Yuce, G., D'Alessandro, W., Italiano, F., Bellomo, S., Yasin, D. and Gülbay, A. H. (2016) Characteristics of the gases and waters issuing from the Kizildag and Erzin ophiolites (Hatay/Turkey): Comparison with the remnants of the peri-Arabian Ophiolitic Belt including Semail ophiolite. [Talk] In: International Water Conference 2016. , 13.03.-16.03.2016, Muscat, Sultanate of Oman .

Abstract

The Kizildag and Erzin (Hatay) ophiolite bodies are an extension of the peri-Arabian ophiolite belt that includes the Troodos (Cyprus), Baër-
Bassit (Syria) and Semail (Oman) ophiolites in the Eastern Mediterranean Region which genetically and tectonically belong to the Southern Tethys oceanic lithosphere (Sengör and Yilmaz, 1981). This study aims to understand the chemical and isotopic characteristics of bubbling and dissolved gases of the hyperalkaline waters related to the serpentinization process in ultramafic rocks at the Amik Basin (Hatay-Turkey) and compare them with the remnants of the peri-Arabian ophiolite
belt. The Amik Basin is seismically very active and many catastrophic earthquakes hit the area at historical times due to the Dead Sea Transform and Karasu Faults which further north
join to the East Anatolian Fault (Mahmoud et al., 2013). The basin is very close to the triple junction point with the tectonic lineaments connecting the Anatolian, Arabian and African plates. Around 23 dry seeps, free and dissolved gas samples were taken from the study area and analyzed their chemical and isotopic
composition. Three main groups of groundwater
have been recognized in the area: i)Low salinity and pH between 6 and 9 (shallow groundwater), ii)High salinity and pH between 7 and 8 (deep groundwater), iii) Low salinity and pH between 10 and 12 (groundwater circulating in the ophiolites).Because of serpentinisation
processes, many hyper-alkaline springs(pH>
9 up to 12.2)are found in the area. Hyper-alkaline springs flow through the creeks along the narrow valleys, having low yields and are characterized by snow-like deposits due to the precipitation of brucite and hydrotalcite. The study shows a great variability in the gas composition of the fluids circulating in the Kizildag ophiolite complex. All gases show very low CO2 and O2 concentrations and their composition is dominated either by H2 or CH4 or N2. He isotopic composition reveals a mixing trend between atmospheric air and a deep end-member of prevailing crustal origin but with a significant mantle contribution (10-20%).Methane has generally an abiotic origin, although for some of the samples a contribution of biotic methane cannot be completely ruled out due to mixing process(Yüce et al., 2014). Dissolved gases collected in the groundwater of the nearby Amik Basin (Yüce et al., 2014 and 2015) show a similar mixing trend for the majority of the shallow (<300m) groundwaters while the remaining shallow groundwaters and all the deep (>800m) groundwater samples align along a mixing trend between atmospheric air and a nearly pure crustal end-member. When we move further to north of the Amik basin towards the Erzin-Dortyol Basin, we have encountered some gas manifestations with abundant CO2 besides methane production wells. Gases in this basin are characterised by a higher mantle helium fraction (up to 48 %) probably due to the presence of seismogenically active faults. The gases of Kizildag ophiolite and Erzin area are compared to gases of other ophiolithic systems. The sampled gases of Kurtbagi and A71 (Erzin) display D and 13C values which are typical of abiogenic methane while other show more negative values especially for D.

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