On sedimentary waves at the western slope of the Middle Caspian Sea

Based on data of high-resolution acoustic profiling performed in the upper part of the sedimentary succession at the western continental slope of the Middle Caspian Sea (at a depth range from 100 to 400 m), we revealed specific accumulative forms of a running wave type. Examination of their morphology and inner structure allowed us to suggest two mechanisms of their formations: (a) by means of flank growth due to migration of channels of sedimentary flow associated with the Samur and other rivers and (b) due to flows of sedimentary material forming sedimentary waves.     

Experimental Model of the Formation of Nanophase Metallic Iron in the Lunar Regolith

Doklady Earth Sciences - One of the signs of “space weathering” on the Moon, including the effect of the solar wind and micrometeorite bombardment, is the formation of nanophase...     

Acid-soluble sulfides in the upper layer of the bottom sediments on the northeastern shelf of the Black Sea: Relation to the pollution and environmental aftereffects

The contents of labile (acid-soluble) sulfides were determined in the upper layer of the bottom sediments at 80 stations of the Caucasian shelf of the Black Sea. The maximum values of this parameter were registered in the black oozes deposited in the zones of intense pollution in Gelendzhik and Tsemess bays and in the shelf areas adjacent to large health resort objects and to seaports. The contents of acid-soluble sulfides in the sediments mentioned ranged from 400 to 900 mg S/dm³ of wet ooze. In the zones of moderate pollution, they ranged from 200 to 400 mg S/dm³ of the sediment. The rate of the sulfate reduction was as high as 10–40 mg S/dm³ of wet sediment per day. The data obtained show that the accumulation of labile sulfides in the upper layer of the bottom sediments on the shelf is directly related to the anthropogenic pollution and constitutes one of its most hazardous environmental aftereffects.     

Petrochemistry, geochemistry, and genesis of the Chek-Chikan gabbronorite Massif, southeastern framing of the North Asian craton

The Chek-Chikan Massif is a typical representative of basic magmatism, which is widely spread within the Dzhugdzhur-Stanovoi superterrane. The massif consists of gabbronorites, amphibole gabbros, gabbroanorthosites, and anorthosites. The geochemical similarity of the gabbronorites, amphibole gabbros, and anorthosites suggests their genetic link and allows us to consider them as products of intrachamber differentiation. The main geochemical peculiarity of this rock association is the high degree of the melt fractionation. The rocks of the considered massif are enriched in large ion lithophile elements such as Sr (424–1018 ppm) and Ba (50–754 ppm) and have moderate to low contents of such high-field strength elements as Nb (1–17 ppm), Hf (0.4–1.0 ppm), and Th (0.05–1.14 ppm). According to the model calculations, the initial melt had a basaltic composition and crystallized at a temperature of ∼1180 °C and pressure up to 4 kbar. The U-Pb zircon age of the massif is 203 ± 1 Ma. The geochemical peculiarities of the massif and its confinement to the northern framing of the eastern segment of the Mongol-Okhotsk fold belt make it possible to presume that its formation was related to either the activity of the Siberian plume, to one of the stages of closure of the Mongol-Okhotsk paleoocean in the rear part of subduction zone, or to the slab break off.     

Infrasonic Signals from Earthquakes of December 5, 2014, in the Water Area of Lake Hovsgol,Northern Mongolia

Doklady Earth Sciences - A comprehensive analysis of waveforms of seismic and infrasonic vibrations from the earthquake that occurred on December 5, 2014, in the water area of Lake Hovsgol was...     

Early Paleozoic monzodiorite–granodiorite association in the northeastern flank of the South Mongolia–Khingan orogenic belt (Nora–Sukhotinsky Terrane): Age and tectonic setting

The paper presents the results of U–Pb geochronological and geochemical studies of the rocks of the monzodiorite–granodiorite association in the northeastern flank of the South Mongolia–Khingan orogenic belt, which composes a tectonic block among the provisionally Lower Paleozoic volcanosedimentary complexes of the Nora–Sukhotinsky Terrane. It is shown that the studied rocks have similar petrographic features (with the presence of transitional varieties) and form common trends in the petrographic diagrams. This suggests that they are members of a single magmatic association. The geochemical features of the monzodiorites, quartz monzodiorites, and granodiorites, in particular their enrichment in large ion lithophile elements (LILE) and depletion in some HFSE, indicate their similarity with island-arc magmatic rocks. The presence of monzonites and quartz monzonites in the studied monzodiorite–granodiorite association along with high K, Rb, Th, and Pb concentrations gives reasons to believe that it formed in active continental margin or ensialic island-arc environments. The granodiorites of the monzodiorite–granodiorite associations of the Nora–Sukhotinsky Terrane are dated at 440 ± 10 Ma and may be considered as a fragment of the early Silurian active continental margin or ensialic mature island arc in the structure of the South Mongolia–Khingan orogenic belt.