On two types of metalliferous carbonaceous rocks

Two types of metalliferous carbonaceous rocks that differ in associated metals are considered. One of them is characterized by gold occurring in finely dispersed arsenopyrite and arsenic-bearing pyrite, and the other, by finely impregnated native metals in carbonaceous matter. Rocks of the first type also contain elements of the platinum group, while those of the second type bear rhenium, silver, iron, molybdenum, and other metals. Graphitic mineralization is usually localized in the shear zone associated with alkaline basalts.     

Computer microtomography of zircon: A new approach to the selection of targets for U-Pb geochronologic studies

The paper reports results obtained by the complex studying of zircon crystals from rocks of various genesis. Zircon is one of the minerals most often used as geochronometers. It also provides genetic information on superimposed processes that is “recorded” in the external and internal morphology of its crystals. This mineral is thoroughly examined to select its unaltered crystals for U-Pb dating by the single-grain method. Zircon grains are selected with the use of optical and electron microscopy and cathodoluminescence. This publication presents the first results obtained by examining zircon by computer microtomography (μCT) and the results of the studying of the external and internal structure by conventional techniques ([optical microscopy and SEM (SE and CL)]. The paper demonstrates the advantages of the application of the μCT techniques to the selection of targets for U-Pb zircon dating: there is no need for the special preparation of the samples and no material is destructed. However, this technique may be not informative enough if the zircon contains inherited core whose density does not differ from the density of the surrounding mineral.     

On global forces of nature driving the Earth’s climate. Are humans involved?

The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible.     

Three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr with an accretor wind

We present three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr taking into account explicitly radiative cooling and the stellar wind of the accretor. Our computations show that flow forces wind out from the orbital plane, where an accretion disk with a radius of 0.4–0.5 and a height of about 0.15–0.17 (in units of orbital separation) is formed. Gas motions directed upward from the orbital plane are initiated in the region of interaction of the flow from L₁ and the accretor wind (x = 0.91, y = ?0.17); i.e., a jetlike structure forms. This structure has the shape of a gas pillar above the orbital plane, where gas moves with the velocity of stellar wind. The number density of the gas in this structure is about 10¹⁴ cm^?3, and its temperature is 20 000–45 000 K. At heights of about 0.15–0.20 above the orbital plane, in the region between the jetlike structure and the disk, two spiral shocks form. It is possible that the emission lines observed in the spectrum of β Lyr binary originate in this region.