Publication Date:
2017-04-04
Description:
The studied area is a 130 km long fast spreading graben in Central Greece. Its complex geodynamical
setting includes both the presence of a subduction slab at depth responsible for the recent (Quaternary)
volcanic activity in the area and the western termination of a tectonic lineament of regional importance
(the North-Anatolian fault). A high geothermal gradient is made evident by the presence of many
thermal springs with temperatures from 19 to 82 C, that discharge along the normal faults bordering the
graben.
In the period 2004e2012, 58 gas and 69 water samples were collected and their chemical and isotopic
analysis revealed a wide range of compositions.
Two main groups of thermal waters can be distinguished on the basis of their chemical composition.
The first, represented by dilute waters (E.C. 〈0.6 mS/cm) of the westernmost sites, is characterised by the
presence of CH4-rich and mixed N2eCH4 gases. The second displays higher salinities (E.C. from 12 to
56 mS/cm) due to mixing with a modified marine component. Reservoir temperatures of 150e160 C
were estimated with cationic geothermometers at the easternmost sites.
Along the graben, from west to east, the gas composition changes from CH4- to CO2-dominated
through mixed N2eCH4 and N2eCO2 compositions, while at the same time the He isotopic composition
goes from typical crustal values (〈0.1 R/RA) up to 0.87 R/RA, showing in the easternmost sites a
small (3e11%) but significant mantle input. The d13C values of the CO2-rich samples suggest a mixed
origin (mantle and marine carbonates).
Description:
Published
Description:
295-308
Description:
2T. Tettonica attiva
Description:
JCR Journal
Description:
restricted
Keywords:
Rift zone
;
geothermal activity
;
Helium isotopes
;
Carbon isotopes
;
03. Hydrosphere::03.02. Hydrology::03.02.02. Hydrological processes: interaction, transport, dynamics
;
03. Hydrosphere::03.02. Hydrology::03.02.03. Groundwater processes
;
03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters
;
03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
;
04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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