26Mg excess in hibonites of the Rumuruti chondrite Hughes 030

Abstract— The Rumuruti chondrites (R chondrites) constitute a new, well-established, chondrite group different from carbonaceous, ordinary, and enstatite chondrites. Most samples of this group are gas-rich regolith breccias showing the typical light/dark structure and consist of abundant fragments of various parent body lithologies embedded in a fine-grained, olivine-rich matrix. Most R chondrites contain the typical components of primitive chondrites including chondrules, chondrule and mineral fragments, sulfides, and rare calcium-aluminum-rich inclusions (CAIs). In Hughes 030, an interesting CAI consisting of abundant hibonite and spinel was found. Mg isotopic analyses revealed excess ²⁶Mg in components of R chondrites for the first time. The hibonite grains with high Al/Mg values (∼1500 to 2600) show resolved ²⁶Mg excess. The slope of the correlation line yields an initial ²⁶Al/ ²⁷Al = (1.4 ± 0.3) × 10⁻⁶, which is ∼40 times lower than the initial value measured in CAIs from primitive meteorites. The inferred difference in ²⁶Al abundance implies a time difference of ∼4 million years for the closure of the Al-Mg system between CAIs from primitive chondrites and the Hughes 030 CAI. Based on mineralogy and the petrographic setting of the hibonite-rich CAI, it is suggested that 4 million years reflect the time interval between the formation of the CAI and the end of its secondary alteration. It is also suggested that most of this alteration may have occurred in the nebula (e.g. Zn- and Fe-incorporation in spinels). However, the CAI could not have survived in the nebula as a free floating object for a long period of time. Therefore, the possibility of storage in a precursor planetesimal for a few million years, resetting the magnesium-aluminum isotopic system, prior to impact brecciation, excavation, and accretion of the final R chondrite parent body cannot be ruled out.     

A heat flow and physical properties package for the surface of Mercury

European Space Agencies fifth cornerstone mission BepiColombo includes a ‘Surface Element’ to land a scientific payload on the surface of Mercury. The current strawman payload includes a heat flow and physical properties package (HP³), focussing on key thermal and mechanical properties of the near-surface material (down to a depth of 2–5 m) and the measurement of heat flow from Mercury's interior, an important constraining parameter for models of the planet's interior and evolution. We present here an overview of the HP³ experiment package and its possible accommodation in a self-inserting ‘mole’ device. A mole is considered to be the most appropriate deployment method for HP³, at least in the currently-assumed case of an airbag-assisted soft landing architecture for the Mercury Surface Element.     

LusTRE: a framework of linked environmental thesauri for metadata management

The paper illustrates a Linked Thesaurus Framework for the Environment, named LusTRE, to facilitate data sharing across different environmental disciplines. It provides a knowledge infrastructure of multilingual thesauri and code lists, interlinking them so that they can be used as one integrated linked data source. This multilingual thesaurus is published according to the Linked Data Best Practices and supports metadata compilation and data discovery for describing and finding Environmental geodata. A human readable web interface is provided for the exploitation of LusTRE as well as a set of web services for programmatic access to the knowledge infrastructure. LusTRE has been exploited within the European directive INSPIRE and SEIS piloting testbeds implemented within the EU project eENVplus in order to support cross-border and cross-domain data sharing. It is aimed at supporting multilingual data search and query refinement. In order to show how interlinked content can help users to more easily express metadata within Spatial Data Infrastructures (SDI), LusTRE web services have been integrated within existing metadata editors and geoportals.     

Visualisation strategies for environmental modelling data

We present a framework that allows users to apply a number of strategies to view and modify a wide range of environmental data sets for the modelling of natural phenomena. These data sets can be concurrently visualised to find inconsistencies or artefacts. This ensures at an early stage that models set up for the simulation of hydrological or thermal processes will not give implausible results due to complications based on input data. A number of generally applicable visualisation techniques are provided by our framework to help researchers detect potential problems. We also propose a number of mapping algorithms for the integration of multiple data sets to resolve some of the most common issues. Techniques for the presentation of input- and modelling data in combination with simulation results are proposed with respect to the benefits of visualisation of environmental data within specialised environments. The complete workflow from input data to presentation is demonstrated based on a case study in Central Germany. We identify typical problems, propose approaches for a suitable data integration for this case study and compare results of the original and modified data sets.     

Recommendation for the discrimination of human-related and natural seismicity

Various techniques are utilized by the seismological community, extractive industries, energy and geoengineering companies to identify earthquake nucleation processes in close proximity to engineering operation points. These operations may comprise fluid extraction or injections, artificial water reservoir impoundments, open pit and deep mining, deep geothermal power generations or carbon sequestration. In this letter to the editor, we outline several lines of investigation that we suggest to follow to address the discrimination problem between natural seismicity and seismic events induced or triggered by geoengineering activities. These suggestions have been developed by a group of experts during several meetings and workshops, and we feel that their publication as a summary report is helpful for the geoscientific community. Specific investigation procedures and discrimination approaches, on which our recommendations are based, are also published in this Special Issue (SI) of Journal of Seismology.     

Visual data exploration for hydrological analysis

Hydrological research projects for integrated water resources management such as the IWAS initiative often accumulate large amounts of heterogeneous data from different sources. Given the number of partners taking part in such projects, surveying and accessing the available data sets, as well as searching for a defined subset, becomes increasingly difficult. We propose an integrated approach for a system combining visual data management and numerical simulation which allows to survey and select data sets based on keywords such as a region of interest or given indicators. An adequate 3D visualisation of such subsets helps to convey information and significantly supports the assessment of relations between different types of data. Furthermore, the interface between the visual data management system and finite element codes allows for the straightforward integration of information into the numerical simulation process and the subsequent visualisation of simulation results in a geographical context. We demonstrate typical workflows for integration and processing within the system based on data from the IWAS model region in Saudi Arabia and the TERENO Bode Observatory in the Harz Mountains in Germany. In addition, we present examples for data import and export based on established standard file formats.     

Absence of oxygen isotope fractionation/exchange of (hemi-) cellulose derived sugars during litter decomposition

Aiming at developing a novel tool for palaeoclimate research, we recently proposed a new method for determining the oxygen isotope composition of monosaccharides (Zech, M., Glaser, B., 2009. Compound-specific δ¹⁸O analyses of neutral sugars in soils using GC-Py-IRMS: problems, possible solutions and a first application. Rapid Communications in Mass Spectrometry 23, 3522-3532). In order to answer the question whether isotope fractionation and oxygen exchange reactions during litter decomposition affect the climatically controlled δ¹⁸O values of plant derived sugars, such as for instance xylose and arabinose from hemicelluloses, we studied the compound specific δ¹⁸O values of five different litter species having been decomposed in a field litterbag experiment for 27 months.While δ¹⁸O values of bulk organic matter yielded a systematic ¹⁸O depletion of 3.3‰ (pine) to 4.6‰ (spruce) accompanying total cellulose decomposition of 51% (beech) to 86% (ash), δ¹⁸O values of individual sugars show no significant trend with time. In addition to the observed absence of isotope fractionation during decomposition, we also rule out ¹⁸O exchange reactions affecting the δ¹⁸O signature of sugar molecules during diagenetic processes as well as during analytical procedure based on experimental findings and on theoretical biochemical mechanistic considerations. We conclude that our new method may become an analytical tool that elegantly overcomes extraction, purity and hygroscopicity problems of previous ¹⁸O cellulose methods. It furthermore has the potential to be applied to a wide range of climate archives such as tree rings, lacustrine sediments and loess palaeosol sequences.     

Conodont distributions,and ages of Silurian and Devonian limestones in the Palmers Oakey district,N.S.W.

Limestones in the Palmers Oakey District, N.S.W., range in age from Middle Silurian to Early Devonian. They occur as sheet‐like, bioclastic beds and/or isolated clasts in three facies: a volcaniclastic facies, a mudstone‐limestone facies, and a limestone‐mudstone breccia facies. Multielement conodont taxa, not previously reported from Australia, include Kockelella absidata, Kockelella stauros, Ozarkodina asymmetrica, Ozarkodina stygia, Ozarkodina transitans, Pseudooneotodus bicornis, and Pseudooneotodus tricornis.     

Impact of recharge variations on water quality as indicated by excess air in groundwater of the Kalahari, Botswana

Groundwater is an important and often exclusive water resource in arid and semi-arid regions. The aim of the present paper was to gain insight into the processes and conditions that control the deterioration of groundwater quality in the semi-arid Kalahari of Botswana. Measurements of ³He, ⁴He, ²⁰Ne, ²²Ne, and of ¹⁴C of dissolved inorganic carbon (DIC) were combined with existing isotopic and hydrochemical data to investigate groundwater from the Ntane Sandstone Aquifer, which is affected by high nitrate concentrations of non-anthropogenic origin. All groundwater samples revealed neon concentrations in excess to air-saturated water, which we attributed to the addition of excess air during recharge. Neon concentrations ranged from values close to air saturation for ¹⁴C DIC rich samples (up to 80.5%MC) up to values of 90% in excess to air-saturated water for lower ¹⁴C DIC contents (2.6-61.3%MC). A strong linear correlation of excess Ne with nitrate concentrations suggests an intimate connection between groundwater quality and the processes and conditions during groundwater recharge. Low groundwater recharge rates under present-day semi-arid conditions are associated with low amounts of excess Ne and elevated nitrate concentrations. In contrast to this, higher excess Ne values in groundwater of lower ¹⁴C DIC and nitrate contents indicate that the high quality groundwater end-member presumably is related to higher groundwater table fluctuations during wetter climatic conditions in the past. We attribute the decline in groundwater quality with respect to nitrate to a decreasing rate and temporal variability of groundwater recharge, and to concurrent changes in biogeochemical activities following a transition to a drier climate during the Holocene. Under such conditions, a much stronger decrease in groundwater recharge compared to the release of nitrate from soil organic matter may result in elevated nitrate concentrations in the vadose zone and groundwater. This implies a strong impact of climate change on the transport of solutes like nitrate through the vadose zone which needs to be considered in predictions of future groundwater quality.