Large compositional differences in the gases released from the Kizildag ophiolitic body (Turkey): Evidences of prevailingly abiogenic origin


D'Alessandro W., YÜCE G. , Italiano F., BELLOMO S., Gulbay A. H. , Yasin D. U. , ...Daha Fazla

MARINE AND PETROLEUM GEOLOGY, cilt.89, ss.174-184, 2018 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 89
  • Basım Tarihi: 2018
  • Doi Numarası: 10.1016/j.marpetgeo.2016.12.017
  • Dergi Adı: MARINE AND PETROLEUM GEOLOGY
  • Sayfa Sayıları: ss.174-184

Özet

We investigated the geochemical features of the gases released from the Kizildag ophiolitic complex (Hatay, Turkey). Twenty-three samples both dissolved in hyperalkaline waters and free gases (bubbling gases and dry seeps) were collected. Samples were analysed for their chemical (He, H-2, O-2, N-2, CH4 and CO2) and isotopic (He, delta C-13-CH4, delta H-2-CH4, delta H-2-H-2) composition including the content and C-isotopic composition of C-2 to C-5 alkanes in free gases. Analytical results evidence H-2 production through low temperature (<80 degrees C) serpentinization processes and subsequent abiogenic CH4 production through Fischer-Tropsch-type reactions. In some sample small additions of methane either of microbial or of thermogenic origin can be hypothesized. At one of the sites (Kisecik) a clear fractionation pattern due to microbial methane oxidation leading to strongly enriched isotopic values (delta C-13 +15 parts per thousand and delta H-2-68 parts per thousand) and depletion in methane concentrations has been evidenced. At the dry gas seep of Kurtbagi methane flux measurements have been made and a preliminary output estimation of about 1000 kg per year has been obtained. (C) 2016 Elsevier Ltd. All rights reserved.