7-3. Questions and Recommendations for Future Research
0. Khlystov, M. De Batist, A. Ohzhirov, B, Baranov, Y. K. Jin and S. Yamashita
By 2010 year shallow gas hydrates accumulations were discovered within 12 mud volcanoes
(from among 14 known mud volcanoes in the Lake Baikal area) using newly elaborated geological
and geophysical indicators of search for gas hydrates. All sampled gas hydrates were located in the
clay part of the cross-section, namely mud volcano breccia. However, during the past two years in
places of gas discharge, gas hydrates were sampled not only in the clay and mud volcano breccia. but
in the diatom layer, which do not show evidence of mud volcano activity (Fig 7-3-1).
Therefore for reconnaissance of such accumulations new searching methods should be
develop. Similar accumulations of gas hydrates in the diatom layer have been well studied in the
North-Eastem Sakhalin slope of the Okhotsk Sea. Also in 2010 year, gas hydrates were found in an
inactive mud volcano Novosibirsk. A distinctive feature of this volcano is that mud volcano flows are
covered by a layer ofpelagic sediments. It could indicate that this volcano is recently non-active.
Gas hydrate:
Goloustnoe
seep site
In diatom ooze
In clay part
Fig. 7-3-1 Photos of flare and samples of gas hydrates in the diatom ooze and clay layers.
1. AreAere any geological or geophysical indicators for hydrates prospecting in the diatom layer of
the OkhotskSea, and how they could be used in places of only gas discharge for hydrates searching at
Lake Baikal?
In the Okhotsk Sea hydrates have been searching only in places where gas flares and
anomalies have appeared on echosouder record and side-scan sonar mosaic, correspondently.
Geological (lithological) indicators of hydrates in sediments are the presence of carbonates and
increasing of the gas saturation in a core, just it is a case when accumulation of the hydrates were
found in the diatom layer.
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Since the Lake Baikal cores
sites of methane discharge may contain carbonates, these
search indicators can be used for reconnaissances of the hydrates in an areas where gas seeps occurred
without the existence of mud volcano.
2. What is the evidence of active or dormant mud volcano?
Only eruption of mud material, rather than gas discharge, could indicate on recent activity of
the mud volcano. In the case, when mud volcano has a gas flare and mud volcano breccia is covered
by sediments with estimated age of thousands of years, we can suggest that recently this volcano is not
.
active.
However, this requires a comprehensive geophysical survey of the mud volcano and a detailed
sampling of its parts to avoid missing of the fresh mud flows.
3. Mounds origin is probably connected with gas formation in the clay part of the cross-sections. Due
to additional matter of hydrates the clay layer starts to expand forming the mounds on the seafloor
similar with formation of bulge hillocks on the land surface as a result of the ground soil freezing
during the winter.
However, cross-sections of these mounds on the Lake Baikal contain mud volcano breccia
while mud breccia was not found in the cores of the Okhotsk Sea. Therefore, it is difficult to suggest
what kind of the mechanism responsible for origin of the mounds on the Lake Baikal, namely mud
volcano formation or increasing volume of clay part of the cross-section because ofhydrates formation.
To answer this question we need to continue the investigations in both regions for comparison of these
structures from the geophysical and geological point of view.
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