Acoustic Monitoring of Gas Emission Processes in the Arctic Shelf Seas

Oceanology - The emission of natural gas from the seafloor to the surface in shelf areas of the Arctic seas is of increasing interest among researchers. Recently, various types of acoustic...     

New isotope–geochemical and mineralogical data on the ultramafic xenoliths in the volcanic rocks of the Kamchatka–Koryak region: Two types of mantle protolith in the modern island-arc system

The paper presents new isotope–geochemical and mineralogical data on mantle xenoliths of the “island-arc” (Avacha, Shiveluch, and Kharchinsky volcanoes) and “within-plate” (Valovayam River, Cape Navarin, and Bakening Volcano areas) types. In terms of paragenesis and mineral composition, the “islandarc” xenoliths correspond to the olivine–plagioclase depth facies, while the “within-plate” xenoliths came from spinel lherzolite to wehrlite facies, which is transitional to the olivine–plagioclase equilibrium. The majority of the “within-plate” xenoliths are enriched in high-field-strength elements (Ti, Nb, Hf, Zr, Yb). The “island-arc” xenoliths in general are depleted in REE, while the “within-plate” xenoliths are enriched in all REE. The former have low Pb isotope ratios, being in isotope equilibrium with lower crustal basites, while most of the latter group are enriched in radiogenic Pb. The island-arc xenoliths are of magmatic origin and were derived from the sublithospheric crust–mantle mixture, while the “within-plate” xenoliths reflect the composition of the asthenospheric mantle source. The primary appearance of the xenoliths is obliterated by secondary recrystallization and metasomatic reworking.     

Expected geological and geomorphological risks along the Northern Sea Route

Degradation of the underwater multiyear permafrost rocks (UMPR) together with intensification of thermal abrasion processes in the coasts are global risks on a planetary scale. Changes in the physical properties of sediments can occur after degradation of the UMPR and can lead to unpredictable consequences especially in the regions of technical development. Drifting ice bottom exaration (ice plucking of bottom sediments), which is increasing based on the data of recent expeditions, is no less dangerous. These processes are hazardous for practically all types of activity.     

Inverse modeling approach for obtaining kinetic parameters of diffusion-controlled metamorphic reactions in the Kharlovo Contact Aureole (South Siberia, Russia)

Summary A new approach for deriving kinetic parameters of diffusion-controlled metamorphic reactions is described. It is based on comparison of models of temperature field evolution near a cylindrical intrusion and observable chemical changes in biotite at the contact aureole of the Kharlovo massif. Unlike other methods used to construct quantitative models of reactions which produce distinctly expressed zoned microtextures, the proposed approach allows better understanding of the processes occurring in texture-homogeneous rocks, where complete consumption of some reactant mineral phases prevent accurate reconstruction of the metamorphic process. The calculations yielded estimates of the effective rates of metamorphic reactions (10⁻¹² s⁻¹) and the effective diffusion coefficient (5.29 × 10⁻¹⁶ cm² s⁻¹). These values are consistent with experimentally and theoretically derived estimates of solid-state diffusion, including grain-boundary diffusion.

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Zusammenfassung Inverse Modellierung zur Bestimmung kinetischer Parameter diffusionskontrollierter metamorpher Reaktionen in der Kontaktaureole von Kharlovo (Südsibirien, Ru?land) Ein neuer Ansatz zur Herleitung kinetischer Parameter diffusionskontrollierter metamorpher Reaktionen wird beschrieben. Er basiert auf einem Vergleich der Modelle für die Temperaturentwicklung um eine zylindrische Intrusion mit beobachtbaren ?nderungen im Chemismus von Biotit in der Kontaktaureole des Kharlovo Massivs. Im Unterschied zu anderen Methoden, die quantitative Modelle von Reaktionen mit deutlich zonierten Mikrotexturen verwenden, erlaubt dieser Ansatz ein besseres Verst?ndnis der Prozesse in texturell homogenen Gesteinen, in denen die vollst?ndige Reaktion einiger Reaktanden (Mineralphasen) sonst die Rekonstruktion des Metamorphoseprozesses verhindert. Die Berechnungen erlauben eine Absch?tzung der metamorphen Reaktionsraten und des effektiven Diffusionskoeffizienten . Diese Werte sind mit experimentell und theoretisch ermittelten Werten der Diffusion in Festk?rpern, einschlie?lich der Diffusion entlang von Korngrenzen, konsistent.

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Received July 14, 1998; revised version accepted June 28, 2000     

Sedimentary Waves of the Southeastern Barents Sea Shelf (Kanin Peninsula–Cheshskaya Bay)

Oceanology - Sedimentary waves are represented by a series of wavelike accumulative features with various degrees of morphological expression. These morphological forms are superimposed on the...     

Geological and Geophysical Studies on Cruise 41 of the R/V Akademik Nikolaj Strakhov in Arctic Seas in 2019

Oceanology - Abstract—The article briefly describes the results of integrated geological, geophysical, and hydrophysical studies on the shelves of the Barents and Kara seas. The research was...     

Modern Mapping of the Seabed Relief Using the Example from the NE Black Sea

Oceanology - Data on seafloor bathymetry are necessary for marine geology and geomorphology, cartography and paleogeography, geoecology and hydroacoustics, and other applied research areas....