Light-toned salty soils and coexisting Si-rich species discovered by the Mars Exploration Rover Spirit in Columbia Hills

Light-toned soils were exposed, through serendipitous excavations by Spirit Rover wheels, at eight locations in the Columbia Hills. Their occurrences were grouped into four types on the basis of geomorphic settings. At three major exposures, the light-toned soils are hydrous and sulfate-rich. The spatial distributions of distinct types of salty soils vary substantially: with centimeter-scaled heterogeneities at Paso Robles, Dead Sea, Shredded, and Champagne-Penny, a well-mixed nature for light-toned soils occurring near and at the summit of Husband Hill, and relatively homogeneous distributions in the two layers at the Tyrone site. Aeolian, fumarolic, and hydrothermal fluid processes are suggested to be responsible for the deposition, transportation, and accumulation of these light-toned soils. In addition, a change in Pancam spectra of Tyrone yellowish soils was observed after being exposed to current Martian surface conditions for 175 sols. This change is interpreted to be caused by the dehydration of ferric sulfates on the basis of laboratory simulations and suggests a relative humidity gradient beneath the surface. Sirich nodules and soils were observed near the major exposures of S-rich soils. They possess a characteristic feature in Pancam visible near-infrared (Vis-NIR) spectra that may be diagnostic of hydrated species, and this spectral feature can be used to search for additional Si-rich species. The exposures of hydrated salty soils within various geomorphic settings imply the potential existence of hydrous minerals in similar settings over a much wider area. Hydrous sulfates represent one of the candidates that may contribute the high level of water equivalent hydrogen in equatorial regions detected by the Neutron Spectrometer on Mars Odyssey.We thank NASA for funding the MER Athena Science team and the JPL engineering team for continuing to successfully operate the Mars Exploration rovers.https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2008JE00312

An analysis of risk management disclosures: Australian evidence

- Purpose\ud \ud Communication of risk management practices are a critical component of good corporate governance. Research to date has been of little benefit in informing regulators internationally. This paper seeks to contribute to the literature by investigating how listed Australian companies in a setting where disclosures are explicitly required by the ASX corporate governance framework, disclose risk management (RM) information in the corporate governance statements within annual reports. \ud \ud - Design/methodology/approach\ud \ud To address our study’s research questions and related hypotheses, we examine the top 300 ASX-listed companies by market capitalisation at 30 June 2010. For these firms, we identify, code and categorise RM disclosures made in the annual reports according to the disclosure categories specified in Australian Stock Exchange Corporate Governance Principles and Recommendations (ASX CGPR). The derived data is then examined using a comprehensive approach comprising thematic content analysis and regression analysis.\ud \ud - Findings\ud \ud The results indicate widespread divergence in disclosure practices and low conformance with the Principle 7 of the ASX CGPR. This result suggests that companies are not disclosing all ‘material business risks’ possibly due to ignorance at the board level, or due to the intentional withholding of sensitive information from financial statement users. The findings also show mixed results across the factors expected to influence disclosure behaviour. Notably, the presence of a risk committee (RC) (in particular, a standalone RC) and technology committee (TC) are found to be associated with improved levels of disclosure. we do not find evidence that company risk measures (as proxied by equity beta and the market-to-book ratio) are significantly associated with greater levels of RM disclosure. Also, contrary to common findings in the disclosure literature, factors such as board independence and expertise, audit committee independence, and the usage of a Big-4 auditor do not seem to impact the level of RM disclosure in the Australian context. \ud \ud - Research limitation/implications\ud \ud The study is limited by the sample and study period selection as the RM disclosures of only the largest (top 300) ASX firms are examined for the fiscal year 2010. Thus, the finding may not be generalisable to smaller firms, or earlier/later years. Also, the findings may have limited applicability in other jurisdictions with different regulatory environments.\ud \ud - Practical implications\ud \ud The study’s findings suggest that insufficient attention has been applied to RM disclosures by listed companies in Australia. These results suggest that the RM disclosures practices observed in the Australian setting may not be meeting the objectives of regulators and the needs of stakeholders. \ud \ud - Originality/value\ud \ud Despite the importance of risk management communication, it is unclear whether disclosures in annual financial reports achieve this communication. The Australian setting provides an ideal environment to examine the nature and extent of risk management communication as the Australian Securities Exchange (ASX) has recommended risk management disclosures follow Principle 7 of its principle-based governance rules since 2007

Fe-sulphate-rich evaporative mineral precipitates from the Rio Tinto, southwest Spain

The soluble metal sulphate salts melanterite, rozenite, rhomboclase, szornolnokite, copiapite, coquimbite, hexahydrite and halotrichite, together with gypsum, have been identified, some for the first time oil the banks of the Rio Tinto, SW Spain. Secondary Fe-sulphate minerals call form directly from evaporating acid, sulphate-rich Solutions as a result of pyrite oxidation. Chemical analyses of mixtures of these salt minerals indicate concentrations of Fe (up to 31 wt.%), Mg (up to 4 wt.%), Cu (up to 2 wt.%) and Zn (up to wt.%). These minerals are shown to act as transient storage Cor metals and can store on average up to 10% (9.5 - 11%) and 22% (20-23%) Zn and Cu respectively, of the total discharge of the Rio Tinto during the summer period. Melanterite and rozenite precipitates at Rio Tinto are only found in association with very acidic drainage waters (pH <1.0) draining directly from pyritic waste piles. Copiapite precipitates abundantly oil the banks of the Rio Tinto by (1) direct evaporation of the river water; or (2) as part of a paragenetic sequence with the inclusion of minor halotrichite, indicating natural dehydration and decomposition. The natural occurrences are comparable with the process of paragenesis from the evaporation of Rio Tinto river water under laboratory experiments resulting in the formation of aluminocopiapite, halotrichite, coquimbite, voltaite and gypsum

Secondary uranium mineralization in southern Finland and its relationship to recent glacial events

Uranium series dating has been carried out on secondary uranyl silicate minerals formed during sub-glacial and post-glacial weathering of Proterozoic uraninite ores in south west Finland. The samples were obtained from two sites adjacent to the Salpauselkä III ice marginal formation and cover a range of depths, from the surface to more than 60 m. Measured ages fall into three distinct groups, 70–100 ka, 28–36 ka and < 2500 yr. The youngest set is associated with surface exposures and the crystals display clear evidence of re-working. The most likely trigger for uranium release at depths below the surface weathering zone is intrusion of oxidising glacial melt water. The latter is often characterised by very high discharge rates along channels, which close once the overpressure generated at the ice margin is released. There is excellent correspondence between the two Finnish sites and published data for similar deposits over a large area of southern and central Sweden. None of the seventy samples analysed gave a U–Th age between 40 and 70 ka; a second hiatus is apparent at 20 ka, coinciding with the Last Glacial Maximum. Thus, the process responsible for uranyl silicate formation was halted for significant periods, owing to a change in geochemical conditions or the hydrogeological regime. These data support the presence of interstadial conditions during the Early and Middle Weichselian since in the absence of major climatic perturbations the uranium phases at depth are stable. When viewed in conjunction with proxy data from mammoth remains it would appear that the region was ice-free prior to the Last Glacial Maximum

Thermal Decomposition of Ammonium Jarosite (NH4)Fe3(SO4)2(OH)6

Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic ammonium jarosite. Five mass loss steps are observed at 120, 260, 389, 510 and 541 degrees Celsius. Mass spectrometry through evolved gases confirms these steps as loss of water, dehydroxylation, loss of ammonia and loss of sulphate in two steps. Changes in the molecular structure of the ammonium jarosite were followed by infrared emission spectroscopy (IES). This technique allows the infrared spectrum at the elevated temperatures to be obtained. IES confirms the dehydroxylation to have taken place by 300 degrees Celsius and the ammonia loss by 450 degrees Celsius. Loss of the sulphate is observed by changes in band position and intensity after 500 degrees Celsius

The reaction branching ^(31)P(p, γ)/^(31)P(p, α) in the RP-process

The reactions ^(31)P(p, γ)^(32)S and ^(31)P(p, α)^(28)Si have been studied in the energy range 280–620 keV to investigate the influence of low-energy resonances on the stellar reaction rates. Several new resonances have been observed and the resonance strengths for both reaction channels have been determined. The reaction rates have been calculated from the present results and are compared with the results of Hauser-Feshbach calculations

Spatial distribution of major and trace elements in a mining dam: sources and relationships among elements of environmental concern

The concentration of major and trace elements have been determined in sediments samples taken from a mining dam, located in the upper area of the Tinto River basin (SW Spain). This dam, built to fulfil water needs for mining operations, is now completed clogged by accumulation of fine sediments. The results obtained for vertical and horizontal distribution of chemical elements showed highest average concentrations of Fe and Al, both with 10 %, and S (about 4 %). Toxic elements, such as As and Pb occur also with high concentrations (2515 and 5172 mg/kg, respectively). Determination of Enrichment Factors (EF) showed that sediments are enriched in elements related with the massive sulphide ore bodies and subsequent acid mine drainage processes. The elements Pb and As are that of major environmental concern, with enrichment factors higher than 10. Application of cluster analysis put in evidence the main sources of elements, allowing for the modelling of the origin of the accumulated matter. Therefore, in addition to contributions from sulphide (Fe, S) and gangue (Al, Mg), there are grouping of elements mobilized from phyllosilicates and feldspars, (e.g. Ca and K) as well as a specific group that reflects the geochemical affinity of rare earth elements in such acidic environment. Moreover, the way how elements are grouped testify the heterogeneity of geological contributions as well as the mining cycles over 4000 years of mining history in this worldwide known river basin.This study is a contribution of the DGCICYT-CGL2010-21268-C02-01 project, which has been financed by the Spanish Ministry of Education and Science, and the Andalusian Autonomous Government Excellence Projects, P10-RNM-6570 project. The Institute of Earth Sciences (ICT) is funding under contract with FCT (the Portuguese Science and Technology Foundation, Reference UID/GEO/04683/2013. The authors greatly appreciate the efforts of the three anonymous reviewers who carefully review the paper, and their valuable suggestions to improve the manuscript.info:eu-repo/semantics/publishedVersio