Trondhjemites,tonalites and diorites in the South Portuguese Zone and their relations to the vulcanites and mineral deposits of the Iberian Pyrite Belt

In the South Portuguese Zone close associations of diorites, tonalites and trondhjemites occur north of the Pyrite Belt. The period of their emplacement is Pre-Carboniferous and not, as has generally been assumed, Variscanpostorogen. The trondhjemitic intrusive suite and the Lower Carboniferous spilite-keratophyre association are related through their comagmatic derivation. Both series share sodium dominance, low concentrations of large-ion lithophile elements, indicators of a water-rich original magma and a deficient scorification of the element potential, which was acummulated in the sulphide and manganese deposits of the Pyrite Belt through post-volcanic hydrothermal processes. The mineralogically and geochemically primitive composition of both plutomtes and vulcanites, their mode of eruption from acid to basic facies as well as their position in the orogenic process indicate that they represent products of a successively proceeding partial melting of subducting oceanic crust. The trondhjemitic intrusives are the initialites in the magmatic-orogenic development.

---

Zusammenfassung In der Südportugiesischen Zone treten nördlich des Pyritgürtels enge Vergesellschaftungen von Dioriten, Tonaliten und Trondhjemiten auf. Der Zeitraum ihrer Platznahme ist päkarbonisch und nicht, wie bisher allgemein angenommen, variszisch-postorogen. Die trondhjemitische Intrusivsequenz und die unterkarbonische Spilit-Keratophyr-Assoziation sind in weiten Bereichen durch komagmatische Herkunft verbunden. Gemeinsamkeiten beider Abfolgen sind ihre Na-Dominanz, die niedrigen Gehalte an gro\ionigen Elementen, die Anzeichen für ein wasserreiches Ausgangsmagma und die mangelhafte Verschlackung des Elementpotentials, das in den Sulfid- und Manganlagerstätten des Pyritgürtels während postvulkanischer, hydrothermaler Proze\e angereichert wurde. Die mineralogisch wie geochemisch primitive Zusammensetzung sowohl der Plutonite wie der Vulkanite, ihr Eruptionsmodus von saurer zu basischer Fazies sowie ihre Position im orogenen Ablauf deuten darauf hin, da\ sie die Produkte einer sukzessiv fortschreitenden Aufschmelzung subduzierender, ozeanischer Kruste darstellen. Die trondhjemitischen Intrusiva sind die Initialite innerhalb der magmatisch-orogenen Entwicklung.

---

Résumé Dans la zone sud du Portugal, il existe, au nord de la ceinture pyriteuse, des associations étroites de diorites, de tonalites et de trondhjémites. Leur mise en place date de la période pré-carbonifère et non, comme on l'avait généralement admis jusqu'à présent, de la période varisque post-orogénique. Le faisceau intrusif trondhjémitique et l'association spilite-kératophyre du Carbonifère inférieur sont liés par une origine comagmatique. Les points communs des deux successions sont leur dominante sodique, les faibles teneurs en éléments à gros ions, les indices d'un magma de départ aquifère et la scorification réduite du potentiel d'éléments qui, dans les gisements de sulfure et de manganèse de la ceinture pyriteuse a été enrichi par des processus post-volcaniques et hydrothermaux. La composition primitive, tant minéralogique que géochimique, de la plutonite comme de la vulcanite, leur mode d'éruption qui va du type acide au type basique, ainsi que leur position dans le processus orogénique indiquent qu'il s'agit de produits successifs de la fusion partielle d'une croûte océanique en voie de subduction. Les intrusions trondhjémitiques représentent le stade initial dans l'évolution orogéno-magmatique.

---

, , , . - , , . - . ; , , , - . , , . - .

     

Lamellar nigerite in Zn-rich spinel from the Falun deposit,Sweden

Lamellar nigerite is found in Zn-rich spinel from a sample that contains chiefly anthophyllite + spinel + cordierite, lesser amounts of quartz and chlorite, as well as sphalerite, pyrite, pyrrhotite, and galena, and rare cassiterite and rutile. Nigerite can be described as interlayering of spinel-like (R²⁺Al₂O₄) and nolanite-like ((Sn, Ti)Al₄O₈) structures. In nigerite, the spinel-like part is also compositionally related to spinel, but in the nolanite-like part only the structural analogy exists. Stoichiometric assumptions that relate the anhydrous cation sum to the amount of R⁴⁺ cations present, allow Fe³⁺ estimates from microprobe analyses, and a representative analysis gives the following anhydrous formula: Mg_1.30Fe _0.65 ²⁺ Zn_3.03Mn_0.03Al_11.65Fe _0.35 ³⁺ Sn_0.32Ti_0.18O₂₄.The nigerite is Zn-rich with a Zn ratio (Zn/(Zn+Mg+ Fe²⁺)) of about 0.59, and the Sn ratio (Sn/(Sn+Ti)) that ranges from about 0.63 to 0.41. The Fe³⁺ content in these samples ranges from 0.35 to 0.52 (24 oxygen basis).Textures suggest that the nigerite could have formed by the breakdown of R ₂ ²⁺ (Sn, Ti)O₄ and R²⁺Al₂O₄ spinel components during more complex reactions. An experimental investigation of the MgAl₂O₄-Mg₂SnO₄ join indicates that the solubility of Mg₂SnO₄ component in spinel over the T interval 500 to 900° C is about 0.5 to 3.0 mole %. This, coupled with the increased solubility expected from the presence of Ti, gives good agreement with the 2.4 to 2.6 mole % R ₂ ²⁺ (Sn, Ti)O₄ component in spinel that is estimated to be the maximum necessary to form the compositions and amounts of observed nigerite.     

Variscan molasse in the Saar-Nahe Basin (W-Germany), Upper Carboniferous and Lower Permian

The Saar-Nahe Basin is a Permocarboniferous molasse basin within the Variscan orogenic chains. Surface access is possible in an area of 100×40 km just south of the Rheinisches Schiefergebirge. Below a thick Mesozoic cover the basin has a total extension of about 300×100 km. 4.1 km Upper Carboniferous and 1.6 km Lower Rotliegend grey fluviolacustrine deposits and additional 1.8 km Upper Rotliegend red alluvial deposits were accumulated.The depositional environments of the Upper Carboniferous to Lower Rotliegend beds, known from surface outcrops and 20 wells, are alluvial only along the northwestern margin of the basin, but braided and meandering fluvial, deltaic and lacustrine within the basin. Coal to a considerable amount only developed in the Westfalian.Paleocurrent data indicate a sediment transport from the northern Rhenohercynicum (Hunsrück) during the Westfalian. They delivered lithic arenites, which found a depocenter S of the Saar-Nahe Basin as it is exposed today. In the Stefanian a sediment transport from the southern Moldanubicum (Schwarzwald, Vosges and Massif Central) became active. The depocenter of the basin shifted to the NE and gradually approached the Rheinisches Schiefergebirge, disconnected from it by the South-Hunsrück Fault. During the late Lower Rotliegend the intense subsidence of the basin ceased. Simultaneously, arcosic arenites with an increasing total and K-feldspar content were provided (a tendency which even enhanced with the beginning of the Upper Rotliegend).A tectonic deformation at the end of the Westfalian induced uplift and gentle folding. After a peneplenization of its beds and a loss of strata of up to 1500 m in places, Stefanian and Lower Rotliegend were deposited discordantly above.At the beginning of the Upper Rotliegend, tectonic activities formed a central anticline together with magmatism (rhyolitic intrusives and explosives as well as melaphyr lavas) and a short-distanced style of alluvial sedimentation. In the post-Rotliegend further narrowing of the basin initiated a southward thrusting of the Saarbrücken Anticline on to the Buntsandstein; together with this the South-Hunsrück Fault became steeper and partly overturned.The stratigraphic section from Namurian to Lower Rotliegend was studied in detail; Upper Rotliegend may stand as an overview.

---

Zusammenfassung Das Saar-Nahe-Becken ist ein permokarbones Molasse-Becken innerhalb der variskischen Gebirgszüge. Von übertage her ist es auf einer Fläche von 100×40 km unmittelbar südlich des Rheinischen Schiefergebirges zugänglich. Unter einer bedeutenden mesozoischen Überdeckung aber hat das Becken eine Ausdehnung von insgesamt 300×100 km. In diesem wurden 4,1 km mächtiges Oberkarbon und 1,6 km mächtiges Unterrotliegend in grauer fluviolakustriner Fazies und schließlich 1,8 km rotes alluviales Oberrotliegend abgesetzt.Die oberkarbonen bis unterrotliegenden Schichten zeigen nach Oberflächenaufschlüssen und 20 Bohrungen nur entlang des Hunsrücks in geringem Umfang alluvialen Sedimenteintrag. Im Becken dagegen ist das Sedimentationsmilieu verzweigt und mäandrierend fluviatil, deltaisch und lakustrin. Kohle wurde nur im Westfal in größerem Umfang gebildet.Messungen zur Paläoströmung weisen im Westfal einen Sedimenttransport aus dem nördlich gelegenen Rhenohercynicum (Rheinisches Schiefergebirge) nach. Dieses lieferte gesteinsbruchstückreiche Sande, die in einem Depozentrum südlich des heute übertage aufgeschlossenen Saar-Nahe-Beckens abgelagert wurden. Im Stefan erlangte ein Sedimenttransport aus dem Moldanubicum (Schwarzwald, Vogesen und Zentralmassiv) an Bedeutung. Das Depozentrum des Beckens wanderte nach NE und näherte sich allmählich dem Rheinischen Schiefergebirge, das seit jener Zeit von diesem durch die Hunsrück-Südrandstörung getrennt ist. Während des späten Unterrotliegend nahm die intensive Absenkung des Beckens allmählich ab. Gleichzeitig wurden feldspatreiche Sande mit zunehmendem Gesamt-und K-Feldspat-Gehalt geliefert (diese Tendenz wurde zu Beginn des Oberrotliegend eher noch verstärkt).Ende Westfal wurde das Becken nachweislich herausgehoben und sanft gefaltet. Nach einer Einebnung der Schichten, was stellenweise zu einem Schichtverlust von bis zu 1500 m führte, folgten diskordant darüber Stefan und Unterrotliegend.Mit Beginn des Oberrotliegend schufen erneute tektonische Bewegungen eine zentrale Aufwölbung. Dies war mit vulkanischer Aktivität (rhyolitische Intrusiva und Explosiva sowie Melaphyr-Laven) verbunden und hatte nun kleinräumigen alluvialen Sedimentationsstil in jetzt kleineren Teilbecken zur Folge. Später, nach dem Rotliegend, schuf die weitere Einengung des Saar-Nahe-Beckens eine südwärts gerichtete Aufschiebung des Saarbrücker Hauptsattels auf den Buntsandstein; hierbei wurde auch das Einfallen der Hunsrück-Südrandstörung steiler, teilweise sogar überkippt.Der stratigraphische Abschnitt vom Beginn des Namur bis Ende Unterrotliegend wurde im Detail untersucht; das Oberrotliegend ist als Übersicht dargestellt.

---

Résumé Le bassin de Sarre-Nahe est un bassin molassique permocarbonifère inclus dans la chaîne orogénique varisque. Il affleure dans une aire de 100×40 Km située immédiatement au sud du Massif Schisteux Rhénan, et son extension totale sous la couverture mésozoïque est de 300×100 Km. L'accumulation comprend: 4,1 Km de Carbonifère supérieur, 1,6 Km de Rotliegende inférieur fluvio-lacustre, et 1,8 Km de Rotliegende supérieur alluvial rouge.Les couches d'âge carbonifère supérieur à Rotliegende inférieur, connues par les affleurements et par 20 sondages, ne montrent un caractère alluvial que dans un domaine restreint à la bordure nord-ouest du bassin, le long du Hunsrück. Dans le reste du bassin, le milieu de dépôt était fluviatile anastomosé, deltaïque et lacuste. Le charbon est présent en grande quantité, dans le Westphalien uniquement.L'examen des paléocourants indique un transport à partir de la zone rhéno-hercynienne (Hunsrück) pendant le Westphalien. Cet apport a fourni des arénites lithiques qui se sont accumulées dans une aire de sédimentation située au sud de la zone d'affleurement actuel du bassin de Sarre-Nahe. Au Stéphanien, l'apport significatif s'est effectué à partir de la zone moldanubienne, située au sud (Forêt Noire, Vosges et Massif Central). L'aire de dépôt s'est déplacée vers le nord-est en direction du Massif schisteux Rhénan, dont elle est séparée par la faille du Sud-Hunsrück. Vers la fin du Rotliegende inférieur, la forte subsidence du bassin a pris fin. Cet épisode est marqué par l'arrivée d'arénites comportant une teneur croissante en feldspath (tendance qui s'est renforcée au début du Rotliegende supérieur).A la fin du Westphalien, le bassin a été soulevé et légèrement plissé. Cette déformation a été suivie d'une pénéplanation, impliquant une érosion qui a pu enlever localement 1500 m de couches; le Stéphanien et le Rotliegende inférieur se sont ensuite déposés en dicordance.Au début du Rotliegende supérieur, de nouveaux mouvements tectoniques ont engendré un dôme central; ces mouvements se sont acompagnés de manifestations magmatiques (rhyolites intrusives et explosives, laves mélaphyriques) et d'une sédimentation de type alluvial proximal. Postérieurement au Rotliegende, un nouveau rétrécissement du bassin a provoqué le chevauchement vers le sud de l'anticlinal de Saarbrücken sur le grès bigarré; simultanément, la faille du Sud-Hunsrück s'est redressée et partiellement renversée.La série stratigraphique Namurien-Rotliegende inférieur a fait l'objet d'une étude détaillée et le Rotliegende supérieur d'un aperçu d'ensemble.

---

Saar-Nahe - . 100 х 40 . , 300 х 100 . 4,1 ; 1,6 - , 1,8 . 20 , . , . . , / /. , . . , Saar-Nahe. / , , /. , . . , — . . , 1500 , . . : , ; . , Saar-Nahe, : , . , , ; .

     

Shock effects in melilite

Shock recovery experiments on melilite samples in the pressure range from 11 to 50.5 GPa have been performed in order to examine the effects of shock waves on this material. The shocked samples were subsequently studied in the transmission electron microscope. All samples displayed the shock-induced amorphous areas, known as diaplectic glass. The amount of diaplectic melilite glass increased from a few percent at 11 GPa to about 85 percent at 50.5 GPa shock pressure. The shock waves also caused deformational effects as planar faults parallel to (001) and dislocations with a density in the order of 10¹⁰ cm^?2. Regarding the present discussion on the origin and nature of diaplectic glass, diaplectic melilite glass is assumed to be the reversion product of a high-density phase produced in the shock front. Deformed melilites in Ca-Al-rich inclusions from chondritic meteorites studied so far do not contain diaplectic glass. It is assumed that the meteoritic melilites were hot (>1,000° C) and thus plastically deformable by shock waves of rather low amplitudes.     

Die Genese der stratiformen Sulfidlagerstätte Kalwang (Steiermark), der Grünsteinserie und einer assoziierten silikatreichen Eisenformation

Zusammenfassung Die bearbeitete Lagerstätte ist dem Typ submarin exhalativer Bildung zuzuordnen. Grünschiefermetamorphe Nebengesteine (ehemalige vulkanosedimentäre Abfolge) unterlagenin situ einer hydrothermalen Alteration. Metallösungen (hot brines), welche zur Bildung der Sulfidlager führten, eruptierten im Bereich submariner Fumarolen. Sie entstammten Interaktionen meteorischer Wässer mit vulkanogenen In- und Extrusivprodukten. Die Lösungen bildeten schichtgebundene Erzlager, die zoniert als hoch-bis niedrigtemperierte Bildung vorliegen. Eine assoziierte silikatreiche Eisenformation schließt die Vererzung sowie die vulkanische Tätigkeit ab. Die Grüngesteine werden als Metabasite kontinentaler bis ozeanbodentholeiitischer Edukte gedeutet. Hinsichtlich der geotektonischen Situation verweisen alle Merkmale auf das Milieu einer MORB-Typ assoziierten, alterationsbedingten sulfidischen Vererzung als Folgeprodukt zunehmender Ozeanisierung eines kontinentalen Riftbereiches.

---

Genesis of the Kalwang stratiform sulphide deposit, Styria, Austria, and of associated metavolcanics and siliceous banded iron formation

Summary The Kaiwang copper deposit (Styria, Austria) occurs within a Lower Paleozoic volcanosedimentary sequence which forms part of the extensive Nördliche Grauwackenzone of the Eastern Alps. Stratiform bodies of pyrite (0.02–0.05% Ni; 0.05–0.08%Co)-chalcopyrite and (Ni,Co-free) pyrrhotite-chalcopyrite ores are associated with mafic metavolcanic rocks; metapelites and marbles are also present in the ore environment. Comprehensive analyses of major and trace elements suggest that the metavolcanites have been derived from tholeiites of intraplate-to ocean floor affinity linked to the development of an intracontinental rift. Regional metamorphism of lower greenschist grade was preceded by spilitization of the volcanic rocks. Mineralization at Kalwang is submarine-exhalative; some copper sulphides have been deposited in supply channels prior to reaching the sea floor. Towards the hanging-wall, the ore-bearing sequence is terminated by a two metres thick manganiferous iron formation; manganese is concentrated almost exclusively in spessartine garnet. The BIF has been derived from a manganiferous, chamositic precursor sediment. Stratabound base metal deposits further west in the Northern Greywacke Zone show similar evolutionary trends; this points towards a coherent metallogenetic pattern for this important tectonic unit.

---

---

Mit 12 Abbildungen     

The winterstorm “Vivian” of 27 February 1990: About the meteorological development,wind forces and damage situation in the forests of Switzerland

Summary During the months January and February 1990 a series of severe cyclones were responsible for enormous wind-induced damage in Europe. The final of this series, on 27 February 1990, cyclone Vivian mainly affected the alpine valleys of Switzerland. 5 Millions m³ of timber were felled by the severe winds, a record number in this century. A complete damage survey of the deforested areas offers in combination with meteorological data an unique data set for a detailed case study of this extreme event.This paper describes the general meteorological development from the synoptic scale down to the mesoscale of Switzerland and presents a general overview of the damage situation. The main results show that a rare situation of a straight frontal zone stretching over the whole Atlantic Ocean and showing a strong gradient in temperature pointed directly toward Central-Europe. Two waves formed along this elongated polar front and deepend rapidly to depressions. The first low travelled on the southernmost trajectory of the whole storm series and affected Switzerland most. North of the Alps the prefrontal warm air was blocked to the east by the arriving coldfront and had to escape into the complex terrain of the alpine valleys. There, the stormy winds were strengthened by channelizing and Föhn effects. The large temperature gradient between the prefrontal and the incoming air masses induced thunderstorm activity which vortices and downdrafts might have enhanced locally. As a result most of the damaged forested areas were found between 1200 and 1600 m MSL on slopes, which were mainly exposed toward the prevailing NW-winds. A comparison of extreme wind speeds for the period 1978–1992 revealed that this event's extreme high speed of 74.5 m/s, measured at a high elevated pass station in the mountains, was exceptional. For lower elevated stations the wind speeds were high but in the range of other observed extreme values. In addition to the severe wind forces the duration of sustained high wind speed was exceptionally long during February 1990.With 16 Figures     

Observation of isotopes in the water cycle—the Swiss National Network (NISOT)

The Swiss National Network for the Observation of Isotopes in the Water Cycle (NISOT) includes eleven precipitation, seven surface water (river) and three groundwater stations, where tritium, deuterium and oxygen-18 are monthly measured in composite samples. The network provides a good overview of the characteristic isotope signatures in recharge waters in Switzerland and of the relations between isotopes and altitude, orography and the amount of precipitation. Mixing of air water vapour and surface waters can be observed along a NW/SE cross section through the Alps. With increasing length of the data series, the network provides a valuable contribution for national and international scientific and practical applications in surface and subsurface hydrology, climatology and biology. The Swiss Geological Survey at the Federal Office for Water and Geology operates the isotope network within the legal framework of the Federal Law on the Protection of Waters and guarantees quality, access and distribution of the isotope data.     

Integrating geophysical and hydrochemical borehole-log measurements to characterize the Chalk aquifer, Berkshire, United Kingdom

Geophysical and hydrochemical borehole-logging techniques were integrated to characterize hydraulic and hydrogeochemical properties of the Chalk aquifer at boreholes in Berkshire, UK. The down-hole measurements were made to locate fissures in the chalk, their spatial extent between boreholes, and to determine the groundwater chemical quality of the water-bearing layers. The geophysical borehole logging methods used were caliper, focused resistivity, induction resistivity, gamma ray, fluid temperature, fluid electrical conductivity, impeller and heat-pulse flowmeter, together with borehole wall optical-imaging. A multiparameter data transmitter was used to measure groundwater temperature, electrical conductivity, dissolved oxygen, pH, and redox potential of the borehole fluid down-hole. High permeability developed at the Chalk Rock by groundwater circulation provides the major flow horizon at the Banterwick Barn study site and represents a conduit system that serves as an effective local hydraulic connection between the boreholes. The Chalk Rock includes several lithified solution-ridden layers, hardgrounds, which imply a gap in sedimentation possibly representing an unconformity. Lower groundwater temperature, high dissolved-oxygen content, and flowmeter evidence of preferential groundwater flow in the Chalk Rock indicated rapid groundwater circulation along this horizon. By repeating the logging at different times of the year under changing hydraulic conditions, other water-inflow horizons within the Chalk aquifer were recognized. Electronic Publication     

Statistical time series decomposition into significant components and application to European temperature

Summary Time series of observed monthly mean temperatures of European stations and at grid points are decomposed into different kinds of trends (linear, progressive, degressive), constant or significantly changing annual cycles, episodic and harmonic components, extreme events and noise. A stepwise regression is used to test whether the components are significant. Special emphasis is given to extreme events which we distinguish from extreme values. While extreme values may likely occur by chance, it is very unlikely that extreme events would be in accordance with the features of the time series. On one hand, extreme events alter the estimates (and test results) of trends and other components. On the other hand, such components have to be known to recognize extreme events. To deal with this problem, an iterative procedure is introduced that converges fast to robust estimates of all the components. Applying this procedure to the last 100 years of European temperatures reveals that the phase of the annual cycle is shifted backward within the year in western Europe but foreward in eastern Europe. In the latter region, the amplitude of the annual cycle has also increased significantly. Most of the trend components found in the time series are positive and linear. Nearly all detected extreme events are cold events which occurred in winter. Their number has significantly grown. Significant harmonic components with a period of 92.3 months (about 7.7 years) are found mainly in northern and western Europe. Received August 15, 2000 Revised June 20, 2001     

Transfer,loss and physical processing of water in hit-and-run collisions of planetary embryos

Collisions between large, similar-sized bodies are believed to shape the final characteristics and composition of terrestrial planets. Their inventories of volatiles such as water are either delivered or at least significantly modified by such events. Besides the transition from accretion to erosion with increasing impact velocity, similar-sized collisions can also result in hit-and-run outcomes for sufficiently oblique impact angles and large enough projectile-to-target mass ratios. We study volatile transfer and loss focusing on hit-and-run encounters by means of smooth particle hydrodynamics simulations, including all main parameters: impact velocity, impact angle, mass ratio and also the total colliding mass. We find a broad range of overall water losses, up to 75% in the most energetic hit-and-run events, and confirm the much more severe consequences for the smaller body also for stripping of volatile layers. Transfer of water between projectile and target inventories is found to be mostly rather inefficient, and final water contents are dominated by pre-collision inventories reduced by impact losses, for similar pre-collision water mass fractions. Comparison with our numerical results shows that current collision outcome models are not accurate enough to reliably predict these composition changes in hit-and-run events. To also account for non-mechanical losses, we estimate the amount of collisionally vaporized water over a broad range of masses and find that these contributions are particularly important in collisions of \(\sim \) Mars-sized bodies, with sufficiently high impact energies, but still relatively low gravity. Our results clearly indicate that the cumulative effect of several (hit-and-run) collisions can efficiently strip protoplanets of their volatile layers, especially the smaller body, as it might be common, e.g., for Earth-mass planets in systems with Super-Earths. An accurate model for stripping of volatiles that can be included in future planet formation simulations has to account for the peculiarities of hit-and-run events and track compositional changes in both large post-collision fragments.