OS4A-1:NEW GAS HYDRATES IN THE OKHOTSK AND JAPAN SEAS (OUTCOMES FROM 2012 AND 2013): MANIFESTATIONS OF PACIFIC GAS HYDRATE BELT

Shakirov RENAT1, Obzhirov ANATOLY1, Shoji HITOSHI2, Young Keun JIN3, Syrbu NADEZHDA1,4, Nguyen Nhu TRUNG4
1. V.I. Il'ichev Pacific Oceanological Institute FEB RAS, ,Russia; 2. New Energy Resources Research Center, Kitami Institute of Technology, Japan; 3. Korea Polar Research Institute, KORDI, Korea; 4. Joint Vietnam-Russia Laboratory for marine science and technology, Institute of Marine Geology and Geophysics, Vietnam Academy of Science and Technology, Vietnam

    Margins of Pacific Ocean present numerous gashydrates sites, distributed as Gashydrates Provinces (referred to the offshore areas) which can be combined to Pacific Gashydrate Belt. In the paper we present a western segment of this global structure. Gas (mainly methane) hydrates accumulation induced by varies active geological features determined by geodynamic and tectonic type and seismic state’s of Pacific and adjoining lithosphere plate’s borders. Bering Sea, Okhotsk Sea, Japan Sea, East-China Sea, South-China Sea (East Vietnam Sea) and southward to New Zealand offshore exposed methane hydrates distribution in sediments. Hydroacoustic, seismics, coring were a prime methods applied to gashydrate searching and exploration. Methane hydrates was explored since 86-th (Okhotsk Sea). Gas hydrates supplying fluid within the thick Cenozoic sediment basins (up to 10 km thickness) are linked to multiple hydrocarbon accumulations: mainly oil and gas deposits, and gas (methane) hydrates – proved for the Bering, Okhotsk and Japan Seas. Methane origin discussed as mixture of thermogenic and biogenic gases. Gas hydrate occupies up to 45% of pore volume. BSR was found globally, but this border means not gas hydrate stability zone only. Methane resources trapped in Western Pacific gas hydrates can be estimated based on latest investigations at least for 5-7×10*14 cubic meters. In 2012 on the western side of Kurile Basin on 1220 m water depth we found new gashydarets – first proved gashydrates on the south of Okhotsk Sea. In this area the highest gas flux of 2200 m above see floor in the World Ocean were found by us also. Another discovery – we found first in the world experience gashydrates in north of Japan Sea on the depth of 322 m gashydrates supplied by thermogenic methane d in Tatar Straight – most shallow gas hydrates in the World Ocean. As we found from Okhotsk and Japan seas, gashydrates also accompanied by helium anomalies which are linked to the deep geological structures (outcomes from Russia-Japan-Korea SSGH Project under coordination of Prof. H. Shoji, Dr. Y.K. Jin and Prof. A. Obzhirov). Those results were detailed and confirmed in 2013 by 62 Cruise of RV “Akademik M.A. Lavrentyev”. Finally, we discussed a Pacific Gas Hydrate Belt as a global circum Pacific structure which also related to the oil-gas and coal accumulations and affected by seismotectonic and volcanic activity.