Mud volcanoes and gas hydrates in the Anaximander mountains (Eastern Mediterranean Sea)

Lykousis, V.; Alexandri, S.; Woodside, John; Lange, de G.; Dählmann, Anke; Perissoratis, C.; Heeschen, Katja; Ioakim, Chryssanthi; Sakellariou, D.; Nomikou, Paraskevi; Rousakis, G.; Casas, David; Ballas, D.; Ercilla, Gemma

doi:10.1016/j.marpetgeo.2008.05.002

Cited by 80 publications

(78 citation statements)

References 43 publications

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“…This is about twice as deep than in the cooler global open ocean (Max & Johnson, 2016). Significant NGH deposits also exist beneath the seafloor, and have been identified in the Mediterranean Basin by seismic interpretation and in-situ (De Lange & Brumsack, 1998;Aloisi et al, 2000;Loncke et al, 2004;Pierre & Rouchy, 2004;Dählmann, 2005;Lykousis et al, 2009;Perissoratis et al, 2011;Marinakis et al, 2015), and in the Nile fan (Praeg et al, 2011). Global models of NGH thicknesses indicate a 100 -250 m thick gas hydrate stability zone (GHSZ) in the Mediterranean region (Wood & Jung, 2008) (Fig.…”

Section: Mediterranean Oceanic Natural Gas Hydratementioning

confidence: 98%

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

Barnard

Max

Gualdesi³

2017

Medit. Mar. Sci.

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We propose that the source water for some abyssal undular vortices cored by cool, low-salinity water identified at depths in excess of 2,500 m in the deepwater region of the Eastern Mediterranean Basin may be related to conversion of natural gas hydrate (NGH) in abyssal marine sediments. The conditions for extensive formation of NGH in the gas hydrate stability zones (GHSZ) of the upper seafloor sediments existed in this region during previous glacial episodes when colder water supported a thicker GHSZ. Seafloor warming during the most recent interglacial caused thinning of the GHSZ at its base and has driven endothermic NGH dissociation that would have released large volumes of low-salinity water and gas that would tend to pond below the base GHSZ. Periodically, trapped low-salinity water and gas would be released into the sea through the overlying sediments. Buoyant low-salinity water masses, supersaturated with gas and locally containing free gas would ascend and introduce a dynamic element into an otherwise generally static environment. As a result of the interaction of the rise of this buoyant plume and Coriolis acceleration the ascending mass would begin to rotate and form a vortex tube in midwater. NGH conversion within the seafloor introduces large coherent masses of low-salinity, lower-temperature water containing a buoyant free gas fraction from near-surface reservoirs into the abyssal depths even where there may only be a weak natural gas petroleum system.

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Section: Mediterranean Oceanic Natural Gas Hydratementioning

confidence: 98%

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

Barnard

Max

Gualdesi³

2017

Medit. Mar. Sci.

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“…Ac tive MVs are as so ci ated, throughout the world, with hy dro car bon oc cur rences (Timor, South Cas pian Sea, the Ca rib bean, Egypt and Cy prus). How ever, future pro duc tion vol umes are spec u la tive be cause meth ane produc tion from hy drates has not been doc u mented be yond small-scale field ex per i ments (Wood side et al, 1998;Aksu et al, 2009;Lykousis et al, 2009;Perissoratis et al, 2011;Foscolos et al, 2012).…”

Section: Methane Hydratesmentioning

confidence: 99%

“…Their tex ture re sem bles com pacted snow and their ex ter nal mor phol ogy re sem bles flakes or lumps or big ice crys tals. Biostratigraphical anal y ses of mud and rock clasts in di cate that they were de rived from sed i men tary rocks un der lying the sea bed (Up per Cre ta ceous lime stones, Paleocene silici clastic rocks, Eocene biogenic lime stones, and Mio cene mud stones; Lykousis et al, 2009). …”

Section: Methane Hydratesmentioning

confidence: 99%

“…The ex ten sive tec ton ics across the whole Hel lenic Pen in sula and the low con tent in gas eous hy dro carbons of the Greek lig nites are the main fac tors which pre vented large gas ac cu mu la tions in the coal de pos its. Ad di tional research to eval u ate the coal-bed gas po ten tial is needed (Papanicolaou et al, 2005;Lykousis et al, 2009;Tsirambides and Filippidis, 2012).…”

Section: Introductionmentioning

confidence: 99%

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The unconventional hydrocarbon resources of Greece

Tsirambides¹

2015

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In ten sive ex plo ra tion of prob a ble con ven tional hy dro car bon res er voirs in Greece is tak ing place, through the in ter pre ta tion of seis mic pro files and of abun dant sur face geo log i cal data. The un con ven tional hy dro car bon po ten tial of the coun try is unknown, as de tailed in ves ti ga tions are lack ing. The most im por tant rock for ma tions which may con tain shale gas are found in the land and off shore bas ins of north east ern, north-cen tral, and west ern Greece. A re-eval u a tion of the data from all boreholes is needed, on the ba sis of new in for ma tion, with the aim of iden ti fy ing pos si ble re serves of un con ven tional hy dro carbons re tained in highly com pacted fine-grained strata. Meth ane hy drates have been de tected in the sub ma rine Anaximander Moun tains, east of Rhodes Is land. They cover an area of about 46 km 2 and the vol ume of meth ane is es ti mated at 2.6-6.4 trillion m 3 . The low con tent of the Greek lig nites in gas eous hy dro car bons and the wide spread tec ton ics in the Hel lenic Pen insula are the main fac tors which pre vented large gas ac cu mu la tions in its 14 main coal de pos its. How ever, ad di tional re search is needed to eval u ate the coal-bed gas po ten tial of the coun try.

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“…The eastern Mediterranean Sea and the eastern part of the central Mediterranean Sea have extensively been investigated for the occurrence of mud volcanism and cold seeps related to the presence of collision zones Lykousis et al, 2009;Mascle et al, 2014). In the western part of the central Mediterranean Sea, the Tyrrhenian Sea, evidences of fluid seepage are limited to the Adriatic Sea (Geletti et al, 2008), Strait of Sicily, Sardinian Margin (Dalla Valle and Gamberi, 2011) and Malta Plateau (Savini et al, 2009;Micallef et al, 2011;Taviani et al, 2013), mostly in the form of pockmarks, occasionally associated with methane-imprinted carbonates (Capozzi et al, 2012;Cangemi et al, 2010;Angeletti et al, 2015;Taviani et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Franchi

Rovere

Gamberi

et al. 2017

Marine and Petroleum Geology

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a b s t r a c tPaola Ridge, along the NW Calabrian margin (southern Tyrrhenian Sea), is one of the few reported deep sea sites of precipitation of authigenic carbonates in the Tyrrhenian Sea. Here, the changing composition of the seeping fluids and the dynamic nature of the seepage induced the precipitation of pyrite, siderite and other carbonate phases. The occurrence of this array of authigenic precipitates is thought to be related to fluctuation of the sulfate-methane transition zone (SMTZ).Concretions of authigenic minerals formed in the near sub-bottom sediments of the Paola Ridge were investigated for their geochemical and isotopic composition. These concretions were collected in an area characterized by the presence of two alleged mud volcanoes and three mud diapirs. The mud diapirs are dotted by pockmarks and dissected by normal faults, and are known for having been a site of fluid seepage for at least the past 40 kyrs. Present-day venting activity occurs alongside the two alleged mud volcanoes and is dominated by CO 2 -rich discharging fluids. This discover led us to question the hypothesis of the mud volcanoes and investigate the origin of the fluids in each different domed structure of the study area.In this study, we used stable isotopes (carbon and oxygen) of carbonates coupled with rare earth element (REE) composition of different carbonate and non-carbonate phases for tracing fluid composition and early diagenesis of authigenic precipitates. The analyses on authigenic precipitates were coupled with chemical investigation of venting gas and sea-water.Authigenic calcite/aragonite concretions, from surficial sediments on diapiric structures, have depleted values. The siderite REE pattern shows consistent LREE (light REE) fractionation, MREE (medium REE) enrichment and positive Gd and La anomalies. As shown by the REE distribution, the 13 C-depleted composition and their association with chemosymbiotic fauna, calcite/aragonite precipitated at time of moderate to high methane flux close to the seafloor, under the influence of bottom seawater. Authigenic siderite, on the other hand, formed in the subseafloor, during periods of lower gas discharges under prolonged anoxic conditions within sediments in equilibrium with 13 C-rich dissolved inorganic carbon (DIC) and 18 O-rich water, likely related to methanogenesis and intermittent venting of deep-sourced CO 2 .

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Mud volcanoes and gas hydrates in the Anaximander mountains (Eastern Mediterranean Sea)

Cited by 80 publications

References 43 publications

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

The unconventional hydrocarbon resources of Greece

Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

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