Kokchetavite: a new potassium-feldspar polymorph from the Kokchetav ultrahigh-pressure terrane

Kokchetavite, a new polymorph of K-feldspar (KAlSi₃O₈), has been identified as micrometer-size inclusions in clinopyroxene and garnet in a garnet-pyroxene rock from the Kokchetav ultrahigh-pressure terrane, Kazakhstan. Kokchetavite has a hexagonal structure with a =5.27(1) Å, c=7.82(1) Å, V=188.09 ų, Z=1, and is found to be associated with phengite + /-cristobalite (or quartz) + siliceous glass ± phlogopite/titanite/calcite/zircon, occurring as multi-phase inclusions in clinopyroxene and garnet. It is concluded that kokchetavite could not be an exsolution phase in host minerals. Instead, it might be metastably precipitated from an infiltrated K-rich melt during rock exhumation. Alternatively, although less likely, kokchetavite might be derived from dehydration of K-cymrite, which, in turn, was formed at high pressures. In either case, kokchetavite is a metastable polymorph of K-feldspar.     

STATE OF THE WORLD ENVIRONMENT MAPPING PROJECT

An international team of cartographers describes the initial concept and methodological principles underlying an IGU-sponsored project to compile a map of the state of the world's environments on the basis of a unified approach and guidelines. The project, which is to involve cartographers and Earth scientists throughout the world, is to provide a comprehensive characterization of the condition of marine and terrestrial ecosystems at a scale of 1:15,000,000 and is to be made available in both digital and paper formats. Translated by Edward Torrey, Alexandria, VA from: Izvestiya Akademii Nauk, seriya geograficheskaya, 1999, No. 1, pp. 108-113.     

Time-dependent stress change during failure of rocks

The energy balance of a solid subject to fracture has been explored using heat and mass transfer equations with regard to the volumetric and superficial components. In the suggested model, brittle fracture of a cracked solid considered as a heterogeneous two-phase medium is described by an equation analogous to the Griffith’s criterion for propagation of a single crack. The derived equation is used, together with estimates of relative change in specific interface area, to study the respective change of free strain energy and pressure in rocks associated with failure.     

Preface: Stars and interstellar medium

This issue presents proceedings of the "Stars and Interstellar Medium" section of the AllRussian Astronomical Conference VAK-2017. Sixteen papers(selected from about 70 talks) cover different problems related to stars, pulsars, interstellar gas and dust, and star formation. The preface briefly reviews these papers.     

The northern sea route as an element of the ICZM system in the Arctic: problems and perspectives

Characteristics of the current state of transportation problems along the Northern Sea Route are given. The required ice data necessary to guarantee the safety of navigation are discussed. A variety of developing transportation prospects along the Northern Sea Route, including international aspects, are disputed. Effective economic alternatives of the Northern Sea Route under the conditions of the current Russian economic crisis are analyzed.     

New variable stars from the photographic archive: semi-automated discoveries,attempts at automatic classification and the new field 104 Her

Using 172 plates taken with the 40-cm astrograph of the Sternberg Astronomical Institute(Lomonosov Moscow University) in 1976–1994 and digitized with a resolution of 2400 dpi, we discovered and studied 275 new variable stars. We present the list of our new variables with all necessary information concerning their brightness variations. As in our earlier studies, the new discoveries show a rather large number of high-amplitude Delta Scuti variables, predicting that many stars of this type remain not detected in the whole sky. We also performed automated classification of the newly discovered variable stars based on the Random Forest algorithm. The results of the automated classification were compared to traditional classification and showed that automated classification was possible even with noisy photographic data. However, further improvement of automated techniques is needed, which is especially important when considering the very large numbers of new discoveries expected from all-sky surveys.