Deep Structure Deep Structure Research Research of the Earthof the Earth after after the International the International Geophysical YearGeophysical Year(Geotraverse (Geotraverse Project Project and and InterMARGINS)InterMARGINS)

A.G.Rodnikov, N.A.Sergeyeva, A.G.Rodnikov, N.A.Sergeyeva, L.P.ZabarinskayaL.P.Zabarinskaya

Geophysical Center, Russian Academy of Sciences

Moscow, Russia

Karl Weyprecht(1838 -1881)

Austro-Hungarian navy officer, Arctic explorer who discovered Franz Josef Land, an archipelago north of Russia, and who advanced a successful scheme for international cooperation in polar scientific investigations but died before it first occurred in 1882-1883 .

First International Polar Year (1882-1883)

The Bureau of the special IGY Committee in Brussels in 1957.

M. Nikolet (Belgium), General Secretary of the Committee, ( in the center); to the left of him:L. Berkner (USA), Vice-President, V. V. Beloussov (USSR), Bureau member and later Vice-President, and to the right of himJ. Kulon (France) Bureau member, C. Chapman (Great Britain), Committee President

The International Geophysical Year 1957 – 1958 inspired by the IPY and occurred 75 years after the first IPY

Emblem of IGY 1957-1958

Academician I. P. Bardin, Chairman of the Soviet Committee for IGY, Vice-President of the USSR Academy of Sciences informs on the conference for press that the Soviet Union intends to launch the artificial satellite of the Earth during the International Geophysical Year (IGY). Barcelona, 1955.

The International Geophysical Year 1957 – 1958

Non-magnetic schooner “Zarja”

Russian non-magnetic oceanographic research vessel ZARJA (or ZARYA). Built 1952 in Finland, 333grt, wood auxiliary three-masted schooner.

Drifting station SP-7* conducting observations in the Arctic regions from April 23, 1957 till April 11, 1959, Distance = 3520 km

North Pole Drifting Station SP-7

*Soviet and now Russian drifting ice stations are named "Severnyy polyus“

(Russian: «Северный полюс»; English: "North Pole") and are abbreviated SP (Russian: «СП»; English: "NP"). Each station is assigned an ordinal number.

Soviet and American Researches

in the South Pole

Results of IGY 1957-1958

Press-conference on IGY results. Professor V. V. Beloussov is speaking. From left to right A. D. Powsner, N. V. Shebalin, N. V. Pushkov and V. A. Magnitsky.

Moscow, 1963.

After the International Geophysical Year 1957 – 1958

New ProjectsNew Projects

Ocean Margins

Ocean Margins

Gulf of California (San Andreas Fault Observatory at Depth)

Drilling the San Andreas Fault at DepthThe first of these drilling projects is making a borehole next to the San Andreas fault near Parkfield, California, at a depth of about 3 kilometers. Drilling began in 2004 with a vertical hole going down 1500 meters, then curving toward the fault zone. The 2005 work season extends this slanting hole all the way across the fault, and is being followed by two years of monitoring.

Project “CRISP” (Costa Rica Seismogenesis Project)

InterMARGINS, Newsletter No 4, 2004

CRISP is a project to understand the initiation of large earthquakes and seismic rupture by drilling on either side of the updip limit of seismogenesis. The shallow dip of the subduction zone off southern Costa Rica and relatively high subducting plate temperature cause this seismogenic environment to rise to drilling depth.Materials, temperature, lithification, fluid flow and chemical changes that occur down the subduction zone are hypothesized to cause the transition from stable to unstable slip that ultimately results in great earthquakes. Along the erosional convergent margin of Costa Rica the seismogenic plate interface is surrounded by eroded debris rather than by trench sediment.

New New Subduction Subduction

Zone inZone inthe Japan the Japan

SeaSea

http://www.gcras.ru/index_e.html

Geophysical Center of the Russian Academy of Sciences took part in the

fundamental researches on the deep cross-sections of the

lithosphere through the marginal seas in a transition zone from Asian continent to the Pacific

Ocean investigated under the Geotraverse International

Projectand InterMARGINS

Area of Area of ResearchResearch

The deep structure of the Eurasia-Pacific transition zone was investigated under the Geotraverse Project and InterMARGINS along the deep sections of the tectonosphere, including the lithosphere and the asthenosphere. The first geotraverse, was preparated in cooperation with Japanese geoscientists, crossed the region of the Japan Sea. The second geotraverse, carried out in cooperation with Japanese and Chinese geoscientists, crossed the region of the Philippine Sea and the North China Plain. The third geotraverse crossed the region of the Okhotsk Sea.

The Eurasia-The Eurasia-Pacific Pacific Transition Transition ZoneZone

SeismicitySeismicity

DDistributioistributionn

ofofHeat Heat flowflow

The Eurasia-The Eurasia-Pacific Pacific Transition Transition ZoneZone

The Japan Sea The Japan Sea GeotraverseGeotraverse

Seismic Profile along Seismic Profile along the Philippine Sea the Philippine Sea

GeotraverseGeotraverse

The North China Plain-The North China Plain-Philippine SeaPhilippine Sea

Geotraverse Geotraverse

There are correction between asthenosphere and formation of deep basins. Under Paleogine West Philippine Basin the asthenosphere lies at the depth of 50-70 km. Under the Neogene Parece Vela basin the asthenosphere lies at the depth of 30 km. Under the Mariana Trough the asthenosphere reaches the crust causing active tectonic and magmatic processes.

The Okhotsk Sea GeotraverseThe Okhotsk Sea Geotraverse

Tectonic Tectonic SSchemecheme

Compiled from the data of Maruyama et al., 1997;

Cruise ..., 2000; Zonenshain et al., 1990;Kiratzi and Papazachos,

1996;

Rodnikov et al., 2001

The Okhotsk Sea region is a large Lithospheric plate of the transition zone from Asian continent to the Pacific. It is located in the contact zone of three Lithospheric plates : Eurasian, North American and the Pacific. Arrows show plate movement direction.

Deep Deep Structure of Structure of

Deryugin Deryugin Basin and Basin and

North North Sakhalin Sakhalin

BasinBasin(Sea of (Sea of

Okhotsk)Okhotsk)

The Deryugin Basin was formed in the Cenozoic at the site of the ancient deep trench after the subduction of the Okhotsk Sea Plate under Sakhalin had been completed in the Early Paleogene. The North Sakhalin oil and gas basin was formed at the site of the Late Cretaceous bark-arc basin. The Deryugin basin is located above a hot plume in the mantle that is asthenospheric diapir of partial melting revealed at a depth of 25 km. The west side is bounded by ophiolite belt of ultramafic magmatic rocks, which confine an ancient (K2-Pg) paleosubduction zone separating Deryugin Basin from North Sakhalin basin.

The Upper Mantle for the Sea The Upper Mantle for the Sea of Okhotskof Okhotsk

Seismic tomography model of the upper mantle in the Okhotsk Sea (Bijwaard, 1998). There are two subduction zones: ancient (Triassic-Cretaceous), the subduction Okhotsk Sea plate under Asian Continent and recent, the subduction Pacific plate under Kamchatka.

Asthenosphere

andMoho

beneaththe Sea of Okhotsk

The Model of the of the Lithosphere structure of the Sea of Okhotsk. A-the Okhotsk Sea floor relief. B - Moho. C - asthenosphere. The asthenosphere in the upper mantle of the Sea of Okhotsk is located at a depth of 50 - 70 km and beneath the Northwestern Pacific basin it is revealed at a depth of 100 km. Diapirs of partial melting come off the asthenosphere, reaching a depth of 25 - 30 km beneath the Tatar Strait Trough, Deryugin Basin and Kuril Basin and causing an active tectonic regime manifested in volcanic, seismic and hydrothermal activity. Red color shows the area of magma formation.

A

B

C

The Okhotsk Sea GeotraverseThe Okhotsk Sea Geotraverse

The Okhotsk Sea Geotraverse crosses the Sikhote Alin, Sakhalin, Kuril Basin, Kuril Island Arc and Pacific. The thickness of the crust varies from 35-40 km under Sakhalin and the Kuril Islands to 8-10 km under the Kuril Basin. In the Cenozoic, the large part of the sedimentary basins was formed. The asthenosphere in the upper mantle is separated mostly from geothermal data. The upper surface of the asthenosphere is an isotherm 1000 -1200C, the temperature of partial melting. The asthenosphere is located in the upper mantle of the Sea of Okhotsk at a depth of 50-70 km. From the asthenosphere the diapirs go off that reach a depth of 20-30 km beneath the sedimentary trough of Tatar Strait and Kuiril Basin, causing an active tectonic regime.

ConclusionsConclusions A distinctive feature of the transitional zone between the Eurasian continent and the Pacific

Ocean is the presence of an asthenosphere in the upper mantle. The tectonically active regions, such as the island arcs and the rifts of the marginal seas,

correlate with a thick, magma-generating asthenosphere. The asthenospheric diapirss are marked on the surface by rift formations and mainly tholeiitic magma eruption.

The asthenosphere resides in a depth of 50-80 km under the old Paleogene deep basins of the marginal seas, at about 30 km under the Neogene basins, and at a depth of 10-20 km under the Pliocene-Quaternary and recent inter-arc basins, causing the breaks of the lithosphere, the formation of rifts, basalt lava eruptions, and hydrothermal activity

Rifts in the marginal seas and island arcs may by accompanied by intense mineralization. The combination of high heat flow, volcanicity and hydrothermal activity in these structures, in the past and at present, can lead to the formation of sulfides and non-metalliferous mineral deposits.

The formation of the sedimentary basins is associated with recent and ancient subduction zones. The sedimentary basins are characterized by:

- rift structures or spreading centers at their basement; - active magmatism at the initial stage of formation; - hydrothermal processes associated with sulphides formation; - high density of heat flow caused by the uplift of the asthenosphere to the crust; - localization of asthenosphere diapirs in the upper mantle; - asthenospheric diapirs are channels, along which hot mantle fluids from the asthenosphere

penetrate into the sedimentary basins and other units transition zone.