Analysis and interpretation of anomalous conductivity and magnetic permeability effects in time domain electromagnetic data: Part II: Sμ-inversion

In the paper by Pavlov and Zhdanov [J. Appl. Geophys. (2001)], we demonstrated that anomalous magnetic permeability of an ore body could result in measurable anomalous effects in TDEM data, which can be used in geophysical exploration. In the current paper, we develop a new method of TDEM data interpretation, which allows simultaneous reconstruction of both electrical and magnetic properties of the rocks. The method is based on a generalization of the S-inversion technique [66th Ann. Int. Mtg., Soc. Expl. Geophys., Expanded Abstr. (1996) 1306; 68th Ann. Int. Mtg., Soc. Expl. Geophys., Expanded Abstr. (1998) 473; J. Appl. Geophys. (1999)] for models containing thin sheets with anomalous conductivity and anomalous magnetic permeability. We call this method Sμ-inversion. Numerical 3-D modeling results demonstrate that Sμ-inversion provides useful information about both subsurface conductivity and magnetic permeability distributions. It can be used as a new tool for imaging TDEM data in mineral exploration.     

Analysis and interpretation of anomalous conductivity and magnetic permeability effects in time domain electromagnetic data: Part I: Numerical modeling

Time domain electromagnetic (TDEM) response is usually associated with eddy currents in conductive bodies, since this is the dominant effect. However, other effects, such as displacement currents from dielectric processes and magnetic fields associated with rock magnetization, can contribute to TDEM response. In this paper we analyze the effect of magnetization on TDEM data. We use a 3-D code based on finite-difference method, developed by Wang and Hohmann [Geophysics 58 (1993) 797], to study transient electromagnetic field propagation through a medium containing bodies with both anomalous conductivity and anomalous magnetic permeability. The remarkable result is that the combination of anomalous conductivity and permeability within the same body could increase significantly the anomalous TDEM response in comparison with purely conductive or purely magnetic anomalies. This effect has to be taken into account in interpretation of TDEM data over electrical inhomogeneous structures with potentially anomalous magnetic permeability.     

Composition and origin of holotype Al‐Cu‐Zn minerals in relation to quasicrystals in the Khatyrka meteorite

We investigated the khatyrkite–cupalite holotype sample, 1.2 × 0.5 mm across. It consists of khatyrkite (Cu,Zn)Al₂, cupalite (Cu,Zn)Al, and interstitial material with approximate composition (Zn,Cu)Al₃. All mineral phases of the holotype sample contain Zn and lack Fe that distinguishes them from khatyrkite and cupalite in the Khatyrka meteorite particles (Bindi et al. 2009 , 2011 , 2012 , 2015 ; MacPherson et al. 2013 ; Hollister et al. 2014 ). Neither highly fractionated natural systems nor geo‐ or cosmochemical processes capable of forming the holotype sample are known so far. The bulk chemistry and thermal history of khatyrkite–cupalite assemblage in the holotype sample hint for its possible industrial origin. Likewise, the aluminides in the Khatyrka meteorite particles may also be derived from industrial materials and mixed with extraterrestrial matter during gold prospecting in the Listvenitovy Stream valley.     

Wide-band high linearity active dipole for low frequency radio astronomy

We have developed an active dipole that is intended for use in new generation low frequency array applications. The preamplifier of the active dipole has very high linearity (input IP2 = 70 dBm, input IP3 = 31 dBm) and low noise temperature (100?C360 K). The frequency dependence of the dipole impedance and the match between the dipole and preamplifier have been optimized to achieve Galactic noise limited operation. The ratio between the antenna temperature due to Galactic noise and the noise temperature of the preamplifier is 10 ± 1.5 dB over the whole 10 to 70 MHz range. The total cost of the active cross-dipole is 220 euro.     

The Dnepr Canyon: evidence for a continuous submarine channel link between the outer shelf and the deep-sea basin of the northwestern Black Sea

Multibeam bathymetric surveys and single-beam profiles were collected in 2003–2010 from aboard the Ukrainian RV Professor Vodyanitskiy (cruises PV-58 and PV-60, 2003 and 2004), and the German RV Meteor (cruise M-72, legs 1 and 4, 2007) and RV Maria S. Merian (cruise MSM-15, leg 2, 2010) along the continental margin of the NW Black Sea. Integrating published, reprocessed and novel data has revealed the existence of a major continuous channel extending from the Dnepr paleo-delta into greater water depths. It is more than 90 km long, 1.1 km wide and up to 125 m deep. On the upper slope (120–960 m water depth), a number of smaller channels merge into the large, Y-shaped Dnepr Canyon, which then continues obliquely downslope via this submarine channel to at least 1,815 m water depth off the Crimean continental margin, NW Black Sea. The channel could be an important, hitherto unknown link between the shallow oxic and deep anoxic environments of the Black Sea, along which sediment and organic matter could be funneled into the deep-sea basin. This would have far-reaching implications for investigations dealing with marine geology and biology, climate change, as well as oil and natural gas exploitation. The unusual alignment of the channel along the margin of the basin, as well as the location and mode of channel termination in deeper waters deserve future research.     

Thermodynamic studies of pyrrhotite-pyrite equilibria in the Ag-Fe-S system by solid-state galvanic cell technique at 518-723 K and total pressure of 1 atm

The reaction FeS₂(cr) + 2Ag(cr) = ‘FeS’(cr) + Ag₂S(cr) was studied by measuring the temperature dependence of the electromotive force (EMF) of the all-solid-state galvanic cell with common gas space:

(-)Pt|Ag|AgI|Ag₂S,‘FeS’,FeS₂|Pt(+)     

Collision of the Kronotskiy arc at the NE Eurasia margin and structural evolution of the Kamchatka–Aleutian junction

Structural evolution of the Kamchatka–Aleutian junction area in late Mesozoic and Tertiary was generally controlled by (1) the processes of subduction in Kronotskiy and Proto-Kamchatka subduction zones and (2) collision of the Kronotskiy arc against NE Eurasia margin. Two structural zones of the pre-Pliocene age and six structural assemblages are recognized in studied region. 1: Eastern ranges zone comprises SE-vergent thrust folded belt, which evolved in accretionary and collisional setting. Two structural assemblages (ER1 and ER2), developed there, document shortening in the NW–SE direction and in the N–S direction, respectively. 2: Eastern Peninsulas zone generally corresponds to Kronotskiy arc terrane. Four structural assemblages are recognized in this zone. They characterize (1) precollisional deformations in the accretionary wedge (EP1) and in the fore-arc basin and volcanic belt (EP2), and (2) syn-collisional deformation of the entire Kronotskiy terrane in plunging folds (EP3) and deformations in the foreland basin (EP4). Analysis of paleomagnetic declinations versus present day structural strike in the Kronotskiy arc terrane shows that originally the arc was trending from west to east. Relative position of the accretionary wedge, fore-arc basin and volcanic belt, as well as northward dipping thrusts in accretionary wedge indicate, that a northward dipping subduction zone was located south of the arc. The accretionary wedge developed from the Late Cretaceous through the Eocene, and it implies that the subduction zone maintained its direction and position during this time. It implies that Kronotskiy arc was neither a part of the Pacific nor Kula plates and was located on an individual smaller plate, which included the arc and Vetlovka back-arc basin. Motion of the Kronotskiy arc towards Eurasia was connected only with NW-directed subduction at Kamchatka margin since Middle Eocene (42–44 Ma). Emplacement of the Kronotskiy arc at the Kamchatka margin occurred between Late Eocene and Early Miocene. This is based on the age of syn-collisional plunging folds in Kronotskiy terrane, and provenance data for the Upper Eocene to Middle Miocene Tyushevka basin, which indicate in situ evolution of the basin with respect to Kamchatka. Collision was controlled by the common motion of the Kronotskiy arc with Pacific plate towards the northwest, and by the motion of the Eurasian margin towards the south. The latter motion was responsible for the southward deflection of the western part of the Kronotskiy arc (EP3 structures), and for oblique transpressional structures in the collisional belt (ER2 structures).     

First Finds of Platinum and Palladium Minerals in Sulfide Ores of the Khudolaz Intrusive Complex (Southern Urals)

Forms of occurrence of platinum (sperrilite, moncheite) and palladium (Sb-michenerite, Pd–Bi phase) minerals in intrusive rocks of the Khudolaz differentiated complex have been studied. Platinum minerals were identified in disseminated Cu–Ni sulfide ores from ultramafic olivine–hornblende rocks of the Khudolaz complex, whereas palladium minerals were found in ores from olivine–hornblende gabbroids. The structural arrangement of grains as inclusions in sulfides of the primary magmatic association testifies that they were formed as a result of segregation of platinum group elements, which partitioned into the composition of sulfides during low-temperature mineral formation process at the late-magmatic stage.     

Dynamics of carbon pools in post-agrogenic sandy soils of southern taiga of Russia

Background  

Until recently, a lot of arable lands were abandoned in many countries of the world and, especially, in Russia, where about half a million square kilometers of arable lands were abandoned in 1961-2007. The soils at these fallows undergo a process of natural restoration (or self-restoration) that changes the balance of soil organic matter (SOM) supply and mineralization.