Modeling the electric structures of two thunderstorms and their contributions to the global circuit

This study examines the electricity in two thunderstorms, typical for their respective locales (the Great Plains and the New Mexico mountains), by modeling them as a set of steady-state horizontal layers of external currents. The model electric sources, corresponding to the charge separation processes in the thundercloud, are embedded in an exponential conducting atmosphere. The source parameters are determined by fitting the model electric field to measured profiles. The resulting currents to the ionosphere (i.e., the Wilson current) from the two storms are 0.53 A and 0.16 A, while the calculated electrical energies of the storms are 2.3 × 10¹⁰ J and 2.8 × 10⁹ J, respectively. The more vigorous storm is estimated to transfer 16 000 C in the global circuit during 8.5 h of its lifetime, while the weaker mountain storm transferred about 1200 C in its entire 2-h lifetime. Removal of the screening charge layer from above the updraft region in one modeled storm leads to only a small increase in the net Wilson current of less than 3%, while it provides a substantial local disturbance of the electric field. Overall, the model findings indicate that differences in the Wilson currents and electrical energies of the two storms result from differences in their internal dynamical and electrical structures as well as their geographical locations.     

Computation of the heat function connected with short-wave radiation fluxes

Summary A report is presented on the use of the method, suggested by H. and K. Lettau, for the purposes of computing short-wave radiation fluxes and the heat function, connected with them, in atmospheric models, used for short-range numerical weather forecasting.Dedicated to 90th Birthday of Professor Frantiek Fiala     

Barium anomaly in Kupa River drainage basin

The objective of this work is to present an example of environmental impact of barite waste management observed in stream sediments of the western part of the Kupa River drainage basin. It is a significant water resource for Croatia and a part of Slovenia. In addition, it is for both countries a region of tourism, sport and fishing. Sediments (fraction < 63 μm) collected within the whole drainage basin have shown a significant barium anomaly in the western part. The highest concentration of total barium (5790 mg/kg) was determined in Kupica, a tributary of Kupa River. The barium anomaly was traced in Kupa River about 120 km downstream. Looking for the contamination source it was found that the anomaly originates from uncareful waste disposal into an abyss, after barite separation in Homer (Lokve), Gorski Kotar, Croatia. From there barite entered Kupica River subterraneous. Barite and albite were identified by XRD near the source of Kupica River as minor minerals, while quartz and dolomite ferroan were major minerals. This preliminary report does not give yet an answer about barium solubility in river water, about its bioavailability and consequently about barium pollution in the western part of the Kupa River drainage basin, however the possibility is highlighted and discussed.     

A comparison of anthropogenic mercury pollution in Kastela Bay (Croatia) with pristine estuaries in Ore (Sweden) and Krka (Croatia)

Anthropogenic mercury pollution was studied in Kastela Bay (Croatia), 10 years after chloralkaline plant (PVC) stopped production. The concentration of total mercury determined in sediments which are composed mainly of calcite and quartz, are in the range 14,280-30,400 ng/g. The values are higher than reported in the literature for Elbe and Seine estuaries and also above 25,000 ng/g used for criterion in remediation project in Minamata Bay. The concentration of methylmercury 6.05-36.74 ng/g are typical for slightly to highly contaminated estuarine sediments. The low ratio of methylmercury to total mercury found in sediments of Kastela Bay is in the range 0.04-0.18%. It can be explained that in this region predominate conditions which do not promote in-situ methylation. Sediments were found to be highly anoxic. Concentrations of total mercury in unfiltered surface waters are in the range 69-145 ng/l and in unfiltered bottom waters in the range 230-1,418 ngl(-1). High concentrations found in bottom waters suggest that either resuspension or partial dissolution of sediments takes place. An experiment performed on filtered and unfiltered waters showed that about 85% of total mercury in surface water and almost 100% in bottom water was retained on 45 microm filters. To demonstrate contrasts, two pristine estuaries from norths and south Europe were studied. Silicious sediments of Ore estuary (Sweden) and calcareous sediments of Krka estuary (Croatia) have total mercury concentrations close to accepted background level. The ratio of methylmercury to total mercury is < or = 1% in all samples with one exception. The highest observed ratio (2.70%) was in the surface sediment from E2 station in Krka estuary measured in March 2000. This location is suitable for studying methylmercury formation in pristine environment.     

Kornerupine parageneses in whiteschists and other magnesian rocks: is kornerupine + talc a high-pressure assemblage equivalent to tourmaline + orthoamphibole?

Kornerupine, (□,Fe,Mg)(Mg,Fe,Al)₉(Si,Al,B)₅ (O,OH,F)₂₂, has been reported with talc in rocks from six localities worldwide, but only at Chilapila Hill in the Lufilian Arc, Zambia do textural relationships imply that kornerupine (Krn) equilibrated with talc (Tlc) during a prograde metamorphic event at T≈ 640 °C, P≈ 13 kbar; a prograde Krn + Tlc assemblage has also been reported from Mautia Hill, Tanzania (P ≤ 13 kbar). In order to estimate possible constraints on the stability range for the kornerupine + talc paragenesis in nature, we constructed a P-T diagram in the model system MgO-Al₂O₃-SiO₂-H₂O (MASH) for seven phases quartz (Qtz), B-free kornerupine sensu stricto, anthophyllite (Ath), chlorite (Chl), cordierite (Crd), kyanite (Ky), and talc. The minimum pressure for Krn + Tlc + Ky stability in MASH is close to that for Ky + Tlc stability, i.e., 6–8 kbar, at T≤ 780 °C. However, in the natural system, B₂O₃ and Na₂O are major constituents in Krn and orthoamphibole (Oam), respectively, and dravitic tourmaline (Tur) is widespread. The critical assemblage alternative to Krn + Tlc in nature is Tur + Oam. The upper pressure limit of Tur + Ath is determined by the upper pressure for anthophyllite: 7.7–10.5 kbar at 682–794 °C in the MgO-SiO₂-H₂O system (Chernosky et al. 1985, Am Mineral 70:223–236), and is undoubtedly higher in the presence of Na₂O, CaO, and Al₂O₃. At three of the six localities, talc is a retrograde phase; nonetheless, it possibly equilibrated with kornerupine on the retrograde path or during a later metamorphic event at P-T conditions appropriate for Ky + Tlc. At the sixth locality (Mulvoj, southwestern Pamir Mountains, Tajikistan), Krn is found in the same thin section as talc and kyanite and all three minerals formed during a prograde metamorphic event at T≥ 650 °C, P near 7 kbar. However, Krn is restricted to a lens 4 to 6 mm thick of phlogopite + anthophyllite + Tur and it does not touch either talc or kyanite. A reaction relating the Mulvoj and Chilapila Hill (Krn + Tlc + Ky + Qtz + Tur) parageneses is calculated from compositions in the Mulvoj rock to be 0.40Tur + 2.55Ath + 1.33H₂O + 0.27F = Krn + 2.16Tlc + 0.36B₂O₃ + 0.02Rutile + 0.19Na₂O + 0.17CaO. Given the difference in metamorphic pressures estimated for Mulvoj and Chilapila Hill, Krn + Tlc is inferred to be favored by increasing pressure as well as by low Na₂O and CaO contents. Some FeO, F, Fe₂O₃, and BeO are present in measurable amounts in at least one of the phases in the Mulvoj and Chilapila Hill whiteschists (e.g., Krn contains 0.24–0.67 wt% BeO), but the effect of these constituents is subordinate to that of Na₂O, CaO and B₂O₃. The Krn + Tlc could be a more important assemblage in B-bearing whiteschists than has been reported to date, particularly at pressures where orthoamphibole is no longer stable. Received: 21 April 1997 / Accepted: 13 October 1997     

The ševĚtín astrobleme,southern Bohemia,Czechoslovakia

The geological, geomorphological, petrological, and geophysical data for the 46 km circular structure evtín (4905N, 1435E), southern Bohemia, are consistent with characteristic of moderately eroded structures that have originated by hypervelocity meteorite impact. The astrobleme, dated as late Cretaceous (probably Coniac-Santon, 85-75 m.y.), is dissected into radial fault segments, which exhibit a variable level of erosion. The classification of the evtín astrobleme as a probable impact structure is based on the geological and geophysical evidence of central »scar« about 8 km in diameter, shock metamorphism in the centre of the structure, and relics of silicified impact breccia including globular and suevite types with structural indications of molten material. Shatter coning and shock metamorphism are documented for several formations and lithologies ranging in age from the hercynian granite of the crystalline basement, through Stephanian-Permian, to the Upper Cretaceous-Lower Klikov Formation. The morphological expression of the crater rim is preserved in the less eroded segments. The central uplift (d=21 km, approximately 0.5 of the total diameter), still preserved in part as a positive morphological feature, is partly burried under the post-impact Upper Klikov Formation. The impact event provided the major tectonic, geomorphological, and paleogeographic resetting, which was known for some time in the evolution of the continental Upper Cretaceous of this area and expressed in the splitting of the Klikov Formation into two divisions.

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Zusammenfassung Geologische, geomorphologische, petrologische und geophysikalische Daten, die über die 46 km im Durchmesser aufweisende Rundstruktur von evtín in Südböhmen (4905N, 1435E) ermittelt wurden, entsprechen der Charakteristik mittelmä\ig erodierten Strukturen, die infolge des Einschlags eines gro\en Meteoriten von Hypergeschwindigkeit entstanden sind. Das Astroblem wird als oberkretazisch (wahrscheinlich von Coniac- bis Santonalter, 85-75 Mill. Jahre) geologisch datiert. Es ist durch Brüche in Radialsegmente aufgegliedert, die verschieden intensiv erodiert sind. Geologische und geophysikalische Belege einer zentralen »Narbe« von 8 km im Durchmesser, eine Sto\wellenmetamorphose im Zentrum der Struktur sowie Relikte silizifierter Impaktbreccien, die globulare und suevitähnliche Typen mit Strukturanzeichen von aufgeschmolzenem Material umfassen, stellen Hauptangaben zur Klassifizierung des Astroblems von evtín als einer wahrscheinlichen Impaktstruktur dar. Die »shatter cones« und die Sto\wellenmetamorphose wurden in mehreren Formationen und verschiedenen Gesteinstypen von dem herzynischen Granit im kristallinen Untergrund, über die stefanischen und permischen Gesteine bis zu der oberkretazischen Klikov-Schichtenfolge (ihrem unteren Teil) ermittelt. Die Morphologie des Kraterrandes ist in weniger erodierten Segmenten durch die Erosion ausgeprägt. Die Zentralerhebung (Durchmesser von 21 km, d.h. ungefähr von einer Hälfte des Kratergesamtdurchmessers) ist morphologisch noch zum Teil erhalten, aber ihr östl. Teil ist von der oberen Abteilung der Klikov-Schichtenfolge überdeckt. In Zusammenhang mit dem Impaktereignis werden bedeutsame tektonische, geomorphologische und paläogeographische änderungen gestellt, die in der Entwicklung der kontmentalen Oberkreide dieses Gebietes bereits früher erkannt wurden und zur Aufgliederung der Klikov-Schichtenfolge in zwei Abteilungen führten.

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Résumé La structure circulaire de evtin (4905N - 1435E, 46 km de diamètre), examinée à la lumière des données géologiques, géomorphologiques, pétrologiques et géophysiques, présente les caractères d'une structure provoquée par l'impact d'une météorite de très grande vitesse, et modérément érodée. Cet astroblème est daté du Crétacé supérieur, probablement du Coniacien-Santonien (environ 85-75 Ma). Il est subdivisé par des cassures radiales en segments qui présentent divers degrés d'érosion. L'assimilation de l'astroblème de evtin à une structure d'impact se base sur les arguments suivants: cicatrice centrale de 8 km de diamètre, métamorphisme de choc dans la partie centrale, restes de brèche d'impact silicifiée comportant des types globulaires et de suévite avec indices de matériaux fondus. Les »shatter cones« et le métamorphisme de choc s'observent dans plusieurs formations, de lithologies diverses, qui s'échelonnent entre le granite hercynien du socle cristallin, le Stéphano-permien, et le Crétacé supérieur (partie inférieure de la formation de Klikov). La morphologie du rempart du cratère est préservée dans les segments les moins érodés. La zone surélevée centrale (21 km de diamètre, soit la moitié du diamètre total) est partiellement préservée et cachée pour le reste sous la partie supérieure de la formation de Klikov. Le phénomène d'impact a été accompagné de modifications tectoniques, géomorphologiques et paléogéographiques marquantes. Ces modifications étaient connues antérieurement dans l'évolution du Crétacé supérieur de cette région et avaient justifié la subdivision en deux parties de la formation de Klikov.

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Perpotassic granulites from southern Bohemia

Garnetiferous, perpotassic granulites associated with voluminous, felsic calc-alkaline garnet-kyanite granulites in the Blanský les massif are described as a new rock type. A K₂O content near 13 wt%, Zr content ranging from 17 to 5877 ppm, primary Ca-Mg-Fe garnet (pyrope up to 33 mol %), and the absence of primary plagioclase and quartz characterize the new type of granulite. Calcium is incorporated only in garnet and apatite. Owing to the content of garnet the bulk syenitic compositions are metaaluminous to peraluminous. The perpotassic granulites are accompanied by subordinated melanocratic perpotassic granulite and alkali-feldspar melanocratic granulite containing up to 20 vol % quartz. These rock types also contain highly variable amounts of zircon. High-pressure, noneutectic partial melting of crustal rocks and crystallization under upper mantle conditions is suggested as the main process in generation of perpotassic granulites. A polyphase, ductile to brittle deformation and recrystallization in pyroxene granulite and later in amphibolite facies accompanied obduction of the granulite massif which carries numerous enclaves of pyrope peridotite. Euhedral equant zircon crystals up to 4 mm long enclosed in large garnet crystals and in the alkali feldspar matrix of perpotassic granulite represent a uniform, high-temperature population with a nearly concordant U-Pb system (Aftalion et al. 1989). The Hercynian age of this zircon indicates the role of the Hercynian anatexis of crustal rocks under upper mantle conditions in generation of granulites in the Moldanubian zone of the Bohemian massif.     

Elasticity of pyrope and majorite-pyrope solid solutions to high temperatures

Majorite-garnet solid solutions are major mineral phases in the Earth’s upper mantle and transition zone. Here we present the first Brillouin scattering measurements of the elasticity of majorite (Mj, Mg₄Si₄O₁₂)-pyrope (Py, Mg₃Al₂Si₃O₁₂) solid solutions (Mj₅₀Py₅₀ and Mj₈₀Py₂₀) and single-crystal elasticity of pure synthetic pyrope at temperatures up to 800°C. The temperature derivatives of the adiabatic bulk (K_S) and shear (μ) moduli for all compositions along the Mj-Py join are the same within the experimental uncertainties (−∂K_S/∂T=14.0-14.5(20) MPa/K, −∂μ/∂T=8.3-9.2(10) MPa/K). The temperature dependence of the acoustic velocities for Mj-Py solid solutions is about half that of other major transition zone minerals. This implies that temperature variations in the transition zone, inferred from lateral velocity heterogeneity, can be significantly underestimated if the properties of majoritic garnet are not taken into account.     

Experimental estimate of a relation between sea wave energies and the Earth’s crust microdeformations

The experimental data in the microseismic frequency range obtained using the seismo-acoustic-hydrophysical measurement complex are analyzed. The emphasis is put on estimating the ratio between the energy of surface sea wind waves in the area of the Japan Sea where the complex was located and the Earth’s crust microdeformations in this frequency range. The experimental evaluate obtained allow us to estimate the energy re-distribution at the hydrosphere-lithosphere boundary.     

Assessment and forecast of changes of reservoir volumes due to thermal settling in permafrost areas of Russia

This paper presents the results of data analyses and assessments of field and theoretical researches on reservoir bed relief transformation due to thermal settling in the permafrost regions of Russia.The resulting changes（increases） of the total volumes of large and small reservoirs are quantified,of which information will be of great use in future reservoir design and exploitation.