ویژگی‌های ژئوشیمیایی و ایزوتوپی گازهای گسیل شده از گل‌فشان پیرگل، جنوب شرق ایران

نوع مقاله : علمی -پژوهشی

نویسندگان

1 گروه ژئوشیمی، دانشکده علوم زمین، دانشگاه خوارزمی، تهران، ایران

2 گروه ژئوشیمی، دانشکده علوم زمین، دانشگاه فلورانس، ایتالیا

3 موسسه کانی‌شناسی تجربی، آکادمی علوم، روسیه

4 موسسه زمین‌شناسی کانسارهای معدنی، پتروگرافی، کانی‌شناسی و ژئوشیمی، آکادمی علوم، روسیه

چکیده

گل­فشان­ها مجراهای مهاجرت رو به بالای سیالات عمیق پرفشار در حوضه­های رسوبی در نتیجه نیروهای عمدتاً فشارشی هستند. گل­فشان پیرگل به عنوان بزرگ­ترین گل­فشان ایران بین دو آتشفشان تفتان و بزمان در جنوب شرق ایران واقع شده ­است. مطالعات ژئوشیمیایی و ایزوتوپی بر روی گازهای منتشر شده از مکان­های تراوش فعال این گل فشان برای تعیین منشأ گازهای هیدروکربوری و غیرهیدروکربوری انجام شد. داده­های ترکیب شیمیایی گاز نشان می­دهد که دی اکسیدکربن گاز خروجی غالب و متان دومین گاز خروجی در این گل­فشان است. مقادیر کمی از گازهای هیدروکربوری سنگین­تر مانند اتان، پروپان، ایزوبوتان و ان- بوتان هم مشاهده شد. منشأ ترموژنیک گازهای هیدروکربوری توسط نسبت متان به مشتقات هیدروکربوری سنگین­تر (C1/C2+) پایین و مقادیر δ13C متان  از ۷/۴۰- تا ‰ ۲/۴۲- آشکار می­شود که ممکن است مرتبط با شکستن حرارتی موادآلی ناشی از وجود فرآیندهای حرارتی یا منابع گرمایی باشد. حضور گازهای هیدروکربنی ترموژنیک در گل­فشان پیرگل می­تواند بیانگر احتمال حضور سیستم هیدروکربوری در این منطقه باشد. مقادیر ایزوتوپی کربن دی اکسیدکربن  از ۹/۱۱- تا ‰۸/۱۳- در گازهای تجزیه شده نیز حدواسط بین دی اکسیدکربن تولید شده در طی فرآیند ترموژنیک موادآلی و دی اکسیدکربن ناشی از سیستم­های آتشفشانی است. نقش گوشته بالایی به عنوان یکی از منشأهای احتمالی گازهای خروجی از گل­فشان پیرگل توسط مقادیر ایزوتوپی هلیم 3He/4He از ۵۸/۱ تا  R/Ra۶۱/۱ مشخص می­شود که ممکن است مرتبط با حضور سیالات سیستم­های زمین گرمایی منطقه باشد.

کلیدواژه‌ها


عنوان مقاله [English]

Geochemical and isotopic characteristic of emitted fluids from Pirgel mud volcano, SE Iran

نویسندگان [English]

  • Mahin Farhadian Babadi 1
  • Behzad Mehrabi 1
  • Franco Tassi 2
  • Michael Zelenski 3
  • Ilya Chaplygin 4
  • Ata Shakeri 1
  • Stefania Venturi 2
1 Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran
2 Department of Geochemistry, Faculty of Earth Sciences, Florence University, Italy
3 Institute of Experimental Mineralogy, Academy of Science, Russia
4 Institute of Geology of Ore Deposits, Petrology, Mineralogy and Geochemistry, Academy of Science, Russia
چکیده [English]

IntroductionMud volcanoes or sedimentary volcanoes, represent one of the most intriguing phenomena of the Earth's crust. They are important for energy resource exploration, seismicity, geo-hazard and atmospheric budget of greenhouse gases. These structures are surface expressions of fluids including gas, water and mud inside hydrocarbon-bearing sedimentary basins. The discharged gas is typically dominated by methane, however where hydrocarbon systems are located close to subducting slabs, relatively high geothermal gradient environments or are related to the final stages of thermogenic gas generation, the gas can be mainly CO2 or N2. The Pirgel mud volcanoes, are the largest Iranian mud volcanos, located between Taftan and Bazman volcanoes.Materials and methodsDuring this study, twelve gas samples were collected from all gas emitting points including pool, gryphon and cone using Giggenbach-alkaline solution in order to evaluate the hydrocarbon and non-hydrocarbon gas sources. The molecular composition of gas consisting methane and heavier hydrocarbon derivatives, CO2, O2, N2, He, Ar and He, carbon isotopic composition of methane and CO2 and He isotopic signature were determined by using GC and GC-MS methods, respectively.Results and discussionThe gases emitted by Pirgel mud volcano are CO2-rich ranging from 83.9 to 88.7 vol. %. The other gas components are CH4 (9.31-12.90 vol. %), N2 (1.28-2.08 vol. %), C2H6 (0.43-0.54 vol. %), C3H8 (0.051-0.098 vol. %), iC4H10 (0.027-0.052 vol. %), nC4H10 (0.016-0.024 vol. %), O2 (0.088-0.180 vol. %), Ar (0.028-0.050 vol. %), He (77.76-111.77 ppm) and Ne (0.44-5.41 ppm).Carbon dioxide in CO2-richgas reservoirs is produced by a variety of organic and inorganic processes.Different CO2 sources can be recognized based on the 13C/12C ratios: 0‰ vs. V-PDB, <−20‰ vs. V-PDB and −6.5 ± 2.5‰ vs. V-PDB for marine limestone, alteration of organic material and Mid-Oceanic Ridge Basalts (MORB), respectively.At a first approximation, the δ13C-CO2 values measured in the CO2-rich Pirgel gases (from −11.9 to −13.8‰ vs. V-PDB) are intermediate between those typical of mantle and a biogenic source. The R/Ra values of these gases are ∼1.6 R/Ra, with low air contamination as indicated by the high He/Ne ratios (14–257). The contribution of upper mantle, as a probable source for discharged gas from Pirgel mud volcano is likely linked to geothermal fluids of nearby volcanic systems which is documented by 3He/4He isotopic ratio of ∼1.61 R/Ra. The CO2/3He ratios, ranging from 20×109 to 30×109, i.e. slightly higher than that typically measured for MORB (2×109–1×1010), coupled with the above mentioned δ13C-CO2 values, suggest that the origin of the CO2 discharged from Pirgel mud volcano is related to both biogenic and volcanic sources. The hydrocarbon gases are thermogenic in origin, evidenced by low methane to heavier hydrocarbon components (C1/C2+) ratio and δ13CCH4 valuesfrom -40.7 to -42.2 ‰. The presence of thermogenic gases are likely related to thermal degradation of organic matters in response to the existence of thermal processes or heat sources.ConclusionPirgel mud volcano emits gases dominated by CO2 and shows relatively high R/Ra values (∼1.6). Gas geochemistry shows that the CO2-rich gases characterizing this mud volcano probably originated from both thermal degradation of sedimentary organics and hydrothermal fluids from the neighboring volcanic complex. The area probably hosts the hydrocarbon systems testified by the presence of thermogenic gases and dark oil appearance slicks in Pirgel mud volcano.

کلیدواژه‌ها [English]

  • Helium isotopes
  • Carbon Dioxide
  • Hydrocarbon and non-hydrocarbon gases
  • Pirgel mud volcano
-آقانباتی، ع.، ۱۳۸۳. زمین‌شناسی ایران، سازمان زمین‌شناسی و اکتشافات معدنی کشور، ۵۸۶ ص.
-آقانباتی، ع.، ۱۹۹۴. نقشه زمین‌شناسی ۲۵۰۰۰۰/۱ خاش، سازمان زمین‌شناسی و اکتشافات معدنی کشور.
-درویش زاده، ع.، ۱۳۸۲. زمین‌شناسی ایران، انتشارات امیرکبیر تهران، 901 ص.
-سهندی، م.ر.، ۱۹۹۶. نقشه زمین‌شناسی ۲۵۰۰۰۰/۱ ایرانشهر، سازمان زمین‌شناسی و اکتشافات معدنی کشور.
-عباس نژاد، الف. و نگارش، ح.، 1388. میکرومورفولوژی روانه‌های گِلی گِل‌فشان ناپگ، فصلنامه جغرافیایی آمایش، دانشگاه آزاد اسلامی واحد ملایر، شماره 7، ص 71-86.
-فرهادیان، م.، مهرابی، ب.، مازینی، آ.، پلودتکینا، ا. و شاکری، ع.، 1395. منشأ گازهای هیدروکربوری گل‌فشان‌های خشکی سواحل مکران ایران، زمین-شناسی نفت ایران، شماره 12، ص 80-93.
-فصل‌بهار، ج. و فصل‌بهار، ش.، 1387. پدیده گل-فشان و اثرات زیست‌محیطی آن، مجله انسان و محیط‌زیست، شماره 17، ص 44-55.
-نژاد افضلی، ک.، لک، ر.، ثروتی، م.ر. و بیاتانی، ف.، 1390. معرفی و بررسی سایت گل‌فشانی نژاد افضلی، گل‌فشان‌های گتان شهرستان جاسک و اهمیت زمین گردشگری آنها، مجله علوم‌زمین، شماره 82، ص 207-214.
-نگارش، ح.، 1383. بررسی گِل‌فشان پیرگل واقع در شرق آتشفشان بزمان و ویژگی‌های آن، مجله جغرافیا و توسعه، دانشگاه سیستان و بلوچستان، شماره 4، ص 191-208.
-نگارش، ح.، فیضی، م.، طاهری، الف.، رحمانی، م.ا. و نگارش، ز.، 1390. ویژگی‌های ژئومورفولوژیکی گِل‌فشان عین (Ain) و تعیین ترکیب معدنی آب و گِل آن با استفاده از روش‌های فیزیکی و شیمیایی، مجله جغرافیا و برنامه‌ریزی دانشگاه تبریز، شماره 37، ص 173-202.
-Barber, A.J., Tjokrosapoetro, S. and Charlton, T.R., 1986. Mud volcanoes, shale diapirs, wrench faults and me´langes in accretionary complexes, eastern Indonesia: AAPG Bull., v. 70, p. 1729-1741.
-Bernard, B.B., Brooks, J.M. and Sackett, W.M., 1978. Light hydrocarbons in recent Texas continental shelf and slope sediments: Journal of Geophysical Research, v. 83, p. 4053-4061.
-Blinova, V.N., Jvanov, M.K. and Böhrmann, G., 2003. Hydrocarbon gases in deposits from mud volcanoes in the Sorokin Trough, North-Eastern Black Sea: Geo-Marine Letters, v. 23, p. 250-257.
-Chung, H.M., Gormly, J.R. and Squires, R.M., 1988. Origin of gaseous hydrocarbons in subsurface environments: theoretical considerations of carbon isotope distribution: Chemical Geology, v. 71, p. 97-103.
-Cita, M.B., Ivanov, M.K. and Woodside, J.M., 1996. The Mediterranean Ridge diapiric belt: Special Issue, Marine Geology, v. 132, p. 1-271.
-Cornides, I., Takaoka, N., Nagao, K. and Matsuo, S., 1986. Contribution of mantle-derived gases to subsurface gases in a tectonically quiescent area, the Carpathian Basin, Hungary revealed by noble gas measurements: Geochemical Journal, v. 20, p. 119-125.
-Delisle, G., von Rad, U., Andruleit, H., von Daniels, C.H., Tabrez, A.R. and Inam, A., 2002. Active mud volcanoes on- and offshore eastern Makran, Pakistan: International Journal of Earth Sciences, v. 91, p. 93-110.
-Dia, A.N., Castrec-Rouelle, M., Boulegue, J. and Comeau, P., 1999. Trinidad mud volcanoes: where do the expelled fluids come from?: Geochimica et Cosmochimica Acta, v. 63, p. 1023-1038.
-Dimitrov, L.I., 2002. Mud volcanoes: the most important pathway for degassing deeply buried sediments: Earth Science Reviews, v. 59, p. 49-76.
-Etiope, G. and Klusman, R.W., 2002. Geologic emissions of methane to the atmosphere: Chemosphere, v. 49, p. 777-789.
-Etiope, G. and Milkov, A.V., 2004. A new estimate of global methane flux from onshore and shallow submarine mud volcanoes to the atmosphere: Environmental Geology, v. 46, p. 997-1002.
-Etiope, G., Feyzullayev, A. and Baciu, C., 2009. Terrestrial methane seeps and mud volcanoes: a global perspective of gas origin: Marine and Petroleum Geology, v. 26, p. 333-344.
-Evans, W.C., White, L.D. and Rap, P., 1998. Geochemistry of some gases in hydrothermal fluids from the southern Juan de Fuca ridge: Journal of Geophysical Research, v. 15, p. 305-313.
-Guliyev, I.S., Feyzulaev, A.A. and Huseinov, D.A., 2004. Geochemical features and sources of fluids in mud volcanoes in the South Caspian sedimentary basin in light of new data on S, N, and O isotopes: Geochemistry International, v. 7, p. 675-683.
-Hoefs, J., 1987. Stable isotope geochemistry: Minerals and rocks: Berlin, Springer-Verlag, 241 p.
-Huang, B.J., Xiao, X.M. and Zhu, W.L., 2004. Geochemistry, origin, and accumulation of CO2 in natural gases of the Yinggehai Basin, offshore South China Sea: AAPG Bulletin, v. 88, p. 1277-1293.
-Hunt, J.M., 1984. Generation and migration of light hydrocarbons: Science, v. 226, p. 1265-1270.
-Isaksen, G.H., Aliyev, A., Barboza, S.A., Plus, D. and Guliev, I.S., 2007. Regional evaluation of source rock in Azerbaijan from the geochemistry of organic-rich rocks in mud-volcano ejecta: In: Yilmaz, P.O. and Isaksen, G.H., (Eds.), Oil and Gas of the Greater Caspian Area: AAPG Studies in Geology, v. 55, p. 51-64.
-Javoy, M., Pineau, F. and Delorme, H., 1986. Carbon and nitrogen isotopes in the mantle: Chemical Geology, v. 57, p. 41-62.
-Kopf, A., 2002. Significance of mud volcanism: Reviews of Geophysics, v. 40, p. 1005-1024.
-Kotarba, M.J., Nagao, K. and Karnkowski, P.H., 2014. Origin of gaseous hydrocarbons, noble gases, carbon dioxide and nitrogen in Carboniferous and Permian strata of the distal part of the Polish Basin: Geological and isotopic approach: Chemical Geology, v. 383, p. 164-179.
-Kotarba, M.J. and Nagao, K., 2008. Composition and origin of natural gases accumulated in the Polish and Ukrainian parts of the Carpathian region: Gaseous hydrocarbons, noble gases, carbon dioxide and nitrogen: Chemical Geology, v. 255, p. 426-438.
-Lavrushin, V.U., Polyak, B.G., Prasolov, R.M. and Kamenskii, I.L., 1996. Sources of material in mud volcano products based on isotopic, hydrochemical, and geological data: Lithology and Mineral Resources, v. 31, p. 557-578.
-Mamyrin, B.A. and Tolstikhin, I.N., 1984. He isotopes in nature: Developments in Geochemistry, v. 3, 274 p.
-Mango, F.D., 1997. The light hydrocarbons in petroleum: a critical review: Organic Geochemistry, v. 26, p. 417-440.
-Mango, F.D., 2000. The origin of light hydrocarbons: Geochimica et Cosmochimica Acta, v. 64, p. 1265-1277.
-Milkov, A.V., 2000. Worldwide distribution of submarine mud volcanoes and associated gas hydrates: Marine Geology, v. 167, p. 29-42.
-Negaresh, H., 2008. Mud volcanoes in Sistan and Baluchestan Province, Makran Coast, SE Iran: Bulletin of the Geological Society of Malaysia, v. 54, p. 1-7.
-Negaresh, H. and khosravi, M., 2008. The geomorphic and morphometric characteristics of Napag mud volcano in the south eastern of Iran: Journal of Humanities the University of Isfahan, v. 30, p. 51-68.
-Oxburgh, E.R., Oʾnions, R.K. and Hill, R.I., 1986. Helium isotopes in sedimentary basins: Nature, v. 324, p. 632-635.
-Palcsu, L., Vető Futo, I., Vodila, G., Papp, L. and Major, Z., 2014. In-reservoir mixing of mantle-derived CO2 and metasedimentary CH4-N2 fluids-Noble gas and stable isotope study of two multistacked fields (Pannonian Basin System, W-Hungary): Marine and Petroleum Geology, v. 54, p. 216-227.
-Planke, S., Svensen, H., Hovland, M., Banks, D.A. and Jamtveit, B., 2003. Mud and fluid migration in active mud volcanoes in Azerbaijan: Geo-Marine Letter, v. 23, p. 258-268.
-Porcelli, D., Ballentine, C.J. and Wieler, R., 2002. Noble gases in geochemistry and cosmochemistry: Reviews in mineralogy and geochemistry, Washington, D.C.: Mineralogical Society of America and Geochemical Society, v. 47, 844 p.
-Rice, D.D. and Claypool, G.E., 1981. Generation, accumulation and resource potential of biogenic gas: AAPG Bulletin, v. 65, p. 5-25.
-Sano, Y. and Marty, B., 1995. Origin of carbon in fumarolic gas from island arcs: Chemical Geology, v. 119, p. 265-274.
-Sano, Y., Tominaga, T., Nakamura, Y. and Wakita, H., 1982. 3He/4He ratios of methane-rich natural gases in Japan: Geochemical journal, v. 16, p. 237-245.
-Schmidt, M., Hensen, C., Morz, T., Muller, C., Grevemeyer, I., Wallmann, K., Mau, S. and Kaul, N., 2005. Methane hydrate accumulation in“Mound 11” mud volcano, Costa Rica forearc: Marine Geology, v. 216, p. 83-100.
-Schoell, M., 1980. The hydrogen and carbon isotopic composition of methane from natural gases of various origins: Geochimica et Cosmochimica Acta, v. 44, p. 649-666.
-Skinner, J.A. and Mazzini, A., 2009. Martian mud volcanism: terrestrial analogs and implications for formational scenarios: Marine and Petroleum Geology, v. 26, p. 1866-1878.
-Stamatakis, M.G., Baltatzis, E.G. and Skounakis, S.B., 1987. Sulfate minerals from a mud volcano in the Katakolo area, western Peloponnesus, Greece: American Mineralogist, v. 72, p. 839-841.
-Takai, K., Nakamura, K., Toki, T., Tsunogai, U., Miyazaki, M., Miyazaki, J., Hirayama, H., Nakagawa, S., Nunoura, T. and Horikosh, K., 2008. Cell proliferation at 122 degrees C and isotopically heavy CH4 production by a hyperthermophilic methanogen under high-pressure cultivation: Proceedings of the National Academy of Sciences of the United States of America, v. 105, p. 10949-10954.
-Tassi, F., Vaselli, O., Luchetti, G., Montegrossi, G. and Minissale, A., 2008. Metodo per la determinazione dei gas disciolti in acque naturali: Report of National Research Council of Italy, Institute of Geosciences and Earth Resources, 10 p.
-Valyaev, B.M., Grinchenko, Y.I., Erokhin, V.E., Prokhorov, V.S. and Titkov, G.A., 1985. Isotopic composition of gases from mud volcanoes: Lithology and Mineral Resources, v. 20, p. 62-75.
-Vaselli, O., Tassi, F., Montegrossi, G., Capaccioni, B. and Giannini, L., 2006. Sampling and analysis of volcanic gases: Acta Volcanology, v. 18, p. 65-76.
-White, R.S., 1982. Deformation of the Makran accretionary sediment prism in the Gulf of Oman (north-west Indian Ocean): In: Leggett, J.K., (Ed.), Trench and Fore-Arc Geology: Sedimentation and Tectonics on Modern and Ancient Active Plate Margins, p. 357-372.
-White, R.S., 1983. The Little Murray Ridge: In: Seismic Expression of Structural Styles, Bally, A., (Ed.): AAPG Stud. Geol., v. 15, p. 1319-1323.
-Whiticar, M.J., 1999. Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methan: Chemical Geology, v. 161, p. 291-314.
-Whiticar, M.J., Faber, E. and Schoell, M., 1986. Biogenicmethane formation in marine and fresh water environments: CO2 reduction vs. acetate fermentation—isotope evidence: Geochimica et Cosmochimica Acta, v. 50, p. 693-709.
-Wycherley, H., Fleet, A. and Shaw, H., 1999. Some observations on the origins of large volumes of carbon dioxide accumulations in sedimentary basins: Marine and Petroleum Geology, v. 16, p. 489-494.
-Yang, T.F., Yeh, G.H., Fu, C.C., Wang, C.C., Lan, T.F., Lee, H.F., Chen, C.H., Walia, V. and Sung, Q.C., 2004. Composition and exhalation flux of gases from mud volcanoes in Taiwan: Environmental Geology, v. 46, p. 1003-1011.
-Yazdi, A., 2013. Potentials of Iran’s geotourism and structure of mud volcanoes: Journal of Basic and Applied Science Research, v. 3, p. 350-358.
-Zhang, T., Zhang, M., Bai, B., Wang, X. and Li, L., 2008. Origin and accumulation of carbon dioxide in the Huanghua depression, Bohai Bay Basin, China: AAPG Bulletin, v. 92, p. 341-358.