Geochronological evidence for late‐Grenvillian magmatic and metamorphic events in central Taimyr,northern Siberia*

U–Th–Pb analyses of zircons from six granites and one metasediment collected in the accretionary Central belt of Taimyr, Arctic Siberia, demonstrate that Neoproterozoic (c. 900 Ma) granites intrude late Mesoproterozoic/early Neoproterozoic amphibolite facies metamorphic rocks. This is the first time in the Mamont–Shrenk region that Neoproterozoic ages have been recognized for these lithologies, previously thought to be Archaean/Palaeoproterozoic in age. The Mamont–Shrenk Terrane (MST) represents a Grenvillian age (micro?) continent intercalated with younger Neoproterozoic ophiolites during thrusting and accreted to the northern margin of the Siberian craton sometime before the late Vendian. Basement to the MST may have been derived from the Grenvillian belt of east Greenland. Viable tectonic reconstructions must allow for an active margin along northern Siberia (modern day coordinates) in the middle Neoproterozoic.     

Geology on the moons of Uranus

In January 1986 the spaceprobe Voyager-2 revealed details of the surfaces of the icy satellites of Uranus for the first time, including grabens, other faulted features, impact craters and possible ice flows. Despite their apparent similarity to some of the moons of Jupiter and Saturn, they highlight many new questions as to the evolution of, and interactions between, such bodies.     

Multi-frequency observations of the 1985 outburst of RS ophiuchi

The 1985 outburst of the bright, recurrent nova RS Oph was almost simultaneously observed at X-ray, UV, optical, IR and radio frequencies at many epochs. The abundances in the ejected shell and the development of the bolometric luminosity as a function of time suggest that the cause of the outburst is a nuclear runaway on a massive white dwarf.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Development, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Population dynamics in the Ukrainian SSR (1959-1984)

Changes in the spatial distribution of the population of the Ukraine between 1959 and 1984 are analyzed. Attention is given to changes in the rural and urban population composition over time as well as to regional variations in population dynamics.     

Magnetic reconnection in high-temperature plasma of solar flares

Quasi-steady high-temperature current sheets are an energy source during the main or hot phase of solar flares. Such sheets are shown to be stabilized with respect to the tearing instability by a small transverse component of magnetic field existing in the sheets.     

A new approach to the librational solution in the Ideal Resonance Problem

The librational motion of the Ideal Resonance Problem (Garfinkel, 1966, Jupp, 1969) is treated through an initialnon-canonical transformation which, however, leaves the equations of motion in a quasi-canonical form, with Hamiltonian expressed in standard trigonometric functions amenable to traditional averaging techniques. The perturbed solutions, similarly expressed intrigonometric near-identity transformations, and their frequencies can be found to arbitrary order, with the elliptic integrals expected of the system introduced only in a final explicit quadrature for a Kepler-type equation in the angular variable. The specific transformations and resulting equations of motion are introduced, and explicit solutions for the original variables are found to second order, with mean motion accurate to fifth. Limitation of the present solution to the librational region, the extension of that solution to higher order, and observations on the form of the associated Hamiltonian are also discussed.     

Silica phase transformations in the petroliferous sequences

The joint evolution of organic matter and silica in petroliferous sequences is considered in the terms of the laws of transformation of dispersion systems. The dispersion systems are transformed under conditions of low-temperature solid-phase processes accompanied by the silica phase transition and dehydration that favors the evolution of organic matter.     

9711号北上台风演变及暴雨过程的位涡诊断分析

通过对 971 1号台风登陆北上穿过山东造成山东特大暴雨过程的湿位涡的分析 ,并从湿位涡的角度研究了台风演变及山东特大暴雨的形成机制 ,揭示了冷空气在台风演变及暴雨过程中的重要作用。结果表明 :倾斜涡度发展是暴雨产生和台风加强的重要机制之一 ,暴雨产生在 θe线陡立密集区内 ;湿位涡在这次暴雨过程中对流层低层具有 MPV1 <0 ,MPV2 >0的特征 ,此次暴雨产生在负的MPV1等值线密集区中 ;对流层上部及平流层下部高位涡的下传使得低层斜压性增大 ,引起低层的对流稳定度减小 ,促使气旋性涡度发展 ,有利于位势不稳定能量的释放 ,使得暴雨增幅 ,导致台风的加强并演变为温带气旋。