Spectroscopic observations of parsamian 21

This work presents spectroscopic observations of Parsamian 21, which has been shown recently by Staude and Neckel to be a fuor-type star. A list of identified absorption lines is given. The results are compared with previous spectroscopic observations over the period 1966–1990. It is shown that the H line profile changed during this period; according to the observations of 1986, the center of the H absorption line was shifted by –140 km/sec from ₀ and reached –600 km/sec at the line edge. It follows from the presented lightcurve that the star has undergone brightness variations of nearly three magnitudes and most likely became a fuor before 1902.Translated fromAstrofizika, Vol. 39, No. 2, pp. 227–235, April–June, 1996.     

First Byurakan Spectral Sky Survey. Late-type stars. VIII. Zone + 80 ≤ δ ≤ + 90°

The eighth list of late-type stars of spectral classes M and C detected on the plates of the First Byurakan Spectral Sky Survey (FBS) in the zone +80 +90° is presented. Of the 79 objects detected, 67 are new discoveries (66 M stars and one carbon star); 16 objects are unidentified IRAS sources. The equatorial coordinates, spectral classes, and magnitudes are given.Translated fromAstrofizika, Vol. 39, No. 4, pp. 523–529, November, 1996.     

Time-space analysis of internal migration in Spain (1962-1993): with special attention to the changes in migration pattern in the 1970s

"In this study, the internal migration in Spain from 1962 to 1993 is analyzed from the viewpoint of migration flows, with special emphasis on the spatial scale and direction of migration as well as the migration fields.... The evolution of the spatial scale and direction of migration shows a radical change in the middle 1970s: migrations from 1962 to 1975 (first period) were unidirectional movements at great distance (interprovincial and interregional), whereas those from 1976 to 1993 (second period) are characterized by the weight of intraprovincial movements and the bidirectionality of interprovincial movements. Through the two periods, the major sector in which migrants are employed has shifted from the industry to the service sector." (EXCERPT)     

Variability of surface roughness and turbulence intensities at a coastal site in India

Surface-layer features with different prevailing wind directions for two distinct seasons (Southwest Monsoon and Northeast Monsoon) on the west coast of India are studied using data obtained from tower-based sensors at a site located about 500 m from the coast. Only daytime runs have been used for the present analysis. The surface boundary-layer fluxes have been estimated using the eddy correlation method. The surface roughnessz ₀ obtained using the stability-corrected wind profiles (Paulson, 1970) has been found to be low for the Southwest monsson season. For the other season,z ₀ is relatively high. The drag coefficientC _D varies with height in the NE monsoon season but not in the season with lowz ₀. This aspect is reflected in the wind profiles for the two seasons and is discussed in detail. The scaling behaviour of friction velocityu _* and the turbulence intensity of longitudinal, lateral and vertical winds _u, _v and _w, respectively) are further examined to study their dependence on fetch. Our study shows that for the non-dimensional case, _u/u_* and _v/u_* do not show any surface roughness dependence in either season. On the other hand, for _w/u_* for the season with lowz ₀, the values are seen to agree well with that of Panofskyet al. (1977) for homogeneous terrain whereas for the other season with highz ₀, the results seem to conform more to the values observed by Smedman and Högström (1983) for coastal terrain. The results are discussed in the light of observations by other investigators.     

The propagation of a single shear crack: A displacement discontinuity model

Numerical studies using the displacement discontinuity method show that a single shear crack under compression propagates in its own direction, because such propagation results in the maximum release of strain energy. The methods of linear elastic fracture mechanics may not be used for such a closed crack, and the stress intensity factors are meaningless in that case. Laboratory observations of propagation by means of kinks at an angle of approximately 70° to the crack may be due to heterogeneities, to the effect of a preexisting crack, to end effects, to microcracking, or to some combination of these factors. Such kinks may thus be local phenomena which cannot release most of the strain energy, and are not incompatible with our numerical results which are based on a global energy balance.     

Optical absorption investigation of Cr3+ ion-bearing minerals in the temperature range 77–797 K

The effect of raising temperature on spin-allowed dd-transitions of octahedral Cr³⁺ was studied for various point symmetries of the Cr³⁺-bearing structural sites, i.e. 3 m and 3 with inversion center in spinel and garnets, respectively, or 32, 3, 2 and 1, lacking the inversion centre, in beryl, corundum, diopside and topaz, respectively. For this purpose, crystals of Cr³⁺-bearing spinel, pyrope, andradite, grossular, uvarovite, emerald, ruby, diopside and topaz were analyzed by microprobe, oriented, and measured in polarized radiation (except for the cubic minerals) in the spectral range 30 000 to 11 100 cm^-1 and at temperatures between 77 and 797 K. The evaluation of the intensities, half widths, and energy positions of bands due to Cr³⁺-transitions derived from ⁴ A _2g ⁴ T _2g (F) and ⁴ T _1g (F) as well as of Dq- and B-values derived, had the following results:In all cases, red shift of the above bands and, hence, independent on the site symmetry of Cr³⁺, decreases in the Dq-values were obtained. The dependcies of Dq on T are nearly linear above room temperature and amount between -1.6% in topaz and -5.1% in pyrope in the temperature range studied. From this, values for the local thermal expansion of the Cr³⁺-centered octahedra, _loc, were derived on the basis of the R _M-0 ^-5 -proportionality of 10Dq. Such values are consistently higher than those obtained from X-ray refinements, a method averaging r_m-o for all the respective octahedral positions.     

Thermodynamic data from redox reactions at high temperatures. IV. Calibration of the Re-ReO2 oxygen buffer from EMF and NiO+Ni-Pd redox sensor measurements

The chemical potential of oxygen defined by the equilibrium:

Pb−Sr−Nd−O isotopic constraints on the origin of rhyolites from the Taupo Volcanic Zone of New Zealand: evidence for assimilation followed by fractionation from basalt

A comprehensive Sr–Nd–Pb–O isotopic study is reported for rhyolites from the Maroa Volcanic Centre in the Taupo Volcanic Zone (TVZ) of New Zealand. The Sr–Nd isotopic compositions of the rhyolites (⁸⁷Sr/⁸⁶Sr=0.705236 to 0.705660 and _Nd = 2.0 to 0.2) are intermediate between those of primitive basalts (⁸⁷Sr/⁸⁶Sr=0.70387 and _Nd = 5.3) and the Torlesse basement (⁸⁷Sr/⁸⁶Sr=0.709 and _Nd = -4.5). The relatively low mantle-like oxygen isotopic compositions of ¹⁸ O = 7 ± 0.5 are consistent with the Nd-Sr isotopic constraints in that they can be accounted for by 15% to 25% crustal contamination of a basaltic parent by relatively ¹⁸ O-rich Torlesse metasediment. High precision Pb isotopic analyses of plagioclase separates from the Maroa rhyolites show that they have essentially the same compositions as the Torlesse metasedimentary terrane which is itself distinctive from the Western or Waipapa metasediments. Due to the high concentration of Pb in the Torlesse metasediments (>20 ppm) compared to the basalts (<2 ppm), the Pb isotopic composition of the volcanics may be controlled by relatively small amounts (>10%) of crustal contamination. All these results are shown to be consistent with derivation of the rhyolites by 15% to 25% contamination of relatively primitive basaltic magmas with Torlesse metasedimentary crust, followed by extensive, essentially closed system fractionation of the basalt to a magma of rhyolite composition. It is argued that the processes of assimilation and fractionation are separated in both space and time. The voluminous high silica rhyolites, which make up >97% of the exposed volcanism in the continental margin back-are basin environment of the TVZ, therefore appear to be a product of predominantly new additions to the crust with assimilation-recycling of pre-existing crust being of secondary importance.     

Aqueous alteration of the Bali CV3 chondrite: evidence from mineralogy, mineral chemistry, and oxygen isotopic compositions

A petrographic, geochemical, and oxygen isotopic study of the Bali CV3 carbonaceous chondrite revealed that the meteorite has undergone extensive deformation and aqueous alteration on its parent body. Deformation textures are common and include flattened chondrules, a well-developed foliation, and the presence of distinctive (100) planar defects in olivine. The occurrence of alteration products associated with the planar defects indicates that the deformation features formed prior to the episode of aqueous alteration. The secondary minerals produced during the alteration event include well-crystallized Mg-rich saponite, framboidal magnetite, and Ca-phosphates. The alteration products are not homogeneously distributed throughout the meteorite, but occur in regions adjacent to relatively unaltered material, such as veins of altered material following the foliation. The alteration assemblage formed under oxidizing conditions at relatively low temperatures (<100 degrees C). Altered regions in Bali have higher Na, Ca, and P contents than unaltered regions which suggests that the fluid phase carried significant dissolved solids. Oxygen isotopic compositions for unaltered regions in Bali fall within the field for other CV3 whole-rocks, however, the oxygen isotopic compositions of the heavily altered material lie in the region for the CM and CR chondrites. The heavy-isotope enrichment of the altered regions in Bali suggest alteration conditions similar to those for the petrographic type-2 carbonaceous chondrites.     

The shoshonite porphyry Cu-Au association in the Goonumbla District,N.S.W., Australia

Summary The Goonumbla porphyry copper-gold deposit in N.S.W., Australia, is hosted by late Ordovician (439.2 ± 1.2 Ma)shoshonitic igneous rocks. In terms of their petrography, the rocks vary from andesitic to dacitic lavas and tuffs which are partly intruded by monzonite stocks; they are characterized by high and variable Al₂O₃ (13.4–19.9 wt%), very high K₂O values (up to 6.8 wt%), and high K₂O/Na₂O ratios (0.58–1.48), which are typical for the shoshonite association. The rocks also have enriched LILE concentrations (Ba up to 1200 ppm, Sr up to 1350 ppm), low HFSE (TiO₂ < 0.67 wt%, Zr < 125 ppm, Nb < 10 ppm, Hf < 3.4 ppm), and very low LREE (La < 22.4 ppm, Ce < 31 ppm), which are typical for potassic volcanic rocks formed in alate oceanic-arc setting.Mineral chemistry of selected magmatic mica and apatite phenocrysts from host rocks reveals relatively high SrO and BaO contents (micas: 0.15 wt% and up to 0.28 wt%, respectively; apatites: up to 0.28 wt% and 0.19 wt%, respectively) and very high halogen concentrations. Micas are characterized by up to 3.9 wt% F and 0.14 wt% Cl, whereas apatites have up to 3.6 wt% F and 0.68 wt% Cl. These very high halogen contents compared to those from barren intrusions imply that the shoshonitic magmatism was the source of mineralization.Copper-gold mineralization consists mainly of bornite, chalcopyrite, chalcocite and minor pyrite and tetrahedrite. Native gold occurs mainly as minute grains within silicates of the host rocks, and more rarely as fine inclusions in the sulphides. Mineralization is accompanied by wallrock alteration comprising a spatially restricted potassic type and a regional propylitic alteration type.Thus, the porphyry copper-gold deposit in the Goonumbla district can be viewed as an additional example of a worldwide association between potassic/shoshonitic magmatism and base- and precious-metal mineralization. More specifically, it appears to be the oldest recorded example of a shoshontie-associated porphyry Cu-Au deposit from a late oceanic-arc setting, a possible modern analogue being Ladolam at Lihir Island, Papua New Guinea

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Die Shoshonit Porphyry Cu-Au Assoziation im Goonumbla Distrikt, N.S.W., Australien

Zusammenfassung Die Porphyry Cu-Au Vererzung im Goonumbla Distrikt in New South Wales, Australien, sitzt in oberordovizischen (ca. 439.2 ± 1.2 Ma) Shoshoniten auf. Das petrographische Spektrum dieser Gesteine reicht von andesitischen bis dazitischen Laven und Tuffen, die lokal von Monzonit-Stöcken intrudiert werden; die Gesteine besitzen hohe, aber variable Al₂O₃ Gehalte (13.4–19.9 Gew%), sehr hohe K₂O Gehalte (bis zu 6.8 Gew%) und hohe K₂O/Na₂O Verhältnisse (0.58–1.48), die typisch sind für Shoshonite. Außerdem weisen sie hohe Konzentrationen an LILE Elementen (Ba bis 1200 ppm, Sr bis 1350 ppm) auf und geringe Konzentrationen an HFSE (TiO₂ < 0.67 Gew%, Zr < 125 ppm, Nb < 10 ppm, Hf < 3.4 ppm) sowie an LREE (La < 22.4 ppm, Ce < 31 ppm), die als typisch gelten für potassische Vulkanite von ozeanischen Plattengrenzen.Die Mineralchemie von repräsentativen Glimmer- und Apatit-Phänokristallen ist charakterisiert durch hohe SrO und BaO Gehalte (Glimmer: 0.15 Gew%, bzw. bis 0.28 Gew%; Apatite: bis 0.28 Gew%, bzw. 0.19 Gew%). Sie enthalten ferner sehr hohe Halogen-Konzentrationen. Die Glimmer enthalten beispielsweise bis zu 3.9 Gew% F und 0.14 Gew% Cl, während Apatite bis zu 3.6 Gew% F und 0.68 Gew% Ci aufweisen. Dies erscheint nicht ungewöhnlich, weil Glimmer und Apatite von vererzten Mag matiten zumeist deutlich höhere Halogengehalte besitzen, als solche von unvererzten Magmatiten. Die hohen Halogen-Gehalte in Phänokristallen aus den Shoshoniten legen nahe, die Vulkanite als den Ursprung der Vererzung zu interpretieren.Die Cu-Au Vererzung besteht überwiegend aus den Sulfiden Bornit, Kupferkies, Kupferglanz und vereinzelt auftretendem Pyrit und Tetrahedrit. Gediegen Gold wird in der Regel nur als kleine Partikel innerhalb von Silikaten der shoshonitischen Wirtsgesteine und seltener als feine Einschlüsse in Sulfiden gefunden.Die Vererzung wird von hydrothermaler Alteration der Wirtsgesteine begleitet und zwei Alterationsarten lassen sich unterscheiden: eine potassische sowie eine regional zu beobachtende propylitische Alteration.Die Porphyry Cu-Au Lagerstätte im Goonumbla Gebiet ist ein Beispiel für die weltweit beobachtete Assoziation von Bunt- und Edelmetallvererzungen und potassisch/shoshonitischem Magmatismus. Der Goonumbla Distrikt stellt die älteste bisher bekannte Porphyry Cu-Au Lagerstätte aus einerspätgenetischen ozeanischen Plattengrenze dar. Einmodernes Beispiel für eine Cu-Au Lagerstätte vergleichbaren Typs ist Ladolam auf Lihir Island, Papua New Guinea.