Article In: cienciavitae
Geothermal fluids circulation at Caldas do Moledo area, Northern Portugal: geochemical and isotopic signatures.
Geofluids Journal
— 2003
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Published in
2003
Abstract
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?Régua shear zone plays an important role in fluid recharge and circulation towards the NNE-SSW Régua?Verin fault system, forming a path for ascent of geothermal fluids. The apparent 14C age of geothermal fluids (15.66 ka BP) was estimated in the TDIC. Geothermometer calculations indicate that, assuming a conductive temperature gradient of 32 ºC/km 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 groundwater 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.
Publication details
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Title of the publication container
Geofluids Journal
First page or article number
189
Last page
201
Volume
3
Issue
3
Fields of Science and Technology (FOS)
earth-and-related-environmental-sciences - Earth and related environmental sciences
Publication language (ISO code)
eng - English
Alternative identifier (URI)
http://www.scopus.com/inward/record.url?eid=2-s2.0-0042565984&partnerID=MN8TOARS
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