Publication Date:
2017-04-04
Description:
The geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins
(Millungera, Galilee and Cooper basin) of the Australian Great Artesian Basin (GAB) consistently indicate the
presence of fluids from multiple gas sources located in the crust (e.g. sediments, oil reservoirs, granites) as
well as minor but detectable contributions of mantle/magma-derived fluids. The gases extracted from 19
water samples and analyzed for their chemical and isotopic composition exhibit amounts of CO2 up to about
340 mlSTP/LH2O marked by a δ13CTDC (Total Dissolved Carbon) ranging from −16.9 to +0.18‰ vs PDB, while
CH4 concentrations vary from 4.4 × 10−5 to 4.9 mlSTP/LH2O. Helium contents were between 9 and N2800
times higher than equilibrium with Air Saturated Water (ASW), with a maximum value of 0.12 mlSTP/LH2O.
Helium isotopic composition was in the 0.02–0.21 Ra range (Ra = air-normalized 3He/4He ratio). The three
investigated basins differ from each other in terms of both chemical composition and isotopic signatures of
the dissolved gases whose origin is attributed to both mantle and crustal volatiles. Mantle He is present in the
west-central and hottest part of the GAB despite no evidence of recent volcanism.Wefound that the partial pressure
of helium, significantly higher in crustal fluids than in mantle-type volatiles, enhances the crustal He signature
in the dissolved gases, thus masking the original mantle contribution. Neotectonic activity involving deep
lithospheric structures and magma intrusions, highlighted by recent geophysical investigations, is considered
to be the drivers of mantle/magmatic volatiles towards the surface. The results, although pertaining to artesian
waters froma vast area of N542,000 km2, provide newconstraints on volatile injection, and showthat fluids' geochemistry
can provide additional and independent information on the geo-tectonic settings of the Great Artesian
Basin and its geothermal potential.
Description:
Published
Description:
75-88
Description:
2T. Tettonica attiva
Description:
JCR Journal
Description:
restricted
Keywords:
dissolved gases
;
great artesian basin
;
mantle fluids
;
tectonic structures
;
05. General::05.02. Data dissemination::05.02.01. Geochemical data
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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