Geochemical features of Sakhalin Island mud volcanoes

Vietnam Journal of Earth Sciences, 40(1), 56-69, Doi: 10.15625/0866-7187/40/1/10916 56  (VAST) Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences Geochemical features of Sakhalin Island mud volcanoes Shakirov R.B.*1, Sorochinskaja A.V.1, Syrbu N.S.1, Tsoy I.B.1, Nguyen Hoang2, Le Duc Anh3 1V.I. Il’ichev Pacific Oceanological Institute (POI), Far Eastern Branch of Russian Academy of Sciences, Vladivostok, Russia 2Institute of Geological Sciences, VAST, Hanoi, Vietnam 3Institute of Marine Geology and Geophysics, VAST, Hanoi, Vietnam Received 20 July 2017; Received in revised form 21November 2017; Accepted 28 November 2017 ABSTRACT The study, based on a complex geochemical research, found that the composition of the most chemical elements in mud breccia from the Yuzhno-Sakhalinsky (YSMV) and Pugachevsky (PMV) mud volcanoes (Sakhalin Island), the unique phenomena of endogenous defluidization in the Hokkaido-Sakhalin fold system (alpine-type folding), are comparable to Clarke (C) contents of these elements (0.8-1.2 ×C). For Na, Li, Zn and Sn, the ratio between the ele- mental contentsand their Clarke values (Csample/Clarke value) vary from 1.4 to 5.2 xC. But the increased contents of Na and Li are due to the ascending endogenous fluid revealed. Study of the mud breccia chemical composition changes in different explosive activity of YSMV under the seismic activity variations allowed to establish that, when the mud-volcanic gryphons are activated against the background of increase in the temperature of the water-mud mix- ture and the emission of spontaneous gases, the contents of a number of elements (iron, calcium, manganese, rare earth elements, etc.) are decreased. This is explained by the formation of soluble hydrocarbonate complexes. Dagin- skie gasgeothermal system (DGHS) trace elements depleted ooze samples were compared with YSMV and PMV samples and exposed that the high ratios of Csample /Clarke values for the majority of elements do not exceed 0.6 ×C. Ooze samples from DGHS having higher elemental contents than Clark contents were observed only for Cd content (2.2-3.4×C) and Pb (0.7-1.5×C). Analysis of diatom flora on the DGHS site indicates the existence of an active fluid dynamic system that drains oil and gas bearing complexes. The factors determining the "weighting" of the methane carbon isotope composition in the southern part of Sakhalin Island are the increased seismic activity of deep-seated faults, as well as the presence of intrusions (diabase) and metamorphically altered rocks. Keywords: Sakhalin Island; mud volcano; methane; hydrocarbon gas; element composition; faulting tectonics; seismic activity. ©2018 Vietnam Academy of Science and Technology 1. Introduction1 Mud volcanoes are the most interesting and rather rare manifestation of defluidization *Corresponding author, Email: ren@poi.dvo.ru processes on the Earth's surface. According to oil-gas geologists V.N. Weber, K.P. Kalitsky, V.D. Golubyatnikova and I.M. Gubkin, one of the main forming factors of the mud volcanic process is the hydrocarbon potential of sedi- mentary basins. According to the literature da- Shakirov R.B., et al./Vietnam Journal of Earth Sciences 40 (2018) 57 ta, mud volcanoes, like other sources of me- thane, are usually found in areas of deep sub- sidence, in marginal basins and in subduc- tionzones of continental margins (Luckge et al., 2002), especially under conditions of tec- tonic compression (Kopf, 2002). The occurrence of mud volcanoes is asso- ciated with the outlet to the surface under the influence of excessive pressure of hydrocar- bon gases concentrated at depth. A high- pressurized fluid is formed in thick clay strata, as a rule, due to phase transformations of clay minerals in the region of high temperatures and pressures and promotes the breakthrough of mud breccias to the surface through volcan- ic eruptive channels (Kholodov, 2002; Shnyu- kov et al., 1992). One of the main factors for the formation of mud volcanoes is faulting (Melnikov and Iliev, 1989; Milkov, 2000). The bulk of solid outputs is elastic clayish rocks, which are common in the continent- oceanic marginal areas. Also, water plays a significant role in the activity of mud volca- noes, such that, firstly, penetrating into voids and pores, it leads to swelling of the rocks, turning them into a viscous mass; and second- ly, together with the gas, promotes extrusion of a clay mass with rock fragments onto the surface. Most of the on-land mud volcanoes are lo- cated within the Alpine-Himalayan, Central Asian and Pacific mobile orogenic belts, whereas underwater mud volcanoes occur both along passive and active continental margins (Kholodov, 2002). By analogy with magmatic volcanoes, mud volcanoes are distinguished by two stages of development: active and passive. The active stage is accompanied by a powerful outlet to the surface of gases and liquids of clay pulps (mud-volcanic or mud breccias). During the passive period (salsas-gryphon), a small amount of gases, coarse dirt and water are re- leased from the gryphons, or the gryphon it- self ceases its activity altogether (Kholodov, 2002). Both stages are subdivided by transi- tion stage: "relaxation" after mud volcanoes activation or preparation stage before erup- tion. The Sakhalin Region is a unique region of Russia, where there are thick sedimentary strata containing oil and gas deposits, with high seismotectonic activity and surfacial mud volcanoes (Ershov et al., 2011; Melnikov and Iliev, 1989; Melnikov et al., 2008). There are four areas of mud volcanism. Three of them are in the south of the island: Yuzhno- Sakhalin mud volcano (YSMV), 24 km northwest of the regional center, Pugachevsky group of mud volcanoes (PMV), about 140 km north of Yuzhno-Sakhalinsk in the Makarovsky district near Pugachevo and Le- snovsky mud volcano in the Korsakovsky dis- trict. In the north of Sakhalin, 30 km north of Nogliki village, the Daginsky gas geothermal field (DGHS) is located. Within the geother- mal field, there are about fifteen water and gas sources that are used for therapeutic and prophylactic purposes (mud baths 'Dagi'). Mud-volcanic manifestations are also noted on the shore of the Gulf of Aniva. Villagers of Vostochny (Terpeniya Bay, Sakhalin Island) recounted their eyewitnesses of the extrusion of clay breccias along the shoreline during a seismo-tectonic activity in August 2006. The study of the chemical composition of mud volcanic activity products (solid, liquid and gaseous) is one of the main directions of the mud volcanoes study (Fedorov et al., 2012; Shnyukov et al., 1992; Yakubov et al., 1980). In this paper, we present the results of a comprehensive geochemical study of mud volcanoes on Sakhalin Island, including the composition of spontaneous gases, the mineral assemblage of the mud breccia and the distri- bution characteristics of the wide range of its chemical elements. The main goal of the pa- per is to reveal the connection of the gas dis- charge changes, element composition, gas ge- ochemical composition and temperature of Vietnam Journal of Earth Sciences, 40(1), 56-69 58 mud-water mixture in mud volcano gryphons with strong earthquakes in the region. 2. Initial data Gas-geochemical monitoring of mud vol- canoes on Sakhalin Island has been carried out since 2001 by employees of the Gas Geo- chemistry Laboratory of the V.I. Il'ichev Pa- cific Oceanological Institute, Far Eastern Branch of Russian Academy of Science (POI FEB RAS). Gas was sampled from the main degassing gryphons of Yuzhno-Sakhalinsky and Pugachevsky mud volcanoes and the Daginsky geothermal system. Gas samples were collected in glass bottles by displace- ment using a saturated solution of NaCl as a buffer. Samples of recent mud-breccias were also collected. The Yuzhno-Sakhalinsky mud volcano (YSMV), the largest and most active, has been studied in more detail (Figures 1, 2). It is located in the field of the Bykovsky suite of Upper Cre- taceous age, one of the thickest siltstone- argillaceous sequences in Sakhalin (up to 3000 m) and tectonically confined to the submeridio- nal Central-Sakhalin deep fault (Tym-Poronaisk uplift) (Geology of the USSR, 1970). Each erup- tion changes the relief and contours of the mud field. In August 2001, after a series of seismic shocks with an intensity of 5-7 magnitude, the southern and central groups of YSMV gryphons practically ceased to function, but the mud gryphons in the northern part became active and new gryphons were formed (Astakhov et al., 2002; Melnikov et al., 2008). From the vents of the gryphons, samples of spontaneous gases and breccias were collected during a passive period (Yu-9, Yu-10, Yu-22) as well as under an active period (Yu-9 / 17.08, Yu-10/17.08). The same group of gryphons, which were in a passive state, was tested in 2007 (samples 'Naparnik' and 'A-1') and in 2008 (samples E-21, E-22, E- 23, E-24, E-25 were provided by V.V. Ershov, IMGG, Yuzhno-Sakhalinsk). Pugachevsky mud volcano (PMV), the second largest, consists of three mud volca- noes that are close together, including the Main and two small ones termed as Small North and Small South. They are located on a rounded hollow (2 by 1.5 km), overgrown with forest (Melnikov, 2011). PMV is also confined to the Tym - Poronaisk uplift and the Bykov suite is the host-terrain, likewise for YSMV (Geology of the USSR, 1970). Four samples were selected from the Main Puga- chev mud volcano (Figures 1, 3), in a passive state: 1 in 2001 (P-2/2-01), 2 in 2005, (P-1-05 and P-2-05) and 1 in 2006 (P-06). The Daghinskaya geothermal system (DGHS), also termed as the Dagin mud vol- canic manifestation, (Melnikov and Iliev, 1989) is located on the coast of the Nyisky Gulf within the North-Sakhalin trough (Geol- ogy of the USSR, 1970) alongside the Dagin- sky thermal springs (Figure 1, 4). Thermo- mineral springs belong to slightly alkaline (pH = 7.4-7.5), chloride-hydrocarbonate sodium waters. The total mineralization is 2-2.5 g/l. The water temperature is 30-40°C (Yakubov et al., 1980). The hydrological regime of the Gulf is determined by the influence of river flows and the tidal currents. During the day time, there are sharp changes in temperature, salinity and water level. In the DGHS there are no explosive eruptions typical for mud volcanoes and mud breccia field, but there is a flow area of gas-and-mud mass from small craters (1.5 to 3 m in diameter), which are rel- atively evenly distributed along the bottom (Figure 4). DGHS is controlled by the Garo- maisky fault (Lobodenko, 2010). The ob- served increased contents of helium (20 ppm) and hydrogen (22 ppm) may indicate the ac- tivity and significant deposition depth of the fault (Shakirov et al., 2012). At a relatively small depth, there are highly elastic clay de- posits of Neogene age (Gladinkov (Editor), 1998; Zharov et al., 2013). According to the literature, DGHS is also associated with the mud volcanic process (Melnikov and Iliev, 1989). Samples from the DGHS were collect- ed in the vicinity of the Kalmar thermal spring located in the tidal zone, including D-01 in 2001; D-05 in 2005; D-12-1, D- 12-2, D-12-3 and D-12-4 in 2012. Shakirov R.B., et al./Vietnam Journal of Earth Sciences 40 (2018) 59 Figure 1. Scheme of mud volcanic sampling sites on Sakhalin Island: 1 - mud volcanoes; 2 - area of Daginsky geo- thermal system; 3 - faults (in brackets: 1 - Central Sakhalin fault, 2 - Hokkaido-Sakhalin fault); 4 - sampling sites and sample number; 5 - Zones of uplifting - subsidence of the mud field; 6-7 - fissures in mud field; 8 - area, flooded with sea tidal water; 9 - thermal springs. N-к -gryphon 'Naparnik'. Remark: The abbreviations are explained in the text Vietnam Journal of Earth Sciences, 40(1), 56-69 60 Figure 2. YSMV: a) general view of YSMV from satellite (google-earth); b) view to northern part of YSMV, gryphonYu-9 Figure 3. PMV: a) general view of PMV from satellite; b) passive gryphon at PMV, August 2005 Figure 4. DGHS: a) view to Daginsky bay; b) output of gases from DGHS, in 2005 3. Study methods Analysis of hydrocarbon gases, nitrogen and carbon dioxide was carried out in the gas geochemistry laboratory of POI FEB RAS us- ing a two-channel gas chromatograph ‘Crys- talLux4000M’ equipped with ionization and (a) (b) (a) (b) (a) (b) Shakirov R.B., et al./Vietnam Journal of Earth Sciences 40 (2018) 61 thermal conductivity sensors having a sensi- tivity of 10-5%. For the analysis of helium and hydrogen, a portable gas chromatograph “Khromatek-Gasochrom 2000” was used with a sensitivity of 1-2 ppm for helium and hy- drogen. The elemental composition (gross content) in samples of recent mud volcano breccias was determined at an analytical chemistry la- boratory in the Far Eastern Geological Insti- tute, FEB RAS. The major (matrix) elements were measured using an inductively coupled plasma atomic emission spectrometry (ICP- AES), whereas the trace elements were de- termined by inductively coupled plasma mass spectrometry (ICP-MS) method. The analyti- cal error for the major elements is ±1 - 2%, for the trace elements is not higher than ±15%. The results of REE contents are interpreted in the form of chondrite normalization (Dubinin, 2006) and following the criteria for estimating the compositions of lanthanides, as follows: Euan =Eu/Eu*=EuN /(SmN+ GdN/2; Сеan=Ce/Ce* =CeN/(LaN+PrN)/2 LL/LH=(LaN+2PrN+NdN)/(ErN+TmN+YbN+LuN) The mineral composition of the mud brec- cia was studied in thin sections and immersion method prepared according to a conventional procedure (Petelin, 1957). Silicate analysis of carbonates was performed also at the analyti- cal chemistry laboratory of the Far Eastern Geological Institute, FEB RAS. The trace el- ement composition of carbonates is acquired using an IXA-8100 microscopic analyzer. The isotopic compositions of carbon and oxygen of authigenic carbonates, as well as carbon of methane and carbon dioxide, were determined at the laboratory of stable isotopes of the Far Eastern Geological Institute, FEB RAS, using a Finnigan MAT-252 mass spectrometer. The sample processing for diatom analysis was carried out using heavy potassium- cadmium liquid chemical-technical technique (Diatomic algae of the USSR, 1974). 4. Study results and discussions 4.1. Gasgeochemical features According to the gas specialization, YSMV and PMV belong to the carbonic- methane type of mud volcanoes. The predom- inant gas component for YSMV is CO2 (up to 74%), while methane (CH4) can reach as high as 24%. The Pugachevsky group of mud vol- canoes is characterized by a low emission in- tensity of free gases. In terms of quantitative ratio, the composition of PMV gases differs from the free gases of YSMV where the rela- tive contents of CO2 and CH4, respectively, are ~ 25% and ~ 70% (with variations). Both mud volcanoes are characterized by the pres- ence of heavy hydrocarbon gases to pentane inclusively, which indicate their common genesis (Table 1). Table 1. Component compositions of free gases from YSMV, PMV, DGHS Remark: Data were acquired at the Laboratory of Gasgeochemistryat POI FEB RAS, nd: not determined Ob jec t CO2, % O2+Ar, % N2, % CH4, % C2H6, ppm C3H8, ppm i-C4H10, ppm n-C4H10, ppm n-C5H12, ppm Не,ppm H2,ppm Year of sampling YSMV 69.2-83.9 0.2-7.4 2-5.2 12.4-28.4 1.6-371 7.5-426 6.9-90.5 0.6-108.7 nd - - 2001 58.6-86.7 0.1-0.9 1.2-6.9 11.8-33.3 0.16-2855 0.04-581 0.005-128 0.005-125 nd - - 2005 68.3-78.8 0.1-3.2 1.1-3.3 12.7-35.6 0.07-0.2 0.02-0.05 0.005-0.01 0.006-0.01 13.16-22.78 11.8-40.9 6.3-15 2007 67.3-84.1 0.2-1.2 1.5-4.6 13.3-29.8 0.1-0.25 0.03-0.1 0.005-0.1 0.005-0.1 15-22 - - 2009 68.4-92.5 0.1-0.3 1.24-2 6.6-29.5 0.06-0.27 0.01-0.06 0.003-0.01 0.005-0.01 7.5-15.2 16.8-43.7 0.2-1.6 2011 72.2-87.0 0.15-4.8 1.4-17.5 10.0-23.5 0.12-0.24 0.02-0.05 0.0007-0.009 0.0009-0.002 3.1-7.6 12-31.7 0.4-5.7 2013 PMV 8.6 18.4 60.4 12.6 92.8 nd nd nd - - 2001 6.4-27 2.7-21.8 - 63.0-83.0 0.5-5.6 0.3-0.9 nd nd - - 2005 18.8 5.3 12.6 63.3 0.02-0.03 nd nd nd 0.32 - - 2009 DGHS 0.3-1.0 0.3-2.0 6.0- 9.0 89.0- 93.2 nd nd nd - - - 2005 Vietnam Journal of Earth Sciences, 40(1), 56-69 62 The Pugachevsky and Yuzhno- Sakhalinsky volcanoes are similar in many re- spects: they have similar mud field dimen- sions and the character of activity; they are situated in the field of gas-bearing, highly plastic Upper Cretaceous aleurolite-argillite formation and are confined to the Central Sa- khalin fault of upthrust-overthrust type. Mud volcanoes are local gas drainage systems in the Earth’s crust, but they are considered in the system of controlling linear structures. In this case, this is a deep-seated active fault with nearly north-south strike. This means that the fault zone is a single fluid-dynamic system, in some parts of which (especially, in the zone of fault crossing or near intrusion bodies), specific conditions appear for the formation of flows of gases with certain com- position. In the southern part of the Central- Sakhalin fault, the source of carbon dioxide for both YSMV and PMV, on the one hand, and in Sinegorskie mineral water springs, on the other hand, likely the same. Within these boundaries, the concentrations of CH4 and CO2 show characteristic variations: a consid-erable portion of methane in mud volcanoes (up to 60%) is replaced sometimes by the pre- dominance of carbon dioxide in Sinegorskie springs. This difference is determined by the different water filling in the mud volcanic channel: YSMV more saturated by water be- cause its location is near freshwater spring. Carbon dioxide dissolves in the water in large portions. In opposite, the PMV has low con- tent of water in the mud flow. Therefore, me- thane dominates in this PMV as compared to the YSMV. Taken into account the equal wa- ter saturation of the both mud volcanoes, we could expect similar proportion between the methane and carbon dioxide. But this study needs additional methods. Remarkably, basic rock diapirs (diabas) located close to the YSMV could also be source of the carbon di- oxide. It should be noted that, in terms of compo- nent composition, the PMV gases match with the gases of the Northern Sakhalin oil fields (Siryk, 1968). The peculiarities of the geolog- ical development of formation area of the mud volcanoes definitely indicate a greater proba- bility of finding hydrocarbon deposits in the sedimentary thickness at the Pugachevsky volcano region (Veselov et al., 2012). For YSMV, the isotopic composition of carbon of carbon dioxide 13C is from -2.8 to -2.7 ‰ PDB and δ13С of methane is -27 PDB; for the Pugachevsky mud volcanic group, δ13С of methane is -24.9 ÷ -20.9 ‰ PDB, for carbon dioxide δ13С is -4.1 ‰ PDB. The main component of the spontaneous DGHS gas is methane (up to 93% by volume) with δ13C-CH4-54÷-57 ‰ PDB. The methane concentration from DGHS is genetically close to the methane in oil and gas-bearing fields of Sakhalin Islandand the nearest shelf, where concentrations are up to 10,000 nl/l (Shakirov et al., 2012). As a result of long-term observations (from 2001 to 2013), the average chemical composition of free gases of Sakhalin mud volcanoes was established during passive periods and shown in Table 1. The idea of a deep gas source in the Puga- chevsky and Yuzhno-Sakhalinsky mud volca- noes is in good agreement with the opinion of a number of researchers (Veselov et al., 2012; Ershov et al., 2011) that mud volcanoes are generated in sedimentary strata at depths about 7-8 km (calculated using isotope geo- thermometers), where thermobaric conditions are favorable for the formation of large vol- umes of gases. There is an empirical dependence of me- thane carbon isotope composition on tempera- ture and its generation (Prasolov, 1990). Ac- cording to this dependence the average value of δ13С methane of the Yuzhno-Sakhalinsky mud volcano corresponds to temperature of methane genesis of about 320-340°C. The av- erage geothermal gradient in the southern part of Sakhalin Island calculated according to work of Veselov and Soinov (1997), shows about 41.1°C/km. Therefore, we believe that a methane source depth for the volcano is locat- ed between 7.8 and 8.3 km. Extent of isotope division of carbon in the CO2-CH4 system depends on temperature conditions of gas generation. The range of Shakirov R.B., et al./Vietnam Journal of Earth Sciences 40 (2018) 63 temperature of isotope balance in this system calculated for average values δ13С-СН4 and δ13С-СО2 by formulas from work of Horita (2001), is 330–350°C, corresponding to the range of generation depths between 8.0 and 8.5 km. 4.2 Geochemical features of the mud breccias Collected samples of recent mud volcano breccias from YSMV and PMV were dark gray liquid silt-pelitic sediment containing a small amount of sand. The mineralogical study of the samples identified two classes of minerals be- longing to carbonates or sulphides. Carbonates are represented by well-formed crystals of beige-brown and red-brown color which con- stitute 92-97% of the heavy fraction. The chemical and microprobe analytical results shown in, respectively, Table 2 and Table 3, suggest their compositions corresponding to the magnesian-ferric variations of siderite- sideroplezites (Sorochinskaya et al., 2008). Table 2. Chemical and isotopic compositions of YSMV major natural gases CH4, % δ13Сpdb-CH4, ‰ CO2, % 13Сpdb-СО2, ‰ Не, ppm H2, ppm Year of sam-pling   13.6 29.9 23.9 49    29.8 27.3 28.8 49      67.5 84.1 73 49    6.3 4 5.3 49    - - 2009   17.9 23.9 21.5 5    29.3 28.9 29.06 5      74 80.4 76.5 5    5.4 4.7 5.1 5    - - 2010   6.6 29.5 23.1 15    27.6 30.3 28.7 15     65.8 80.3 74.9 15    4.7 6.7 5.6 15      16.8 32.4 28.3 15    0.2 1.6 0.7 15  2011   10.9 24.2 18.9 24  -   72.2 87 77.9 24  -   12 30.2 23.8 24    0.4 24.6 2.9 24  2013 Remark: In numerator - minimum/maximum values, in denominator – an average, in () - the number of the ana- lysed samples Table 3. Chemical composition of major components in authigenic carbonates from YSMV and PMV (in mass%) Object Components SiO2 Al2O3 TiO2 FeO Fe2O3 MnO CaO MgO K2O Na2O P2O5 H2O * YSMV 8.4 2.65 0.056 32.45 5.73 0.52 6.60 5.34 0.34 0.47 0.07 0.64 36.4 PMV 8.8 2.65 0.056 32.21 5.86 0.14 6.53 5.80 0.37 0.39 0.09 0.37 36.3 (*): loss on ignition The maximal contents of Mn (4.68%), Hg (0.59%) and Sr (0.25%) are in carbonates col- lected in YSMV from an active gryphon (sample Yu-9 / 17.08). The isotope composi- tion of carbon (δ13C) of authigenic carbonates from YSMV and PMV varies within narrow limits, from -0.3 to -0.7 ‰ PDB, δ18O values varying from 2.6 to 4.4 ‰ PDB (Table 4). Samples from DGHS are represented by pelite - aleurite sediment of dark gray color with up to 70% organic remains (spicules of sponges, diatoms). The main authigenic min- eral is framboidal pyrite (up to 90% of the heavy fraction) in the form of nonmagnetic pseudomorphs by organic residues and dark gray globules. The main lines on the X-ray diffraction pattern of sample D-1: 2.729 (10); 2.428 (7); 2.226 (5); 2.044 (2); 1.636 (6). Sin- gle crystals of red-brown sideroplezites are noted, which are similar in composition to those previously described in the samples from YSMV and PMV (Table 4). Vietnam Journal of Earth Sciences, 40(1), 56-69 64 Table 4. Compositions of trace elements in individual crystals in authigenic carbonates determined by microscopic analysis Object Sample Elemental content, wt.% Мn Ni Cu Zn Sr Ba Hg YSMV Yu-22(1) 0.77 nd nd 0.19 0.16 0.14 0.49 Yu-22(2) 0.82 nd 0.13 0.1 nd nd nd Yu-22(3) 0.43 0.09 0.09 0.03 0.17 nd 0.14 Yu-22(4) 0.93 0.16 0.16 0.1 0.08 0.08 nd Yu-22(5) 1.92 nd 0.09 0.06 0.11 0.11 nd Yu-9/17.08(6) 0.59 0.15 0.13 0.11 0.21 nd 0.38 Yu-9/17.08(8) 0.41 0.13 0.19 nd 0.23 nd nd Yu-9/17.08(11) 4.68 0.1 0.02 nd nd nd 0.59 Yu-9/17.08(12) 1.55 nd nd nd 0.25 0.1 nd PMV P-06(13) 0.31 0.14 0.17 0.12 0.16 0.13 nd P-06(14) 0.15 nd nd nd 0.17 nd 0.44 P-06(15) 0.18 nd nd nd 0.29 0.07 0.45 DGHS D1/1(16) 0.81 0.11 nd 0.03 0.13 0.05 nd. D1/1(19) 0.72 nd 0.04 0.07 nd 0.11 nd D1/1(21) 0.55 nd 0.11 0.09 0.13 nd 0.08 D1/1(22) 0.54 nd 0.03 nd 0.24 0.2 nd D1/1(23) 0.61 0.13 0.04 nd 0.12 nd nd D1/1(23) 0.63 nd 0.02 0.05 0.19 0.15 nd Remarks: Yu-22(1) - Yu-22(5) - individual crystals of sideroplezites selected from the sample Yu-22; Yu-9/17.08(6) - Yu-9/17.08(12) - individual crystals of sideroplezites selected from the sample Yu-9/17.08; P-06(13) - P-06(14) - crystals of sideroplezites selected from the sample P-06; D1/1(16) - D1/1(16) - crystals of si- deroplezites selected from the sample D1/1; nd- not determined Analysis of diatom flora in samples from DGHS showed the prevalence of marine and brackish-water species, among which the ma- rine plankton-benthic species Paralia sulcata (Ehrenberg) Cleve, characteristic of shelf wa- ters, dominates (Diatoms eic algae of the USSR, 1974; Hasle and Syvertsen, 1996). A significant number of freshwater diatoms (up to 32%) and an admixture (up to 5.5%) of ma- rine species, extinct in the Neogene, (Actino- cyclus ingens Rattray, Ikebea tenuis (Brun) Akiba, Cosmiodiscus insignis (Brun) Jousé, Eupyxidicula zabelinae (Jousé) Blanco & Wetzel Pyxidicula zabelinae (Jousé) Makarova et Moisseeva et al.), supposedly in- troduced from the clay strata of the Okobykai and Nutovsky Neogene formations distrib- uting lower at a relatively shallow depth (Gladenkov (Editor), 1998; Lobodenko, 2010; Zharov et al., 2013). This indicates the exist- ence of an active fluid dynamic system, which drains oil and gas bearing complexes (Table 5). Elemental compositions of mud volcanic breccias from YSMV, PMV, and DGHS. The chemical compositions of the mud volcanic breccias (Table 5) were normalized to their average contents (Clarke: C) in clays and shales (Vinogradov, 1962; Grigoriev, 2008). Most of the elemental contents in the YSMV breccia are in the range of 0.8-1.2 xC, which is comparable to the Clark content (C) of each element. Elevated concentrations in the mud volcanic breccia presented by the Na (2.9-5.2 ×C), Li (1.5-2.0), Zn (1.4-1.9) and Sn (1.6-2.4), although the contents of Mn, Ca, Zr, Mo, Cd, Hf, U are lower than their Clarke values (<0.5 ×C). A similar feature is observed in the mud volcanic breccia from PMV that, the content of most elements is close to their Clarke con- centrations. The samples contain rather high Na (2.9 ×C), Li (1.7 ×C), Zn (1.6 ×C), Sn (1.9-4.3 ×C); whereas Mn, Ca, Zr, Mo, Cd, Hf, Ta and U concentrations are lower than their Clarke values (<0.5 ×C). Shakirov R.B., et al./Vietnam Journal of Earth Sciences 40 (2018) 65 Table 5. Elemental compositions of mud volcanic breccia from YSMV, PMV, DGHS Elemental concentrations in ooze samples collected from the Daginsky gasgeothermal field are much lower than in the samples from YSMV and PMV. The ratios between the bulk major to minor elemental concentrations are about Csample/Clarke<0.6; while the concentra- tion ratios in DGHS oozesamples are high- erthan their Clarke contents, e.g., Cd= 2.2-3.4 Ele me nt YSMV PMV DGHS Yu-9 Yu-917_08 Yu -10 Yu-10 17_08 Yu- 22_01 N-k А-1 Е-21 Е-22 Е-23 Е-24 Е-25 P2/2-01 P-1-05 P-2-05 P-06 D-01 D-05 D-12-1 D-12-2 D-12-3 D-12-4 Weight.% Ti 0.37 0.36 0.36 0.36 0.37 0.36 0.35 0.36 0.35 0.35 0.3 0.36 0.36 0.36 0.36 0.37 0.22 0.26 0.27 0.27 0.20 0.31 Al 8.72 8.64 8.62 7.92 8.72 8.45 8.27 8.51 8.41 8.62 8.59 8.58 8.58 8.30 8.15 8.29 6.05 6.63 6.48 6.13 5.14 6.49 Fe 3.58 3.09 3.84 2.77 3.78 3.56 3.78 3.92 3.95 3.44 3.80 3.85 3.72 3.75 4.60 3.60 1.08 1.11 2.00 2.19 1.75 1.89 Ca 0.51 0.39 0.54 0.50 0.82 0.54 0.63 0.58 0.68 0.55 0.63 0.70 0.46 0.68 0.63 0.50 0.52 0.55 0.74 0.66 0.51 0.65 Mg 1.01 0.95 1.03 1.20 1.03 1.01 1.06 1.04 1.05 0.99 1.05 1.04 0.91 0.89 0.95 0.88 0.38 0.47 0.45 0.47 0.43 0.57 K 2.49 2.49 2.42 2.41 2.47 2.44 2.37 2.43 2.40 2.48 2.44 2.44 2.43 2.38 2.33 2.40 2.51 2.32 2.33 2.29 2.42 2.32 Na 1.93 1.97 1.89 3.40 2.05 1.96 2.15 2.01 2.00 2.24 2.18 2.14 1.94 1.91 1.90 1.87 2.03 2.03 2.15 2.08 1.67 1.94 Mn 0.04 0.03 0.05 0.02 0.06 0.04 0.05 0.05 0.05 0.04 0.04 0.05 0.02 0.03 0.03 0.02 0.02 0.02 0.02 0.02 0.02 0.01 P 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.01 0.02 0.01 0.01 0.02 0.01 g/t Li 52.54 49.91 50.28 65.13 52.25 53.94 51.96 51.69 50.03 54.70 53.15 53.03 54.24 55.87 54.35 57.73 17.98 22.03 20.80 19.90 17.40 23.70 Be 1.72 1.70 1.59 1.48 1.52 1.68 1.71 1.61 1.68 1.69 1.66 1.52 1.67 1.75 1.84 1.80 1.11 1.27 1.26 1.19 0.93 1.30 Sc 16.50 15.00 17.20 12.70 17.30 16.20 16.90 17.40 18.90 16.40 17.20 17.00 15.40 15.30 17.50 15.00 6.70 8.20 6.65 6.27 4.82 7.39 V 98.60 96.00 97.10 93.70 99.80 96.80 95.20 101.60 102.90 97.70 98.50 97.50 86.30 83.90 86.10 83.10 30.10 37.60 47.90 47.10 34.30 56.00 Cr 47.33 46.78 45.34 43.18 46.28 45.97 44.83 45.53 46.00 46.08 45.60 64.26 46.72 46.04 46.23 46.00 30.76 41.70 36.80 36.10 28.50 46.60 Co 18.40 15.10 17.30 16.00 17.50 17.20 16.50 16.60 17.40 17.50 16.90 16.80 15.80 16.00 16.00 15.80 7.30 9.00 5.38 4.98 4.60 5.54 Ni 28.90 25.80 28.30 27.30 30.20 29.70 31.50 29.20 31.40 28.80 30.50 33.90 26.60 27.70 28.50 26.30 17.80 20.90 17.70 18.30 16.40 20.00 Cu 38.50 40.50 36.50 36.60 37.70 37.70 38.80 36.60 37.30 38.10 35.80 35.50 27.30 27.30 27.70 26.50 6.30 6.30 8.90 6.52 6.40 7.96 Zn 85.70 87.10 85.80 70.70 86.30 83.00 98.90 83.40 83.00 80.20 82.70 87.10 85.80 83.30 83.20 81.50 35.40 32.70 42.50 43.60 37.20 49.20 Ga 16.99 17.38 16.25 15.77 16.64 16.97 16.27 16.43 16.07 16.92 16.36 16.52 16.09 16.22 15.75 16.79 10.63 11.77 14.80 14.50 11.10 15.60 As 7.72 7.34 8.06 6.06 8.16 8.72 8.07 8.03 7.62 8.54 8.50 9.01 10.16 10.95 10.73 11.50 4.32 4.20 5.49 7.35 5.73 7.40 Rb 104.64 102.56 100.39 79.22 100.60 103.72 98.98 98.58 98.39 104.97 98.58 99.92 103.52 105.4 100.8 106.6 83.51 84.62 110.0 106.0 101.0 112.0 Sr 219.70 193.10 220.40 247.60 234.30 230.60 227.10 222.40 220.40 224.80 221.30 233.10 233.7 220.9 253.7 214 221.6 219.8 271.0 240.0 191.0 224.0 Y 19.00 18.10 18.90 10.70 20.20 19.20 19.10 20.00 20.30 18.70 19.10 18.80 19.1 18 19.9 18.5 11.4 13.2 12.00 12.50 9.95 13.80 Zr 93.83 90.06 91.06 86.70 91.86 123.48 88.17 90.52 90.67 90.67 91.02 87.13 78.07 71.07 77.65 81.65 42.79 52.03 66.70 67.70 45.10 74.40 Nb 8.08 7.99 7.62 7.50 7.67 7.95 7.67 7.57 7.56 7.82 7.63 7.53 8.55 8.51 8.47 8.86 5.40 6.40 7.98 8.15 6.01 8.98 Mo 0.38 0.39 0.42 0.33 0.45 0.36 0.42 0.70 0.51 0.57 0.39 0.50 0.43 0.49 0.69 0.40 0.71 1.03 1.11 1.47 1.22 1.78 Ag 0.15 0.15 0.16 0.16 0.15 0.21 0.23 0.17 0.16 0.17 0.16 0.15 0.16 0.15 0.16 0.18 0.16 0.14 0.19 0.19 0.19 0.19 Cd 0.13 0.17 0.09 0.11 0.13 0.13 0.14 0.14 0.13 0.13 0.11 0.13 0.16 0.10 0.09 0.09 0.26 0.24 0.22 0.29 0.35 0.25 Sn 7.45 6.42 8.41 6.39 5.67 7.01 6.69 6.88 7.23 6.57 7.51 6.31 15.00 7.77 6.69 6.68 0.01 0.25 1.70 1.61 1.28 1.89 Cs 8.00 7.37 7.70 7.48 7.77 8.05 7.19 7.57 7.51 8.08 7.58 7.61 7.29 7.47 7.21 7.56 4.19 4.47 6.27 5.68 5.03 6.84 Ba 446.70 455.50 449.40 537.50 454.50 457.00 466.90 444.40 438.10 499.80 451.00 458.30 510.90 512.80 515.00 482.90 659.90 568.50 543.10 508.90 521.20 497.00 La 20.90 20.88 20.20 9.62 20.88 20.13 19.80 19.96 19.43 19.75 18.99 19.05 19.58 19.49 18.95 20.13 16.03 17.57 22.80 26.40 19.70 28.60 Ce 47.94 47.53 46.74 23.96 48.10 47.02 45.35 47.05 45.69 46.0 44.89 44.5 45.45 46.28 45.75 47.17 34.00 37.79 48.30 55.60 42.0 59.90 Pr 5.27 5.13 5.10 2.93 5.27 4.97 5.06 5.15 4.93 5.06 4.84 4.97 5.05 5.25 4.99 5.27 3.85 4.33 5.57 6.26 4.75 6.89 Nd 19.70 19.85 20.07 11.78 20.19 19.74 19.04 19.98 19.62 19.21 18.96 19.33 20.02 20.88 20.45 20.77 14.79 16.97 20.10 22.60 17.60 24.90 Sm 3.90 3.83 3.85 2.47 3.84 3.70 3.68 3.93 3.98 3.74 3.74 3.72 3.89 4.13 3.93 4.10 2.66 2.93 3.84 4.43 3293 4.77 Eu 0.80 0.73 0.80 0.50 0.81 0.81 0.79 0.82 0.81 0.79 0.79 0.78 0.83 0.83 0.81 0.84 0.63 0.69 0.91 0.92 0.72 0.96 Gd 3.86 3.65 3.79 2.43 3.99 3.70 3.74 3.92 3.88 3.73 3.63 3.72 4.08 4.03 3.92 4.11 2.54 2.96 3.68 4.10 3.19 4.43 Tb 0.50 0.50 0.54 0.34 0.54 0.52 0.51 0.5 0.54 0.51 0.50 0.55 0.55 0.56 0.55 0.55 0.33 0.40 0.50 0.54 0.43 0.59 Dy 2.97 2.96 3.0 1.95 3.19 3.02 3.08 3.07 2.96 2.90 3.03 3.08 2.99 2.95 3.07 3.11 1.85 2.07 2.68 2.84 2.26 3.15 Ho 0.58 0.55 0.57 0.38 0.61 0.60 0.59 0.61 0.59 0.58 0.57 0.58 0.54 0.56 0.60 0.57 0.35 0.41 0.53 0.57 0.44 0.61 Er 1.76 1.79 1.90 1.18 1.91 2.03 1.77 1.76 1.83 1.80 1.82 1.75 1.68 1.66 1.70 1.65 1.06 1.18 1.56 1.60 1.28 1.77 Tm 0.25 0.26 0.26 0.16 0.2 0.24 0.26 0.25 0.24 0.25 0.26 0.24 0.24 0.22 0.23 0.25 0.14 0.15 0.23 0.23 0.19 0.26 Yb 2.55 2.53 2.61 1.95 2.68 2.54 2.51 2.66 2.76 2.51 2.63 2.5 2.51 2.33 2.65 2.34 1.29 1.4 1.51 1.53 1.23 1.68 Lu 0.28 0.27 0.25 0.17 0.25 0.25 0.25 0.27 0.26 0.26 0.26 0.24 0.25 0.21 0.22 0.24 0.15 0.15 0.23 0.22 0.18 0.24 Hf 2.70 2.71 2.81 2.48 2.79 2.73 2.63 2.74 2.64 2.63 2.57 2.63 2.35 2.29 2.36 2.44 1.40 1.50 1.81 2.06 1.47 2.09 Ta 0.53 0.52 0.51 0.50 0.51 0.52 0.53 0.52 0.50 0.52 0.51 0.48 0.59 0.58 0.59 0.62 0.32 0.41 0.65 0.68 0.50 0.85 W 2.32 1.98 2.2 1.96 2.26 2.55 1.72 2.27 2.19 2.53 2.28 2.36 3.23 3.60 3.50 3.57 0.97 1.25 1.38 1.45 0.98 1.69 Pb 16.06 16.46 15.84 13.77 16.63 17.01 17.05 15.86 15.91 16.19 18.49 16.57 15.75 17.14 17.00 16.56 10.24 9.44 20.70 19.60 18.40 19.00 Th 9.62 9.83 9.47 7.31 9.62 9.51 9.37 9.46 9.15 9.41 9.26 9.22 9.79 9.64 9.60 9.99 5.10 6.05 7.99 9.29 6.27 11.00 U 1.86 2.04 1.78 1.55 1.88 1.78 1.81 1.81 1.79 1.86 1.79 1.85 1.92 1.82 1.87 1.91 1.24 1.44 1.98 2.08 1.60 2.49  REE 111.2 110.4 109.7 59.8 112.5 109.3 106.4 110.0 107.5 107.1 104.9 105.1 107.7 109.4 107.8 111.1 79.7 89.0 112.4 127.8 97.5 138.7 LaN/YbN 5.53 5.56 5.22 3.33 5.25 5.34 5.32 5.06 4.75 5.31 4.87 5.02 5.26 5.64 4.82 5.80 8.38 8.46 10.18 11.63 10.80 11.48 GdN/YbN 1.22 1.16 1.17 0.74 1.01 1.18 1.20 1.19 1.13 1.20 1.11 1.11 1.31 1.40 1.19 1.42 1.59 1.71 1.97 2.16 2.09 2.13 Eu/Eu* 0.62 0.59 0.64 0.62 0.63 0.66 0.65 0.64 0.62 0.64 0.65 0.64 0.64 0.62 0.62 0.62 0.73 0.71 0.73 0.65 0.67 0.63 Ce/Ce* 1.07 1.08 1.08 1.08 1.08 1.10 1.06 1.09 1.10 1.08 1.10 1.08 1.08 1.08 1.11 1.08 1.01 1.01 1.00 1.01 1.02 1.00 LnL/LnH 4.45 4.43 4.24 3.29 4.27 4.15 4.29 4.27 4.06 4.28 4.04 4.25 4.47 4.84 4.33 4.84 6.15 6.31 6.44 7.24 6.84 7.17 Vietnam Journal of Earth Sciences, 40(1), 56-69 66 ×C) and Pb= 0.7-1.5 ×C. The concentrations of other elements such as Cr, Zn, Sr, Ag and Ba are comparable with their Clark concentra- tions of about 0.7-1.3 ×C. The increase in the content of Cd and Pb in the sediment is obvi- ously associated with the processes occurring at the river-sea geochemical barrier, where the precipitation of suspended and dissolved forms of metals increases sharply (Oreshkin and Gordeev, 1983). Also, the human eco- nomic activity can also increase the concen- tration of these metals in the sediment. A comparison was made of the activity of individual gryphons in their passive and active phases. It was found that with an active gryphon, the output volume of spontaneous gases increases sharply (from 0.5 to 7l/min), and the temperature of the water-mud mixture increases (from +10ºC to +16ºC) (Astakhov et al., 2001). The content of a number of chemi- cal elements in mud breccias also changes (Astakhov et al., 2001; Sorochinskaya et al., 2008). During the activation of the Yu-9 and Yu-10 gryphons (samples Yu-9 / 17.08 and Yu-10 / 17.08), the contents of many elements such as Fe, Na, Mg, Mn, Sc, Rb, As, V, Cr, Co, Ni, Zn, Zr, Y, Sn, Cs, W, Pb are de- creased, while the contents of Ba, Li, Na are increased. A more contrasting feature is ob- served for the Yu-10 gryphon (Figure 5). Ac- tivation of gryphons is accompanied by a de- crease in the content of REE, in the sample Yu-9/17.08, for example, from 111.25 g/t de- creasing to 110.45 g/t, and in the sample Yu- 10/17.08, the content being from 109.71 g/t decreasing to 59.83 g/t (Figure 6). The most significant decrease is observed in the content of light lanthanides (La and Ce), where the ratio of LREE/HREE for gryphon Yu-10 dur- ing the activation is reduced from 4.89 to 3.91. The europium anomaly (Eu/Eu*) in the breccia is also reduced when the gryphon is activated, for example, for Yu-9 gryphon from 0.62 to 0.59, for Yu-10 gryphon from 0.64 to 0.62. Figure 5. Changes in chemical compositions of mud volcanic breccia in active and passive eruptive mud; I, II- Fe/Al, Ca/Al, Mn/Al, Ba/Al in samples selected from passive gryphons Yu-9 and Yu-10 respectively, I_A, II_A - Fe/Al, Ca/Al, Mn/Al, Ba/Al in samples selected with activation of gryphons (samples Yu-9/17.08 and Yu-10/17.08) Since YSMV refers to the carbonic- methane-type mud volcanoes, under activa- tion, the rate of CO2, CH4 and N2 increases sharply (Shakirov, 2016). This promotes the formation and migration of soluble hydrocar- bonate complexes of many elements, in par- ticular iron, calcium, manganese and REE, etc. This is associated with a decrease in the content of these cations in the mud volcanic breccia during the activation of a gryphon. But an increase in the contents of a number of elements such as Na, Li, Ba, Hg, B, character- ized by the mud breccia, is associated with endogenous supply along with the deep hy- drocarbon gases (Aliyev et al., 2009; Shnyu- kov et al., 1992; Yakubov et al., 1980). Shakirov R.B., et al./Vietnam Journal of Earth Sciences 40 (2018) 67 Figure 6. Rare earth element chondrite normalized of samples collected at active and passive gryphons of YSMV 5. Conclusions The chemical and isotope compositions of free gases, and the chemical composition of the mud breccia including complex of authi- genic minerals, indicate the genetic relation- ship of the Yuzhno-Sakhalinsky and Puga- chevsky mud volcanoes. YSMV and PMV are located in the field of the sedimentary se- quence (Bykovskaya suite), and are confined to one tectonic structure (Central-Sakhalin deep fault) and are of the carbonic-methane- type mud volcanoes. The carbon isotope com- position of carbon dioxide (δ13С= -2.8 to - 2.7‰ PDB) and methane (δ13С= -27.1‰ PDB) indicates the formation of these gases as a result of deep thermogenic transformation of organic matter. The contents of the most chemical elements in the mud breccia of YSMV and PMV are comparable to the Clarke contents of these elements (0.8-1.2 ×C). For Na, Li, Zn, Sn, the Csample/Clarke ra- tio varies from 1.4 to 5.2 ×C. Elevated con- tents of Na and Li are due to the ascending endogenous fluid. The study of the chemical composition of the mud breccia during the change in the ex- plosive activity of YSMV under the seismic activity allowed to clarify: when the gryphons are under activation against the background of an increase in the temperature of the water mud mixture and the volumes of spontaneous gases, the content of a number of elements (iron, calcium, manganese, rare earths, etc.) is decreased. This is explained by the formation of soluble hydrocarbonate complexes. When excess CO2 is removed, the above cations are precipitated from the solution in the form of iron - sideroplezite carbonates. The resulting carbonates are enriched with trace elements, which saturate the associated water during the activation period and inherit the carbon iso- tope composition of carbon dioxide. For the Daginsky geothermal system, the main component of the spontaneous gas is methane having an isotopic composition of δ13С from -58.8 to -57.0 ‰ PDB. This me- thane resulted from the mixture: a result of anaerobic decomposition of organic matter (thermogenic) and involving methane-forming bacteria (microbial). In such physicochemical conditions, the ferrous iron is bound to sul- fides, and the main authigenic mineral on the DGHS is pyrite. Ooze samples from DGHS are depleted with trace elements compared to samples from YSMV and PMV, and Csam- ple/Clarke values for the majority of the ele- ments are 0.6 ×C. In DGHS ooze samples, on- ly Cd (2.2-3.4 ×C) and Pb (0.7-1.5 ×C) are higher than the Clarke content. Vietnam Journal of Earth Sciences, 40(1), 56-69 68 Deep shears are the supply channels for both fluids from sedimentary basins (hydro- carbons) and magmatic rock fluids (helium, hydrogen, carbon dioxide). The mud volcanic gas emission from sedimentary basins is en- hanced during seismic activity. The presence of active mud volcanoes and mineral springs proves the activity of deep faults, through which deep fluids migrate. The factors deter- mining the 'weighting' of the methane carbon isotope composition in southern Sakhalin are probably the increased seismic activity of deep-seated faults, as well as the presence of intrusions and hydrothermally altered rocks. Yuzno-Sakhalinsky and Pugachevsky mud volcanoes are sharply varied from the Dagin- skie gas-geothernal springs. 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