Application of the photoacoustic method for characterization of natural galena (PbS)

Electron transport properties of single crystal and polycrystalline natural mineral galena (PbS) samples from the Trep?a mine, Yugoslavia, were determined using the photoacoustic frequency transmission technique. Their thermal diffusivity (D _T≈0.16 × 10^?5 m² s^?1), the coefficient of diffusion (D between 0.15×10^?2 0.16×10^?2 m² s^?1) and lifetime of the excess carrier (τ≈35 μs and the front and rear recombination velocity (s _g≈65.5 m s^?1 and s _b≈66.4 m s^?1, respectively), were calculated by comparing the experimental results and the theoretical photoacoustic amplitude and phase signals. The lattice parameter obtained by X-ray work was a?=5.936?Å. The free carrier concentration of these single-crystal samples was measured using the Hall method (N?=?3×10¹⁸ cm^?3). Measurements of the optical reflectivity of the same samples, as a function of wavelength, in the infrared and far infrared ranges, were performed. In the far infrared range a free electron plasma frequency was observed and numerically analyzed, using the least-squares fitting procedure. The values of optical parameters were calculated and the value of the free carrier concentration obtained by the Hall method was confirmed.     

Eduard Suess' relations to the Pre-1950 schools of thought in global tectonics

Two main schools of thought in global tectonics are recognized during the first half of the XXth century on the basis of their proponents' attitude towards the principle of uniformitarianism and their belief in an inherent order and regularity vs. disorder and irregularity in tectonics. One group, here called the Wegener-Argand school, had a unifomitarian approach to global tectonics and believed in an inherently irregular Nature, in which probability rather than determinism was believed to be a realistic approach. The other, here called the Kober-Stille school, was largely non-uniformitarian (neocatastrophist) and believed in an orderly, regular Nature. These two schools correspond to Argand's mobilists and fixists respectively. In this paper I show that Eduard Suess was a convinced uniformitarian as far as his views on global tectonics are concerned and denied any inherent regularity in tectonic phenomena, temporal or spatial. In his interpretations of the causes and nature of orogeny, nature of geosynclines, and causes and nature of stabilisation, Suess appears to be the predecessor of the Wegener-Argandians, i. e. of the mobilists and not of the Kober-Stilleans as hitherto assumed. Although he remained a fixist and contractionist to the end Suess seems to have paved the way for the mobilists much as he did for the nappists during the last quarter of the XIX^th century.

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Zusammenfassung Während der ersten Hälfte des XX. Jahrhunderts kann man zwei globaltektonische Denkungsweisen oder Großschulen unterscheiden, die gekennzeichnet sind durch ihre Stellungnahme zum aktualistischen Prinzip in der Tektonik und ob sie an eine ordentliche und regelmäßige Natur glaubten oder nicht. Die erste, hier die Wegener-Argand-Schule genannt, hatte die Gültigkeit des aktualistischen Prinzips in der Tektonik anerkannt und die Natur, im Grunde genommen, als unordentlich und unregelmäßig betrachtet. Die Anhänger dieser Denkweise glaubten, daß probablistische Lösungen tektonischer Probleme realistischer seien als deterministische. Die andere Großschule, hier die Kober-Stille-Schule genannt, war im Grunde genommen anti-aktualistisch (Neo-Katastrophistisch) und glaubte, daß die Natur ordentlich und regelmäßig sei. Diese zwei Schulen entsprechen Argands' Einteilung in Mobilisten und Fixisten. In diesem Artikel zeige ich, daß E. Suess ein überzeugter Aktualist in bezug auf seine tektonischen Ansichten war, und daß er jede Regelmäßigkeit, zeitlicher oder räumlicher Art, der tektonischen Ereignisse ablehnte. In seinen Interpretationen der Ursachen und der Art der Orogenese, der Art der Geosynklinalen und der Ursache und der Art der Erstarrung, erscheint Suess als ein Vorgänger der Wegener-Argand-Schule, d. h. der Mobilisten, deren Gedankengänge er viel näher stand als dem der Kober-Stille-Schule. Obwohl Suess selbst bis zuletzt ein Fixist und Kontraktionist blieb, bereitete er eigentlich den Weg für die Mobilisten, wie er es früher auch für die Nappisten getan hatte.

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Résumé Durant la première moitié du XX^e siêcle, on peut distinguer deux principales écoles de pensée en tectonique globale, selon l'attitude de ses adhérents envers le principe de l'actualisme et selon leur croyance ou non à un ordre et une régularité intrinsèques en tectonique. Le premier groupe, ici appelé l'école de Wegener-Argand, suivit une voie actualiste et crût la Nature essentiellement irrégulière, de telle sorte qu'un traitement probabiliste fût considéré plus réaliste qu'un traitement déterministe. L'autre, appelé ici l'école de Kober-Stille, était essentiellement non-actualiste (néo-catastrophiste) et crût à une Nature ordonnée, régulière. Ces deux écoles correspondent aux mobilistes et aux fixistes d'Argand. Dans cet article, je montre que E. Suess, fût un actualiste convaincu, du moins en ce qui concerne ses opinions sur la tectonique globale, et qu'il rejetta toute notion de régularité dans les phénomènes tectoniques, autant spatiaux que temporaux. Dans ses interprétations des causes et de la nature de l'orogenèse, de la nature des géosynclinaux, et des causes et de la nature de la «stabilisation», Suess est un des précurseurs des «Wegener-Argandiens», c'est à dire des mobilistes. Bien qui'il fût demeuré, jusqu'à la fin de sa vie, fixiste et un avocat de la contraction, il semble que Suess ait préparé la voie aux mobilistes, de la mème façon qu'il l'avait fait pour les nappistes pendant le derier quart du XIX^e siècle.

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IR photometry and dust-shell models for two carbon stars

We present JHKLM photometry of the carbon stars ST And and T Lyn acquired in 2000–2010. Along with brightness variations due to pulsations, changes on timescales of 2000–3000 days are also observed. Our combined light curves can be satisfactorily represented with light elements derived from visual observations, but the maxima are delayed relative to the calculated times. A color-index analysis demonstrates that the dust shell of ST And is fairly weak, and is manifest only episodically, while the presence of hot dust was always detected for T Lyn. These results confirm models of spherically symmetric stellar dust shells based on mean-flux data, supplemented with observations in the intermediate IR from the IRAS and AKARI satellites. The visual optical depth of the relatively cool dust shell of ST And assuming a dust temperature at the inner edge of T ₁ = 510 K is very low: τ _V = 0.047. The dust shell of T Lyn is considerably hotter (T ₁ = 940 K), with τ _V = 0.95. We estimate the mass-loss rate to be 1.8 × 10⁻⁷ M _⊙/year for ST And and 3.7 × 10⁻⁷ M _⊙/year for T Lyn.     

New observations of anomalous X-ray pulsars at low frequencies

We report the results of new observations of three anomalous X-ray pulsars: 1E 2259+586, 4U 0142+61, and XTE J1810-197. The observations were carried out on high-sensitivity radio telescopes of the Pushchino Radio Astronomy Observatory: the Large Phased Array at 111MHz and the DKR-1000 at 62 MHz. New, digital, multi-channel receivers designed for pulsar observations were used. Pulse profiles and dynamical spectra for the three pulsars are presented. The mean flux density for XTE J1810-197 is estimated to be ∼160 mJy at 62 MHz. An estimated spectral index for this pulsar is also presented.     

A Raman spectroscopic study on the structural disorder of monazite–(Ce)

This study addresses whether Raman spectra can be used to estimate the degree of accumulated radiation damage in monazite-(Ce) samples whose chemical composition was previously determined. Our results indicate that the degree of disorder in monazite–(Ce), as observed from increasing Raman band broadening, generally depends on both the structural state (i.e., radiation damage) and the chemical composition (i.e., incorporation of non-formula elements). The chemical effects were studied on synthetic orthophosphates grown using the Li-Mo flux method, and non radiation-damaged analogues of the naturally radiation-damaged monazite–(Ce) samples, produced by dry annealing. We found that the “chemical” Raman-band broadening of natural monazite–(Ce) can be predicted by the empirical formula, $$ {\hbox{FWHM}} {\hbox{[c}}{{\hbox{m}}^{ - {1}}}{]} = {3}{.95} + {26}{.66} \times {\hbox{(Th}} + {\hbox{U}} + {\hbox{Ca}} + {\hbox{Pb)}} {\hbox{[apfu]}} $$ where, FWHM = full width at half maximum of the main Raman band of monazite–(Ce) (i.e., the symmetric PO₄ stretching near 970?cm^?1), and (Th+U+Ca+Pb) = sum of the four elements in apfu (atoms per formula unit). Provided the chemical composition of a natural monazite–(Ce) is known, this “chemical band broadening” can be used to estimate the degree of structural radiation damage from the observed FWHM of the ν₁(PO₄) band of that particular sample using Raman spectroscopy. Our annealing studies on a wide range of monazite–(Ce) reference materials and other monazite–(Ce) samples confirmed that this mineral virtually never becomes highly radiation damaged. Potential advantages and the practical use of the proposed method in the Earth sciences are discussed.     

Ore belts of the Greater Altai and their ore resource potential

The results of comprehensive geological and metallogenic studies of the Greater Altai are presented. This project has been carried out since 1997 under the guidance of Academician G.N. Shcherba. The importance of these investigations is determined by the need to enhance and further develop mineral resources of nonferrous, noble, rare, and other metals for operating mining and metallurgical enterprises of Kazakhstan. The great body of information on the geology, geophysics, and metallogeny of the region obtained over many years has been integrated on the basis of new global tectonics. The Greater Altai embraces the Hercynides of the Rudny Altai, Qalba-Narym, West Qalba, Zharma-Saur, and the adjacent territories of Russia and China. The present-day tectonic units are considered to be detached blocks of ancient continental massifs that drifted in the Paleoasian ocean and then amalgamated into the structure of the Greater Altai during the Hercynian collision. The tectonic and metallogenic demarcation of the studied territory made possible the recognition of the Rudny Altai, Qalba-Narym, West Qalba, and Zharma-Saur ore belts, different in geology, geodynamic evolution, and metallogeny. The formation conditions and localization of volcanic-hosted massive sulfide, gold, and rare-metal deposits pertaining to certain ore-bearing geochronological levels were specified, and the potential of the region for various mineral resources was estimated.     

Melanterite and szomolnokite as weathering products of pyrite from the Bazhenovo Formation

Weathering of pyrite in the core recovered from black shales of the Bazhenovo Formation (Upper Jurassic-Lower Cretaceous) in the West Siberian marine basin promoted the successive formation of melanterite (FeSO₄ · 7H₂O) and szomolnokite (FeSO₄ · H₂O). Szomolnokite was detected in West Siberia for the first time.     

Geophysical investigation using resistivity and GPR methods: a case study of a lubricant oil waste disposal area in the city of Ribeirão Preto,São Paulo,Brazil

Geophysics has been shown to be effective in identifying areas contaminated by waste disposal, contributing to the greater efficiency of soundings programs and the installation of monitoring wells. In the study area, four trenches were constructed with a total volume of about 25,000 m³. They were almost totally filled with re-refined lubricating oil waste for approximately 25 years. No protection liners were used in the bottoms and laterals of the disposal trenches. The purpose of this work is to evaluate the potential of the resistivity and ground penetrating radar (GPR) methods in characterizing the contamination of this lubricant oil waste disposal area in Ribeirão Preto, SP, situated on the geological domain of the basalt spills of the Serra Geral Formation and the sandstones of the Botucatu Formation. Geophysical results were shown in 2D profiles. The geophysical methods used enabled the identification of geophysical anomalies, which characterized the contamination produced by the trenches filled with lubricant oil waste. Conductive anomalies (smaller than 185 Ωm) immediately below the trenches suggest the action of bacteria in the hydrocarbons, as has been observed in several sites contaminated by hydrocarbons in previously reported cases in the literature. It was also possible to define the geometry of the trenches, as evidenced by the GPR method. Direct sampling (chemical analysis of the soil and the water in the monitoring well) confirmed the contamination. In the soil analysis, low concentrations of several polycyclic aromatic hydrocarbons (PAHs) were found, mainly naphthalene and phenanthrene. In the water samples, an analysis verified contamination of the groundwater by lead (Pb). The geophysical methods used in the investigation provided an excellent tool for environmental characterization in this study of a lubricant oil waste disposal area, and could be applied in the study of similar areas.     

Composition and formation conditions of pay zones in the lower Cretaceous Nizhnyaya Kheta and Yakovlevo formations within the Vankor oil-and-gas field (in the Northeast of West Siberia)

Sedimentologic analysis of cores from wells sunk in the Vankor petroleum field allowed refinement of the accumulation conditions producing the sandy strata of the Nizhnyaya Kheta River (Nizhnekhetsky) Formation accumulated in the coastal marine zone and of the Yakovlevo (Yakovlevsky) Formation accumulated under alluvial-deltaic conditions. Petrographic examination of the sandstones added information on the sources, transport, and accumulation conditions of the terrigenous material in the northeastern marginal part of the West Siberian sedimentation basin.     

Surface changes on crystalline stones due to salt crystallisation

This study assesses the changes on the surface of crystalline stones due to salt crystallisation. Efflorescence was forced to grow on the surface of granite and marbles through 60 cycles of salt crystallisation with sodium sulphate. Changes on surface roughness, gloss and colour were measured every 15 cycles and the specimens were examined with naked eye and SEM. Sodium sulphate produces damage which depends on mineral composition. Results show that granites experience a mechanical decay with an increase in roughness. Peaks of mica can be observed on the surface and cracks widen and grow deeper. Colour and gloss do not show any significant change, although gloss decreases with an increase in surface roughness. In marbles, the decay is mainly chemical. Surface roughness increases due to dissolution of the calcite. White marbles exhibit yellowing. Gloss decreases during the first cycles—as grain boundaries become more visible—but tends to regain almost its initial value as the number of cycles increases. In this case, gloss does not show any relation with surface roughness.