Tracing the Initiation of the Tribeč Mountain Exhumation by Laser-Probe ⁴⁰Ar/³⁹Ar Dating of Seismogenic Pseudotachylytes (Western Carpathians, Slovakia)

The seismogenic pseudotachylytes from the Tribeč Mountains (Western Carpathians, Slovakia) were dated by means of the laser microprobe 40Ar/39Ar method. The Tribeč Mountain crystalline basement was buried to 5–7.5-km depths, where it experienced approximately >110°C and <210°C thermal conditions. The dated pseudotachylytes have spot ages between 58 ± 1 and 46 ± 1 Ma with a weighted mean age of 49.7 ± 1.3 Ma, indicating that seismic activity caused their origin, the propagation of subvertical basement marginal faults, and/or the inception of basement unroofing processes in the southern part of the Central Carpathian Paleogene Basin. The extensional tectonics were responsible for the exhumation of basement highs and the opening of the intramontane depressions on the northwest margin of the Pannonian Basin

A laser probe ⁴⁰Ar /³⁹Ar and INAA investigation of four Apollo granulitic breccias

Infrared laser probe 40Ar/39Ar geochronology, instrumental neutron activation analysis (INAA) and analytical electron microscopy have been performed on four 0.5 x 1.0 x 0.3 cm polished rock tiles of Apollo 16 and 17 granulitic breccias (60035, 77017, 78155, and 79215). Pyroxene thermometry indicates that these samples were re-equilibrated and underwent peak metamorphic sub-solidus recrystallization at 1000 – 1100°C, which resulted in homogeneous mineral compositions and granoblastic textures. 40Ar/39Ar data from this study reveal that three samples (60035, 77017, and 78155) have peak metamorphic ages of ~4.1 Ga. Sample 79215 has a peak metamorphic age of 3.9 Ga, which may be related to Serenitatis basin formation. All four samples contain moderately high concentrations of meteoritic siderophiles. Enhanced siderophile contents in three of the samples provide evidence for projectile contamination of their target lithologies occurring prior to peak metamorphism. Post-peak metamorphism, low-temperature (<300ºC) events caused the partial resetting of argon in the two finer-grained granulites (60035 and 77017). These later events did not alter the mineralogy or texture of the rocks, but caused minor brecciation and the partial release of argon from plagioclase. Interpretation of the low-temperature data indicates partial resetting of the argon systematics to as young as 3.2 Ga for 60035 and 2.3 Ga for 77017. Cosmic ray exposure ages range from 6.4 to ~339 Ma. Our results increase the amount of high-precision data available for the granulitic breccias and lunar highlands crustal samples. The results demonstrate the survival of pre-Nectarian material on the lunar surface and document the effects of contact metamorphic and impact processes during the pre-Nectarian Epoch, as well as the low-temperature partial resetting of ages by smaller impact events after 3.9 Ga. The mineralogy and chemical composition of these rocks, as well as exhumation constraints, indicate that the source of heat for metamorphism was within kilometres of the surface via burial beneath impact melt sheets or hot ejecta blankets

Explanatory Journeys: Visualising to Understand and Explain Administrative Justice Paths of Redress

Administrative justice concerns the relationships between individuals and the state. It includes redress and complaints on decisions of a child's education, social care, licensing, planning, environment, housing and homelessness. However, if someone has a complaint or an issue, it is challenging for people to understand different possible redress paths and explore what path is suitable for their situation. Explanatory visualisation has the potential to display these paths of redress in a clear way, such that people can see, understand and explore their options. The visualisation challenge is further complicated because information is spread across many documents, laws, guidance and policies and requires judicial interpretation. Consequently, there is not a single database of paths of redress. In this work we present how we have co-designed a system to visualise administrative justice paths of redress. Simultaneously, we classify, collate and organise the underpinning data, from expert workshops, heuristic evaluation and expert critical reflection. We make four contributions: (i) an application design study of the explanatory visualisation tool (Artemus), (ii) coordinated and co-design approach to aggregating the data, (iii) two in-depth case studies in housing and education demonstrating explanatory paths of redress in administrative law, and (iv) reflections on the expert co-design process and expert data gathering and explanatory visualisation for administrative justice and law.Comment: 11 pages with 10 figures, accepted for publication in IEEE Transactions on Visualization and Computer Graphic

Observation of centimetre-scale argon diffusion in alkali feldspars: implications for ⁴⁰Ar/³⁹Ar thermochronology

New data from a gem-quality feldspar from Itrongay, Madagascar, record naturally occurring 40Ar/39Ar age profiles which can be numerically modelled by invoking a single diffusion mechanism and show that microtexturally simple crystals are capable of recording complex thermal histories. We present the longest directly measured, naturally produced 40Ar*-closure profiles from a single, homogeneous orthoclase feldspar. These data appear to confirm the assumption that laboratory derived diffusion parameters are valid in nature and over geological timescales. Diffusion domains are defined by crystal faces and ancient cracks, thus in gem-quality feldspars the diffusion domain size equates to the physical grain size. The data also illustrate the potential of large, gem-quality feldspars to record detailed thermal histories over tens of millions of years and such samples should be considered for future studies on the slow cooling of continental crust

Spatially heterogeneous argon-isotope systematics and apparent 40Ar/39Ar ages in perlitised obsidian

In situ laser ablation Ar-isotope analyses of variably hydrated and devitrified obsidian from the ~ 27 Ma Cochetopa Dome, San Juan, USA, reveal complex interplay between degassing of initial Ar and absorption of atmospheric Ar. These processes have locally modified the Ar-isotope composition of the obsidian and led to spurious, spatially-heterogeneous Ar-isotope and 40Ar/39Ar age data. Small perlite beads exhibit older apparent Ar-ages at the rims than the cores. This is interpreted as an apparent excess of 40Ar at the rims, produced either by a) diffusion of excess 40Ar into the bead during flushing of the lava with excess 40Ar-bearing volcanic gas, or by b) isotopic fractionation during degassing of initial Ar, causing preferential loss of 36Ar over 40Ar at the bead rims. The second interpretation is favoured by a relative enrichment of 36Ar in the core of a perlite bead along a microlite-free (poorly degassed) flow band, and by a lack of age variation in a larger, fresh, well-degassed perlite bead. These isotopic gradients were later overprinted during glass hydration by absorption of Ar with near-atmospheric composition, resulting in elevated 36Ar and reduced radiogenic 40Ar* yields at the rims of perlite beads. These complex interactions essentially represent the mixing of three distinct Ar reservoirs: initial trapped Ar that may or may not be fractionated, an isotopically atmospheric Ar component introduced during hydration, and radiogenic 40Ar*. Such reservoir mixing is the underlying reason for poor correlations on isotope correlation diagrams and the difficulties in validating the composition of the non-radiogenic Ar component. We thus suggest that high 36Ar yields are a combination of the incomplete degassing of initial (possibly magmatic) Ar and the gain of Ar during interaction between the obsidian and meteoric/atmospheric fluids. Our analyses emphasise the challenging nature of 40Ar/39Ar dating obsidian samples, but also point to possible solutions by careful sample characterisation and selection of highly degassed samples

Textural characterization, major and volatile element quantification and Ar-Ar systematics of spherulites in the Rocche Rosse obsidian flow, Lipari, Aeolian Islands:A temperature continuum growth model.

Spherulitic textures in the Rocche Rosse obsidian flow (Lipari, Aeolian Islands, Italy) have been characterized through petrographic, crystal size distribution (CSD) and in situ major and volatile elemental analyses to assess the mode, temperature and timescales of spherulite formation. Bulk glass chemistry and spherulite chemistry analyzed along transects across the spherulite growth front/glass boundary reveal major-oxide and volatile (H2O, CO2, F, Cl and S) chemical variations and heterogeneities at a ≤5 μm scale. Numerous bulk volatile data in non-vesicular glass (spatially removed from spherulitic textures) reveal homogenous distributions of volatile concentrations: H2O (0.089 ± 0.012 wt%), F (950 ± 40 ppm) and Cl (4,100 ± 330 ppm), with CO2 and S consistently below detection limits suggesting either complete degassing of these volatiles or an originally volatile-poor melt. Volatile concentrations across the spherulite boundary and within the spherulitic textures are highly variable. These observations are consistent with diffusive expulsion of volatiles into melt, leaving a volatile-poor rim advancing ahead of anhydrous crystallite growth, which is envisaged to have had a pronounced effect on spherulite crystallization dynamics. Argon concentrations dissolved in the glass and spherulites differ by a factor of ~20, with Ar sequestered preferentially in the glass phase. Petrographic observation, CSD analysis, volatile and Ar data as well as diffusion modeling support continuous spherulite nucleation and growth starting at magmatic (emplacement) temperatures of ~790–825 °C and progressing through the glass transition temperature range (T g ~ 750–620 °C), being further modified in the solid state. We propose that nucleation and growth rate are isothermally constant, but vary between differing stages of spherulite growth with continued cooling from magmatic temperatures, such that there is an evolution from a high to a low rate of crystallization and low to high crystal nucleation. Based on the diffusion of H2O across these temperature ranges (~800–300 °C), timescales of spherulite crystallization occur on a timescale of ~4 days with further modification up to ~400 years (growth is prohibitively slow <400 °C and would become diffusion reliant). Selective deformation of spherulites supports a down-temperature continuum of spherulite formation in the Rocche Rosse obsidian; indeed, petrographic evidence suggests that high-strain zones may have catalyzed progressive nucleation and growth of further generations of spherulites during syn- and post-emplacement cooling

The ⁴⁰Ar–³⁹Ar dating and geochemistry of the Carpathian C1 obsidians (Zemplín, Slovakia)

In situ 40Ar–39Ar UV laser ablation dating of the Carpathian C1 obsidians from the Slovakian part of the Zemplín –Tokaj area yielded new 40Ar–39Ar obsidian glass ages that fall in a narrow time interval of 12.07 ± 0.37 to 11.44 ± 0.39 Ma. This indicates that most of the Zemplín obsidian findings come from one short-time monogenic volcano, forming part of a long-lasting volcanism over the 15–10 Ma period. Chemical compositions of the Carpathian C1 obsidians clearly indicate common similarities between all examined localities (Brehov, Cejkov, Hraň, and Viničky). Geochemically, these obsidians belong to the silica-rich, peraluminous, high-potassium, calc-alkaline rhyolite series volcanic rocks of ferroan character. They were derived by multi-stage magmatic processes, from mixed mantle and crustal sources, and generated during subduction in a volcanic arc tectonic setting. The primary basaltic magma formed from the melting of the lower crustal source at the mantle/crust boundary. Subsequent formation of melt reservoirs in the middle and upper crust, accompanied by secondary melting of the surrounding rocks with continual addition of ascending melt, and repeated processes of assimilation and fractionation produced rhyolitic rocks with obsidians in the Zemplínske vrchy Mts

Geology of Tindfjallajökull volcano, Iceland

The geology of Tindfjallajökull volcano, southern Iceland, is presented as a 1:50,000 scale map. Field mapping was carried out with a focus on indicators of past environments. A broad stratocone of interbedded fragmental rocks and lavas was constructed during Tindfjallajökull’s early development. This stratocone has been dissected by glacial erosion and overlain by a variety of mafic to silicic volcanic landforms. Eruption of silicic magma, which probably occurred subglacially, constructed a thick pile of breccia and lava lobes in the summit area. Mafic to intermediate flank eruptions continued through to the end of the last glacial period, producing lavas, hyaloclastite-dominated units and tuyas that preserve evidence of volcano-ice interactions. The Thórsmörk Ignimbrite, a regionally important chronostratigraphic marker, is present on the SE flank of the volcano. The geological mapping of Tindfjallajökull gives insights into the evolution of stratovolcanoes in glaciated regions and the influence of ice in their development

Awareness and support: students’ views about the prevention of sexual assault on UK campuses

Purpose: Sexual assault is prevalent on UK University campuses, and prevention efforts are being increased. However, at present there is limited evidence about UK students’ attitudes towards sexual assault prevention and what they think should be done to effectively address the issue. The purpose of this study was to explore these views to provide a foundation for the development of a new intervention. Methods: A cross sectional anonymous online survey was completed by 515 students (73% women; M age 21.56; 79% heterosexual; 82.9% White). There were quantitative questions about experiences of sexual assault, attitudes towards sexual consent and victim blaming. Qualitative data was collected regarding participants’ views on what universities should do to target sexual assault. Findings: In line with previous studies, we found evidence of commonplace and normalised sexual assault behaviours. Women had more positive attitudes towards explicit consent than men, and were less likely to blame victims of sexual assault who had been drinking. Consent behaviour was predicted by positive views towards consent and lower levels of blaming. Themes relating to ‘awareness’, ‘attitudes’, ‘environment’ and ‘opposition’ were identified in the qualitative data. Practical implications: Findings highlight the importance of engaging with students to develop effective prevention measures. Students are likely to find university led prevention strategies acceptable, but this topic needs to be addressed in the context of the prevailing culture, which may provide an environment where certain behaviours are tolerated. New prevention programmes need to treat the issue as one that is relevant to all students and not just target men as perpetrators and women as victims. Such strategies need to do more than treat this as an isolated issue, to which the solution is re-education about the meaning of consent