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New insights into fluid-rock interaction mechanisms at mud volcanoes: Implications for fluid origin and mud provenance at Bahar and Zenbil (Azerbaijan)
Abstract
Understanding the fluid-rock interactions occurring in terrestrial mud volcanoes is a premise for elucidating the (bio)geochemical processes involved in the release of aqueous fluids, mud and gases to the Earth's surface and atmosphere. For the first time, fluid and mud ejecta from the mud volcanoes at Bahar and Zenbil, located in eastern Azerbaijan and in the shallow coastal water of the South Caspian, were collected and analyzed for their mineralogical, textural and chemical composition. The expelled aqueous fluids have a Na-Cl-(HCO3) composition and are generated by the mixing of evaporitic Caspian seawater and ancient, low- to high-salinity, sedimentary pore water at temperatures of 32 ± 3 °C and 42 ± 5 °C for the mud volcanoes at Bahar and Zenbil, consistent with mud chambers to be situated in the Pliocene sediments at 2–3 km depth. These aqueous fluids are strongly enriched in major solutes, like Na, Cl, HCO3, B, Br, NH4 and DOC, as well as in some trace elements (As, Ba, Cu, Fe, Li, Sr and Zn), with concentrations up to 220 times that of the current Caspian seawater. This chemical concentration is caused mainly by a combination of (i) strong surface evaporation, ion exchange and adsorption-desorption involving smectite clays, redox-driven reactions and carbonate mineral precipitation at relatively shallow depths (not deeper than 4 km) as well as (ii) thermal breakdown of organic matter and methane production in deeply buried (4 to 7 km depth) organic-rich strata. Biogenic processes are only of minor importance. The mud is sourced from all horizons the mud volcanoes are cross-cutting, partly altered by diagenetic processes. Alteration is comprised of illitization of smectite during burial diagenesis (120 to 150 °C), replacements of feldspar by kaolinite and smectite, weathering of sulfide minerals, Fe-(oxy)hydroxide formation, as well as oxidation of methane and organic matter in the near sub-surface environments at low temperature (<40 °C). Our results indicate that fluid-mud mixtures expelled from mud volcanoes of the South Caspian basin can influence the chemistry of local surface and ground water as well as of (sub-)surface sediments.
... They produce scenic landscapes and morphological features on the Earth's surface, such as gryphons, mud and scoria cones, salses, springs and fire columns [3][4][5][6]. However, the release of toxic and radioactive elements (arsenic, As; barium, Ba; copper, Cu; strontium, Sr; uranium, U; zinc, Zn, etc.) and (a) biogenic gases (e.g., methane, CH 4 and minor carbon dioxide, CO 2 ) during the active and dormant periods of volcanoes can impact the chemistry of local surface water, groundwater, interstitial solutions and sediments, as well as the Earth's atmospheric gas budget [7][8][9][10][11][12][13][14][15][16]. In many places, mud volcanic activity is triggered by the rapid subsidence of soft, fine-grained sediments rich in water and organic matter in a compressive tectonic setting, which promotes the generation of hydrocarbons and, subsequently, the formation The widespread, active and passive mud volcano systems located onshore in East Azerbaijan are relatively well documented with respect to their fluid and solid ejects [4,11,[26][27][28]. ...
... For instance, more than eight new islands formed within the Baku archipelago and the Caspian Sea region as a result of (sub)recent mud volcanic eruptions, but these sites remain unexplored (Khara-Zire, Garasu, Gil and Sangi-Mughan). To the best of our knowledge, only Baldermann et al. [16] have reported on the mineralogical, textural and chemical compositions of fluid and mud ejects from Zenbil island, which is located in the coastal water of the Caspian Sea. The authors compare the mud mineralogy from Zenbil with onshore material collected from the mud volcano system at Bahar, concluding that the mud has a homogenous composition at the two localities, thus originating from the same shallow-seated mud chamber. ...
... The chemical compositions of the fluids expelled from the gryphon-type emissions are reported in Table 1. The fluids extracted from the offshore mud volcanoes in Hamamdagh and Bendovan have pH values of 8.32 and 8.55, which is well within the range of published values since the pH of~130 mud volcanoes from Azerbaijan varies between 6.51 and 8.84 [16,26,28]. These values are slightly lower compared to the onshore mud volcanoes at Garasu, Khara-Zire and Sangi-Mughan, which exhibit pH values between 8.58 and 9.10. ...
We present geochemical and mineralogical datasets for five new mud volcanoes in continental Azerbaijan (Hamamdagh and Bendovan) and the adjacent Caspian Sea (Khara-Zire, Garasu and Sangi-Mughan). The fluid ejects have a Na–Cl-type composition and are generated by the mixing of evaporated Caspian seawater and low- to high-salinity pore waters, as indicated by Br–B and Cl–B systematics and Na–K and SiO2 geo-thermometers. The fluids contain high concentrations of As, Ba, Cu, Si, Li, Sr and Zn (60 to 26,300 ppm), which are caused by surface evaporation, pyrite oxidation, ion exchange reactions and hydrocarbon maturation in Oligocene-Miocene ‘Maykop’ shales. The solid ejects comprise liquid, oily and brecciated mud, mud/claystones and sandstones. The mud heterogeneity of the volcanoes is related to the geological age and different sedimentological strata of the host rocks that the mud volcanoes pass through during their ascent. All ejects show evidence of chemical alterations via water–rock–gas reactions, such as feldspar weathering, smectite illitization and the precipitation of Fe-(hydr)oxides, calcite, calcian dolomite, kaolinite and smectite. The studied localities have petrographic similarities to northern extending mud volcano systems located on Bahar and Zenbil islands, which suggests that mud volcanoes in the Caspian Sea region are sourced from giant shallow mud chambers (~1–4 km depth) located in Productive Series strata. Our results document the complex architecture of the South Caspian Basin—the most prolific hydrocarbon region in the world.
... The evidence of high B and Li concentration as well as elevated δ 18 O in MV LGH waters (Chao et al. 2022) also supports the occurrence of smectite-illite transformation (e.g. Sokol et al. 2019;Baldermann et a., 2020;Chen et al. 2020). In summary, the general pattern of trace element distribution in waters of MV LGH is similar to low temperature submarine springs under anoxic conditions with the occurrence of clay dehydration. ...
... The average values of trace element over chloride ratios in Azerbaijan MV waters show higher Al/Cl, Zn/Cl/ Br/ Cl, Mo/Cl, Sb/Cl, Pb/Cl, and U/Cl ratios, similar Cu/Cl, and lower Rb/Cl and Cs/Cl ratios relative to LGH waters (Lavrushin et al. 2015;Baldermann et al. 2020; Additional file 2: Table S2). Azerbaijan MVs are distributed on the area similar to Taiwan Island. ...
... 3. There is large discrepancy between trace element concentrations in MV LGH and limited previous reports, including MV LS, 35 km north, and MVs in Azerbaijan (Lavrushin et al. 2015;Baldermann et al. 2020;Chao et al. 2021). Although trace elements in MV waters are release through water-rock interaction, they are easily masked by secondary mechanisms during migration and occurrence in the mud pools. ...
Mud volcano (MV) is one of the most important channels for deep seated volatile materials to migrate to Earth’s surface in the sedimentary basins at subduction zones. It plays a meaningful role of elemental budget in hydrosphere. Waters of MV fluid emitted from 46 mud pools in MV Lei-Gong-Huo (LGH) in eastern Taiwan were sampled from October 2015 to July 2016 monthly. Previous research indicates that the chemical characteristic of fluid expelled by MV LGH is dominated by two-end-member mixing of water–rock interaction with sedimentary and igneous rocks (Chao et al., Front Earth Sci 9:750436, 2022). Trace elements of 165 mud pool samples, including Al, Co, Ni, Cu, Zn, As, Br, Rb, Mo, Sb, I, Cs, Pb and U, were measured. The results show that waters of MV LGH reveal similar chemical characteristics to low-temperature ridge-flank hydrothermal spring and marine pore water in anoxic conditions coupled with the addition of clay dehydration. Principle component analysis (PCA) with previous published variables (Chao et al., Front Earth Sci 9:750436, 2022) indicates the important factors are the source of water–rock interaction, the surface ion exchange, the redox condition of mud pool, and the evaporation. In summary, the concentration of trace elements in the waters expelled by MV LGH is in the range of nM to pM. Their behaviors are dominated by secondary factors during and after migration such as surface ion exchange in response to changes in pressure and temperature, redox state of the mud pool, and evaporation. Trace elements in MV water are not suitable for fluid source or provenance studies.
... Lakin istisna kimi Saxalinin vulkanlarında aşkarlanan metanın əmələ gəlməsi üçün abiogen və bakterial əmələgəlmə səciyyəvi xarakter daşıyır. Azərbaycan vulkanlarında da metanın əmələ gəlməsi üçün bakterial fəaliyyətin cüzi rolu bir sıra tədqiqatlarda [18,21] qeyd olunur. Ümumilikdə, ölkə ərazisi üçün karbohidrogen qazəmələgətirən üzvi maddəli süxurların yetkinlik intervalları 10-16 km, akkumlyasiya dərinlikləri isə 7 km-dək qiymətləndirilir [21,22]. ...
... Azərbaycan vulkanlarının səthə gətirdikləri flüidlər ilə əlaqədar aparılan son tədqiqatlar [18] göstərir ki, dəniz akvatoriyasında və sahildə yerləşən vulkanların suları üçün Na-Cl (HCO3) tərkibi daha xarakterikdir. Belə ki, ada və sahilyanı vulkanların sularının formalaşmasında qarışıq mənbələrin, o cümlədən Xəzərin evaporit dəniz suyu ilə bərabər, həm də 2-3 km dərinlikdə (32 ± 3°C və 42 ± 5°C temperatura malik intervallarda) yerləşən Pliosen çöküntülərinin az və yüksək duzlu sularının rolu olmuşdur. ...
... Belə ki, ada və sahilyanı vulkanların sularının formalaşmasında qarışıq mənbələrin, o cümlədən Xəzərin evaporit dəniz suyu ilə bərabər, həm də 2-3 km dərinlikdə (32 ± 3°C və 42 ± 5°C temperatura malik intervallarda) yerləşən Pliosen çöküntülərinin az və yüksək duzlu sularının rolu olmuşdur. Ümumilikdə, palçıq vulkanlarının suları Na + , Cl -, HCO3 -, B3 -, Br -, NH4 --lə, həll olunmuş üzvi maddələrlə, həmçinin As, Ba, Cu, Fe, Li, Sr və s. səpələnmiş elementlərlə zəngindir [18,19]. ...
Məqalədə, Azərbaycan palçıq vulkanlarının intişar tapdığı sahələrin geoloji, dərinlik-stratiqrafik, tektonik səciyyələri ilə bərabər, onların daxili quruluşları, püskürmələri haqqında seysmik stansiyaların qeydləri, həmçinin süxur tullantılarının vizual və geokimyəvi xarakteristikaları araşdırılır. Kompleks məlumatlar əsasında vulkan köklərinin maksimal dərinliyinin Təbaşir və Eosen yaşlı çöküntülər yerləşən intervallarla mümkün assosiasiyaları korrelyasiya olunur. Şıxzərlinin Üst Maykop yaşlı kəsilişindən götürülən yanar şistdən reper kimi istifadə edilməklə, vulkan tullantılarının zəngin üzvi maddə saxlayan (> 8 %), lakin geoloji yaşları mübahisə doğuran şistli süxurlarının üzvi-geokimyəvi göstəriciləri, tərkiblərində adsorbsiya sularının miqdarca paylanması və paleohövzə əmələgəlmə şəraitləri müqayisəli şəkildə öyrənilmiş, nəticə etibarı ilə onların Üst Maykopa və Orta Eosenə bağlılıqları ilə əlaqədar geoloji qanunauyğunluq müəyyənləşdirilir.
... This occurred during the collision of the African-Arabian-Eurasian plates, a drop in global sea-level and the rise of the Alpine and Himalayan mountain belt (Popov et al., 2004;Rögl, 1998Rögl, , 1999. These events led to dramatic changes in biodiversity, hydrological regime, sedimentary facies and depositional environments extending from central Europe to western Asia (Baldermann et al., 2020a(Baldermann et al., , 2020bJones and Simmons, 1996;Popov et al., 2010Popov et al., , 2004. Moreover, this time also marked the continuation of a period of longterm climate cooling in the Cenozoic, which began after the Paleocene-Eocene Thermal Maximum and culminated in severe glaciation periods during the Pleistocene. ...
... Notable variations occurred in the concentration of redox-sensitive trace metals, total organic carbon and sulphur in the Middle and Late Miocene sediments. These are considered to represent an abrupt shift from strictly anoxic to generally oxygenated conditions in the sedimentary basins caused by an increased freshwater Sedimentary Geology 411 (2021) 105794 influx and the establishment of a dominantly lacustrine environment (Baldermann et al., 2020a(Baldermann et al., , 2020b. ...
... Ma; Böhme, 2003). Possible source areas for the Diatom Suite sediments are the Russian Platform, the Greater Caucasus or the Lesser Caucasus (Abdullayev and Leroy, 2016;Baldermann et al., 2020aBaldermann et al., , 2020bMorton et al., 2003). The Russian Platform is characterised by Precambrian, Palaeozoic and Mesozoic rocks with sequences consisting of biotite-garnet-gneiss, garnetgneiss, amphibolite, amphibolite-gneiss, kaolin beds, conglomerates, sandstones, quartz sandstone with clay lenses, schist, dolostone and limestone, marls as well as shale (Mammadov and Karimov, 1987;Buryakovsky et al., 2001). ...
The Miocene Diatom Suite sediments of the Eastern Paratethys Sea, Azerbaijan, provide significant information to establish how Middle Miocene climate influenced erosion, sedimentation and deposition in the marine environments and continental source areas of Western Asia. Discriminant function analyses, ratios of Ti/Al, Si/Ca and Sr/Ca as well as mineralogical composition data indicate the Karaganian-Konkian sediments from the Pereküşkül-Diatom section were derived largely from the Greater Caucasus with a recognizable input from the Russian Platform during earliest Konkian. The chemical index of alteration and detrital clay mineral content document a change in climatic conditions from humid to relatively arid conditions occurred in the Greater Caucasus and Russian Platform area during the Karaganian-Konkian. The distribution of redox-sensitive elements across the Miocene Diatom Suite indicates oxic conditions prevailed in the Eastern Paratethys Sea Basin during the deposition of the Karaganian-Konkian sediments. Geochemical proxies suggest that, despite the Cenozoic been a period of global cooling, eastern Azerbaijan mainly characterised by a moderately humid to arid climate during this time. This indicates that warm climatic conditions, as seen during the mid-Miocene Climatic Optimum, were notably prolonged in the region of the Eastern Paratethys Sea basins and adjacent source areas, possibly reflecting palaeo-geographic changes in ocean and wind circulation patterns and/or local climate forcing associated with regional volcanic methane emissions.
... Isotopic signatures (δ 13 C CH4 and δ 2 H CH4 ) and the Noble-gas concentrations are useful tools to constrain the crustal origin of methane emission from theNirano mud volcano, Italy (Sciarra et al., 2019). The fluid-mud mixtures released by the South Caspian basin's mud volcanoes have the potential to alter the chemistry of nearby surface and groundwater as well as surface and subsurface sediments (Baldermann et al., 2020). The seepage gases from the vents/craters of mud volcanoes at the southern boundary of the Junggar Basin, NW China were found to be relatively enriched in methane and have lower concentrations of ethane and propane . ...
... Liu et al. (2013) reported that Na + and Cl − are dominating the other ions content in the samples of Wushanting mud volcanoes in China. The study conducted in Hsiaokunshui, China by Liu et al. (2013) also shows domination by Na + and Cl − , similar to the water samples in the Bahar mud volcanoes in Azerbaijan (Baldermann et al., 2020). Liu et al. (2013) also reported that high ionic strength in both locations of mud volcanoes. ...
... Back in the 1980s, the study of the geochemical properties of the gryphon muds of the volcanoes of Azerbaijan led to the fact that they were first used as a therapeutic drug [5]. In recent years, several studies have been carried out on the accessory mineralization of the gryphon breccia of volcanoes registered in East Azerbaijan [3], as well as on the study [1; 7; 8; 15; 16; 17; 18] of mud brought to the surface as a result of eruptions, according to © Baloglanov Elnur, 2023 geochemical and mineralogical proxies. Our analysis shows that, so far, the published literature has not assessed the regularity of the chemical composition of the gryphon breccia, which is characteristic of mud volcanoes located in different tectonic zones of Azerbaijan, belonging to different depths, as well as stratigraphic units. ...
... The relative height is 25 m, the size of the edifice is 1 x 0.8 km, and the diameter of the crater is 1 km. Volcanic breccia has an area of 54 ha, an average thickness of 60 m, and a volume of 30 million m 3 [10]. This volcano is located at the intersection of longitudinal and transverse faults. ...
The paper is devoted to the study of the patterns of distribution of major oxides and trace elements in the gryphon breccia of 12 active mud volcanoes located in various oil and gas regions (Absheron, Gobustan and Lower Kura) of Azerbaijan. Interpretations of the chemical elements found in gryphon breccia samples have allowed the composition of their source rocks, sedimentation conditions, and sedimentation areas to be determined. Purpose. The main goal of the study is to conduct geochemical studies of gryphon breccias belonging to various oil and gas regions, determine spatial patterns, achieve their explanation, and at the same time determine the conditions for the deposition of mud sediments. Methods. The chemical composition of mud volcanic breccia samples was analyzed using an "S8 TIGER Series 2" spectrometer and an "Agilent 7700 Series ICP-MS" mass spectrometer. Based on the results obtained, in addition to identifying patterns in the areas, modern approaches based on geochemical interpretation were used to explain them. The results on the genesis of breccias are consistent with the results of the published literature on the development of geodynamic and paleobasin conditions in the region. Results. Samples with the lowest Si content are characteristic of the Lower Kura mud volcanoes, where the youngest (Quater-nary) deposits are recorded. In samples from these mud volcanoes, relatively high contents of Mg and P are also noticeable. High contents of Ca are characteristic of volcanoes located near the Caspian Sea. These mud volcanoes are also rich in trace elements such as Li, Ga, Rb, Zr, Mo, Cs, Pr, Tl, Pb, Th, U and others, but depleted in Ni, Sr, Ba and etc. Conclusions. Plagioclase-rich source rocks and oxygen-dominated paleobasin environments played a key role in the formation of breccia deposits belonging to the mud volcanoes of Azerbaijan. Geochemical proxies make it possible to link the paleobasin conditions of the formation of the gryphon breccia of the most mud volcanoes of South and Central Gobustan with the continental setting, especially in comparison with some volcanoes of the Lower Kura, as well as Gobustan and Absheron, located on the shores of the Caspian Sea and relatively close to it. The breccias of mud volcanoes located at a relatively large distance from the modern sea boundary and in the steepest northern part of the Lower Kura are associated with marine conditions, as are breccias of mud volcanoes located in the south of this tectonic zone (subjected to intense subsidence) and at a short distance from the Caspian Sea, may be due to geological factors. In cites: Baloglanov Elnur (2023). Geochemical proxies of the gryphon breccia of mud volcanoes in east Azerbaijan: regularities in the distribution of chemical elements and spatial characteristics of sedimentation.
... In addition to surface outcrops, oil shales found in ejecta from mud volcanoes were included in their studies . In publica-tions (Isaksen et al., 2007;Hudson et al., 2008;Baldermann et al., 2020;Aghayeva et al., 2021) covering this period, along with samples taken from the mud volcano areas, several outcrop sections which contains oil shale layers were also investigated using modern approach-es. In these studies, a small number of oil shale samples have been investigated not as oil shales, but as shale and argillite. ...
... In other words, the study of formation conditions of such rocks in previously known oil shale areas of Eastern Azerbaijan was not based on the methodological principles of the researches performed in this direction on a global scale, but at best, based on the hypotheses formed on the basis of analyzes of lithostratigraphic changes observed in the studied outcrop sections. However, in the few works published by foreign researchers together with local researchers (Baldermann et al., 2020;Aghayeva et al., 2021), more detailed studies were carried out in the study of two outcrops (Pirekeshkul and Islamdag sections). However, in these studies, oil shales found among the lithofacies of the sections were considered as argillaceous rocks. ...
Based on the results of many years of field surveys, new information is presented on previously unknown oil shale outcrops in Azerbaijan. New boundaries of the distribution of oil shale-bearing facies were established. Role of stratigraphic controls in the distribution of oil shales within areas and outcrop sections, and their oil or gas generation capabilities were substantiated. The study of the source of oil shale parent rocks, and the features of oil shale basin that formed in the Eocene, Lower Maikop (first discovered in this study) and Miocene (Upper Maikop, Chokrakian and Diatom), made it possible to obtain some new regularities. Our results show that the kerogens of Eocene and Diatom oil shales demonstrate similar evolutionary histories that are noticeably different from the Maikop ones. Eocene oil shale kerogens, which show a closer connection with the marine environment demonstrate the ability to generate only oil, like Diatom kerogens, while the kerogen evolved in the Upper Maikop basin, which is subject to more terrigenous inputs and formed in a relatively freshwater environment, mainly shows the ability to generate gas.
... Isotopic signatures (δ 13 C CH4 and δ 2 H CH4 ) and the Noble-gas concentrations are useful tools to constrain the crustal origin of methane emission from theNirano mud volcano, Italy (Sciarra et al., 2019). The fluid-mud mixtures released by the South Caspian basin's mud volcanoes have the potential to alter the chemistry of nearby surface and groundwater as well as surface and subsurface sediments (Baldermann et al., 2020). The seepage gases from the vents/craters of mud volcanoes at the southern boundary of the Junggar Basin, NW China were found to be relatively enriched in methane and have lower concentrations of ethane and propane (Xu et al., 2022). ...
... Liu et al. (2013) reported that Na + and Cl − are dominating the other ions content in the samples of Wushanting mud volcanoes in China. The study conducted in Hsiaokunshui, China by Liu et al. (2013) also shows domination by Na + and Cl − , similar to the water samples in the Bahar mud volcanoes in Azerbaijan (Baldermann et al., 2020). Liu et al. (2013) also reported that high ionic strength in both locations of mud volcanoes. ...
... Ölkə ərazisində əksər neftli-qazlı rayonlarda yanar şistlərin yerüstü çıxışlarının intişarı və qənaətbəxş ehtiyatları haqqında çap olunmuş ədəbiyyatlarda məlumat verilir [1,5,6,7,[9][10][11]. Onu da vurğulayaq ki, həmin rayonlarda aşkarlanan yanar şist çıxışları, məhz palçıq vulkanlarının inkişaf tapdığı sahələrə demək olar ki, yaxın məsafədə yerləşirlər. Bu səbəbdən də, əsasən paleogen-miosen yaşlı yerüstü yanar şistlərin analoqları tez-tez palçıq vulkanlarının tullantı məhsullarında rast gəlinir [2][3][4]8]. Püskürmə nəticəsində yer səthinə yanar şist parçalarının xaric edilməsi bir sıra amillərdən, o cümlədən vulkanın yerləşdiyi ərazinin geoloji quruluşundan, tektonik səciyyələrindən və xüsusən püskürmə kanalının dərinliyindən asılı olduğu qeyd olunur [2][3][4]. ...
... Onu da vurğulayaq ki, həmin rayonlarda aşkarlanan yanar şist çıxışları, məhz palçıq vulkanlarının inkişaf tapdığı sahələrə demək olar ki, yaxın məsafədə yerləşirlər. Bu səbəbdən də, əsasən paleogen-miosen yaşlı yerüstü yanar şistlərin analoqları tez-tez palçıq vulkanlarının tullantı məhsullarında rast gəlinir [2][3][4]8]. Püskürmə nəticəsində yer səthinə yanar şist parçalarının xaric edilməsi bir sıra amillərdən, o cümlədən vulkanın yerləşdiyi ərazinin geoloji quruluşundan, tektonik səciyyələrindən və xüsusən püskürmə kanalının dərinliyindən asılı olduğu qeyd olunur [2][3][4]. ...
Tədqim edilən tədqiqat işində, fərqli geoloji quruluşa və tektonik səciyyəyə malik Şamaxı-Qobustan və Abşeron neftli-qazlı rayonlarında qeydə alınan və Azərbaycanın ən aktiv vulkanları sayılan Lökbatanın, Şıxzərli və Torağayın sonuncu püskürmələri nəticəsində tullanılan yanar şistlərin mineralogiyası və geokimyası təhlil olunur.
Süxurların kimyəvi tərkibləri “S8 TIGER Series 2 WDXRF” spektrometrinin, mineraloji komponentləri isə “MiniFlex 600” X-ray difraksiya cihazı ilə AMEA Geologiya və Geofizika İnstitutunda tədqiq edilmişdir.
Tədqiqatlar nəticəsində, analiz edilmiş süxurların tərkibindəki müxtəlif sinifləri təmsil edən minerallar müəyyənləşdirilmiş, öyrənilən üç vulkan sahəsi üzrə mineraloji xüsusiyyətlərin dəyişməsi ilə bağlı qanunauyğunluqlar aşkar olunmuş, həmçinin ümumilikdə, yanar şistlərin mineraloji təsnifatı təqdim edilmişdir. Şistli süxurlarda tapılan əsas elementlərin oksidlərinin ayrı-ayrı sahələr üzrə yayılması ilə əlaqədar variyasiyalar da izlənilmişdir. Bundan əlavə, yanar şistlərin geokimyəvi təsnifatı aparılmaqla yanaşı, Estoniyanın məşhur kukersit və ABŞ-ın tanınmış “Green River” formasiyasının eyniadlı süxurları ilə mineraloji və geokimyəvi müqayisələr həyata keçirilmişdir. Araşdırmalara, analiz olunmuş şistlərin mineraloji yetkinlik xüsusiyyətlərinin qiymətləndirilməsi də daxil edilmişdir. Geokimyəvi təsnifat diaqramı və ICV indeksi ilə bağlı alınan nəticələr geniş təhlil olunaraq, öyrənilən sahələrin yanar şistlərinin əmələgəlmə şəraitləri haqqında fikir formalaşdırılmışdır.
... Bakı arxipelaqı şimalda Balıqburnu burnundan başlayaraq cənubda Qızılağac körfəzinə qədər uzanan ada və banka (sualtı təpə) qrupu ilə təmsil olunur. Arxipelaqda və ona bitişik Cənubi Xəzərin dərinsu hissəsində 92 palçıq vulkanı -8 ada (Zənbil, Gil, Xərə Zirə, Qarasu, Səngi Muğan və b.) və bankalar vardır [12,13]. Vulkan brekçiyasının sualtı axınları dəniz dibində sualtı silsilələr və geniş örtüklər əmələ gətirirlər. ...
Yeni məlumatlara əsasən Şamaxı-Qobustan, Aşağı Kür və Bakı arxipelaqı neftli-qazlı rayon- larına aid palçıq vulkanlarının sopka brekçiyası ilk dəfə olaraq inteqrativ öyrənilmiş, onların yayıl- dıqları sahələrin geoloji quruluşları və struktur-tektonik xüsusiyyətləri nəzərə alınaraq, vulkan məhsulunun kimyəvi və mineraloji tərkibləri ilə əlaqəli bəzi qanunauyğunluqlar qeydə alınmışdır. Belə ki, Mərkəzi Qobustandan Bakı arxipelaqı istiqamətində palçıq vulkanlarının gündəlik fəaliyyə- ti nəticəsində səthə xaric olunan sopka brekçiyalarının paleohövzə şəraiti baxımından əmələ gəlmə- sində dəniz mühitinin təsirinin artdığı məlum olmuşdur. Mərkəzi Qobustana aid nümunələrdə Cu, V və Mo kimi mikroelementlərin daha yüksək göstərici nümayiş etdirmələri, zəngin üzvi maddə saxla- yan Eosen-Miosen yaşlı çöküntülərin sopka brekçiyasına verdiyi töhfə ilə əlaqələndirilir. Mərkəzi Qobustandan Xəzər dənizi istiqamətində, o cümlədən ada palçıq vulkanlarına doğru gil mineralla- rının konsentrasiyasının azalması, əvəzində çölşpatının artması tendensiyası brekçiyanı formalaşdı- ran ana süxurların paleoaşınma xüsusiyyətləri ilə, yəni qırıntıların paleohövzəyə gətirilmə məsafəsi və sürətindən asılı ola bilər.
... Последнее время в связи с расширением минеральносырьевой базы Азербайджана большое внимание уделяется изучению и освоению природных битумов. Основные скопления природных битумов в республике приурочены к нефтегазоносным районам (Апшерон, Шамахы-Гобустан и Нижняя Курия) и зонам распространения грязевого вулканизма [1][2][3][4]. ...
The current state and prospects for the development of bitumen deposits of Azerbaijan, which are of industrial importance, are considered. Detailed information about the types of bitumen and their classification is presented. It is shown that Azerbaijan has sufficient reserves of natural bitumen, which can be gradually involved in industrial exploitation
... Although mud volcanoes are not igneous volcanoes but they could be driven by magmatic activity. The largest mud volcanoes are to~700 m high (e.g., Odonne et al., 2020;Baldermann et al., 2020) but usually they are much smaller (e.g., see Fig. 13). They are oten associated with oil elds. ...
... Флюидо-грязевая смесь влияет как на химический состав подземных и поверхностных вод, так и глубинных и поверхностных отложений, а также на формирование геоэкологически сложных ландшафтов [35]. При ежедневной грифонно-сальзовой деятельности вулкана, из брекчии выделяются жидкие и газовые компоненты, что приводит к формированию морфологической структуры грязевого вулкана. ...
Влияние деятельности грязевых вулканов, расположенных на
территории нефтяных месторождений, на изменение уровня добычи нефти (на
примере грязевого вулкана Локбатан). В исследовании, используя различные
подходы и методологии, основное внимание уделено извержениям грязевого
вулкана Локбатан за последние два столетия, а также производственным
показателям, полученным в результате эксплуатационных работ на площади
его расположения и возможной взаимосвязи между ними. В связи с этим,
наряду с геологическими, глубинно-стратиграфическими и другими
свойствами площади расположения рассматриваемого вулкана, также были
изучены сейсмические показатели его извержений и продукты деятельности с
визуальной, минералогической, физико-геохимической точки зрения и
сформулировано мнение о корне вулкана и нефтегазопродуцирующих
материнских породах.
Изучена связь между происходящими на относительно больших
глубинах пароксизмами вулкана и пластовым давлением в находящейся на
глубине не более 2-х км Продуктивной толщи (из которой извлекаются запасы
углеводородов). Кроме того, в диссертации предусмотрено рассмотрение
влияния увеличения показателей производственности на активность вулкана,
а также вопроса непрерывной миграции углеводородов вверх по каналу
вулкана в Продуктивную толщу.
В работе отражены возможные закономерности и противоречивые
факты, в связи с силой извержений, происходящих после больших и малых
периодов покоя вулкана.
... Several authors have made attempts to investigate the rock-water interaction under different temperatures and different pressures. For example, Ellis and Mahon, (1964) and Baldermanna et al. (2020) carried out an experimental investigation on the chemical exchange and between water and rocks (e.g. volcanic and sedimentary rocks) at 150-600 • C and pressures ranging from 50 to 150 MPa. ...
Water-rock interactions exist between the geothermal host rock (GHR) and the cold injected water for Enhanced (or Engineered) Geothermal Systems (EGS), changing permeability and thermal conductivity of GHR, influencing the heat extraction of EGS. Therefore, a water-rock interaction experiment is performed under high temperature and pressure conditions for heat-treated granite. The variation in permeability and thermal conductivity, mineral composition, and solution composition of the rock matrix is consequently analyzed, and their influence on the heat extraction of EGS is discussed. The thermodynamic analysis of the chemical processes of the experiment is presented using batch chemical simulators, PHREEQC 3.0, reproducing the chemical time series of the water-rock reactions. Water-rock reaction changes the composition of the rock and the circulating fluid. For primary minerals, albite, anorthite, and k-feldspar dissolve, biotite tends to be stable, and quartz gradually increases. Secondary minerals, muscovite, calcite, kaolinite, and chlorite, are formed in our simulation results, and their source and generation mechanisms are discussed. However, the kaolinite and chlorite were not detected in the experiment due to their low quantity. Both the dissolution of primary mineral and the formation of secondary mineral change the permeability and the thermal conductivity of the granite. The permeability exhibits a transition from increasing to decreasing while the thermal conductivity shows an opposite variation. Both approach constant values but only at 60% of the initial value. However, from the long-term perspective, the change in permeability and thermal conductivity of the granitic host rock around the fracture will not exert a strong impact on the heat extraction of EGS. The test results in this context could facilitate our understanding of permeability characteristics and the evolution of thermal conductivity of a granitic host rock during the water-rock interaction, and their influence on the heat extraction of EGS during the operation process.
... Most of the outcrops found in these regions are located near areas of mud volcanoes. Therefore, analogues of the Maikop and Eocene shale rocks are often found in the ejecta of active mud volcanoes [2][3][4]8]. ...
... Şək.2.2.3. İslamdağ kəsilişinin təsviri[29]. ...
Azərbaycanda yerüstü yanar şistlərin proqnoz resursları təxminən 500 milyon ton ətrafında qiymətləndirilir. Onların kompleks tədqiqat nəticələri, o cümlədən üzvi-geokimyəvi səciyyələri və zəngin mineraloji tərkibləri belə süxurların gələcək istismarı üçün böyük perspektivlər formalaşdırır. Lakin respublikanın mövcud neftli-qazlı rayonlarının hüdudlarında inkişaf tapmış palçıq vulkanlarının tullantı məhsulları arasında da çoxlu yanar şistli süxurlar aşkarlanır. Yanar şistlər neft-qaz əmələgətirici süxur nöqteyi-nəzərindən perspektivli hesab olunduğundan, palçıq vulkanlarının tullantılarında rast gəlinən belə süxurların mineraloji və geokimyəvi baxımdan inteqrativ tədqiqi olduqca aktual hesab edilir.
Məlumdur ki, Azərbaycanın quru əraziləri ilə bağlı palçıq vulkanlarının ən geniş yayıldığı geoloji rayon Şamaxı-Qobustandan sonra Abşerondur. Bu rayonların geoloji və stuktur-tektonik xüsusiyyətlərindən irəli gələrək, palçıq vulkanları müxtəlif aspektlərdən fərqlənirlər. Xüsusən, Şamaxı-Qobustanın mərkəzində yerləşən palçıq vulkanları paleogen-miosen strukturları ilə əlaqələndirilir ki, sözügedən rayonun cənubunda və qonşu Abşeronda bu çöküntülər daha dərinə gömülür. Ona görə də bu rayonlarda yerləşən palçıq vulkanlarının paleogen-miosen yaşlı yanar şist tullantılarının tədqiqi, məhz müqayisə baxımından maraq doğurur.
Qeyd olunanlarla əlaqədar, dissertasiya işində sözügedən rayonların ən aktiv palçıq vulkanlarından olan, həmçinin müxtəlif geoloji, struktur və tektonik xüsusiyyətli sahələrdə yerləşən Şıxzərli, Torağay və Lökbatanın son püskürmə sahələrində aşkarlanan yanar şistlərin mineralogiyası və geokimyası ilə bağlı müqayisəli tədqiqatların aparılması ideyası irəli sürülmüşdür. Bundan başqa, tədqiqatlarda Şıxzərli palçıq vulkanına yaxın ərazidə təzahür edən eyniadlı sahənin maykop kəsilişinin yerüstü yanar şistli süxurları da korrelyasiya məqsədilə istifadə olunmuşdur.
... Changes in solution pH were followed with a WTW Multi350i combi instrument equipped with a SenTix41 electrode (Xylem Analytics Germany Sales GmbH & Co. KG, Weilheim, Germany), which was calibrated using buffer solutions of pH 4.01, 7.00 and 10.01 at 25 • C (analytical error: < 0.07 pH units; Baldermann et al., 2020a). ...
Nanoscale zero-valent iron (nZVI) based (nano)composites supported by clay mineral substrates are a promising technology for the in-situ remediation of groundwater and (sub)soils contaminated with chlorinated hydrocarbons, such as trichloroethene (TCE). However, the physicochemical processes and interaction mechanisms between nZVI particles, clay minerals and TCE are poorly understood, yet. We immobilized nZVI particles on a commercial bentonite substrate to prepare a novel nZVI-B nanocomposite and tested its performance for TCE removal from solution against pure nZVI in batch reactors. The nZVI-B exhibited a higher reactivity (2.2·10⁻³ L·h⁻¹·m⁻²) and efficiency (94 %) for TCE removal than nZVI (2.2·10⁻⁴ L·h⁻¹·m⁻²; 45 %). Sorption of TCE onto the clay surfaces and reductive de-chlorination in “micro-reactors” developing within the nZVI-B controlled the kinetics and the magnitude of TCE loss from solution. Contrary to pure nZVI, no signs of nZVI particle agglomeration or inactivation due to oxide shell formation were found in nZVI-B. We attribute this to the uptake of dissolved Fe species that are liberated via progressing nZVI particle corrosion by the bentonite substrate to form Fe-smectite (nontronite domains), which prevented from a deterioration of the properties and reactivity of the nZVI-B. The use of nZVI-B in permeable reactive barriers at contaminated field sites could be feasible, where a system-inherent reduction of the soil-bearing capacity has to be minimized.
... Açar sözlər: neftli qum, geokimya, mineralogiya, təsnifat, yetkinlik Giriş Azərbaycanda zəngin karboghidrogen resursları ilə yanaşı, bir sıra alternativ yanacaq-enerji və xammal statuslu faydalı qazınlıar (yanar şistlər, qazhidratlar və s.) vardır ki (4,5,10,12,13,19), onların sırasında neft saxlayan qumlu tərkiblər olduqca perspektivli hesab olunur (2, 3, 6, 17). Ölkənin əsas resursları karbohdrogen yataqları ilə bağlı olduğundan, ikincidərəcəli xammal ehtiyatlarının öyrənilməsi məsələsi bir qədər qənaətbəxş səviyyədə deyildir. ...
The paper is devoted to the study of two outcrops of oil sands located in the Absheron and Shamakhi-Gobustan oil and gas regions of Azerbaijan. The main goal of the study is aimed at forming an understanding of the genetic nature and classification of oil sands by their mineralogical and chemical indicators. In addition, the research priorities included the application of new approaches to the study of the mineralogical and geochemical properties of sandy rocks of Azerbaijan in comparison with those in Athabasca (Canada). Also, ideas about some of the features of the genesis were put forward on the basis of new (previously unknown) data obtained from the characteristics of maturity and classification of the studied sand samples.
... The fluids occurring in gryphons, pools and salsa lakes on the outskirts of the craters often display elevated salinity and even enrichments in metal and radioactive elements due to the underlying saline sediment layer, the high level of surface evaporation and diagenesis processes (Baldermann et al. 2020;Baloglanov et al. 2018;Conti et al. 2000;Liu et al. 2011;Mazzini et al. 2009). A number of studies (Huang et al. 2016;Mardanov et al. 2020;Ratnikova et al. 2020;Sepanian et al. 2018;Slobodkina et al. 2020;Tu et al. 2017Yakimov et al. 2002Yang et al. 2012;) reported halophilic prokaryotes from terrestrial mud volcanoes, as well. ...
Terrestrial mud volcanoes usually develop in overpressured, hydrocarbon-bearing sedimentary basins where argillaceous, viscous fluids and gases find passages to the surface. In this study mud samples collected at the Beciu mud volcano area (Romania) were examined using 16S rRNA gene amplicon sequencing technique. Bacterial communities were dominated by Proteobacteria, Patescibaceria, Bacteriodota, and Campilobacterota while Archaea by Halobacterota and Nanoarchaeota. All the most abundant taxa can be connected to the characteristic methane production of the onshore mud volcanism and/or the presence of a deep subsurface salt layer. The discharged methane might be utilized by the detected ubiquitous anaerobic methane oxidizers (ANME-1, ANME-2a-2b, ANME-3) coupling the reaction with the sulfate or sulfur reduction by representatives of genera Sulfurovum, Sulfurimonas, Desulfobacterales, Desulfuromonadales, Halanaeroarchaeum, and Halodesulfurarchaeum. In addition to methanotrophs, methylotrophic and acetoclastic methanogens were also detected. Most of the identified OTUs were associated with halophilic taxa. The results suggest that prokaryotes inhabiting the mud volcanoes can be participated in the closely interconnected methane and sulfur cycles.
This study describes the molecular dynamics (MD) simulations to investigate the effects of sulfur atom position on the solubility and aggregation properties of asphaltenes extracted from Zaghli crude oil (East Azerbaijan). Two different asphaltene models were studied, i.e., A1 with sulfur in the aromatic ring and A2 with sulfur in the aliphatic side chain. The radial distribution function (RDF) analysis revealed significant differences in aggregation trends. A1 exhibited rapid aggregation in both solvents used in the experiments, as evidenced by a significant decrease in the radius of gyration from 0.6 to 0.4 Å in octane and from 0.8 to 0.5 Å in xylene. In contrast, A2 showed increased solubility; especially in xylene with a marked increase in the radius of gyration from 0.5 to 2 Å. Furthermore, the energy analysis confirmed these results, i.e., A2 exhibited a higher total energy (451.16 kcal/mol) than A1 (221.28 kcal/mol); indicating a more energetically favorable and less aggregated state of A2. These computational results open up new possibilities for understanding the critical role of the sulfur atom position in the asphaltene structure on its aggregation propensity, which can be used to prevent asphaltene-related problems in the petroleum industry. The work is very useful in the oil industry for enhancing oil production by studying asphaltene solubility and aggregation.
MD simulations were performed using the COMPASS force field and Material Studio V.6 2017 software to evaluate the solubility of asphaltenes in octane and xylene solvents. Geometric optimization was carried out to address unstable interactions, with periodic boundary conditions applied. Simulations were conducted in the NVT ensemble at 298 K and 1 atm pressure, using a time step of 1 fs, a Nose thermostat for temperature control, and a Berendsen thermostat for pressure control. RDF analysis was utilized to examine the behavior of two distinct asphaltene models, which differed in the positioning of the sulfur atom, in the solvents. The total energy contributions, including van der Waals and electrostatic interactions, were also analyzed.
Статья посвящена изучению горючих сланцев палеоген-миоценового возраста из поверхностных выходов и твердых выбросов грязевых вулканов Шамахы-Гобустанского района и Абшеронского полуострова. Приводится подробное описание минералов горючих сланцев по соответствующим категориям. Проведены анализы на основании химических свойств и некоторых классификаций. Исследования особенностей палеовыветривания выполнены на основании «Химического индекса изменения» (ХИИ), «Химического индекса выветривания» (ХИВ), «Плагиоклазового индекса изменения» (ПИИ), «RR = SiO2/Al2O3» - Химического индекса выветривания, «(Al2O - K2O) – CaO – Na2O», «A-CN-K», а также диаграмм, отражающих мобильные свойства элементов, на основе результатов оценки больших ионов литофильных элементов.
Mud volcanoes are widespread in the Azov-Black Sea, Caspian and some other regions of the World. Much researches have shown that mud volcano breccias contain important information about deep sedimentary rocks that are drained by mud volcanoes.
Thus, the study of the breccias composition makes it possible to obtain information about deep drained rocks composition and its stratigraphic level and realize mud volcanoes as a “free of charge boreholes”.
Azərbaycanda, ümumilikdə 55 bitumlu sahə aşkarlanmışdır. Onlar, əsasən Abşeron,
Şamaxı-Qobustan və Aşağı Kür neftli-qazlı rayonlarında qeydə alınırlar. Bitum saxlayan çöküntülərin
geoloji yaşları, əsasən miosen-pliosenlə əlaqələndirilir. Adıçəkilən rayonların ən
perspektivli sahələri sırasında Axtarma-Puta (Abşeron), Çeyildərə (Şamaxı-Qobustan) və Aralıq
(Aşağı Kür) xüsusi yer tutur ki, onlar palçıq vulkanları inkişaf edən strukturlarla əlaqədardır.
Tədqiqat işində də məhz adları çəkilən sahələrin miosen-pliosen yaşlı neftli qumları mineraloji və
geokimyəvi nöqteyi-nəzərindən geniş araşdırılır.
Azərbaycanda zəngin karbohidrogen resursları ilə yanaşı, bir sıra alternativ yanacaq-enerji və xammal statuslu faydalı qazıntılar (yanar şistlər, qazhidratlar və s.) vardır ki, onların sırasında neft saxlayan qumlu tərkiblər olduqca perspektivli hesab olunur. Ölkənin əsas resursları karbohidrogen yataqları ilə bağlı olduğundan, ikincidərəcəli xammal ehtiyatlarının öyrənilməsi məsələsi bir qədər qənaətbəxş səviyyədə deyildir. Lakin bununla yanaşı, bəzi bitum saxlayan sahələrin müəyyən geoloji və geokimyəvi xüsusiyyətlərinin öyrənilməsi, həmçinin proqnoz resurslarının qiymətləndirilməsi ilə bağlı təqdirəlayiq tədqiqatlar da az deyildir.
Təqdim olunan dissertasiya işi, Azərbaycan üçün qeyri-ənənəvi yanacaq-enerji resurslarının əldə olunması üçün xammal mənbəyi hesab olunan neftli qum sahələrinin, o cümlədən Axtarma-Putanın, Çeyildərənin və Aralığın mineraloji və geokimyəvi araşdırılmasına həsr olunur.
Tədqiqat obyektlərinin bitumlu qumlarının sözügedən araşdırmaları, müasir müvafiq yanaşma və metodologiyaların tətbiqi ilə həyata keçirilmişdir.
Ərsəyə gətirilən dissertasiya işində, neftli qumların ümumi əmələgəlmə xüsusiyyətləri, tərkibləri, təsnifatları, dünya üzrə yayılma coğrafiyaları, geoloji xüsusiyyətləri və proqnoz resursları və s. geniş müzakirə olunur. Bundan başqa, tədqiqat sahələrinin neftli qum təzahürlərinin geoloji və struktur-tektonik xüsusiyyətləri, mineraloji və geokimyəvi səciyyələri geniş araşdırılaraq, dünyanın ən çox tanınan bitumlu qum yatağı hesab olunan Atabaskanın eyniadlı süxurları ilə müvafiq müqayisələr aparılmış, eyni zamanda araşdırılan obyektlərin timsalında Azərbaycanın bitum tərkibli qumlarının və onun karbohidrogenli hissəsinin bəzi ümumi xarakteristikaları müəyyənləşdirilimişdir. Analiz edilmiş nümunələrin mineraloji təbiəti, geokimyəvi təsnifatları və geokimyəvi yetkinlik xüsusiyyətləri müəyyənləşdirilərək, ümumilikdə, öyrənilən sahələrin neftli qum saxlayan çöküntülərinin paleohövzə və paleotektonik əmələgəlmə xüsuiyyətləri haqqında fikir formalaşdırılmışdır.
The study examines the mineralogical and geochemical characteristics of oil shales of the Lokbatan and Shikhzarli, located in various oil and gas regions and considered the most active mud volcanoes in Azerbaijan. In addition, the samples of the Maikopian oil shale from the Shikhzarli outcrops were used for comparison. The mineral classes in the composition of shale rocks were determined and a mineralogical classification is given. In terms of major oxide composition, the famous Estonian kukersite and the well-known oil shale of the Green River Formation in the USA were compared. The results of the geochemical classification diagram and ICV were widely discussed and the genetic characteristics of the shale samples have been investigated. Based on the obtained results, the similarities and differences between the oil shale of the two regions were determined.
The chemical classifications, provenience, palaeoweathering and maturity characteristics of the Middle Eocene oil shale sampled from the outcrops and ejecta products of mud volcanoes in Shamakhi-Gobustan and Absheron Peninsula, Azerbaijan were widely considered using mineralogical and bulk-rock geochemical signatures. The concentrations of major and trace elements and minerals were measured by “S8 TIGER Series 2 WDXRF”, “Agilent 7700 Series ICP-MS” mass spectrometers and XRD “MiniFlex 600”. The microscopes “Loupe Zoom Paralux XTL 745” and “MC-10” and a digital camera “OptixCam” were used to determine the age of the samples.
The major and trace elements in the composition of samples were compared with average shale, NASC, PAAS and average black shale as well as oil shale from the Green River Formation of the USA, Kukersit of Estonia, etc. studied in the published literature. A diagram and index were used for the classifications and determination of maturity of rocks. The palaeoweathering characteristic was determined based on CIA versus ICV and some other plots and ratios.
The minerals found in oil shale were classified according to their classes. It was established that all studied samples correspond to shale based on the used classification diagram. A superiority of clay minerals in the composition of oil shale compared to K-minerals, including K-feldspar was found.
The estimates based on geochemistry and some ratios of elements confirm the instability of oxides and minerals, and immaturity features of samples.
The values of the CIA, CIA versus ICV plot, etc. suggest a moderate to high degree of weathering. The results confirm a conclusion that the original sediments were derived from mafic and intermediate source terrains.
The reconstruction of regional long‐term patterns recorded in marine sedimentary successions of the Eastern Paratethys is important in understanding the role of Cenozoic climate change and orogenic activity on the depositional environment and sedimentation dynamics in Western Asia. In this study, the environmental conditions in the early to middle Miocene (Islam Dağ section) in eastern Azerbaijan are elucidated using petrographic‐mineralogical relations, detrital indicators, weathering indices and δ13C and δ18O signatures of organic‐rich (total organic carbon: ca 3 to 6 wt. %) argillites. Sedimentary facies and chemical proxies (Na/K, K/Al, Si/Al Ti/Al ratios, chemical index of alteration values) indicate arid conditions, reduced weathering rates in the hinterland and sediment deposition in an euhaline and poorly oxygenated deep‐water basin during the early Miocene, followed by a shift to humid conditions, higher weathering rates and an oxygenated water column in the mid‐early Miocene. Long‐term aridification and deposition of gypsiferous and calcareous argillites under generally more oxygenated, euhaline to polyhaline conditions in a lacustrine or restricted shelf setting until the middle Miocene is evidenced by gradual changes in element ratios and the chemical index of alteration. Discriminant function analysis suggests the Russian Platform, drained by the Palaeo‐Volga and Palaeo‐Don river systems, to be the source area for the siliciclastic input throughout the Miocene, although a minor contribution of volcanogenic detritus and mafic components from the Greater Caucasus is possible. C–S–Fe associations and increasing Fe/Al ratios toward the middle Miocene support the concept of continuous influx of detrital Fe and total organic carbon. The formation of ferruginous smectite from alteration of volcanic ash layers could have affected the preservation of total organic carbon and therefore the sedimentary C and Fe budget in the Eastern Paratethys basins. Palaeo‐climatic reconstructions based on δ13C (‐34·5 to +1·7 ‰ VPDB) and δ18O (‐34·7 to ‐4·8 ‰ VPDB) records of authigenic carbonates should be made with great caution, as the pristine marine signatures may be affected by the oxidation of organic matter and meteoric diagenesis. This article is protected by copyright. All rights reserved.
This paper is devoted to the vein and dispersed carbonates from ejecta of mud volcanoes of Azer-baijan. The vein calcites are morphologically diverse and related to the healing of fracture systems. Most of them have δ 13 C (from-4 to +2‰) and δ 18 O (from +20 to +26‰) typical of marine carbonates. Some volcanoes contain fragments of the vein calcites enriched in light carbon (δ 13 C from-49.2 to-6‰), which could be formed in methane seep discharge sites during the Caspian Sea highstand period. In the dispersed carbonates from the clay pulp, the values of δ 13 C and δ 18 O change from-6.1 to +11.9‰ and from +23.8 to +32.7‰, respectively. It is shown that the studied carbonate matter has no genetic relation with the modern mud volcanic waters, which are characterized by high concentrations of (up to 8 g/L) and values of δ 13 C(TDIC) (δ 13 C av = +20.0‰) and δ 18 O(H 2 O) (δ 18 O av = +4.0‰). Based on isotope characteristics and REE patterns, the vein calcites can be ascribed to the products of seawater-assisted postsedimentation transformation of sedimentary carbonates. The obtained data revealed a complete hydrodynamic isolation of mud volcanic channels from aquiferous complexes of host rocks.
There are 2508 mud volcanoes in 42 geographic regions of the world. The territory of East Azerbaijan and the adjacent Caspian Sea is characterized by a wide distribution of mud volcanoes on a global scale. The total number of mud volcanoes in Azerbaijan is 353, of which 154 are marine. Compared to other geographic regions, the country's mud volcanoes differ in the number of eruptions and their daily gryphon and salse activity. In addition, the registration of all types of mud volcanoes in Azerbaijan has led to the fact that the country is called "the land of mud volcanoes". In this regard, the mud volcanoes of Azerbaijan create favorable conditions for the study of volcanic activity from the point of view of environmental hazard. The article studies the content and total amount of gases emitted into the atmosphere, and the degree of mineralization of waters, as well as the organic and elemental composition of breccias. Areas with a high anomalous radioactive background in the crater area were identified and the reasons for its occurrence were explained. An associative relationship was found between an increase in the level of gamma radiation and the concentration of uranium for breccia samples taken from an area with a higher radioactive background. The chemical, including the radioactive contents of the water and breccia samples, were compared to the average concentration of the elements in drinking water and sedimentary rocks, respectively.
The capacity and mechanism of the adsorption of aqueous barium (Ba), cobalt (Co), strontium (Sr), and zinc (Zn) by Ecuadorian (NatAllo) and synthetic (SynAllo-1 and SynAllo-2) allophanes were studied as a function of contact time, pH, and metal ion concentration using kinetic and equilibrium experiments. The mineralogy, nano-structure, and chemical composition of the allophanes were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and specific surface area analyses. The evolution of adsorption fitted to a pseudo-first-order reaction kinetics, where equilibrium between aqueous metal ions and allophane was reached within <10 min. The metal ion removal efficiencies varied from 0.7 to 99.7% at pH 4.0 to 8.5. At equilibrium, the adsorption behavior is better described by the Langmuir model than by the Dubinin–Radushkevich model, yielding sorption capacities of 10.6, 17.2, and 38.6 mg/g for Ba 2 + , 12.4, 19.3, and 29.0 mg/g for HCoO 2 − ; 7.2, 15.9, and 34.4 mg/g for Sr 2 + ; and 20.9, 26.9, and 36.9 mg/g for Zn 2 + , by NatAllo, SynAllo-2, and SynAllo-1, respectively. The uptake mechanism is based on a physical adsorption process rather than chemical ion exchange. Allophane holds great potential to effectively remove aqueous metal ions over a wide pH range and could be used instead of other commercially available sorbent materials such as zeolites, montmorillonite, carbonates, and phosphates for special wastewater treatment applications.
The paper is devoted to a detailed study of oil shale that is considered a new alternative energy and fuel resource for Azerbaijan. More than 60 surface manifestations of oil shale, related to sediments between Eocene and Miocene in the territories Shamakhi-Gobustan, Absheron, Pre-Caspian-Guba, Vandam-Lahij and etc. of the Republic are investigated on its distribution regularity and geochemical properties. Oil shale of these epochs, which can’t be reached due to exploration wells, but brought from the different depths to the Earth’s surface (where oil shale surface manifestations widely distributed) by eruptions of mud volcanoes have been studied as well. Along with geochemical study of oil saturated rocks, found in ejected production of mud volcanoes, a comparative analysis have been conducted on heavy fractions, obtained from these rocks and oil shale. The results of these studies show that bitumen (its heavy fractions) of Eocene-Miocene oil shale and oil-saturated rocks are similar, and may cause to formation and accumulation of hydrocarbons in ultra-deep sediments of mud volcanic areas. All conducted investigations are increasing the topicality of perspectives of shale gas in Azerbaijan, which is non-traditional for the country.
Azerbaijan is a classic country of oil and gas. The fact prevent use of other types of minerals which are spread over a wide range in some regions of Republic. However, in recent years, due to the dynamic development of the industrial and consumer sectors in Azerbaijan, the requirement for new energy resources are growing, and the idea of exploring alternative energy sources such as oil shale becomes very important. The article is devoted to the study of geology and geochemistry of oil shale, founded in the surface and ejected rocks of mud volcanoes, and estimation its probable reserves. Oil shale manifestations and deposits are located mainly in Guba, Ismayilli, Shamakhi, Gobustan, Absheron and other regions in Azerbaijan, and associated with Cretaceous-Miocene sediments. The calculations of oil shale reserves (probable) were performed only using surface and extrapolation data. However, a study ejected products of mud volcanoes confirms that deeper sediments of mudvolcanic areas contain large stock of oil shale. There is no doubt that total reserves will increase with drilling deep wells in these areas. In the paper, to estimate of hydrocarbon potential of deep sediments on the basis of geological and geochemical study of oil shale and oil-bearing rocks association in ejected products of mud volcanoes is the first investigation.
The Valley of Lakes is approximately a 500-km elongate depression in Central Mongolia, where Eocene to
Miocene continental sediments are long known for their outstanding fossil richness. The palaeontological record of this region is an exceptional witness for the evolution of mammalian communities during the Cenozoic global cooling and regional aridification. In order to precisely elucidate the climatic evolution of the region, we studied the mostly siliciclastic sediments with several levels of paleosols for their sedimentology,
mineralogy, major and trace element composition and δ13C and δ18O composition. The obtained results show that temperate hydrothermal fluids induced a strong illitization of the fluvial and lacustrine sediments. This finding contradicts the current conceptual view that the fine fraction of the sediments is of aeolian origin. Moreover, the diagenetic growth of illite resulted in a strong overprinting of the sediments and, subsequently, largely disturbed the pristine mineralogical and geochemical composition of the sediments that could have
carried any palaeo-climatic information. An exception is the δ13C (and δ18O) isotope values of authigenic carbonate found in calcrete horizons that still record the ambient climatic conditions prevailing during paleosol formation. Our novel δ13C and δ18O record suggests an early Oligocene aridification in Central Asia at ∼31 Ma, whereas the Oligocene glacial maximum shows no increase in aridification. A second, regionalscale aridification occurs at ~25 Ma and corresponds to a late Oligocenemarkedmammalian turnover in the Valley of Lakes sediments.
The research work presents clay mineral composition in the sediment of the Pliocene Productive Series from western South Caspian Basin and identify potential source areas for the different research regions. The Productive Series is a main reservoir unit in the South Caspian Basin and divided into a lower division and an upper division. The clay mineral assemblages document coinciding changes in provenance. At the time of the deposition of the Lower Division, the Russian Platform was a potential source area for the Absheron Peninsula and drained by Palaeo-Volga River. However, at the time deposition of the Upper Division three different sediment source could be identified for the three research areas: Absheron Peninsula - the Russian Platform was drained by the Palaeo-Volga; South Absheron Offshore Zone - the Greater Caucasus was drained by the Palaeo Samur River; Baku Archipelago - the Lesser Caucasus was drained by the Palaeo-Kura River.
During repository building measures a natural river was relocated and the water was directed through a new, artificial river bed lined with a concrete basement and local colluvium. Shortly after, centimetre-thick, beige-colored sinter-crusts were observed in the river bed. An environmental monitoring program launched in order to understand the rapid precipitation process revealed pH values up to 12.9 and high Ca2+ concentrations (196 mg/l) at near-freezing water-temperatures. A first set of crystal aggregates collected was found to disintegrate into a light-colored calcite powder at ambient temperature within few days only. Thus, the metastable precipitates were recovered in original solution and stored in a constantly-cooled refrigerator box. Immediate XRD, FT-IR and ESEM analyses revealed “ikaite” – calcium carbonate hexahydrate – being the rarely documented mineral never reported from such an environmental setting before. Ikaite typically forms in a narrow temperature range (<4-8 °C) from strongly supersaturated solutions, e.g. some specific lake-, sea- and spring-water mixing locations, Arctic- and Antarctic sea-ice. In the present case, enhanced portlandite (Ca[OH]2) dissolution from the concrete river basement by water inflowing during wintertime provided exceptional hydrochemical conditions suitable for rapid ikaite crystallization, e.g. of up to 2 kg d-1 m-2 in a particular stream section. Sampling sites from which ikaite was documented yielded pH >11 probably reflecting some lower limit of ikaite formation. Our findings do not support nucleation inhibitors (aqueous phosphate, magnesium, organic constituents), strongly elevated ionic strength (brines), or water-mixing as a crucial demand for ikaite precipitation. In this “natural laboratory” distinct ikaite vs. calcite spatial distribution encountered along the stream, and thus the spatiotemporal evolution of fluid-solid interaction could be studied. Finally, the prominent and widespread ikaite precipitates vanished rapidly during pronounced springtime air- and water-temperature rise >6 °C superimposed on more gradual hydrochemical changes, e.g. decrease of pH and Ca2+. The latter development highlights the critical temperature restriction of ikaite occurrence and stability. Anthropogenic combined with natural hydrogeochemical processes observed in this study are of interest for both applied and fundamental environmental research.
A transition from incipient to extensive illitization in these sandstones is associated with a present burial depth of 3.7 km below the sea floor, corresponding to a formation temperature of 140°C. Illite has formed by reaction between K-feldspar and earlier diagenetic kaolinite and probably also by alteration of mica. -from Authors
A synopsis of the stratigraphy of Eastern Paratethys is provided. Particular emphasis is placed on the Black Sea. An attempt is made to place the regional stratigraphy in a (global) sequence stratigraphie framework for the first time.
Solute geothermometers (i.e. silica and cation) for the Bath Mineral hot springs discharged from fissures and fractures at the ground surface in eastern Jamaica were compared to estimate the temperature of the geothermal reservoir. Partial equilibrium exists between aqueous species in the reservoir fluids and the mineral assemblage quartz. The Na-K-Mg Geoindicator by Giggenbach (1988), Na-K geothermometers and the silica geothermometer based on quartz solubility appear to be the most reliable indicators of reservoir temperature. Temperatures estimated using Na-K-Ca geothermometers were either too high or low to be considered reliable. Overestimation of reservoir temperatures by the Na-K-Ca geothermometer may be due to (1) equilibration at conditions that are hotter and deeper than existing areas of mixing and circulation of groundwater and (2) conductive heat loss. Alignment of the hot springs is related to the structural and tectonic setting of a major strike-slip fault-the Plantain Garden Fault. Hydrogeochemical investigations of the hot springs resulted in reliable estimates of reservoir temperatures ranging 80ºC-102ºC at depths of 1-1.8 km. Results indicate that the localized upwelling of low enthalpy geothermal waters at Bath have sufficient heat-generating capacities and warrants further exploration using geophysical techniques and hyperspectral imaging.
The effects of the human impact on the coastal environments and relative biota can be different and even greater than those derived by natural fluctuations. The major disturbance causes in the coastal systems are rivers that may be important sources of nutrients and pollutants, particularly in a semi-closed basin such as the Adriatic Sea. In this context, we investigated the distribution of both meiobenthic and nematode assemblages in the Central Adriatic Sea to evaluate whether and how they are influenced by riverine discharges and which faunal descriptors are the most effective in detecting this type of stress. On the basis of our results, the disturbance effects in the studied area might be caused by both local streams and Po plume, and even if the latter might be considered of lesser extent, it is worthy to note its real impact at a short distance from the coastline. Meiobenthic assemblage structure appears as a good tool for detecting short-term responses of the benthic domain, whereas nematode assemblages seem more useful for defining long-term responses. Accordingly, the former highlighted from poor to sufficient ecological quality status (EQS) of this area, whereas the latter from moderate to bad EQS. Life strategy traits prove to be the most informative faunal descriptor due to their high correspondence with the environmental variables and particularly with this type of disturbance.
In paper based on the results of previous stud-ies and latest investigations of mud volcanoes in the South Caspian basin the depth occur-rence of fluid, mud and rocks are calculated and modeled. Major factors causing formation of diapirism/mud volcanism in the South Caspian basin are Pliocene-Quaternary high sedimenta-tion rates (up to 3 km/my), super thick sedi-mentary cover (up to 25 -30 km), predominance of clayey rocks (reaching 80%) in the section, low temperatures (with 15˚C -18˚C/km gradient), overpressures reaching lithostatic, the onset of petroleum generation lowered to considerable depths. The majority of the mud volcanoes are associated with the petroleum bearing struc-tures. Depths where the liquid, gaseous and solid products of mud volcanoes are sourced appear to be different. The gases have the deep-est roots (7 -15 km) which are the main force in formation and activity of MVs. Source of the fluidized clayey mass does not lie below 3 -4 km. Oils emitted by mud volcanoes are the product of destruction of petroleum accumulations oc-curring beneath them.
High sedimentation rates (as much as 2500 m/Ma) during Pliocene-Pleistocene, with a resultant undercompacted section as thick as 10,000 m, and lower than normal geothermal gradients are the main characteristics which have created all the means for generation and preservation of oil at deep layers in the Lower Kura Depression.Oils collected from eight different oil fields for analyses seem to have originated from a common source rock which probably is clastic, deposited in relatively subanoxic to suboxic transitional marine environment receiving low to moderate input of terrestrial organic matter.Oils from shallow (< 3000 m) and cold (< 70–80°C) reservoirs have been altered to various extent by bacterial activity.A computer-aided basin modeling study has been carried out to outline the spatial variation of the oil window and thus help in further identification of possible source rocks for the reservoired oil in the Lower Kura Depression. Results suggest that the potential hydrocarbon source horizons of the Miocene and Pliocene Red Bed Series of the so called Productive Succession are, even at depocenter areas, immature with respect to oil generation, and thus, are very unlikely to have been source rocks for the reservoired oils. However, the Oligocene-Lower Miocene Maykop rocks are marginally mature to mature depending on locality and the Eocene and older rocks are mature with respect to oil generation at all representative field locations. Oil generation commenced at the end of Pliocene and continues at present at depths between 6000 and 12,000 m.An unusually deep (> 10,000 m) oil window in the depocenter areas has been caused by the depressed isotherms due to extremely high sedimentation rates (up to 3000 m/Ma) for the last two million years. The main phase of oil generation is taking place at depths greater than what most of the wells in the study are have reached.
Understanding fluid sources, water-rock interactions and the biogeochemical processes involved in terrestrial mud volcanoes is necessary in order to predict the chemical processes most responsible for methane emissions to the atmosphere. Mud sediments ejected from the Dushanzi and Sikeshu mud volcanoes, located along the southern margin of the Junggar Basin, northwestern China, were collected by hand core sampling in order to explore whether surface and subsurface geochemical processes occur in their fluids. The ionic compositions of the pore fluids, minerals and major elements of the ejected sediments and surface sediments were analyzed. The pore fluids were mainly derived from ancient deeper sedimentary fluids which had mixed with meteoric surface water, but altered by diagenesis processes. Relative to seawater, the mud volcano pore fluids have higher ratios of Na/Cl and Li/Cl and lower ratios of K/Cl and Mg/Cl. The mud sediments are also enriched in illite, chlorite and calcite, but depleted in smectite. In addition, they are enriched in Ca and Mn, followed by Fe, Mg and P, and depleted in Si relative to the wall rocks. These chemical and mineralogical changes in the mud sediments and pore fluids are related to diagenesis processes. Clay mineral dehydration (mainly involving the conversion of smectite to illite) released large amounts of water. Ion exchange among clay minerals increased Na+ in the pore fluid. Water-rock interaction increased Fe and Mn, but decreased Si in the mud sediments. Carbonate precipitation decreased Ca2+ and Mg2+ concentrations of the pore fluid but increased Fe, Mg and P in the mud sediments. These results indicate that the mud volcanoes system is continuously recharged from deeper sedimentary sources. The difference in fluid and sediment geochemistry of the mud volcanoes can be ascribed to the different depths of the fluid and mud sources and the different diagenesis processes during the rising of fluid and mud.
Mud volcanism and diapirism have puzzled geoscientists for ~2 centuries. They have been described onshore and offshore in many places on Earth, and although they occur in various tectonic settings, the majority of the features known to date are located in compressional tectonic scenarios. This paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described. Mud volcanoes show variable geometry (up to tens of kilometers in diameter and several hundred meters in height) and a great diversity regarding the origin of the fluid and solid phases. Gas (predominantly methane), water, and mud may be mobilized at subbottom depth of only a few meters but, in places, can originate from several kilometers depth (with minor crustal or mantle input). The possible contribution of mud extrusion to global budgets, both from quiescent fluid emission and from the extrusive processes themselves, is important. In regions where mud volcanoes are abundant, such as the collision zones between Africa and Eurasia, fluid flux through mud extrusion exceeds the compaction-driven pore fluid expulsion of the accretionary wedge. Also, quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and, hence, to greenhouse climate.
This paper presents new geochemical data of hydrocarbon-rich gases released from some mud volcanoes of Azerbaijan. Methane is considerably the most abundant component of all the sampled gases, which show δD-CH4 and δ13C-CH4 values likely related to a dominant thermogenic source. These gases are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several μmol/mol. A similar gas composition has recently been found to characterize many mud volcanoes of the Northern Apennines and Sicily (Italy). The data of the Azerbaijan mud volcanoes corroborate the notion that cyclic compounds can be considered reliable tracers for hydrocarbon gas production at considerable depths and temperatures up to 120-150 °C, which correspond to a 6.5-8.3 km depth range assuming an average geothermal gradient of 18 °C/km. This depth interval is consistent with both the depth of potential source rocks imaged seismically beneath some mud volcanoes, and the results of previous estimates that used the 13C/12C values of methane and ethane. Such deep-sourced gases and material (fluidized clayey mass and rock fragments) ascend into the core of anticlines and accumulate at shallower reservoirs, where fold-parallel outer-arc faults or fold-orthogonal fractures may penetrate and transfer the fluids to the surface. Finally, the basically equivalent composition of the different hydrocarbon groups (C2-C10 alkanes, aromatics and cyclic) determined in the gases sampled in both Azerbaijan and Italy manifests the lack of evident relationships between the chemistry of light hydrocarbons and the type of source rock.
To understand the role played by microorganisms in the formation of cold seep carbonates, we conducted an integrated microbial, mineralogical and organic geochemical study of methane-related authigenic carbonate crusts formed on eastern Mediterranean mud volcanoes. We show that supersaturation with respect to carbonate minerals is induced by microbial anaerobic oxidation of methane. Combined lipid biomarker analysis and 16S rRNA gene surveys identified a highly diversified methane-consuming archaeal community possibly comprising novel species, implying that the anaerobic oxidation of methane is phylogenetically widespread and directly implicating these organisms in the process of crust precipitation. Moreover, pore-water sulphate gradients produced by co-occurring methane-based sulphate reduction exert the main control on aragonite versus magnesian calcite precipitation. We propose that this may be the dominant mode of carbonate crust formation at cold seeps world-wide, in agreement with aquatic chemistry predictions and explaining carbonate mineralogy.
The SEM, XRD, FTIR and DTA analyses of different size-fractions of clay material from sandstone reservoirs which have experienced a large range of burial conditions have been used to examine the different steps of the depth-related kaolinite-dickite reaction. Dickite progressively replaced kaolinite within a range of burial depths estimated between about 2500 m and 5000 m. The kaolinite-to-dickite reaction proceeds by gradual structural changes concomitant to crystal coarsening and change from booklet to blocky morphology. The crystallization of dickite proceeds by two distinct paths: (1) Accretion of new material from either dissolution of smaller unstable kaolinite crystals and/or detrital minerals (chiefly feldspars), on early-formed coarser metastable kaolinite crystals which exert extended morphological control on the growing crystals. (2) Neoformation of ordered dickite which will continue to grow by a dissolution-crystallization process. The kaolinite-todickite reaction is kinetically controlled and anomalies in the kaolinite/dickite ratio observed in certain sandstone reservoirs may be used to assess the timing of invasion by hydrocarbons.
ABSTRACT In the foothills of the Northern Apennines mud volcanoes are locally aligned along active normal faults, which allow surface leakage of fluids derived from deep sources (>3–6 km). The chemical and isotopic analysis of the fluids of a mud volcano, coupled with the reconstruction of its geological setting, allowed an investigation of the processes of migration and fluid flow. The fault system associated with the Regnano mud volcano drains a deep Miocene reservoir (foredeep marine deposits), which supplies formation water and thermogenic methane that has migrated from underlying Mesozoic carbonates. The muds from the volcano contain late Eocene microfossils and are extruded only during paroxysmal events. They have a shallower origin (about 1 km) from the base of Tertiary marine deposits deposited upon the upper tectonic nappe of the chain (Ligurian unit). This case study suggests that normal faults are very effective in controlling surface emissions.
A B S T R A C T
Numerous mud volcanoes (MVs) of the Kerch Peninsula emit water and mud with extreme boron enrichment. Boron content correlates with the burial depth of the source Oligo-Miocene Maykop mudrocks yielding the highest boron contents in illite-dominated mud (up to ~900–1500ppm B) and clay fractions found in the Bulganak MV, which represent the deep endmembers (up to 3.5km) in the Kerch Peninsula. Smectite-dominated mud and clay fractions from shallow depths (1–1.5km) at small MVs are poorer in both illite and boron (66–250ppm).
B-enrichment of the parent shale and diagenetically-driven smectite illitization and dewatering may be main prerequisites for boron enrichment in MVs. The majority of both Cl-HCO3/Na and HCO3-Cl/Na highly evolved saline MV waters sampled in large MVs are enriched in 18O (δ18O=+9.8 to +14.5‰ VSMOW) and D (δD=−30 to −4‰ VSMOW) isotopes being also rich in boron (average 650ppm). Waters of small MVs with shallow roots are poorer in 18О (δ18O=+3.6 to +6.1‰) and B (average 130ppm). MV waters are mainly related to diagenetically altered basinal water diluted by 18O-enriched fresh water released during smectite illitization. The fluid generation temperatures inferred to be ТMg/Li=34 to 117°С correspond to source depths of 1.0 to 3.5km, at 30–35°C/km regional geothermal gradients. In the hot season, MV waters reach a salinity of 40–70g/L total dissolved
solids and precipitate halite, ulexite, borax and tincalconite. At the Bulganak MV field, there is a unique accumulation of MV-related non-marine borates. Such borate deposits can form at the following essential conditions: venting of B-rich MV waters; environment akin to playa lake; long dry and hot seasons; evaporation and ensuing increased boron concentration in shallow close MV pools; pH of MV water between 8.5 and 9.5; low permeability of clayey mud cover.
Mud volcanoes are feature of the coastal margins where anaerobic oxidation of methane triggers geochemical signals. Elemental composition, percentage of fine particles and loss on ignition were determined in sediment layers of eleven gravity cores retrieved from four mud volcanoes (Sagres, Bonjardim, Soloviev and Porto) and three undefined structures located on the deep Portuguese margin of the Gulf of Cadiz. Calcium was positively correlated to Sr and inversely to Al as well as to most of the trace elements. Vertical profiles of Ba, Cd and As concentrations, and their ratios to Al, in Porto and Soloviev showed pronounced enhancements in the top 50-cm depth. Sub-surface enhancements were less pronounced in other mud volcanoes and were absent in sediments from the structures. These profiles were interpreted as diagenetic enrichments related to the anaerobic oxidation of methane originated from upward methane-rich fluxes. The observed barium fronts were most likely caused by the presence of barite which precipitated at the sulphate-methane transition zone. Cd and As enrichments have probably resulted from successive dissolution/precipitation of sulphides in response to vertical shifts of redox boundaries.
The calcium carbonate hexahydrate mineral ikaite (CaCO3 ⋅ 6 H2O) has been documented in aquatic environments at near-freezing temperatures. An increase of the prevailing temperature in the depositional environment, results in the transformation of natural ikaite into less soluble calcium carbonate phases occasionally leaving calcite pseudomorphs in the sediments, which are considered as an indicator for primary cold water temperatures. Detailed understanding on physicochemical parameters controlling ikaite (trans-)formation however, such as temperature and reactive solution chemical composition, are still under debate. In order to study the formation of ikaite, we conducted precipitation experiments under controlled physicochemical conditions (pH = 8.3 ±0.1; T = 6, 12, and 18 ±0.1 °C) at distinct aqueous molar Mg/Ca ratios. The transformation of ikaite into anhydrous calcium carbonate polymorphs was investigated in solution and at air exposure. The obtained results reveal formation of ikaite at temperatures up to 12°C, whereas Mg-rich amorphous calcium carbonate precipitated at 18°C. In contact with the reactive solution ikaite transformed into aragonite at aqueous molar Mg²⁺/Ca²⁺ ratios of ≥ 14. In contrast, ikaite separated from the Mg-rich solution and exposed to air transformed in all cases into calcite/vaterite. The herein obtained temperature limit of ≤ 12 for ikaite formation is significantly higher than formerly expected and most probably caused by the (i) high saturation degree of the solution with respect to ikaite and the (ii) slow dehydration of the aqueous Ca²⁺ ion at low temperature. This result questions the suitability of calcite pseudomorphs (i.e. glendonites) as a proxy for near-freezing temperatures. Moreover, our findings show that the CaCO3 polymorph formed from ikaite is strongly controlled by the physicochemical conditions, such as aqueous molar Mg²⁺/Ca²⁺ ratio of the reactive fluid and H2O availability throughout the transformation process.
The widespread formation of interstratified glauconite-smectite (Gl-S) and illite-smectite (I-S) in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral authigenesis. To date, however, significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry, temperature and reaction kinetics on the evolution of composition, mineralogy and microstructure of Gl-S and I-S. Herein, we present a study on the reaction mechanisms and the physicochemical conditions that led to the precipitation of early diagenetic Gl-S and late diagenetic I-S on a stable carbonate platform during the Cenomanian at Langenstein in the Northern German Basin. The texture and the K-Ar age (95.0 ± 1.8 Ma) of the green glauconitized grains revealed that green-clay authigenesis progressed in initially organic-rich, semi-confined micromilieus, i.e., in fecal pellets and in foraminifera, close to the sediment-seawater interface. The composition of Gl-S varied in the range (K⁺0.20–0.74Na⁺0–0.10Ca2 +0–0.05)0.28–0.75 (Fe3 +0.63–1.20Fe2 +0.08–0.24Al3 +0.19–0.97 Mg2 +0.29–0.52)2.01–2.12 [Al3 +0.09–0.35Si4 +3.65–3.91O10](OH2), and depended on the rate of aqueous Fe2 + and K⁺ ion diffusion, the micromilieu of glauconitization and on the bulk sedimentation rate. The mineralogical, microstructural and chemical changes of the ongoing Gl-S products revealed the following reaction for green-clay authigenesis at Langenstein: Fe(III)-smectite reacted with monosilicic acid, goethite and aqueous K⁺, Mg2 + and Fe2 + to form glauconite and aqueous Na⁺, Ca2 + and H⁺ ions. This process considers complex mineral transformations commonly associated with glauconitization, such as early diagenetic oxidation of organic matter and microbial-catalyzed dissolution of Fe-(oxy)hydroxides, carbonates and detrital silicates. In contrast, the K-Ar age of I-S (68.0 ± 1.6 Ma) and its compositional variability, (K⁺0.29–0.45Na⁺0–0.10Ca2 +0–0.06)0.30–0.55 (Fe3 +0.16–0.29Fe2 +0–0.10Al3 +1.37–1.68Mg2 +0.18–0.43)2.00–2.12 [Al3 +0.17–0.39Si4 +3.61–3.83O10](OH2), indicate a burial diagenetic origin for this mineral phase, rather than transformation of illitic clays into I-S during weathering under warm and humid climatic conditions. The results from kinetic modelling support a diagenetic origin of I-S (50–60%I layers and 50–40%S layers) and imply its formation by the replacement of pre-existing K-feldspar at high pore-fluid activity K/Na ratios and at low Fe2 + concentrations. We propose that the substitution of Al3 + for Fe3 +, Fe2 + and Mg2 + in the octahedral sheet shifts the stability field of the kaolinite–Fe-Al-Mg-smectite–Fe-Al-Mg-illite (or glauconite) triple point to much lower monosilicic acid activities, and stabilizes the I-S (or Gl-S) structure. This reaction supports the idea that the (bio)availability of Fe is the rate-limiting factor for glauconitization, which is not the case for the diagenetic growth of I-S, whereby the pore water Fe2 + concentration may be limited by the competing formation of Fe-(oxy)hydroxides and/or Fe-sulfides.
Oil and gas seeps on the western flank of the South Caspian Basin are associated with mud volcanoes, outcrops of oil-bearing strata, and mineral water springs. Most of the seepage occurs in faulted zones along the basin flanks. Gas seepage can be subdivided into three groups based on gas composition, isotopic composition, and the age of exposed rocks. Neogene-Quatemary seeps are predominantly methane and are derived from low-maturity organic matter and biogenic sources. Mesozoic-Paleogene seeps have more wet gas and nonhydrocarbon components and were generated during late catagenesis. Paleozoic-Mesozoic seeps have the greatest amount of methane, nitrogen, and carbon dioxide and have undergone the highest degree of catagenesis. Oil seepage can be subdivided into isotopically light and heavy groups. The chemical and isotopic changes in the gas and oil seepages are regular and systematic, allowing the data to be used for correlation. Reservoir oils can also be subdivided into two groups: isotopically heavy Neogene oils and isotopically light Paleogene oils. In general, the surface hydrocarbon seepages correlate to the subsurface hydrocarbon distribution. A methodology was developed that predicts that the petroleum prospects of the deeply buried basin deposits are favorable.
The South Caspian Basin comprises a unique set of geologic parameters that rank it among the most prolific hydrocarbon regions of the world. Surrounded by compressional orogens, the basin has accumulated up to 25 km of sediment, with more than 10 km of this fill deposited in the last 6 m.y. This recent, rapid burial has resulted in such low temperature gradients that hydrocarbons are still being actively generated at depths between 8 and 12+ km. The anticlinal structures in the basin are large, and interpreted to be buckle folds overlying a regional detachment based on the analysis of regional 2-D seismic data. The combination of a prolific hydrocarbon system, large undrilled structures, and a favorable political climate for foreign investment has focused considerable industry attention on the potential of this basin.
This paper discusses the nature of the phenomenon of “mud volcanism” with respect to degassing of deeply buried sediments. Mud volcanoes are defined as geological structures and their main elements are described. Based on the nature of activity, mud volcanoes are grouped in to three main types and the relationship between each type and corresponding morphological expression is discussed. The presented up-to-date data of the world geographical distribution of mud volcanoes show that they approximate to 1800 individuals. A detail overview of geological environments in which they occur helps to deduce some necessary conditions for mud volcano formation. The basic mechanisms of mud volcano formation are discussed, specifically the fluid-pressure hypothesis, and some triggering events are identified. The most common investigation approach and some criteria for recognizing of a submarine mud volcano on side-scan sonar records and seismic sections are given. Mud volcanism in the Mediterranean Ridge (an accretionary complex) and Black Sea Abyssal Plane (a back ark basin with tectonic regime of extension) are described as case studies to show variety in morphology and common factors in development of mud volcanoes. The manifestation of continuous gas migration through mud volcanoes is clarified, and the attempt made to quantify the gas release shows that mud volcanoes are one of the significant natural sources of atmospheric methane emitting a total amount of about 10.3 to 12.6 Tg annually.
In order to establish the origin of fluids expelled from mud volcanoes in Trinidad, we analyzed their major-element, trace-element, and isotopic (H, O, Sr) compositions. The mineralogical, chemical, and Sr isotope compositions of associated expelled muds were also determined.On the basis of their chemical and Sr isotope compositions, the fluids were divided into two groups—those southwest and northeast of a major right lateral wrench fault (the Los Bajos fault) that both controls the chemical quality of the fluids and acts as a drain. Strontium isotopes were derived via mixing between a radiogenic source (0.71135) and a nonradiogenic source (≤0.70671) for both southwest and northeast groups. However, the nonradiogenic source possibly feeding the northeast group showed a lower Sr concentration than that of the southwest group. H and O isotope data show that the fluids became enriched in δ18O through interaction with wall rocks. The fluids were originally oceanic, but their properties were subsequently modified by diagenesis as evidenced by chemical data, and mixing between fluids issued from two deep-seated reservoirs and surface aquifer end-members.The gas phase expelled with the mud and the fluid through the mud volcanoes is composed mainly of methane with minor carbon dioxide. The amount of expelled gas seems the same in samples from both sides of the Los Bajos fault. The almost unique methane content of the gas phase and the large positive δ18O shifts of the reservoir end-member, as well as B, Li, and Ba contents, reveal that the fluids from the deep-seated reservoirs inherited their chemical compositions at high-temperature fluid–rock interactions. Estimates of equilibrium temperatures of the two deep-seated reservoirs suggest that, to acquire the estimated higher temperature (150°C), the mud volcanoes must have been fed partly by a reservoir located at a depth of more than 3 km. This depth corresponds to previous geologic information, which located the deep-seated reservoir in Miocene sediments at such a comparable depth. The mixing of the original fluids with a less deep-seated reservoir and meteoric waters on the ascending path suggests the presence of a recharge mechanism and contributes to the dynamics of the expulsion itself.
Studies of hydrothermal circulation within partly buried basement on the eastern flank of the Juan de Fuca Ridge (JFR) have shown that ridge-flank geochemical fluxes are potentially important for the global budgets of some elements. There are major uncertainties in these flux calculations, however, because the composition of these basement fluids is strongly dependent on temperature and because they may be modified by interaction with the overlying terrigenous sediments, either by diffusive exchange with basement or during upwelling to the seafloor. To better understand the nature and temperature control of basalt-fluid and sediment-fluid reactions at the JFR flank, we have conducted laboratory experiments between 51 and 350°C and at 400 bars pressure. K, Rb, and Si are leached from basalt between 150 and 351°C, and Sr and U are taken up. The direction of exchange of Li and Ca with basalt varies with temperature. Li and Sr are removed from fluid at 150°C, but isotope studies show that there is simultaneous release of both elements from basalt, indicating that uptake is controlled by the formation of secondary minerals. Moreover, our experiments confirm that Sr isotope exchange with oceanic crust occurs at moderate temperature and is not confined to high-temperature axial hydrothermal systems. Our data and field data from the JDR flank indicate that uptake of U into basalt at moderate temperature could remove between 9.9 and 15 × 106 mol U yr−1 from the oceans. This is higher than a recent estimate based on measurements of U in altered ocean crust (5.7 ± 3.3 × 106 mol yr−1), which concords with arguments that the Δelement/heat ratios of JDR flank fluids are too large to be representative of average global flank fluids. K, Ca, Sr, Ba, Li, Si, and B are leached from terrigenous sediments between 51 and 350°C, and U is taken up. Cs and Rb are removed from the fluid below 100°C and leached from the sediment at higher temperature. Sr isotope data show that Sr is preferentially mobilised from volcanic components within terrigenous sediments, which may lead to an overestimation of the ridge-flank Sr isotope flux at the JDR if there is exchange of sediment pore fluids with basement.
This study examines the use of specific mud volcano features (i.e., elongated calderas, aligned vents and elongated volcanoes) as potential indicators of tectonic stress orientation. The stress indicator principles, widely recognised for magmatic systems, have been discussed and applied to mud volcano settings such as in the Northern Apennines and the Azerbaijan Greater Caucasus, as well as in other instances where the analysis was fully based on a remote sensing study. The results of these applications are promising, the obtained maximum horizontal stress (SH) directions generally showing a good correlation with those determined in the upper crust by classical methods (i.e., earthquake focal mechanism solutions, well bore breakouts). Therefore, stress information from mud volcanoes could be used as a proxy for stress orientation (1) where stress data is lacking, (2) where settings are inaccessible (i.e., underwater or the surface of planets), or simply (3) as supplementary stress indicators. This study also pays special attention to structural elements that may control fluid expulsion at various length scales, and pathways that should have spawned the mud volcanoes and controlled their paroxysmal events and eruptions. Different types of sub-planar brittle elements have been found to focus fluid flow rising up-through fold cores, where the vertical zonation of stresses may take part in this process by creating distinctive feeder fracture/fault sets. On a regional scale, mud volcanoes in active fold-and-thrust belts may occur over wider areas, such as the prolific mud volcanism in Azerbaijan, or may cluster along discrete structures like the steep Pede-Apennine thrust in the Northern Apennines, where the generation of overpressures is expected to establish a positive feedback loop allowing for fault movement and mud volcanism.
The exposed crust consists mainly of plagioclase (35%), quartz (20%), K-feldspar (11%), volcanic glass (12%), biotite (8%), and muscovite (5%). Quartz is a resistate, thus feldspars and glass represent approximately 75 percent of the labile minerals. The weathering characteristics of these constituents are summarized in the context of thermodynamic, mass balance and kinetic considerations. Experimentally determined release rate constants were used to predict the proportions of Ca, Na and K released by feldspars of plutonic rocks (granites to gabbros) to weathering solutions. The chemical weathering trends of the weathered residues, calculated from the kinetic data, conform closely to the initial trends observed in some recent weathering profiles, demonstrating the accuracy of the predictions. Since the weathering of feldspars is controlled by processes that should not change through geological time, the relative release rates of Ca, Na, and K from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering. Experimentally determined release rate constants are not available for a wide range of volcanic glass compositions, but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks. The kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile.
The South Caspian basin has been a major petroleum-producing province for more than a century. While the basin's oil has been the focus of a number of studies the region's gas has been largely understudied. This study examines 31 gas samples from 14 fields with the primary purpose of determining their mode(s) of formation and the role that microbial activity has had in their formation and alteration.The basin's natural gas accumulations display significant differences in both molecular and isotopic composition. Gas wetness ranges from less than 1% at Absheron to greater than 12% at Guneshli. Methane carbon isotopic composition ranges from −57 to −37‰ relative to the PDB standard. The stable carbon isotopic composition of the wet gas (C2+) components also displays a very broad range (e.g. C2 ranges from −37 to −20‰; C3 ranges from −31 to −10‰; and nC4 ranges from −30 to −11‰).No strong depth-related trends were observed in any of the geochemical attributes. The absence of a trend implies that the gases have not been generated in situ but have migrated vertically, been altered, or represent a mixed product. Mixing is also suggested by the differences in the calculated thermal maturity levels between the C2+ components and methane. In some accumulations (e.g. Karabagly) as much as 55% of the methane may have a biogenic origin. These data further indicate that among the gas samples studied those from Bakhar appear to be the most mature, with thermal maturity values consistent with the ‘condensate-window’.In several fields, including Guneshli and Neftchala, the wet gas components display evidence for microbial alteration. This is largely manifested in anomalously heavy isotopic compositions of propane, n-butane, and n-pentane.
Authigenic carbonates are common at cold seep sites as a result of microbial oxidation of hydrocarbons. Seep carbonate samples were collected from the surface of the Bush Hill (Green Canyon Block 185, Gulf of Mexico), a mound containing gas hydrate. The carbonates consisted of oily, porous limestone slabs and blocks containing bioclasts and matrix. Analysis by X-ray diffraction shows that aragonite is the dominant mineral (89–99wt% with an average of 94wt%) in the matrix of seep carbonate. This cement occurs in microcrystalline, microspar, and sparite forms. The moderate 13C depletion of the seep carbonate (the most depleted one has δ13C value of −29.4‰, and 26 of 38 subsamples have δ13C values >−20.0‰) indicates that the non-methane hydrocarbons was incorporated during seep carbonate precipitation. Relative enrichment of 18O may be related to localized destabilization of gas hydrate or derived from 18O-enriched pore water originated from smectite–illite transition in the deep sediments. The total content of rare earth elements (REE) of the 5% HNO3-treated solution of the carbonates is from 0.40ppm to 30.9ppm. The shale-normalized REE patterns show varied Ce anomalies from significantly negative, slightly negative, and no to positive Ce anomalies. Variable content of trace elements, total REE, and Ce anomalies in different samples and even in the different carbonate mineral forms (microcrystalline, microspar and sparite) of the same sample suggest that the formation condition of the Bush Hill seep carbonate is variable and complex, which is possibly controlled by the rate of fluid flux.
Relative Na, K, Mg, and Ca contents of thermal waters in full equilibrium with a thermodynamically stable mineral system derived through isochemical recrystallization of an average crustal rock are, at a given temperature and salinity, uniquely fixed. Together with the compositions of waters resulting from isochemical rock dissolution, they provide valuable references for the assessment of the degree of attainment of fluid-rock equilibrium. The subsystems are combined to obtain graphical techniques for the evaluation of deep temperatures and COâ-partial pressures by use of Na, K, Mg and Ca contents of geothermal water discharges.
A mud volcano field was recently discovered within the Malta Plateau in the Strait of Sicily (Central Mediterranean Sea). Box-core sediments and associated authigenic carbonates have been collected in water depths of 140–170m from two distinctive sectors of the area, and analyzed for major, trace and rare earth elements, stable isotopes, and mineralogy. Relative homogeneity in the mineralogy and geochemistry of bulk sediments, and 210Pb activity distributions, argue against an active mud ejection activity. In the Malta Plateau western sector, the sediments show high concentrations of Fe, As, Sb, and Mo, exceeding the background values estimated for the Strait of Sicily. Active fluid seepage in this area is thought to be responsible for these enrichments and for the formation of authigenic carbonate crusts. Evidence of bacterial involvement in carbonate (mainly aragonite) formation is recorded in the authigenic crusts, which contain flat and spiralled filaments resembling Beggiatoa-like sulphide oxidising bacteria and biofilm-like remains which occur inside the interspaces. Carbonate crusts consistently show extremely negative δ13C values (down to −49‰) that suggest contribution of carbon originating from anaerobic methane oxidation. Heavy oxygen isotopic compositions of the authigenic carbonates (2−3‰ higher than those in box-core sediments) are interpreted as due to precipitation from fluids enriched in 18O due to seepage of deep, isotopically-heavy, relict Messinian brines.
Extract
Subsurface sediment mobilization (SSM) — which includes soft sediment deformations, sand injections, shale diapirs and mud volcanoes — is more widespread than previously thought. The ever-increasing resolution of subsurface data yielded many new observations of SSM, not only from regions obviously prone to sediment remobilization, such as an active tectonic setting or in a region with exceptionally large sediment supply, but also from tectonically quiescent areas. Until now, all the different aspects of SSM have largely been treated as separate phenomena. There is very little cross-referencing between, for example, studies of mud volcanoes and those of sand injections, although both are caused by sediment fluidization. Divisions according to sediment type, mobilization depth or triggering mechanism make little sense when trying to understand the processes of SSM. There is a gradation in mobilization processes that cause considerable overlap between categories in any classification. Hence, it is necessary to integrate our understanding of all types of SSM, regardless of scale, depth, location, grain size or triggering mechanism. In addition, polygonal faults are important in this context, as this nontectonic structural style is closely associated with sedimentary injections and may also reflect large scale mobilization.
The main goal of this volume is to help develop a more integrated understanding of subsurface sediment mobilization. It contains specific case studies and a number of overview papers about the mechanisms of sediment mobilization in the subsurface (Maltman & Bolton), about polygonal faulting (Cartwright) and about shale diapirs (Morley). Other recent review papers were published about sand
Shah Deniz is a large four-way dip closed structure in the South Caspian located approximately 35 km to the southeast of Bahar and 70 km southwest of the Guneshli–Chirag–Azeri (GCA) Oil Field. A large 3D survey (800 km2) was acquired over the PSA area in the summer of 1997 and the first exploration well was spudded in the summer of 1998, the second in the summer of 1999. 3D data has shown many interesting details about the development of mud volcanoes and associated features over Shah Deniz and this information has been used to help in the drilling of exploration wells. Mud volcano features on Shah Deniz range from small (hundreds of square-meter) cones to a large “collapse caldera” (10–15 km2) that overlies much of the northern part of the crest. All mud volcano features appear to be associated with the crests of deep (pre-Maykop) structural highs. Isochron maps of seismic intervals within the Quaternary and Apsheron show that the Shah Deniz structure started to form at around the end of Productive Series deposition and continued through into the upper Quaternary. Mud volcano activity did not begin until middle Apsheron. There is therefore a delay between the start of structural development and the appearance of mud volcano flows of approximately 0.5 million years. Mud volcanoes appeared first at the southern end of the structure, while the major mud volcano on the crest did not start to develop until slightly later within the Apsheron. This is consistent with the observation that the structure initially developed in the south, before the major direction of shortening, NW–SE, seen today, became more dominant in the Mid-Apsheron. The mud volcano flows that are relatively high amplitude seismically can be clearly seen on the seismic, using voxel-based volume visualization, when stratigraphy parallel time slices are viewed. The opacity of the amplitude spectrum can be varied such that any particular amplitude ranges can be highlighted. This technique has shown moderate to high amplitude flows coming from the major central mud volcano that have a lateral extent of up to 17 km and widths of around 0.5 km. The impact of seabed topography can also be seen on the flows as well as the different characteristics of the individual mud volcanoes.
As a part of the Dutch–French MEDINAUT diving expedition in 1998, cold seeps and mud volcanoes were studied and sampled in two distinctive tectonic settings in the eastern Mediterranean Sea. The first setting was the Olimpi Mud Volcano field (OMV area), including Napoli, Milano, Maidstone and Moscow mud volcanoes, south of Crete on the Mediterranean ridge. The second setting was the Anaximander Mountains (AM area), southwestern Turkey, where Amsterdam, Kazan and Kula mud volcanoes were explored. Large methane concentrations (45–892nmol/kg) were measured in the water column not only above mud volcanoes but also in seeps and vents along related fault systems, indicating intense degassing related to fluid circulation in sediments. The tracer results show that there is considerable variability in terms of gas seepage and matter flux between these mud volcanoes. Brine accumulations found as shallow pools on Napoli or associated with deep faults (Nadir Lake) outside mud volcanoes exhibit variable chlorinity, mineral and gas composition. The brines are significantly enriched in δ18O relative to ambient seawater and are consistent with evaporated seawater. In the Nadir Brine Lake, the level of methane is as high as 5.93mmol/kg, lower than the methane saturation level of 120mmol/kg theoretically found at the salinity (120), pressure (200bar), and temperature (13.6°C) conditions of Nadir lake. In contrast, the shallow brine pools on Napoli mud volcano (also OMV area) have methane levels of only 4.45μmol/kg. In all brines, helium data show a clear radiogenic isotopic ratio (R=0.06×Ra), in excellent agreement with recently published data for the Urania basin. Methane to ethane ratios (>1000) and δ13C(CH4) values (−65.6‰PDB) indicate that the CH4 is microbially produced. Unlike mid-ocean ridges, where abiogenic methane and helium have a common origin in the brines, the large variation in the CH4/He ratio indicates that CH4 and helium sources are unrelated, a fact that adds further support to the biogenic origin of methane. These results show that mud volcanoes in the eastern Mediterranean Sea are important sites of extensive biogenic methane fluxes, which are probably related to widespread occurrences of gas hydrates.
This paper discusses the origin and the dynamics of subsurface sediment mobilization processes in tectonically mobile regions and shale-rich environment. This is illustrated by the example of Trinidad and the south of the Barbados prism. In this area of the southeast Caribbean, geophysical acquisitions have spectacularly shown the widespread development of sediment mobilization features in the interference area between the southern part of the Barbados prism and the active turbidite system of the Orinoco. Numerous mud volcanoes are especially developed along ramp anticline crests through hydraulic fracture systems. The area also exhibits trends of structures that correspond to massive uplifts of well-preserved turbidite and hemipelagic sediments that cut up the surrounding sediments. Some of these structures are complicated by the development of collapse structures, calderas and superimposed mud volcanoes. The mobilized sediments expelled by the mud volcanoes are not only liquefied argillaceous but also fine sandy material from deep horizons, and various shallower formations pierced by the mud conduits. Both in the Barbados prism and in Trinidad, the expelled mud is rich in thin, angular and mechanically damaged quartz grains, which are probably cataclastic flows issued from sheared and collapsed deep sandy reservoirs. The exotic clasts and breccias result mostly from hydraulic fracturing. In Trinidad, the gas phase is mainly deep thermogenic methane associated with hydrocarbon generation at depth. Subsurface sediment mobilization notably differs from salt mobilization by the role taken by the fluid dynamics that control overpressured shale mobilization and induce sediment liquefaction. A reaction chain of several deformation processes develops around the conduits. Massive sedimentary uplift corresponds to large movements of stratified solid levels, possibly due to the tectonic inversion of pre-existing mud volcano systems. All these phenomena are controlled by the development of overpressure at depth. No evidence for piercing shale diapirs has been observed in the area studied.
Mud volcanism is an abundant, global phenomenon whereby fluid-rich, low-density sediments extrude both on land and offshore. Methane, which generally exceeds 90vol% of the gas phase, is emitted at high rates during and after emplacement of the mud domes and is known for its high global warming potential (GWP). This comprehensive estimate of the annual contribution of mud volcano degassing assesses the significance of mud volcanism for the accumulation of greenhouse gases in the atmosphere. A first-order estimate for the earlier, pre-anthropogenic volume of methane released through mud volcanoes further supports their profound effect on the Earth''s climate since at least the Paleozoic (570Ma).