Geothermal fluids circulation at Caldas do Moledo area, Northern Portugal: geochemical and isotopic signatures

• Type: Article in International Scientific Journal
• Date: 2003

Authors

Marques, JM (Author) Other; Marques, JE (Author) FCUP; Carreira, PM (Author) Other; Graca, RC (Author) Other; Aires Barros, L (Author) Other; Carvalho, JM (Author) Other; Chamine, HI (Author) Other; Borges, FS (Author) Other

Journal

Title: Geofluids

Vol. 3

Pages: 189-201

ISSN: 1468-8115

Publisher: Hindawi

Indexing

ISI Web of Knowledge - 28 Citations

Scopus - 36 Citations

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Authenticus ID: P-000-FPH

DOI: 10.1046/j.1468-8123.2003.00059.x

Abstract (EN): A hydrogeological conceptual model of the Caldas do Moledo geothermal site is proposed that shows mixing between geothermal waters and local shallow groundwaters. Stable isotope values of Caldas do Moledo geothermal waters indicate recharge areas located at relatively high altitudes (850-1250 m a.s.l.). The NW-SE Vigo-Regua shear zone plays an important role in fluid recharge and circulation towards the NNE-SSW Regua-Verin fault system, forming a path for ascent of geothermal fluids. The apparent C-14 age of geothermal fluids (15.66 +/- 2.86 ka BP) was estimated in the total dissolved inorganic carbon (TDIC). Geothermometer calculations indicate that, assuming a conductive temperature gradient of 32 degreesC per kilometer for northern Portugal, the maximum depth of circulation is roughly 1.8 +/- 0.4 km. The K, Ca and SO4 concentrations found in some Caldas do Moledo geothermal spring waters show mixing between deep geothermal and shallow groundwater systems. Local shallow groundwaters showing the highest SO4 concentrations were found at low elevation areas, originating from fertilisers and pesticides applied to the Port wine vineyards in the Douro River valley. Geothermal waters from boreholes AC1 and AC2 do not show evidences of direct pollution from the spreading of such agrochemicals.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 13