Evolution of the Seven Devils Volcanic Arc and Period of Amalgamation with the North American Craton Based on Zircon U/Pb Geochronology and Hf Isotope Geochemistry of Intrusions in the Seven Devils Mountains,Western Idaho (USA)

Geotectonics - The Seven Devils Mountains are located in the Wallowa-Whitman National Forest in western Idaho. These mountains expose a geologically complex and variably metamorphosed terrane which...     

Inverted Barrovian Metamorphic Zones in the Poly-Deformed Domains of the Western Wadi Allaqi Shear Zone (South Eastern Desert,Egypt): Geochemical and Structural Constraints

Geotectonics - Poly-deformed late-Proterozoic metamorphic domains covering Um Ashira area at the western segment of Wadi Allaqi shear zone, South Eastern Desert of Egypt, show evidences of inverted...     

Content and Composition of Organic Compounds in Suspended Particulate Matter and Bottom Sediments in the Kara Sea during the Period of Seasonal Ice Melting

Doklady Earth Sciences - The first data on the content of organic compounds (OCs), i.e., Corg, lipids, and hydrocarbons (aliphatic (AHCs) and polycyclic aromatic (PAHs)) in the suspended...     

Age and growth rates of ferromanganese concretions from the gulf of Finland derived from 210Pb measurements

The formation of ferromanganese concretions on continental shelves is a widespread recent biogeochemical process, which is particularly intense in the Baltic Sea. The proposed new technique for dating ferromanganese concretions is based on the equilibrium ²¹⁰Pb, which is produced immediately within them due to the decay of ²²⁶Ra, which is intensely sorbed by concretions from the seawater. This method is principally different from the traditional dating of bottom sediments using nonequilibrium ²¹⁰Pb, which represents a decay product of atmospheric Ra. A mathematical tool for the calculation of the concretion ages is proposed. The latter is used for calculating the ages and growth rates of ferromanganese concretions belonging to two morphological varieties. The age and average growth rates of spheroidal concretions are estimated to be 670–850 years and 0.014 mm/year, respectively. The central part of a pancake-shaped concretion is dated back to 2500–3800 years, and its calculated respective horizontal and vertical growth rates are approximately 0.028 and 0.004 mm/year.     

Statistical study of the north–south asymmetry of the solar differential rotation based on various solar structures during 1966–1985

The time variation and latitude dependence of the solar rotation are found using observational data on Hα filaments and compact magnetic features with different polarities during solar activity cycles 20 and 21 (1966–1985). Statistical analysis of the observational data shows that there is a north–south asymmetry in the rotation, both for the Hα filaments and for compact magnetic features (structures) with negative and positive polarities. The N-S asymmetry in the differential rotation of the Hα filaments and the compact magnetic features with both polarities shows up quite distinctly in solar activity cycles 20 and 21, but the asymmetry for the compact magnetic features with positive polarity is comparatively lower in cycle 21. The confidence level is lower the compact magnetic features with positive polarity than for the compact magnetic features with negative polarity.     

Isotopes of sulfide and sulfate sulfur in nitrogen hot springs of the Bauntov group (Baikal Rift Zone)

Doklady Earth Sciences -