Stratiform and vein U,Mo and Cu mineralization in the Novoveská Huta area,CSFR

U-Mo and Cu mineralization occurs in horizons as well as in veins in the Permian formations near Novoveská Huta. Ore mineralization is represented by uraninite, U-Ti oxides, coffinite, molybdenite, chalcopyrite, tennantite and pyrite. The isotopic composition of S and C displays a larger variability in the stratiform ores (³⁴S from –32.7 to +2.7 and ¹³C from –27.1 to — 0.5) These data suggest mixing of meteoric solutions with fluids of volcanic origin and a complex history. There is a narrower range of ³⁴S from –18.8 to –4.6 and ¹³C from –6.3 to –2.5% in quartz-carbonate veins with Cu mineralization suggesting a deep source of ore-bearing solutions. The Permian volcanics were a significant source of ore elements.Their contents of U, Mo, Cu and Y are from two to eight times higher than in sedimentary rocks. Accumulations of ore elements in the horizons were formed by the reduction and adsorption processes 240 ± 30 Ma ago according to U-Pb isotopic dating. Due to Alpine tectonism, these low-grade ores (U<0.1 wt%) were remobilized and higher-grade U-Mo ores (U>0.1 wt%) were formed 130 ± 20 Ma ago at temperatures ranging from 110 to 120° C, according to fluid inclusions. Younger veins with Cu mineralization were formed 115 ± 10 Ma according to the model age of Pb at temperatures ranging from 95 to 190°C.     

Infiltration Metasomatism of Cumulates by Intrusive Magma Replenishment: the Wavy Horizon, Isle of Rum, Scotland

The Eastern Layered Intrusion of the Rum Layered Suite comprisespaired peridotite and allivalite (troctolite and gabbro) layersforming 16 macro-rhythmic units. Whereas the majority of thesemacro-units are believed to have formed by a process of crystal–liquiddifferentiation involving successive accumulation of crystalsfrom multiple picritic replenishments of the chamber, the Unit9 peridotite is interpreted as a layer-parallel picrite intrusion.Closely correlated with this discontinuous peridotite body isa distinctive feature generally known as the Wavy Horizon, whichdivides the overlying allivalite into a lower troctolite andan upper gabbro along a well-defined undulating contact. Wepropose that the Wavy Horizon is a metasomatic feature formedconsequent to the removal of clinopyroxene from an originalgabbroic mush. Foundering of the mush into the picritic sillresulted in the replacement of the original interstitial liquidby one saturated only in olivine (± plagioclase). Progressivethrough-flow of this liquid resulted in the stripping out ofclinopyroxene from the lower parts of the allivalite. We interpretthe Wavy Horizon as a reaction front, representing the pointat which the invading liquid became saturated in clinopyroxene.The distinctive pyroxene-enriched zone immediately above theWavy Horizon could have formed when mixing of the interstitialliquids on either side of the reaction front formed a supercooledliquid oversaturated in pyroxene, as a result of the curvatureof the olivine–plagioclase–clinopyroxene cotectic.The presence of many such approximately layer-parallel features,defined by differences in pyroxene content, in the Eastern LayeredIntrusion of Rum suggests that such an infiltration–reactionprocess was not unique to Unit 9. KEY WORDS: cumulate; infiltration metasomatism; Rum; Eastern Layered Intrusion     

Numerical study of an oscillating smaller cylinder in the wake of an upstream larger cylinder

A numerical study of flow around two tandem cylinders with unequal diameters was carried out. The upstream larger cylinder was fixed and the downstream smaller cylinder was allowed to oscillate in the transverse direction only. Comparisons of the experimental and numerical results were made to investigate the effects of the gap ratio on the maximum vibration amplitude and vortex shedding frequency. The results showed that the vibration response of the smaller cylinder was significantly affected by the presence of the upstream larger cylinder, and resulted in greatly reduced vibration amplitudes. With an increasing gap ratio, the vibration amplitude increased. However, the magnitude was lower than that corresponding to a single cylinder (with the same diameter as that of the downstream smaller cylinder) under the same flow conditions.     

The impact of the Laacher See Volcano (11 000 yr B.P.) on terrestrial vegetation and diatoms

Late-glacial lake sediments containing the Laacher See Tephra (LST, 11 000 yr B.P.) have been analyzed for their pollen and diatom content at three sites at varying distances from the volcano and on different bedrock geologies. The aim was to test the null hypothesis that this major volcanic eruption had no effect on terrestrial pollen or aquatic diatom assemblages. The pollen spectra at all sites show a short-lived increase in grass pollen following the LST. Partial redundancy analysis and associated Monte Carlo permutation tests suggest, however, that the LST had no statistically significant effect at two sites but it had a statistically significant impact on the pollen assemblages at the site nearest (60 km) to the volcano.The diatom assemblages at the three sites changed individualistically after the LST deposition, with increases inAchnanthes minutissima at one site, an expansion ofAulacoseira species at another, and an increase ofAsterionella formosa andFragilaria brevistriata at the third site. Partial redundancy analysis and associated permutation tests suggest a statistically significant change in diatoms in relation to the LST and associated changes in sediment lithology at the one site situated on acidic bedrock. No significant impacts were found at the sites on volcanic or calcareous rocks. Due to the interaction between tephra and sediment lithology, it is not possible to conclude if the statistically significant diatom changes were a direct result of the LST deposition or an indirect result of lithological changes following LST deposition.This is the first paper in a series of papers published in this issue on high-resolution paleolimnology. These papers were presented at the Sixth International Paeolimnology Symposium held 19–21 April, 1993 at the Australian National University, Canberra, Australia. Dr A. F. Lotter and Dr. M. Sturm served as guest editors for these papers.     

Thick sections of layered ultramafic cumulates in the Oman ophiolite revealed by an airborne hyperspectral survey: Petrogenesis and relationship to mantle diapirism

Using the HyMap instrument, we have acquired visible and near infrared hyperspectral data over the Maqsad area of the Oman ophiolite (~ 15 × 60 km). This survey allowed us to identify and map the distribution of clinopyroxene-rich cumulates (inter-layered clinopyroxenites and wehrlites) whose occurrence was previously undocumented in this area. The cumulates reach several hundred meters in thickness and crop out at distances exceeding 15 km on both sides of the Maqsad former spreading centre. They occur either in mantle harzburgites, as km-sized layered intrusions surrounded by fields of pegmatitic dykes consisting of orthopyroxene-rich pyroxenite and gabbronorites, or at the base of the crustal section where they are conformably overlain by cumulate gabbros. These ultramafic cumulates crystallized from silica- and Mg-rich melts derived from a refractory mantle source (e.g. high Cr#, low [Al₂O₃], low [TiO₂]). These melts are close to high-Ca boninites, although, strictly speaking, not perfect equivalents of present-day, supra-subduction zone, boninites. Chemical stratigraphy reveals cycles of replenishment, mixing and fractional crystallization from primitive (high Mg#) melts, typical of open magma chambers and migration of inter-cumulus melts. The TiO₂ content of clinopyroxene is always low (≤ 0.2 wt.%) but quite variable compared to the associated pegmatites that are all derived from a source ultra-depleted in high field strength elements (HFSE). This variability is not caused by fractional crystallization alone, and is best explained by hybridization between the ultra-depleted melts (parent melts of the pegmatites) and the less depleted mid-ocean ridge basalts (MORB) parent of the dunitic–troctolitic–gabbroic cumulates making up the crustal section above the Maqsad diapir.We propose that, following a period of magma-starved spreading, the Maqsad mantle diapir, impregnated with tholeiitic melts of MORB affinity, reached shallow depths beneath the ocean ridge. This diapir induced melting of the formerly accreted and hydrothermally altered lithosphere. At this stage, these boninitic-like lithospheric melts crystallized as pegmatitic dykes. As the diapir continued to rise, the amount of MORB reaching shallow depths increased, together with the surrounding temperature, leading to the formation of magma chambers where the crystallization of layered cumulates became possible. These cumulates remained rich in pyroxene and devoid of plagioclase as long as the contribution of MORB-derived melts was moderate relative to the lithospheric-derived melts. As the contribution of MORB to the refilling of the magma chamber increased, gabbroic cumulates started to crystallize.     

Structure of the αFexAl1:xOOH solid solution

The three-dimensional local organisation around Fe atoms in a natural diaspore (Al_0.9955Fe_0.0045OOH) has been investigated by angular measurements of X-ray absorption spectra. It is demonstrated that in a single crystal of diaspore, the absorption cross-section exhibits the special case of trichroism where three independent measurements are needed to determine the absorption cross-section for any direction of polarization. Extended X-ray absorption fine structure (EXAFS) spectra were thus recorded at the following orientations of the polarization vector: , , and . The incoming white beam was monochromatized using two Si(331) crystals, which deliver at the Fe K-edge a completely linearly polarized X-ray beam. The reliability of our measurements was checked by comparing the isotropic EXAFS spectrum calculated from the three orthogonal measurements to the one of the diaspore powder recorded at the magic angle. It is shown that Fe³⁺ ions are not randomly distributed within the diaspore framework. Furthermore, only part of the Fe³⁺ ions substitutes Al, the others being located in the channels of the structure. The 3D local structure of the Fe domains has been modeled assuming hematite-like clusters of three Fe octahedra topotactically grafted to aluminous chains. These Fe clusters are thought to represent ancient multinuclear Fe surface complexes having formed at the time of the diaspore growth, and being sealed in its bulk structure. The whole crystal of diaspore is then thought to have kept the memory of the heterogeneous nucleation mechanism of these hematite nuclei. In addition to the well-known examples of atom segregations, ion vacancies, and intergrowths of discrete phases, this new type of crystal defect represents another evidence of non-equilibrium crystallization process under the thermodynamic and kinetic conditions that prevail at the earth's surface.     

Template-based classification of SDSS-<Emphasis Type="BoldItalic">GALEX</Emphasis> point sources

We have classified a sample of 37,492 objects from SDSS into QSOs, galaxies and stars using photometric data over five wave bands (u, g, r, i and z) and UV GALEX data over two wave bands (near-UV and far-UV) based on a template fitting method. The advantage of this method of classification is that it does not require any spectroscopic data and hence the objects for which spectroscopic data is not available can also be studied using this technique. In this study, we have found that our method is consistent by spectroscopic methods given that their UV information is available. Our study shows that the UV colours are especially important for separating quasars and stars, as well as spiral and starburst galaxies. Thus it is evident that the UV bands play a crucial role in the classification and characterization of astronomical objects that emit over a wide range of wavelengths, but especially for those that are bright at UV. We have achieved the efficiency of 89% for the QSOs, 63% for the galaxies and 84% for the stars. This classification is also found to be in agreement with the emission line diagnostic diagrams.     

Using δN values in algal tissue to map locations and potential sources of anthropogenic nutrient inputs on the island of Maui, Hawai‘i, USA

Macroalgal blooms of Hypnea musciformis and Ulvafasciata in coastal waters of Maui only occur in areas of substantial anthropogenic nutrient input, sources of which include wastewater effluent via injection wells, leaking cesspools and agricultural fertilizers. Algal δ¹⁵N signatures were used to map anthropogenic nitrogen through coastal surveys (island-wide and fine-scale) and algal deployments along nearshore and offshore gradients. Algal δ¹⁵N values of 9.8‰ and 2.0-3.5‰ in Waiehu and across the north-central coast, respectively, suggest that cesspool and agricultural nitrogen reached the respective adjacent coastlines. Effluent was detected in areas proximal to the Wastewater Reclamation Facilities (WWRF) operating Class V injection wells in Lahaina, Kihei and Kahului through elevated algal δ¹⁵N values (17.8-50.1‰). From 1997 to 2008, the three WWRFs injected an estimated total volume of 193 million cubic meters (51 billion gallons) of effluent with a nitrogen mass of 1.74 million kilograms (3.84 million pounds).