Localization of the solar flare SF900610 in X-rays with the WATCH instrument of the GRANAT observatory

During the solar flare of June 10, 1990, the WATCH instrument of the GRANAT space observatory obtained 110 localizations of the X-ray source in the X-ray range 8–20 keV. Its coordinates were measured with an accuracy of ～2 arcmin at a 3σ confidence level. The coordinates of the X-ray source do not coincide with the coordinates of the Hα-line flare. The X-ray source moved over the solar disk during the flare. This probably implies that, as the X-ray emission was generated, different parts of one loop or a system of magnetic loops dominated at different flare times.     

Detection of giant radio pulses from the pulsar PSR B0656+14

Giant pulses (GPs) have been detected from the pulsar PSR B0656 + 14. A pulse that is more intense than the average pulse by a factor of 120 is encountered approximately once in 3000 observed periods of the pulsar. The peak flux density of the strongest pulse, 120 Jy, is a factor of 630 higher than that of the average pulse. The GP energy exceeds the energy of the average pulse by up to a factor of 110, which is comparable to that for other known pulsars with GPs, including the Crab pulsar and the millisecond pulsar PSR B1937+21. The giant pulses are a factor of ～6 narrower than the average pulse and are clustered at the head of the average pulse. PSR B0656+14 along with PSR B0031-07, PSR B1112+50, and PSR J1752+2359 belong to a distinctive group of pulsars in which GPs have been detected without any extremely strong magnetic field on the light cylinder.     

Olivine in the Udachnaya-East Kimberlite (Yakutia, Russia): Types, Compositions and Origins

Olivine is the principal mineral of kimberlite magmas, and isthe main contributor to the ultramafic composition of kimberliterocks. Olivine is partly or completely altered in common kimberlites,and thus unavailable for studies of the origin and evolutionof kimberlite magmas. The masking effects of alteration, commonin kimberlites worldwide, are overcome in this study of theexceptionally fresh diamondiferous kimberlites of the Udachnaya-Eastpipe from the Daldyn–Alakit province, Yakutia, northernSiberia. These serpentine-free kimberlites contain large amountsof olivine (50 vol.%) in a chloride–carbonate groundmass.Olivine is represented by two populations (olivine-I and groundmassolivine-II) differing in morphology, colour and grain size,and trapped mineral and melt inclusions. The large fragmentalolivine-I is compositionally variable in terms of major (Fo_85–94)and trace element concentrations, including H₂O content (10–136ppm). Multiple sources of olivine-I, such as convecting andlithospheric mantle, are suggested. The groundmass olivine-IIis recognized by smaller grain sizes and perfect crystallographicshapes that indicate crystallization during magma ascent andemplacement. However, a simple crystallization history for olivine-IIis complicated by complex zoning in terms of Fo values and traceelement contents. The cores of olivine-II are compositionallysimilar to olivine-I, which suggests a genetic link betweenthese two types of olivine. Olivine-I and olivine-II have oxygenisotope values (+ 5·6 ± 0·1 VSMOW, 1 SD)that are indistinguishable from one another, but higher thanvalues (+ 5·18 ± 0·28) in ‘typical’mantle olivine. These elevated values probably reflect equilibriumwith the Udachnaya carbonate melt at low temperatures and ¹⁸O-enrichedmantle source. The volumetrically significant rims of olivine-IIhave constant Fo values (89·0 ± 0·2 mol%),but variable trace element compositions. The uniform Fo compositionsof the rims imply an absence of fractionation of the melt'sFe²⁺/Mg, which is possible in the carbonatite melt–olivinesystem. The kimberlite melt is argued to have originated inthe mantle as a chloride–carbonate liquid, devoid of ‘ultramafic’or ‘basaltic’ aluminosilicate components, but becameolivine-laden and olivine-saturated by scavenging olivine crystalsfrom the pathway rocks and dissolving them en route to the surface.During emplacement the kimberlite magma changed progressivelytowards an original alkali-rich chloride–carbonate meltby extensively crystallizing groundmass olivine and gravitationalseparation of solids in the pipe. KEY WORDS: kimberlite; olivine; partial melting; carbonatitic melt; oxygen isotopes; H₂O     

Inclusions of Cr- and Cr–Nb-Rutile in pyropes from the Internatsionalnaya kimberlite pipe,Yakutia

The results of study of rutile inclusions in pyrope from the Internatsionalnaya kimberlite pipe are presented. Rutile is characterized by unusually high contents of impurities (up to 25 wt %). The presence of Cr₂O₃ (up to 9.75 wt %) and Nb₂O₅ (up to 15.57 wt %) are most typical. Rutile inclusions often occur in assemblage with Ti-rich oxides: picroilmenite and crichtonite group minerals. The Cr-pyropes with inclusions of rutile, picroilmenite, and crichtonite group minerals were formed in the lithospheric mantle beneath the Mirnyi field during their joint crystallization from melts enriched in Fe, Ti, and other incompatible elements as a result of metasomatic enrichment of the depleted lithospheric mantle.     

Inclusions of crichtonite group minerals in pyropes from the Internatsionalnaya kimberlite pipe,Yakutia

The results of study of crichtonite group minerals in pyropes from the Internatsionalnaya kimberlite pipe are reported. Most of the studied samples are characterized by high concentrations of Sr, Ca, Na, and LREEs in comparison with minerals of the LIMA series from kimberlites of South Africa, whereas the average concentrations of Ba and K are significantly lower. Crichtonite group minerals in pyropes are characterized by predomination of Na over K in most samples and by a high concentration of Al₂O₃ (up to 4.5 wt %). Findings of inclusions of crichtonite group minerals with high concentrations of incompatible elements provide evidence for the metasomatic origin of host chromium-rich pyropes.     

Changes in the manner of tectonic movements under the Earth’s evolution

Variations in the O, Sr, Nd, and Hf isotopic compositions in rocks of various ages, minerals, and mantle temperature in the geological history are considered. Two periods in the Earth’s history are studied: the beginning of the formation of the planet until the turn of (3.4) 2.7–2.5 Ga and the tectonic movement period in the last 2 Ga, and also the transitional period within 2.7–2.0 Ga.     

Elemental composition of peat organic matter as an indicator of trophic conditions of marsh ecosystems in the south of the Baikal region

Based on measurements of the concentrations of C, N, P, and chlorophyll-a, as well as on palynological analysis of the core Vdr 2011 of peaty sediments from the Vydrinaya River along the southern coast of Lake Baikal, the geochemical characteristics of eutrophy were compared to pollen indices of changes in the environment and the mode of marsh ecosystem transformations into various trophic states was specified. It was shown that geochemical parameters of the changes in the environment may be considered as the characteristics of trophic conditions in ecosystems in the course of paleo-reconstructions.     

Stages of Trap Magmatism in the Norilsk Area: New Data on the Structure and Geochemistry of the Volcanic Rocks

A periodic character of the evolution of trap magmatism was inferred by many researchers from the fact that sequences of volcanic rocks consist of alternating units of lava flows and tuff. A new phase of studying magmatic rocks in the Siberian Platform was related to the possibility of apply high-precision geochemical techniques in studying trace elements and Sr, Nd, and Pb isotopic compositions. The use of these techniques made it possible not only to identify small individual cycles in the vertical sections of volcanic rocks but also to distinguish larger stages. The currently most widely acknowledged scenario of the origin of volcanic rocks involves three stages, during which oceanic-island basalts (OIB), transitional series (intermediate between OIB and WPB), and within-plate basalts (WPB) were formed. This scenario was inferred mostly from data on rocks in the western part of the Norilsk area (Kharaelakh Trough). This publication presents recently obtained data on the inner structure of the sequences of volcanic rocks and the geochemistry of basalts in the eastern part of the territory, where no rocks show transitional characteristics have ever been found. They can be classified into two types that have clearly different composition and occur in different areas. These types characterize two major stages of the origin of volcanic rocks: rift-related and trap magmatism itself. The rocks produced during these stages occur at neighboring territories.     

Influence of Climate Changes in the Late Pleistocene–Holocene on Composition of Bottom Sediments of the Selenga–Buguldeika Saddle,Lake Baikal

The study of bottom sediments of Lake Baikal recovered by submarine drilling at the Selenga–Buguldeika saddle (core VER93-2 st. 24GC) allowed us to reconstruct the climatic events in the Baikal region in the last 20–25 k.y. On the basis of the data on distribution of chemical elements in the core section, the mineral composition of sediments was calculated by the physicochemical modeling method. A study of how ratios of clay minerals changed in the section allowed us to identify the Pleistocene–Holocene boundary, Bølling–Allerød postglacial warming, and Late Dryas cooling. The calculated data on mineral composition of bottom sediments from the core VER93-2 demonstrate a good fit to the X-ray diffraction analysis results. The proposed approach can be used in calculation of mineral compositions of other sedimentary sequences with known chemical composition.     

Paleoproterozoic Granitoids of the Yurovka Swell Basement (Okhotsk Massif): First U–Pb SIMS Geochronological and Nd–Sr Isotope–Geochemical Data

The first results of U–Pb SIMS geochronological and Nd–Sr isotope–geochemical studies of the Yurovka Complex metavolcanics and granitoids of the Luktur Complex belonging to the Yurovka Swell yielded a Paleoproterozoic age of their formation pointing to a considerable Paleoproterozoic continental crust formation event. These data allow us to reconsider existing ideas about the similarity of the composition and age of the basement of the Yurovka Swell and that of the Paleoarchaean Kukhtui Swell of the Okhotsk Massif.