Sampling of Mars analogue materials in a laboratory environment

Acta Geotechnica - Two laboratory test series were performed with the aim of ensuring the proper functionality of the key sampling mechanisms installed aboard the Mars rover ExoMars, currently...     

Petrologische Untersuchungen am Mauthausner Granit im österreichischen Moldanubikum

Zusammenfassung Der Mauthausner Granit bildet im österreichischen Moldanubikum eine Anzahl von gang- und stockförmigen Durchbrüchen. Er wurde an Hand von vier Vorkommen—Mauthausen selbst, Gloxwald (bei Sarmingstein), Plöcking und Schrems—einer detaillierten chemischen und mineralogischen Untersuchung unterzogen.Das Gestein ist ein Biotitgranit mit geringen Mengen primären Muskovits. Der Plagioklas (bis 38 Vol. %) besitzt einen progressiven und oszillatorischen Zonarbau, primäre und sekundäre Verzwillingung und einen durchschnittlichen An-Gehalt von An=20% (Plöckinger Granit An=25%). Der Alkalifeldspat (durchschnittlich 28 Vol. %) ist ein scharf gegitterter perthitischer Mikroklin (entmischte Phase Or=89%, >90) mit durchschnittlich Ab+15%. Der Biotit (ca. 10 Vol.%) bildet 2M₁ Polymorphe, ebenso der Muskovit (<1 Vol.%). Der Zirkon bildet zwei Typen verschiedener Herkunft; das Gestein ist hybrid. Aus den Komponentenanalysen ergeben sich als Bildungsbedingungen: relativ rasche Kristallisation bei steigendem pH₂O im Bereich von ca. 5000 bar, fallende Temperatur und fallender Belastungsdruck, was auf große Bildungstiefen hinweist. Die Intrusion erfolgte während der Plagioklaskristallisation und während des Abklingens der variskischen Regionalmetamorphose in eine relativ kühle Umgebung.

---

Summary The Mauthausen granite belongs to the Moldanubian zone of Austria, and is represented by a number of dike-and plug-like minor intrusions. Four representative localities were chosen for a detailed chemical and mineralogical investigation (Mauthausen, Gloxwald near Sarmingstein, Plöcking and Schrems).The rock is a biotite granite with subordinated amounts of primary muscovite. The rock contains up to 38 vol.-% plagioclase which shows progressive and oscillatory zoning, primary and secondary twinning and an average An-content of 20% (Plöcking 25%). The alkali feldspar forms about 28 vol.-% of the rock. It is strongly cross-hatched microcline-perthite with average Ab 15%. Its unmixed potassium phase contains Or=89%, >90. Biotite (ca. 10 vol.-%) and muscovite (<1 vol.-%) are 2M₁ polymorphs. Investigations on zircons show types of different origin expressing a remarkable hybridity of the rock in question. From the analyses of the components the following conclusions elucidate: Relatively rapid crystallisation under increasing pH₂O around 5000 bar, falling temperature and load pressure. This indicates great depth of formation. The intrusion took place during the crystallisation of the plagioclase into a relatively cool surrounding. The time of intrusion can be fixed near the end of the variscian regional metamorphism.

---

---

Mit 8 Textabbildungen

---

Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.     

Monazite dating of granitic gneisses and leucogranites from the Kerala Khondalite Belt,southern India: implications for Late Proterozoic crustal evolution in East Gondwana

Two stages of granitic magmatism occurred during the Pan-African evolution of the Kerala Khondalite Belt (KKB) in southern India. Granitic gneisses were derived from porphyritic granites, which intruded prior to the main stage of deformation and peak-metamorphism. Subsequently, leucogranites and leucotonalites formed during fluid-absent melting and intruded the gneiss sequences. Monazites from granitic gneisses, leucogranites and a leucotonalite were investigated by conventional U-Pb and electron microprobe dating in order to distinguish the different stages of magma emplacement. U-Pb monazite dating yielded a wide range of ages between 590–520 Ma which are interpreted to date high-grade metamorphism rather than magma emplacement. The results of this study indicate that the KKB experienced protracted heating (>50 Ma) at temperatures above 750–800 °C during the Pan-African orogeny. The tectonometamorphic evolution of the study area is comparable to southern Madagascar which underwent a similar sequence of events earlier than the KKB. The results of this study further substantiate previous assertions that the timing of high-grade metamorphism in East Gondwana shifted from west to east during the Late Proterozoic.     

On the soil erosion problem in the temperate humid area of Central Europe

Conclusion Previous research on soil erosion in Central Europe was mainly focused on historical aspects, with soil erosion forms and their regional setting. It is now time to utilize a more quantitative approach. Furthermore in the future, soil erosion should be seen in the context of the entire equilibrium of landscape systems, that means as part of economic-ecological research.     

Quaternary sediment dynamics in the Belgica mound province,Porcupine Seabight: ice-rafting events and contour current processes

The Belgica cold-water coral banks on the eastern slope of the Porcupine Seabight are closely associated with bottom currents. In order to better understand the local temporal and spatial characteristics, as well as the palaeoclimatologic influences, a 26 m long core, taken on a small contourite drift, was studied. This sediment record of approximately 100 ka BP reveals new insights into the regional glacial and sedimentary processes, which are intrinsically linked to several geological, climatological, biological and hydrodynamic variables. The glacial sequences in the core contain six ice-rafting events (IRE). They are comparable with the North Atlantic Heinrich Events, although their characteristics show dominant influences from the proximal British–Irish Ice Sheet (BIIS). These IRE have a low magnetic susceptibility and are deposited during two or three ice-rafting pulses. The record of ice-rafting suggests a millennial-scaled BIIS destabilisation and confirms the start of a final retreat about 25 ka ago. Additionally, the glacial sequence corresponds to a muddy contourite, influenced by bottom-current strength variations during interstadials, possibly triggered by sporadic reintroductions of Mediterranean Outflow Water in a glacial North Atlantic Ocean. The interglacial sequence features an 11-m thick deep-water massive sand unit, probably deposited under a high-energy bottom-current regime.     

Climate shifts vs. edaphic humidity and the difficulty of palaeoreconstructions – a malacological study on stable isotopes in Quaternary dune sequences of Fuerteventura

Dune palaeosurface sequences on the Eastern Canary Islands were investigated for stable isotope records in gastropod shells of the genus Theba. Due to the ecology of the taxon and the special oceanic insularity of the study site, we assume that δ¹⁸O_shell signals in our case mainly reflect shifts in δ¹⁸O signals of sea surface water. We found that a rapid decrease in δ¹⁸O_shell signals is associated with significant changes in gastropod associations. We suggest that these faunal changes were caused by strong (hot) winds at the end of glacial phases, that were described previously by Moreno et al. In addition, we assume that rapid declines in δ¹⁸O_shell signals due to marine transgressions were followed by geomorphologically stable phases, dominated by dust enrichment. Such palaeosurfaces correlate with maxima of gastropod biodiversity and with more negative δ¹³C_shell signals indicating a higher proportion of C3 plants. Based on our results, we also assume that these silty palaeosurfaces were associated with increased soil moisture conditions due to a higher water storage capacity of the finer substrate, independent of climatic moisture conditions.     

In situ oxygen,magnesium, and silicon isotopic compositions of the FUN inclusion Vigarano 1623-5

Oxygen, magnesium, and silicon isotopic abundances in Vigarano 1623-5 were studied using secondary ion mass spectrometry to investigate correlations between isotopic and petrologic properties of this unique forsterite-bearing FUN inclusion. Vigarano 1623-5 displays large, correlated mass-dependent fractionation effects, tightly linked to mineralogy within distinct petrologic units of the inclusion. The pyroxene-rich and melilite-rich interior parts of the inclusion display highly mass-fractionated isotopic compositions of oxygen, magnesium, and silicon, consistent with Rayleigh distillation during evaporation of a melt with initial oxygen composition close to a solar composition. However, the chemical composition, enriched in magnesium and silicon, suggests a precursor already fractionated by prior melt evaporation. A discontinuous igneous rim was produced by a flash-melting event followed by isotopic exchange in the rim melilite with planetary-like oxygen, mechanical fragmentation, and reassembly with an accretionary rim of heterogeneous materials. Al-rich minerals in 1623-5 show evidence for having crystallized with live ²⁶Al but at less than the “canonical” level of most CV calcium-aluminum-rich inclusions. However, well-defined ²⁶Al-²⁶Mg isochrons are not found and temporal implications are ambiguous.     

Sidescan backscatter variations of cold seeps on the Hikurangi Margin (New Zealand): indications for different stages in seep development

Cold seeps on the Hikurangi Margin off New Zealand exhibit various seabed morphologies producing different intensity patterns in sidescan backscatter images. Acoustic backscatter characteristics of 25 investigated seep sites fall into four distinct types characterised by variations in backscatter intensity, distribution and inferred structural heights. The types reflect different carbonate morphologies including up to 20-m-high structures (type 1), low-relief crusts (type 2), scattered blocks (type 3) and carbonate-free sites (type 4). Each seep corresponds to a single type; intermediates were not observed. This correlates well with published data on seep fauna at each site, with the four types representing three different faunal habitats of successive stages of seep development. Backscatter signatures in sidescan sonar images of cold seeps may therefore serve as a convenient proxy for variations in faunal habitats.