Polar Marine Geosurvey Expedition

Saint Petersburg, Russia

Polar Marine Geosurvey Expedition

Saint Petersburg, Russia
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Popov S.V.,Polar Marine Geosurvey Expedition | Polyakov S.P.,Arctic and Antarctic Research Institute | Pryakhin S.S.,Arctic and Antarctic Research Institute | Martyanov V.L.,Arctic and Antarctic Research Institute | Lukin V.V.,Arctic and Antarctic Research Institute
Earth's Cryosphere | Year: 2017

The main results of GPR sounding and ice core sampling carried out in the area of the Russian Mirny Station during the austral summer field season of 60th Russian Antarctic Expedition (2014/15) have been presented. The GPR data were collected at the frequencies of 270 MHz and 900 MHz. The total length of the profi les was 20 km. Five ice cores about 7 m long were selected. The upper part of the glacier was found to consist of a snow-firn layer and meteoric ice underneath. The effective permittivity values of the media were determined to be 2.13 and 3.0, accordingly. In the study area the snow-firn layer thickness varied between zero ("blue ice") and approximately 40 m.

Kuznetsov V.,Saint Petersburg State University | Maksimov F.,Saint Petersburg State University | Zheleznov A.,Saint Petersburg State University | Cherkashov G.,Institute for Geology and Mineral Resources of the Ocean VNIIOkeangeologia | And 2 more authors.
Geochronometria | Year: 2011

A radiochemical study was carried out on massive sulfides from Semyenov hydrothermal district at the Mid-Atlantic Ridge. New and published results provide evidence that 230Th/U ages obtained for massive sulfides are reliable. The sulfide deposits from the West, North-West, North-East, and East hydrothermal sites at the Semyenov hydrothermal district were formed between ~124 ka and ~37 ka ago. The hydrothermal activity might have started in the eastern part of the district and moved to the west by episodic ore formation. © 2011 Silesian University of Technology.

Richter A.,TU Dresden | Fedorov D.V.,FGUP Aerogeodeziya | Fritsche M.,TU Dresden | Popov S.V.,Polar Marine Geosurvey Expedition | And 7 more authors.
Journal of Glaciology | Year: 2013

Repeated Global Navigation Satellite Systems (GNSS) observations were carried out at 50 surface markers in the Vostok Subglacial Lake (East Antarctica) region between 2001 and 2011. The horizontal ice flow velocity vectors were derived with accuracies of 1 cma-1 and 0.5°, representing the first reliable information on ice flow kinematics in the northern part of the lake. Within the lake area, ice flow velocities do not exceed 2ma-1. The ice flow azimuth is southeast in the southern part of the lake and turns gradually to east-northeast in the northern part. In the northern part, as the ice flow enters the lake at the western shore, the velocity decreases towards the central lake axis, then increases slightly past the central axis. In the southern part, a continued acceleration is observed from the central lake axis across the downstream grounding line. Based on the observed flow velocity vectors and ice thickness data, mean surface accumulation rates are inferred for four surface segments between Ridge B and Vostok Subglacial Lake and show a steady increase towards the north.

Siegert M.J.,University of Edinburgh | Popov S.,Polar Marine Geosurvey Expedition | Studinger M.,Lamont Doherty Earth Observatory | Studinger M.,NASA
Geophysical Monograph Series | Year: 2011

Vostok Subglacial Lake is the largest and best known sub-ice lake in Antarctica. The establishment of its water depth (>500 m) led to an appreciation that such environments may be habitats for life and could contain ancient records of ice sheet change, which catalyzed plans for exploration and research. Here we discuss geophysical data used to identify the lake and the likely physical, chemical, and biological processes that occur in it. The lake is more than 250 km long and around 80 km wide in one place. It lies beneath 4.2 to 3.7 km of ice and exists because background levels of geothermal heating are sufficient to warm the ice base to the pressure melting value. Seismic and gravity measurements show the lake has two distinct basins. The Vostok ice core extracted >200 m of ice accreted from the lake to the ice sheet base. Analysis of this ice has given valuable insights into the lake's biological and chemical setting. The inclination of the ice-water interface leads to differential basal melting in the north versus freezing in the south, which excites circulation and potential mixing of the water. The exact nature of circulation depends on hydrochemical properties, which are not known at this stage. The age of the subglacial lake is likely to be as old as the ice sheet (~14 Ma). The age of the water within the lake will be related to the age of the ice melting into it and the level of mixing. Rough estimates put that combined age as ~1 Ma. Copyright © 2010 by the American Geophysical Union.

Skolotnev S.G.,Russian Academy of Sciences | Bel'tenev V.E.,Polar Marine Geosurvey Expedition | Lepekhina E.N.,Russian Academy of Sciences | Ipat'eva I.S.,Russian Academy of Sciences
Geotectonics | Year: 2010

Local U-Pb dating of zircons separated from various rocks in the crest zone of the Mid-Atlantic Ridge (MAR) and Carter Seamount (Sierra Leone Rise) is performed. Younger zircons formed in situ in combination with older xenogenic zircons are revealed in enriched basalts, alkaline volcanic rocks, gabbroic rocks, and plagiogranites. Only older zircons are found in depleted basalts and peridotites. Older zircons are ubiquitous in the young oceanic lithosphere of the Central Atlantic. The age of the younger zircons from the crest zone of the MAR ranges from 0.38 to 11.26 Ma and progressively increases receding from the axial zone of the ridge. This fact provides additional evidence for spreading of the oceanic floor. The rate of half-spreading calculated from the age of the studied zircons is close to the rate of half-spreading estimated from magnetic anomalies. The age of the younger zircons from Carter Seamount (58 Ma) corresponds to the age of the volcanic edifice. Older zircons make up an age series from 53 to 3200 Ma. Clusters of zircons differing in age reveal quasiperiodicity of about 200 Ma, which approximately corresponds to the global tectonic epochs in the geological evolution of the Earth. Several age groups of older zircons combine grains close in morphology and geochemistry: (1) Neoproterozoic and Phanerozoic (53-700 Ma) prismatic grains with slightly resorbed faces, well-preserved or translucent oscillatory zoning, and geochemical features inherent to magmatic zircons; (2) prismatic grains dated at 1811 Ma with resorbed faces and edges, fragmentary or translucent zoning, and geochemical features inherent to magmatic zircons; (3) ovoid and highly resorbed prismatic grains with chaotic internal structure and metamorphic geochemical parameters; the peak of their ages is 1880 Ma. The performed study indicates that older xenogenic zircons from young rocks in the crest zone of the MAR were captured by melt or incorporated into refractory restite probably in the sublithospheric mantle at the level of magma generation in the asthenosphere. It is suggested that zircons could have crystallized from the melts repeatedly migrating through the asthenosphere during geological history or were entrapped by the asthenosphere together with blocks of disintegrated and delaminated continental lithosphere in the process of breakup of the continents older than Gondwana. The variability in the age of older zircons even within individual samples may be regarded as evidence for active stirring of matter as a result of periodically arising and destroyed within-asthenospheric convective flows varying in orientation and scale. © 2010 Pleiades Publishing, Ltd.

Ewert H.,TU Dresden | Popov S.V.,Polar Marine Geosurvey Expedition | Richter A.,TU Dresden | Schwabe J.,TU Dresden | And 2 more authors.
Geophysical Journal International | Year: 2012

Based on the Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, the hydrostatic equilibrium (HE) condition for the subglacial Lake Vostok, East Antarctica, is evaluated. A digital elevation model (DEM) of the ice surface is derived by a regional crossover adjustment. The analysis of the DEM and its comparison with GPS derived ice-surface elevations and an ice-surface DEM based on radar altimetry data reveal an overall accuracy of better than ± 0.7 m for the lake area. The DEM is combined with an ice-thickness model and a regional geoid model to determine the deviation of the local ice-surface height from HE. For large parts of the lake, the ice sheet fulfils the HE. Our results reveal a strong positive deviation of about 10 m along the lake shoreline. In addition, positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio-echo sounding. In the southern part of the lake, we find a linear negative deviation (-4.0 m) which coincides with the convoy route from Vostok station to Mirny base. In addition to the DEM, relative biases for the ICESat laser operational periods are determined in the regional crossover adjustment. © 2012 The Authors Geophysical Journal International © 2012 RAS.

Pertsev A.N.,RAS Institute of Geology and Mineralogy | Bortnikov N.S.,RAS Institute of Geology and Mineralogy | Vlasov E.A.,Moscow State University | Beltenev V.E.,Polar Marine Geosurvey Expedition | Ageeva O.A.,RAS Institute of Geology and Mineralogy
Geology of Ore Deposits | Year: 2012

The oceanic core complexes and large-offset detachment faults characteristic of the slow-spreading Mid-Atlantic Ridge are crucial for the structural control of large hydrothermal systems, including those forming sub-seafloor polymetallic sulfide mineralization. The structural-geological, petrographic, and mineralogical data are considered for the oceanic core complex enclosing the Semenov-1, -2, -3, -4, and -5 inactive hydrothermal sulfide fields recently discovered on the Mid-Oceanic Ridge at 13°31′ N. The oceanic core complex is composed of serpentinized and talc-replaced peridotites and sporadic gabbroic rocks, however, all hydrothermal fields reveal compositional indications of basaltic substrate. The volcanic structures superposed on the oceanic core complex are marked by outcrops of pillow lavas with fresh quenched glass. Dolerites regarded as volcanic conduits seem to represent separate dike swarms. The superposed volcanic structures develop largely along the near-latitudinal high-angle tectonic zone controlling the Semenov-1, -2, -5, and -3 hydrothermal sulfide fields. The manifestations of hydrothermal metasomatic alteration are diverse. The widespread talcose rocks with pyrrhotite-pyrite mineralization after serpentinite, as well as finding of talc-chlorite metabasalt are interpreted as products of hydrothermal activity in the permeable zone of detachment fault. Chloritization and brecciation of basalts with superposed quartz or opal, barite, and pyrite or chalcopyrite mineralization directly related to the sub-seafloor sulfide deposition. The native copper mineralization in almost unaltered basalts at the Semenov-4 field is suggested to precipitate from ore-forming fluids before they reach the level of sub-seafloor sulfide deposition. Amphibolites with plagiogranite veinlets are interpreted as tectonic fragments of the highest-temperature portions of hydrothermal systems, where partial melting of basic rocks in the presence of aqueous fluid with formation of plagiogranitic melt is possible. Silicic rocks (plagiogranite, tonalite and diorite) revealed in the tectonic zone controlling the Semenov-1, -2, -5, and -3 hydrothermal sulfide fields are related to both plutonic and subvolcanic bodies and considered to be products of partial melting of basic rocks at deep levels of the hydrothermal systems. The hydrothermal fields differ in their structural position. The giant Semenov-4 field is located at the area where the hanging-wall basalt wedges out and the detachment fault zone reaches the oceanic floor. The range of relatively small Semenov-1, -2, -3, and 5 fields develops on the oceanic core complex massif, being localized in the superposed volcanic structures within the near-latitudinal steeply dipping tectonic zone. The structural control of the hydrothermal fields at 13°31′ N is also interpreted in different ways. For the Semenov-4 field, the ascending fluid flow can be related to the permeable detachment fault zone. The root zone of the hydrothermal system with a magmatic heater could have been localized at a significant distance beneath the axial spreading zone. For the other four relatively small fields, it is suggested that the ascending fluid flows and roots of the hydrothermal systems are controlled by the volcanic structures superposed on the oceanic ore complex within the steeply dipping tectonic zone. © 2012 Pleiades Publishing, Ltd.

Richter A.,TU Dresden | Popov S.V.,Polar Marine Geosurvey Expedition | Schroder L.,TU Dresden | Schwabe J.,TU Dresden | And 4 more authors.
Geophysical Research Letters | Year: 2014

The question whether Antarctica's largest lake, subglacial Lake Vostok, exchanges water is of interdisciplinary relevance but has been undecided so far. We present the potential pathway, outlet location, and threshold height of subglacial water discharge from this lake based on a quantitative evaluation of the fluid potential. If water left Lake Vostok, it would flow toward Ross Ice Shelf. Discharge would occur first to the east of the southern tip of the lake. At this location the bedrock threshold is 91 ± 23 m higher than the hydrostatic equipotential level of Lake Vostok. It is concluded that Lake Vostok is not likely to reach this level within climatic timescales and that no discharge of liquid water is to be expected. We show that in absence of the ice sheet the Lake Vostok depression would harbor a lake significantly deeper and larger than the present aquifer. Key Points Lake Vostok is not expected to discharge liquid water in climatic timescalesDischarge would lead from east of the lake's southern tip to Ross Ice ShelfLake Vostok would be significantly deeper and larger without ice sheet ©2014. American Geophysical Union. All Rights Reserved.

Beltenev V.E.,Polar Marine Geosurvey Expedition | Skolotnev S.G.,Russian Academy of Sciences | Rozhdestvenskaya I.I.,Polar Marine Geosurvey Expedition
Doklady Earth Sciences | Year: 2014

The whole-rock geochemistry and isotopic composition of the basalts dredged from the Mid-Atlantic Ridge (MAR) segment between the Mercury and Vema fracture zones during cruise 32 of the R/V Professor Logachev were studied. In addition to typical basalts with moderate petrochemical parameters, there are high-Ca and low-Na types of basalts representing higher degree melts and high-Fe varieties generated at great depths. The basalts derived by high degrees of melting exhibit a close spatial association with the central portions of three on-axis rises on the rift valley, which reach a height of 300–500 m above the floor of the valley and represent the loci of the subaxial mantle upwelling. The position of the Northern rise at the northern intersect of the Mercury transform fault is inconsistent with focused upwelling. The basalts with a more radiogenic Nd, Sr, and Pb composition are identified above the loci of the subaxial upwelling. They are compositionally similar to basalts, which have HIMU-like affinities and are interpreted to be derived under the influence of the 14° N plume between the Marathon and Cape Verde fracture zones. The relatively high isotopic ratios of these basalts anti-correlate with their low (La/Sm)n values typical of the depleted N-MORB-type basalts. The results show that enriched melts contributing to basalts from the central portions of on-axis rises are associated with one of the flows of plume material channeled from the 14° N anomaly to these rises. The partial melting of the rising plume material causes the formation of localized accumulation of magmas at structural barriers and creates new centers of upwelling, which, being enhanced by the regular upwelling, lead to increased magma production and changes in the composition of basalts. © 2014, Pleiades Publishing, Ltd.

Egorov M.S.,Polar Marine Geosurvey Expedition | Semenov V.S.,Russian Academy of Sciences | Alekseev N.L.,Polar Marine Geosurvey Expedition
Geology of Ore Deposits | Year: 2015

This paper presents results of the study of norite complex from the Vestfold Hills (East Antarctica) containing a low-sulfide type of mineralization. The ore mineralization occurs in specific rock types and along the contact of norites the host rocks. Three mineralization types: Fe–Ni–Cu sulfide, oxide, and PGE-bearing are known. PGE mineralization is represented by palladium–bismuth tellurides of the michenerite–merenskyite series. A model of ore-formation succession and a concept of the origin of low-sulfide PGE mineralization by means of crystallization and subsequent evolution of monosulfide and intermediate solid solutions have been developed. © 2015, Pleiades Publishing, Ltd.

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