Radon emanation from giant landslides of Koefels (Tyrol,Austria) and Langtang Himal (Nepal)

The identification of extremely high indoor radon concentrations in the village Umhausen (Tyrol, Austria) initiated a scientific program to get information about the source and distribution of this noble gas. The high concentrations can not be related to U anomalies or large-scale fault zones. The nearby giant landslide of Koefels, with its highly fractured and crushed orthogneisses, are the only possible source of radon, despite the fact that the U and Ra content of the rocks is by no means exceptional. The reasons for the high emanation rates from the landslide are discussed and compared to results gained from a similar examination of the giant landslide of Langtang Himal (Nepal). The exceptional geologic situation in both cases, as well as the spatial distribution of different concentration levels, indicate that both landslides must be considered as the production sites of radon. Independent of the U and Ra contents of the rocks, the most important factors producing high emanation rates are the production of a high active surface area and circulation pathways for Rn-enriched soil air by brittle deformation due to the impact of the landslidemass.     

Mineralogical and chemical composition of some carbonate minerals from the Zillerthal Alps,Tyrol (Austria)

Summary 32 carbonate samples from a series of metamorphic rocks of greenschist to almandine-amphibolite facies in the Zillerthal Alps were investigated by optical and chemical methods, X-ray diffractometry, and the scanning electron microscope.The carbonates consist mainly of calcite which contains up to 11 mole % (MgCO₃+FeCO₃). Some of the calcites are characterized by skeleton-like dolomitic exsolutions of rhombohedral shape that are orientated on rhombohedron planes of the calcite matrix.The relations between metamorphic grade and calcite composition will be discussed. The (FeCO₃+MgCO₃)-content of calcite depends on the temperature of formation, CO₂ pressure, and the Fe and Mg concentrations of the carbonate-forming solutions.

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Mineralogische und chemische Zusammensetzung von Karbonaten aus den Zillertaler Alpen, Tirol (Österreich)

Zusammenfassung 32 Karbonatproben aus den Zillertaler Alpen (Tirol, Österreich) wurden mit optischen und röntgendiffraktometrischen Methoden sowie mit dem Elektronenrastermikroskop untersucht.Die Karbonate sind Calcite, die bis zu 11 Mol% (MgCO₃+FeCO₃) enthalten. Die Calcitkristalle zeichnen sich durch skelettartige Dolomitentmischungen aus, die parallel zu Rhomboederflächen des Calcites orientiert sind.Die Karbonate stammen aus einer Serie metamorpher Gesteine der Grünschiefer- bis Almandin-Amphibolitfazies. Es werden die Beziehungen zwischen der Calcitzusammensetzung und dem Metamorphosegrad diskutiert. Der (FeCO₃+MgCO₃)-Gehalt der Calcite hängt von der Bildungstemperatur, vom CO₂-Druck und vom Fe- und Mg-Gehalt der Lösungen ab, aus denen sich die Karbonate gebildet haben.

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With 10 Figures     

Magnesite diagenesis in redbeds: a case study from the Permian of the Northern Calcareous Alps (Tyrol, Austria)

The Upper Permian Gröden Formation of the Northern Calcareous Alps (Austria) is composed of alluvial fan and playa lake sediments that were deposited in intramontane basins. A conspicuous feature of these redbeds is the abundance of magnesite in the form of nodules and discrete layers in mudstones as well as intergranular cement in sandstones. Sedimentological observations indicate that the bulk of these carbonates formed during early diagenesis and were probably syndepositional. Petrographically, most magnesites consist of micrite or, less commonly, microspar. An early non-ferroan magnesite is post-dated by later stage ferroan magnesites. Nodules consisting of recrystallized, sparry magnesite were observed only at one location. The general absence of relics of a non-magnesite precursor mineral and the occurrence of shrinkage features suggest that the fine grained magnesites formed by transformation of a hydrated magnesium carbonate mineral, e.g. hydromagnesite. Carbon, oxygen, sulphur and strontium isotope ratios in conjunction with sedimentological criteria support a model of (hydro)magnesite precipitation in an inland playa lake system, which was fed by run-off from the surrounding hinterland. The scarcity of evaporites and the dominance of magnesite over calcite and dolomite suggest that the playa lake brines were low in sulphate and had high Mg/Ca ratios. The source for the high magnesium concentrations is thought to be the weathering of Devonian dolostones and associated massive magnesite deposits in the catchment area.     

The metamorphosed molybdenum vein-type deposit of the Alpeinerscharte,Tyrol (Austria) and its relation to Variscan granitoids

 The molybdenite deposit of the Alpeinerscharte (Austria) is situated in Variscan greenschist- to amphibolite-facies metamorphosed granodiorites and granites of the western Tauern Window. These granitoids represent strongly fractionated calc-alkaline I-type magmas with minor S-type components and reveal post-orogenic affinities. Molybdenum contents (average 4.3 ppm) are slightly above the general background of average granites. Molybdenite mineralization is restricted to narrow quartz veins and quartz vein selvages which are presently composed of biotite and (almandine-grossular) garnet. These selvages show geochemical features typical of intermediate argillic alteration in a hydrothermal system postdating granite intrusion: instability of plagioclase causes removal of Na, Ba, Sr, Pb and Eu, while K and Ca remain nearly constant. Rare earth elements (apart from Eu) and metals are extremely enriched. Application of Fe-Mg exchange (garnet-biotite) and oxygen isotope (quartz-garnet, quartz-plagioclase) geothermometers to vein selvage mineral assemblages reveals temperatures of the late-Alpine (35–55 Ma) metamorphic overprint (∼540 ^°C, 7–10 kbar). Leucocratic rocks composed of mainly orthoclase and plagioclase are occasionally spatially related to molybdenite-bearing veins; they are interpreted as episyenites formed by hydrothermal alteration of the host granite. This episyenitic alteration is characterized by a mass loss of ca. 30%, relative enrichment of plagioclase components, extreme depletion of Si, and minor depletion of Fe, Zn, Cu and Mo. Received: 5 December 1993/Accepted: 24 October 1995     

Occurrence and breakdown of paragonite and margarite in the Greiner Schiefer Series (Zillerthal Alps,Tyrol)

Margarite and Paragonite are found coexisting in amphibolites of the Untere Schieferhülle in the area of the upper Schlegeistal (Zillerthal Alps, Northern Tyrol). These amphibolites are metamorphosed under conditions of the low grade amphibolite facies. The chemical composition of the two micas was determined by the electron microprobe. A maximum of 14 Mol-% margarite and 18 Mol-% muscovite enters into the paragonite, the margarite being entered by 20 to 50 Mol-% paragonite and a maximum of 10 Mol-% muscovite. There seems to be a solubility gap between margarite and paragonite in a range between 15 and 50 Mol-% margarite.At their margins the margarites and paragonites breakdown into a mixture of feldspar and into a fine, microscopically not identifiable phase. Plagioclases having An 28 to An 42 result from breakdown of paragonite, feldspars between An 50 and An 60 probably arose from breakdown of margarite. A definite statement on this probelem is not possible because the smallness and the inhomogeneity of the feldspar grains.Based on the experimental data concerning the stability of margarite, paragonite (±quartz, ±CO₂) and kyanite, the P-T-range of the metamorphosis is discussed.     

Alpine overdeepenings and paleo-ice flow changes: an integrated geophysical-sedimentological case study from Tyrol (Austria)

We present a study of the inneralpine basin of Hopfgarten focused on the analysis of basin fill in order to reveal its formation in relation to paleo-ice flow and tectonics. The study is based on geological mapping as well as seismic (reflection and refraction) and geoelectrical surveys. The oldest sequence in the basin, identified by seismic stratigraphy at 400 m below surface, consists of coarse grained sediments of supposedly Oligocene to Miocene age, which subsided along faults linked to the Inn fault. Three superimposed sequences, each displaying baselaps in contact with a subglacially formed unconformity and sigmoid foresets, show pleniglacial conditions followed by a glaciolacustrine environment. The uppermost of these three sequences lies on top of last glacial maximum till (LGM; Würmian Pleniglacial; MIS 2) and represents Termination I. The middle sequence is classified as Termination II following the Rissian Pleniglacial (MIS 6). The oldest glacial sequence cannot be constrained chronostratigraphically but might correlate with Termination V following the major glaciation of MIS 12. Limited glacial erosion during the LGM occurred only during the ice build-up phase. Further overdeepening was impeded due to topographic barrier and mutual blockades of glaciers within this highly dissected landscape. The occurrence and relative timing of the impediment was controlled by the onset of transfluences and thus by the altitude of coles. The higher amount of overdeepening during older glacial periods is explained by longer phases of free ice advance in the ice build up phase due to higher transfluences routes at that time. Thus, the preservation of older Pleistocene sequences within the basin may be the result of the lowering of watersheds from one glaciation to the next. Our model of an inverse relationship between glacial shaping of the surface and the subsurface may apply to similar Alpine landscapes as well.     

The role of olivine in the crystallization of the prehistoric Makaopuhi tholeiitic lava lake,Hawaii

On eruption, the tholeiitic basalt lava of the prehistoric Makaopuhi lake contained nearly seven percent euhedral olivine phenocrysts of approximately Fa₁₄ composition. In the center of the 225 foot vertical section of the lake, the lava became more than 90 percent solid at 1000° C after about 30 years. At the surface the lava was quenched to air temperature, whereas, at the bottom, quenching to 800° C was followed by a 40 year period before the temperature reached 700° C. The olivine phenocrysts settled at an average rate of about 4 × 10^–6 cm Sec^–1 to form a zone that contains 21 percent olivine 75 feet above the base. Sinking of olivines continued until some time after the beginning of the crystallization of augite and plagioclase. Thin rims of iron-rich olivine (up to Fa₅₅) surrounding the phenocrysts, and a second generation of fine-grained olivines (Fa₂₀ Fa₄₈) restricted to the uppermost 20 feet indicate local extensions of the period of crystallization of olivine. During crystallization of the groundmass and later subsolidus cooling in the range 1000° C to at least as low as 800° C, the olivine phenocrysts were converted to Fa_30–40 by interdiffusion of Fe, Mg, Ni, and Mn. Homogenization of Mg-rich cores and Fe-rich margins and equilibration of olivine composition with the groundmass phases was progressively less well achieved toward the top of the lake. Reaction rims around the olivines are composed primarily of Ca-rich pyroxene. Pigeonite crystallized alongside augite except in the uppermost 5 feet where there is abundant ground mass olivine. Poikilitic hypersthene grew at the expense of pre-existing ferromagnesian minerals in the cumulate zone.Publication authorized by the Director, U.S. Geological Survey.     

Complex zoning and resorption in Breunnerite from hall in Tyrol,Austria: Evidence from back-scattered electron microscopy

Summary Back-scattered electron imagery (BSE) coupled with energy-dispersive X-ray elemental analysis was applied to petrographic investigations of recrystallized, anchimetamorphic breunnerites (ferroan magnesites). Analyses of polished thin sections allowed the recognition of a complex zoning pattern, invisible by transmitted or reflected light microscopy. Breunnerite precipitation and replacement started with (Mg_0.90Fe_0.07Ca_0.01Mn_0.02) CO₃ and proceeded towards (Mg_0.73Fe_0.22Ca_0.00Mn_0.05)CO₃. This precipitation sequence was interrupted by at least two major events of reverse zoning (i.e. Fe-rich zones followed by Fe-poor ones). Resorption surfaces in Fe-poor zones are common and prove that short-term fluctuations occurred in the paleobrine composition and/or paleotemperature.

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Nachweis komplexer zonierung und resorption im breunnerit mittels Rückstreuelektronenbilder

Zusammenfassung Breunnerit-Proben von der Typlokalität evaporitischer Magnesitlagerstätten (ehemaliger Salzbergbau Hall in Tirol/Österreich) wurden an Hand von Rückstreuelektronen(BSE)-Bildern und energiedispersiven Röntgenanalysen (EDS) untersucht. Während Durch- und Auflichtmikroskopie lediglich eine zweiphasige Kristallisationsgeschichte erkennen ließen, konnte mittels BSE-Bildern eine detaillierte Rekonstruktion der spätdiagenetischen bzw. anchimetamorphen Breunneritbildung durchgeführt werden. Ein genereller Trend zu Fe-reicheren, häufig oszillierend-zonierter Mischkristalle der Reihe Magnesit-Siderit konnte erkannt werden, der jedoch von mindestens zwei invers zonierten Phasen unterbrochen wurde. Resorptionserscheinungen in den Fe-ärmeren Zonen sind verbreitet und belegen kurzfristige Fluktuationen in der Paläofluid-Zusammensetzung und/oder dessen Paläotemperatur.

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With 5 Figures     

Unusual catchment runoff in a high alpine karst environment influenced by a complex geological setting (Northern Calcareous Alps,Tyrol, Austria)

Garber Schlag (Q-GS) is one of the major springs of the Karwendel Mountains, Tyrol, Austria. This spring has a unique runoff pattern that is mainly controlled by the tectonic setting. The main aquifer is a moderately karstified and jointed limestone of the Wetterstein Formation that is underlain by nonkarstified limestone of the Reifling Formation, which acts as an aquitard. The aquifer and aquitard of the catchment of spring Q-GS form a large anticline that is bound by a major fault (aquitard) to the north. Discharge of this spring shows strong seasonal variations with three recharge origins, based on δ¹⁸O and electrical conductivity values. A clear seasonal trend is observed, caused by the continuously changing portions of water derived from snowmelt, rainfall and groundwater. At the onset of the snowmelt period in May, the discharge is composed mainly of groundwater. During the maximum snowmelt period, the water is dominantly composed of water derived from snowmelt and subordinately from rainfall. During July and August, water derived from snowmelt continuously decreases and water derived from rainfall increases. During September and October, the water released at the spring is mainly derived from groundwater and subordinately from rainfall. The distinct discharge plateau from August to December and the following recession until March is likely related to the large regional groundwater body in the fissured and moderately karstified aquifer of the Wetterstein Formation and the tectonic structures (anticline, major fault). Only a small portion of the water released at spring Q-GS is derived from permafrost.

     

OH-bearing planar defects in olivine produced by the breakdown of Ti-rich humite minerals from Dabie Shan (China)

The partial breakdown of Ti-chondrodite and Ti-clinohumite during exhumation from ultra-high pressure to amphibolite facies conditions in garnet-pyroxenites from Dabie Shan (China) produces coronas of olivine coexisting with ilmenite blebs. Fourier transform infrared (FTIR) spectra of this newly formed olivine exhibit absorption bands in the hydroxyl-stretching region. Two intense peaks were observed at 3,564 and 3,394 cm⁻¹, identical in energy to peaks in Ti-clinohumite. Transmission electron microscopy (TEM) of the same olivine domains revealed the presence of a complex (001) planar intergrowth. These interlayers have a 1.35 nm repeat distance, which is characteristic of clinohumite. Such interlayers are also enriched in Ti with respect to the adjacent olivine as shown by energy dispersive spectrometry. The combined evidence from FTIR spectroscopy and TEM indicates that OH is incorporated along Ti-clinohumite planar defects. This study provides evidence that the nominally anhydrous phase olivine may contain OH as a humite-type defect beyond the breakdown of the hydrous humite minerals and confirms earlier suggestions that Ti plays a key role in OH incorporation in mantle olivine. We suggest that olivine containing Ti-clinohumite defects is an important phase for water transport in subduction zones and for the storage of water in cold subcontinental mantle. However, these defects are unlikely to be stable in hotter parts of the oceanic mantle such as where basaltic magmas are generated.     

The structural vulnerability in the framework of natural hazard risk analyses and the exemplary application for storm loss modelling in Tyrol (Austria)

In the context of natural hazard-related risk analyses, different concepts and comprehensions of the term risk exist. These differences are mostly subjected to the perceptions and historical backgrounds of the different scientific disciplines and results in a multitude of methodological concepts to analyse risk. The target-oriented selection and application of these concepts depend on the specific research object which is generally closely connected to the stakeholders’ interests. An obvious characteristic of the different conceptualizations is the immanent various comprehensions of vulnerability. As risk analyses from a natural scientific-technical background aim at estimating potential expositions and consequences of natural hazard events, the results can provide an appropriate decision basis for risk management strategies. Thereby, beside the preferably addressed gravitative and hydrological hazards, seismo-tectonical and especially meteorological hazard processes have been rarely considered within multi-risk analyses in an Alpine context. Hence, their comparative grading in an overall context of natural hazard risks is not quantitatively possible. The present paper focuses on both (1) the different concepts of the natural hazard risk and especially their specific expressions in the context of vulnerability and (2) the exemplary application of the natural scientific-technical risk concepts to analyse potential extreme storm losses in the Austrian Province of Tyrol. Following the corresponding general risk concept, the case study first defines the hazard potential, second estimates the exposures and damage potentials on the basis of an existing database of the stock of elements and values, and third analyses the so-called Extreme Scenario Losses (ESL) considering the structural vulnerability of the potentially affected elements at risk. Thereby, it can be shown that extreme storm events can induce losses solely to buildings and inventory in the range of EUR 100–150 million in Tyrol. However, in an overall context of potential extreme natural hazard events, the storm risk can be classified with a moderate risk potential in this province.     

The Cretaceous and younger thermal history of the KTB site (Germany): apatite fission-track data from the Vorbohrung

A detailed fission-track analysis was carried out on 41 apatite samples from the 4001-m-deep pilot hole of the German Continental Deep Drilling Program (KTB). The investigations include dating by the population method and length measurements of horizontal confined tracks. Age and length information indicate that all samples above the present-day partial annealing zone cooled from temperatures above 120?°C in the Cretaceous. The top two kilometres of the profile show less variation of age with depth than was expected. Modelling of the profile indicates that the distribution of fission track ages with depth requires that the profile was disturbed during or after cooling through the partial annealing zone. Modelling of individual samples reveals that at least the upper 2?km experienced reverse faulting, effectively thickening the upper part of the rock column by up to 1000?m in the Tertiary. A present-day partial annealing zone for apatite was observed between 2000 and 4000?m (～60–110?°C). This confirms earlier in situ observations of the position of the partial annealing zone.     

Metal contamination and retention of the former mining site Schwarzwand (Salzburg,Austria)

The Schwarzwand is a unique hygric, Cu-contaminated habitat formed by mining activities from the 16th to 18th century. Today, a large spoil heap and several creeks fed by Cu-rich mine drainage are present. The vegetation of the Schwarzwand differs clearly from the surrounding subalpine forests. It is by no means impoverished but rather a hotspot of biodiversity. Interestingly, most of the Cu precipitates within the Schwarzwand and the creeks leave the Schwarzwand virtually clean. This study maps the distribution of Cu within the Schwarzwand and within selected vascular plants, moss and microorganisms and correlates them with water and soil chemistry in order to identify the sinks of Cu and to elucidate the remarkable capability of the Schwarzwand for natural attenuation.Two types of water could be distinguished, one acidic precipitating limonite with a constant Cu content of about 0.6 mg L⁻¹, and one circumneutral, which decreases far more rapidly in Cu content than would be expected due to chemical considerations. A dense microbial mat covering most of the bed of the circumneutral creeks could be identified as the main sink. It consists of the cyanobacterium Phormidium sp. and retains Cu both by adsorption to mucilaginous sheaths and by precipitation as secondary minerals such as sampleite. Layers of dead biofilm can be found covered by a few centimetres of soil at the banks of the circumneutral creeks; the extremely high concentration and the low solubility of Cu in this soil indicates permanent immobilisation of the metals. High concentrations of Cu were also found in mosses of the family Bryaceae which, however, play a negligible role for the metal retention of the habitat due to their low biomass.The retention of Cu within the Schwarzwand is a remarkable example of the sustainable self-cleaning of a contaminated habitat which takes place without any human intervention. The artificial establishment of microbial communities similar to the Schwarzwand could result in cheap and sustainable strategies for the remediation of suitable metal-contaminated waters.     

Petrological study and radiometric age determination of the migmatites in the Penninic rocks of the Zillertaler Alpen (Tyrol/Austria)

Summary Migmatites are very common in the Penninic Zentralgneis series of the Western Tauern Window. Nebulitic migmatites occurring near the Berliner Hütte (Zillertaler Alpen) have been studied by petrological and geochronological methods in order to determine the conditions and time of their formation. These migmatites occur in an area in which Alpine metamorphism attained its highest grade.An Rb/Sr isochron for the migmatites yielded a Hercynian age of 283±28 m.y. This age probably corresponds to the climax of Hercynian metamorphism in the Penninic area of the Tauern Window. Rb/Sr age determinations on the phengites and biotites of these migmatites give ages of 21 and 14 m.y., respectively. These ages are the result of cooling of the rocks below 500°C and 300°C, respectively, during Alpine times.From the chemical composition of the migmatites a solidus temperature of about 670°C at 4 kb is inferred. Consideration of oxygen isotope and mineral stability data for minerals formed during high grade Alpine metamorphism indicates that these P-T conditions were not achieved during Alpine times. This also supports a pre-Alpine age for the migmatization.

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Petrologische Studie und radiometrische Altersbestimmung an penninischen Migmatiten der Zillertaler Alpen (Tirol, Österreich)

Zusammenfassung In den penninischen Zentralgneisarealen des westlichen Tauernfensters treten weit verbreitet Migmatite auf. Für die Migmatisation wurde sowohl ein prä-alpidisches als auch ein alpidisches Alter angenommen. Zur Festlegung des Alters der Migmatisation wurden die in der Nähe der Berliner Hütte auftretenden nebulitischen in-situ gebildeten Migmatite petrologisch untersucht und ihr Bildungsalter geochronologisch bestimmt. Diese Migmatite liegen in dem Gebiet höchstgradiger alpidischer Metamorphose. Eine Rb/Sr-Isochrone ergab für diese Gesteine ein herzynisches Bildungsalter von 283±28 m.y. Dieses Alter entspricht wahrscheinlich dem Höhepunkt der herzynischen Metamorphose. Rb/Sr-Altersbestimmungen an den Phengiten und Biotiten ergaben für die Abkühlung dieser Gesteine unter 500 bzw. 300°C ein alpidisches Alter von ca. 21 bzw. 14 m.y.Aus der chemischen Zusammensetzung der Migmatite und einer Druckabschätzung für die herzynische Metamorphose von ca. 4 kb ergibt sich für das Leukosom der Migmatite eine Solidustemperatur von ca. 670°C.Aus den Stabilitätsbeziehungen alpin gebildeter Minerale, den¹⁸O/¹⁶O Temperaturen und der Soliduskurve des Leukosoms der Migmatite ergibt sich, daß eine alpidische Migmati sation selbst unter den Bedingungen der höchstgradigen alpidischen Metamorphose nicht möglich ist.

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With 8 Figures     

Isotopic constraints on fluid/rock ratios in carbonate rocks: Barite-sulfide mineralization in the Schwaz Dolomite, Tyrol (Eastern Alps, Austria)

The significance of isotopic data on constraining the physical conditions of fluid-rock interaction and mineralization processes in carbonate rocks is discussed, based on the example of barite-tetrahedrite mineralization in Lower Devonian platform carbonates of the Western Greywacke Zone (Tyrol, Austria). Available strontium, oxygen, carbon and sulfur isotopic data are complemented with oxygen isotopic data for barite. Barites are homogeneous in δ¹⁸O_V-SMOW and δ³⁴S_CDT with values of + 15.4 and + 23.5‰, respectively. Their ⁸⁷Sr/⁸⁶Sr ratios vary between 0.7128 and 0.7113 for the first generation and between 0.7117 and 0.7123 for younger remobilization. The dolomitic host rock shows a significant variation in Sr, O and C isotopic composition between non-mineralized and mineralized zones: ⁸⁷Sr/⁸⁶Sr ratios vary between 0.7076 and 0.7133, δ¹⁸O_V-SMOW-values between +28.11 and +20.65‰, and δ¹³C_PDB-values between −1.15 and + 3.06‰. Fluid/rock volume ratios on the order of 1.3–3.2 are calculated for open-system behaviour by modelling Sr, O and C isotopic shifting capacities. The isotope data combined with other geological evidence support the following genetic model: Subsequent to synsedimentary sulfide mineralization during an Early Devonian rifting stage, collision tectonics in Carboniferous time led to the expulsion of Ba- and Sr-rich orogenic brines, which evolved from metamorphic fluids consisting essentially of H₂O and some CH₄, into an external sedimentary fold-and-thrust belt. The brines remobilized the synsedimentary sulfides, mixed with meteoric waters in the platform carbonates, reacted with evaporitic horizons and finally caused the recrystallization of dolomite and the precipitation of Sr-rich barite in structurally weak zones at 70–130°C. During the later Alpine orogeny supergene oxidation products were formed, and sulfates, sulfides and carbonates were further remobilized into late faults and fractures.     

Geochemical investigations of slags from the historical smelting in Freiberg, Erzgebirge (Germany)

The Freiberg area in the Saxon Erzgebirge (Ore Mountains) represents one of the oldest mining districts in Germany. Argentiferous ore mineralizations with lead, zinc and copper are dominating in this region. Various waste products of mining can be found around Freiberg. In particular, the slags from ore smelting were and are regarded as unusable waste products. However, they preserve information on the smelting and weathering behaviour of slag, which makes them very useful sources of information for our purposes. To reconstruct the chemical processes during ore smelting, historical slag represents a most valuable archive. Therefore, the historical slag dump in Halsbach (Germany) was examined exemplarily for the Freiberg deposit. The slag was dumped approx. 400 years ago and is rich in lead. An interrelation between the slag and the metallurgical process applied can be made on the basis of chemical composition, appearance and microscopic results. The slags of the heap in Halsbach contain high concentrations of heavy metals (average contents in mg kg⁻¹: Zn 40,000; Pb 10,000; Cu 1500; U 1000). Enrichments of heavy metals in the organic-rich soil horizons within the range of the dump foot (maximum contents in the A-horizon in mg kg⁻¹: Zn 3719; Pb 9198; As 3017; Cu 963) imply a faint discharge of metals from the dump.     

Petrographic and trace-element distribution studies on the dolomite-calcite in the regional metamorphic marble of the Griesscharte,Tyrol, Austria/Italy

Petrographic investigations on the light yellow marble outcrops in the Griesscharte, Tyrol, Austria/Italy revealed them to be dolomite. The white to blue-grey veins in these marbles were those of calcite. Inside these calcites and along the calcite-dolomite phase boundaries minute and microscopically unidentifiable crystallites (? 10 μ) were observed. These crystallites were recognised by X-ray diffractometry as dolomite and their form and distribution were established by scanning electron microscopy. Trace-element distributions on the calcite-dolomite neighbours were studied by neutron-activation method to elucidate the formation mechanism of these calcites in the marble.Genetic relationships of the dolomite crystallites, the calcite host and the surrounding dolomite marble have been discussed in the light of the petrographic and chemical studies. These findings substantiate a deposition of a new formed vein of calcite from the solution circulating in the fissures of the dolomite marble during prograde metamorphism rather than a simple deposition of mobilized sedimentary calcite. The dolomite crystallites in the calcite seem to have been formed post-tectonically, partly by the nucleation in the calcite cleavage planes during Mg-metasomatism and partly from the exsolutions during retrograde metamorphism.     

浙江大榭史前制盐遗址人工土台的堆土特征及来源分析*

位于浙江省宁波市大榭岛的大榭遗址,是迄今所发现的中国最早的史前海盐业遗址,与一般遗址沉积地层不同,其主体区系人工堆筑土台。本研究在遗址发掘过程中,采集了泥质和砂质2种类型堆土、废弃陶器堆中的白色硬化物和盐灶坑表层白色硬化物,同时采集本岛自然堆积物,进行了粒度、无机元素地球化学和重矿物分析,以探讨堆土的原料构成、古人的制盐工艺及制盐活动对堆土地层产生的影响。研究结果显示: 来自盐灶遗迹附近的7个泥质堆土样品,其中5个具有陆相元素富集特征,但是后期受海水影响,另外2个显示滩涂盐泥特征;废弃陶器堆中的白色硬化物元素组成与盐泥相似,盐灶坑表层白色硬化物具高Ca、Sr、Ba含量,推测是烧煮卤水产生的沉淀物。砂质堆土的粒度和重矿物组成显示其属于河流冲积物,且具强烈的化学风化特征,推测其原始地层不仅限于全新统。该研究显示了钱山漾文化时期古人利用岛屿上的潮上带、山麓黄土、河流冲积物等原材料在滩涂营建土台,并在土台上利用“淋卤煎炼”工艺从事制盐活动。     

Tectonics and sedimentation in the Fohnsdorf-Seckau Basin (Miocene, Austria): from a pull-apart basin to a half-graben

The Miocene intramontane Fohnsdorf-Seckau Basin is situated at the junction of the sinistral Mur-Mürz-fault system and the dextral Pöls-Lavanttal fault system. The basin comprises a 2,400-m-thick coal-bearing fluviodeltaic-lacustrine succession (Lower to Middle Miocene, Upper Karpatian?/Lower Badenian) which is overlain by a 1,000-m-thick alluvio-deltaic conglomeratic succession (Apfelberg Formation, ?Middle/Upper Badenian) in the south. A three-stage model for the basin evolution has been reconstructed from structural analysis and basin fill geometries. During a first pull-apart phase, subsidence occurred along ENE-trending, sinistral strike-slip faults of the Mur-Mürz fault system and NE-SW to N-S-trending normal faults, forming a composite pull-apart basin between overstepping en-echelon strike-slip faults. The Seckau and Fohnsdorf sub-basins are considered as two adjacent pull-aparts which merged into one basin. During the second phase, N-S to NNW-SSE extension and normal faulting along the southern basin margin fault formed a half-graben, filled by wedge-shaped alluvial strata (Apfelberg Formation). During the third phase, after the end of basin sedimentation, the dextral Pöls-Lavanttal fault system reshaped the western basin margin into a positive flower structure.     

Li-bearing, disordered Mg-rich tourmaline from a pegmatite-marble contact in the Austroalpine basement units (Styria, Austria)

Pale-blue to pale-green tourmalines from the contact zone of Permian pegmatites to mica schists and marbles from different localities of the Austroalpine basement units (Rappold Complex) in Styria, Austria, are characterized. All these Mg-rich tourmalines have small but significant Li contents, up to 0.29 wt% Li₂O, and can be characterized as dravite, with FeO contents of ?~?0.9–2.7 wt%. Their chemical composition varies from ^X (Na_0.67Ca_0.19?K_0.02?_0.12) ^Y (Mg_1.26Al_0.97Fe²⁺ _0.36Li_0.19Ti⁴⁺ _0.06Zn_0.01?_0.15) ^Z (Al_5.31?Mg_0.69) (BO₃)₃ Si₆O₁₈ ^V (OH)₃? ^W [F_0.66(OH)_0.34], with a?=?15.9220(3), c?=?7.1732(2) Å to ^X (Na_0.67Ca_0.24?K_0.02?_0.07) ^Y (Mg_1.83Al_0.88Fe²⁺ _0.20Li_0.08Zn_0.01Ti⁴⁺ _0.01?_0.09) ^Z (Al_5.25?Mg_0.75) (BO₃)₃ Si₆O₁₈ ^V (OH)₃? ^W [F_0.87(OH)_0.13], with a?=?15.9354(4), c?=?7.1934(4) Å, and they show a significant Al-Mg disorder between the Y and the Z sites (R1?=?0.013–0.015). There is a positive correlation between the Ca content and?<?Y-O?>?distance for all investigated tourmalines (r?≈?1.00), which may reflect short-range order configurations including Ca and Fe²⁺, Mg, and Li. The tourmalines have X_Mg (X_Mg?=?Mg/Mg?+?Fe_total) values in the range 0.84–0.95. The REE patterns show more or less pronounced negative Eu and positive Yb anomalies. In comparison to tourmalines from highly-evolved pegmatites, the tourmaline samples from the border zone of the pegmatites of the Rappold Complex contain relatively low amounts of total REE (~8–36 ppm) and Th (0.1–1.8 ppm) and have low La_N/Yb_N ratios. There is a positive correlation (r?≈?0.91) between MgO of the tourmalines and the MgO contents of the surrounding mica schists. We conclude that the pegmatites formed by anatectic melting of mica schists and paragneisses in Permian time. The tourmalines crystallized from the pegmatitic melt, influenced by the metacarbonate and metapelitic host rocks.