Chlorinated hydrocarbons in seawater: Analytical method and levels in the northeastern Pacific

A method is described for analyzing nanogram quantities of chlorinated hydrocarbons from 1-1 samples of seawater. Seawater samples are pumped through a copper column containing a mixture by weight of 5% activated carbon powder, 10% MgO and 85% refined diatomaceous earth. The chlorinated hydrocarbons in the seawater are adsorbed or trapped on the column and subsequently eluted with 30% benzene in acetone (v/v) for analysis by gas-liquid chromatography.This procedure was used to analyze chlorinated hydrocarbon levels in samples collected off the southern California coast. We suggest that anthropogenic chlorinated hydrocarbons can be used for the investigation of large-scale ocean currents and mixing processes.     

Deformations and Manifestations of Degassing in the Sedimentary Cover of the Equatorial Segment of the West Atlantic: Implications for Lithospheric Geodynamics

Manifestations of fluids and deformations in the sedimentary cover, which are both factors of brightening (blanking anomalies) in seismoacoustic records, in the equatorial segment of the Atlantic coincide with the sublatitudinal zones of the activated passive parts of transform faults and with zones of lower gravity anomalies and higher values of remnant magnetization, which form as a result of serpentinization. The cause-and-effect sequence of intraplate phenomena includes: the contrasting geodynamic state → horizontal movements that form macrofractures → water supply to the upper mantle → serpentinization of rocks in the upper mantle → deformations associated with vertical uplift of basement and sedimentary cover blocks, coupled with fluid generation → and fluid accumulation in the sedimentary cover, accompanied by the formation of anomalies in seismoacoustic records. Based on the seismic data, we have identified imbricate-thrust deformations, diapir structures, stamp folds, and positive and negative flower structures, indicating the presence of strike-slip faults in the passive parts of transform faults. The general spatial distribution of deformation structures shows their concentration in cold mantle zones. Correlative comparison of the structural characteristics of deformations shows the direct relationship between the heights of structures and the development of serpentinization processes. As per the age of the basement, deformations range from 27–38 to 43–53 Ma; a quite thick sedimentary cover makes it possible to reveal them based on the characteristic types of seismoacoustic records. The formation of the Antilles arc ca. 10 Ma ago affected the equatorial segment of the Atlantic; it formed kink bands where lithospheric blocks underwent displacements with counterclockwise rotations, deformations related to compression and vertical uplift of crustal fragments, and local extension that favored degassing of endogenous fluids. Sublatitudinally oriented imbricate-thrust deformations with different vergences indicate irregularity and alternating strike-slip directions as blocks between fractures were laterally influenced.     

Nonlinear dynamics of gravity flows in sloping channels

Doklady Earth Sciences -     

Enhanced geochemical gradients in a marine shallow-water hydrothermal system: Unusual arsenic speciation in horizontal and vertical pore water profiles

The shallow marine hydrothermal vents near Ambitle Island in eastern Papua New Guinea discharge hot, slightly acidic, As-rich, chemically reduced fluid into cool, slightly alkaline, oxygenated seawater. Gradients in temperature, pH, and total As (As^T), among others, are established as the two aqueous phases mix. The hydrothermal fluid contained 900 μg/L As^T, almost exclusively present as the reduced As^III, while local seawater measured between 1.2 and 2.4 μg/L As, with approximately equal levels of As^III and As^V. Of particular interest in this study was As speciation and abundance in pore waters as a function of sediment depth and as a function of distance from the area of focused venting. With increasing distance, As^T concentration in the pore water decreased rapidly, but remained elevated up to 300 m from the area of focused venting when compared to a non-hydrothermal control site. As a function of depth (to 100 cm) As^T concentration in the pore water profiles was elevated and generally increased with depth. Surprisingly, aqueous As^V far exceeded aqueous As^III at almost all distances and depths investigated, while at the control site the As^III concentration exceeded that of As^V. In the Tutum Bay hydrothermal system, chemical disequilibria among As species provide potential metabolic energy for arsenite oxidizing microorganisms where hydrothermal fluid mixes with seawater near the vent orifice, and for arsenate reducing microorganisms with increasing distance and depth from the hydrothermal point source.     

The relation between geomagnetic pulsations and an increase in the fluxes of geosynchronous relativistic electrons during geomagnetic storms

The dynamics of the Pc5 and Pi1 pulsation characteristics and relativistic electron fluxes at geostationary orbit were comparatively analyzed for three nine-day intervals, including quiet periods and periods of geomagnetic storms. It was shown that relativistic electron fluxes increase considerably when the power of global Pc5 pulsations and the index of midlatitude irregular Pi1 pulsations increase simultaneously. The correlation between the characteristics of Pi1 and Pc5 geomagnetic pulsations and the level of the relativistic electron flux at geostationary orbit during the magnetic storm recovery phase were studied. It was shown that the correlation coefficient of the relativistic electron maximal fluxes during the magnetic storm recovery phase with the parameter of midlatitude Pi1 pulsations is slightly higher than such a correlation coefficient with the solar wind velocity.     

Recognition of the Cambrian Timan–Severnaya Zemlya orogen and timing of geological evolution of the North Kara sedimentary basin based on detrital zircon dating

New data on the ages of detrital zircons from folded basement rocks and cover sediments of the Severnaya Zemlya archipelago and Izvestiy TSIK islands have been obtained. The basement age is defined as Cambrian (pre-Ordovician). The Ordovician and Silurian sandstones were mainly formed by erosion of the basement rocks. The Devonian sandstones were formed by debris sourced from the Caledonian orogen. The Carboniferous–Early Permian molasse was formed simultaneously with the erosion of the Carboniferous granitoids and weathering of the Ordovician volcanic arc rocks and the Cambrian basement. The North Kara basin was formed in the Ordovician as a back-arc basin. It experienced its main compression deformations at the boundary of the Devonian and Carboniferous and in the Carboniferous.     

The assemblage quartz — Sillimanite — Garnet — Cordierite as an indicator of metamorphic conditions in the Daly Bay Complex,N.W.T.

If cordierite is treated as an anhydrous mineral, the composition of garnet and cordierite, coexisting with quartz and silliminate, depends on total pressure and temperature. Phase relations may be deduced by combining some available experimental work with several approximations. Assuming ideal ionic solution in garnet and cordierite, analyses of coexisting garnet and cordierite permit the determination of total pressure and temperature. Five rocks from the Daly Bay Complex, N. W. T., collected from locations up to 35 miles apart, indicate a range of 610–760 and 5.3–6.6 kb.