Abiotic methane seepage in the Ronda peridotite massif, southern Spain

التفاصيل البيبلوغرافية
العنوان: Abiotic methane seepage in the Ronda peridotite massif, southern Spain
المؤلفون: Iñaki Vadillo, B. Urresti, Paula M. Carreira, Pablo Jiménez, José M. Marques, José Benavente, Giuseppe Etiope, Igor Tiago, Michael J. Whiticar
المصدر: Applied Geochemistry. 66:101-113
بيانات النشر: Elsevier BV, 2016.
سنة النشر: 2016
مصطلحات موضوعية: Peridotite, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Geochemistry, Planetary geology, Massif, 010502 geochemistry & geophysics, 01 natural sciences, Pollution, Methane, law.invention, chemistry.chemical_compound, chemistry, Geochemistry and Petrology, law, Facies, Dissolved organic carbon, Spring (hydrology), Environmental Chemistry, Radiocarbon dating, Geology, 0105 earth and related environmental sciences
الوصف: Abiotic methane in serpentinized peridotites (MSP) has implications for energy resource exploration, planetary geology, subsurface microbiology and astrobiology. Once considered a rare occurrence on Earth, reports of MSP are increasing for numerous localities worldwide in low temperature, land-based springs and seeps. We report the discovery of six methane-rich water springs and two ponds with active gas bubbling in the Ronda peridotite massif, in southern Spain. Water is hyperalkaline with typical hydrochemical features of active serpentinization (pH: 10.7 to 11.7, T: 17.1 to 21.5 °C, Ca–OH facies). Dissolved CH4 concentrations range from 0.1 to 3.2 mg/L. The methane stable C and H isotope ratios in the natural spring and bubbling sites (δ13CCH4: −12.3 to −37‰ VPDB; δ2HCH4: −280 to −333‰ VSMOW) indicate a predominant abiotic origin. In contrast, springs with manmade water systems, i.e., pipes or fountains, appear to have mixed biotic-abiotic origin (δ13CCH4: −44 to −69‰; δ2HCH4: −180 to −319‰). Radiocarbon (14C) analyses show that methane C in a natural spring is older than ca. 50,000 y BP, whereas dissolved inorganic carbon (DIC) analysed in all springs has an apparent 14C age ranging from modern to 2334 y BP. Therefore most, if not all, of the CH4 is allochthonous, i.e., not generated from the carbon in the hyperalkaline water. Methane is also released as bubbles in natural ponds and as diffuse seepages (∼101–102 mg CH4 m−2d−1) from the ground up to several tens of metres from the seeps and springs, albeit with no overt visual evidence. These data suggest that the gas follows independent migration pathways, potentially along faults or fracture systems, physically isolated from the hyperalkaline springs. Methane does not seem to be genetically related to the hyperalkaline water, which may only act as a carrier of the gas. Gas-bearing springs, vents and invisible microseepage in land-based peridotites are more common than previously thought. In addition to other geological sources, MSP is potentially a natural source of methane for the troposphere and requires more worldwide flux measurements.
تدمد: 0883-2927
DOI: 10.1016/j.apgeochem.2015.12.001
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::cb1ff56b468d2a60ff8c164ed3babaf0
https://doi.org/10.1016/j.apgeochem.2015.12.001
Rights: CLOSED
رقم الانضمام: edsair.doi...........cb1ff56b468d2a60ff8c164ed3babaf0
قاعدة البيانات: OpenAIRE
الوصف
تدمد:08832927
DOI:10.1016/j.apgeochem.2015.12.001