Contrasting stable isotope behavior between calcite and dolomite marbles,Lone Mountain,Nevada

 Late Proterozoic to Cambrian carbonate rocks from Lone Mountain, west central Nevada, record multiple post-depositional events including: (1) diagenesis, (2) Mesozoic regional metamorphism, (3) Late Cretaceous contact metamorphism, related to the emplacement of the Lone Mountain granitic pluton and (4) Tertiary hydrothermal alteration associated with extension, uplift and intrusion of silicic porphyry and lamprophyre dikes. Essentially pure calcite and dolomite marbles have stable isotopic compositions that can be divided into two groups, one with positive δ¹³C values from+3.1 to +1.4 ‰ (PDB) and high δ¹⁸O values from +21.5 to +15.8 ‰ (SMOW), and the other with negative δ¹³C values from –3.3 to –3.6‰ and low δ¹⁸O values from +16.9 to +11.1‰. Marbles also contain minor amounts of quartz, muscovite and phlogopite. Brown and blue luminescent, clear, smooth textured quartz grains from orange luminescent calcite marbles have high δ¹⁸O values from +23.9 to +18.1‰, while brown luminescent, opaque, rough textured quartz grains from red luminescent dolomite marbles typically have low δ¹⁸O values from +2.0 to +9.3‰. The δ¹⁸O values of muscovite and phlogopite from marbles are typical of micas in metamorphic rocks, with values between +10.4 and +14.4‰, whereas mica δD values are very depleted, varying from −102 to −156‰. No significant lowering of the δ¹⁸O values of Lone Mountain carbonates is inferred to have occurred during metamorphism as a result of devolatilization reactions because of the essentially pure nature of the marbles. Bright luminescence along the edges of fractures, quartz cements and quartz overgrowths in dolomite marbles, low δD values of micas, negative δ¹³C values and low δ¹⁸O values of calcite and dolomite, and depleted δ¹⁸O values of quartz from dolomite marbles all indicate that meteoric fluids interacted with Lone Mountain marbles during the Tertiary. Partial oxygen isotopic exchange between calcite and low ¹⁸O meteoric fluids lowered the δ¹⁸O values of calcite, resulting in uniform quartz-calcite fractionations that define an apparent pseudoisotherm. These quartz-calcite fractionations significantly underestimate both the temperature of metamorphism and the temperature of post-metamorphic alteration. Partial oxygen isotopic exchange between quartz and meteoric fluids also resulted in ¹⁸O depletion of quartz from dolomite marbles. This partial exchange was facilitated by an increase in the surface area of the quartz as a result of its dissolution by meteoric fluids. The negative δ¹³C values in carbonates result from the oxidation of organic material by meteoric fluids following metamorphism. Stable isotopic data from Lone Mountain marbles are consistent with the extensive circulation of meteoric hydrothermal fluids throughout western Nevada in Tertiary time. Received: 1 February 1994/Accepted: 12 September 1995     

Current controlled sediment deposition from the shelf to the deep ocean: the cenozoic evolution of circulation through the SW pacific gateway

 The circulation of cold, deep water is one of the controlling factors of the Earth's climate. Forty percent of this water enters the world ocean through the Southwest Pacific as a deep western boundary current (DWBC) flowing northwards at bathyal to abyssal depths, east of the New Zealand microcontinent. South of latitude 50°S, the DWBC is intimately linked with the Antarctic circumpolar current (ACC), which is the prominent force for the shallow-water circulation. The Pacific DWBC is presently the largest single contributor of deep ocean water, and deciphering its evolution is of fundamental importance to understanding ocean and climate history, and global ocean hydrography. The evolution of the DWBC system, and of related circum-Antarctic currents, has taken place since 30–25 Ma when plate movements created the first oceanic gaps south of Australia and South America. The stratigraphic record preserved in sediment drifts of the Southwest Pacific, in eastern New Zealand, is the best available for deciphering the Neogene history of Southern Ocean water masses, and of the circulation of the ACC, DWBC and their precursor systems. Major current activity commenced on the New Zealand margin in the late Eocene or early Oligocene (Hoiho Drift; early ACC) and was widespread by the mid-late Oligocene (Marshall Paraconformity and Weka Pass Limestone drift; ACC). During the Neogene the eastern South Island continental shelf built seawards by accretion at its outer edge of large Miocene current drifts up to tens of kilometres long and hundreds of metres thick (Canterbury drifts). Also commencing in the mid-Cenozoic, but in depths >2000 m, the DWBC emplaced large deep-water sediment drifts. Rates of drift deposition accelerated considerably in the late Neogene, when climatic change (and particularly glacial sea-level falls) caused the delivery of large volumes of turbiditic sediment into the path of the DWBC via the Bounty and Hikurangi channels. Received: 9 August 1995 / Accepted: 15 January 1996     

Mineral inclusions in diamonds from the Sputnik kimberlite pipe, Yakutia

The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO₂ content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m² conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle.     

A mean behavior model of aerobic biodegradation in heterogeneous formation

It has been observed that the field biodegradation rates for soluble hydrocarbon plumes are significantly smaller than the aerobic rates observed in the laboratory. It is believed that this difference is related to the fact that in the field oxygen and hydrocarbon must be mixed before the biodegradation reaction can occur, and that the effective degradation rate is controlled by the actual, not mean, concentrations of oxygen and hydrocarbon. In this work, we present a conceptual model of oxygen-mixing limited biodegradation, which indicates that the effective degradation rate should depend on the cross correlation between the oxygen and hydrocarbon concentration fluctuations. This is followed by a development of a rigorous, field-scale model.     

Numerical simulation of the mutual conversion of ordinary and extraordinary waves in a magnetised plasma by artificial ionospheric turbulence

Some effects of normal mode coupling in weakly anisotropic inhomogeneous plasma are analysed on the basis of the numerical solution of transfer equations for the Stokes parameters. The numerical analysis of normal mode conversion on a set of isolated irregularities demonstrates the possibility of an effective polarisation transformation on such structures. It is shown that by the appropriate selection of discrete irregularities of the external magnetic field direction or plasma electron concentration resulting in radio-wave refraction, one can control electromagnetic radiation polarisation characteristics. Analytical expressions for mean Stokes parameters have been obtained for the rare isolated irregularities. The opportunity for the simulation of mutual wave conversion processes in the ionospheric heating experiments is discussed.     

Remote sensing detection of atmospheric pollutants by differential absorption LIDAR 510M/SODAR PA2 mobile system

Summary Air pollution problem in the Czech Republic is very complex due to large number of factors as turbulent dispersion and chemical reactions concurring in the status of the PBL. For this 3D distribution of pollutants is a key information that cannot be given by conventional monitoring stations. Combined use of DIAL lidar and sodar can give access to such information. Case studies of air pollutants transport are presented using 3D concentration fields of NO₂ and ozone measured by lidar and meteorological conditions monitored by Doppler Sodar.     

俄罗斯远东金属矿床形成条件的古地球动力学分析

根据本区地质构造的新资料,提出了区域板块构造模型。研究了从俯冲到加利福尼亚型转换和由后者又到俯冲的古地球动力学环境更替的意义。这种更替发生在对本区最重要的中—新生代历史时期,对区域成矿带整体乃至一些金属矿床的形成具有重要影响。论证了一些地体性质,尤其是俯冲-增生杂岩对矿床形成的重要意义。     

横穿贝加尔湖山脉北部寒区的线性工程

The development of North Transbaikalye mineral resources (e. g. the Chiney deposit of iron titanium-vanadium-magnetite ores and Udokan copper deposits) is impossible without the establishment of industrial and transport infrastructure, one component of which are linear engineering constructions (drive railways, by-line auto roads, platform passages, protecting constructions, and others). However,on condition of spreading permafrost rocks this is conjugated with certain ecological risk just as from the transport network objects so for the objects themselves. A special attention is paid in the paper to considering of problems of projecting and constructing railways on the Udokan ridge.     

探测冰盖和多年冻土层的融冰探头研发

The exploration of ice sheets by melting vertical holes into the ground has some tradition in terrestrial glaciology. Such probes have been used since the 1960's to investigate the vertical structure of the ice in Greenland and Antarctica and in alpine glaciers. In this paper we look into the possibility to develop similar devices for use on extraterrestrial icy bodies, like e.g. the polar areas on Mars or the icy satellites of the outer solar system. We report on some basic experiments performed in the cryo-vacuum laboratory of the Space Research Institute of the Austrian Academy of Sciences, Graz. In these experiments the penetration of a simple melting probe into compact and porous water ice (with a snow-like texture) was monitored, both under vacuum conditions and under air pressure. The observed penetration speeds for a given power supply are compared with a simple mathematical model. We conclude that a miniature melting probe with small overall dimensions and a reasonable power demand could well be part of the payload of a future planetary mission, for example to the poles of Mars. Such missions are currently under discussion in several space agencies. Moreover such probes could also e? ectively be used in terrestrial environments. A possible design is presented at the end of the paper.