa Rica contain abundant authigenic carbonate concretions dominated by high-Mg calcite (14–20 mol-% MgCO₃). Pore fluid geochemical profiles (sulfate, sulfide, methane, alkalinity, Ca and Mg) indicate recent carbonate precipitation within the zone of anaerobic oxidation of methane (AOM) at variable depths. The current location of the authigenic carbonate concretions is, however, not related to the present location of the AOM zone, suggesting mineral precipitation under past geochemical conditions as well as changes in the flow rates of upward migrating fluids. Stable oxygen and carbon isotope analysis of authigenic carbonate concretions yielded δ¹⁸O_carbonate values ranging between 34.0 and 37.7 ‰ Vienna standard mean ocean water (VSMOW) and δ¹³C_carbonate values from ?52.2 to ?14.2 ‰ Vienna Pee Dee belemnite (VPDB). Assuming that no temperature changes occurred during mineral formation, the authigenic carbonate concretions have been formed at in situ temperature of 4–5 °C. The δ¹⁸O_carbonate values suggest mineral formation from seawater-derived pore fluid (δ¹⁸O_porefluid = 0 ‰ VSMOW) for Mound 12 carbonate concretions but also the presence of an emanating diagenetic fluid (δ¹⁸O_porefluid ≈5 ‰) in Mound 11. A positive correlation between δ¹³C_carbonate and δ¹⁸O_carbonate is observed, indicating the admixing of two different sources of dissolved carbon and oxygen in the sediments of the two mounds. The carbon of these sources are (1) marine bicarbonate (δ¹³C_porefluid ≈0 ‰) and (2) bicarbonate which formed during the AOM (δ¹³C_porefluid ≈?70 ‰). Furthermore, the δ¹⁸O_porefluid composition, with values up to +4.7 ‰ Vienna standard mean ocean water (VSMOW), is interpreted to be affected by the presence of emanating, freshened and boron-enriched fluids. Earlier, it has been shown that the origin of ¹⁸O-enriched fluids are deep diagenetic processes as it was indicated by the presence of methane with thermogenic signature (δ¹³C_CH4 = ?38 ‰). A combination of present geochemical data with geophysical observations indicates that Mounds 11 and 12 represent a single fluid system interconnected by deep-seated fault(s).