Abstract (EN):
The aim of this paper is to review the results of the assessment of low temperature geothermal resources (issue tern peratures between 41 and 77 degrees C) that occur in the Portuguese mainland For this purpose, a multidisciplinary approach, including geologic tectonic geochemical, geophysical and isotopic (delta H-2, delta O-18, delta C-13 H-3 and C-14) techniques was applied in order to update local and/or regional conceptual circulation models Three case studies of N Portugal are presented and discussed This paper describes different low temperature geothermal waters presenting similar hydrogeological conceptual models but rather different geochemical signatures (e g, HCO3-Na with pH approximate to 8, HCO3/Na/CO2 rich with pH approximate to 7 and HCO3-Na with pH approximate to 9 type waters) In fact in the studied low temperature geothermal systems local/regional high altitude sites associated with highly fractured rocks play an important role in conducting the infiltrated meteoric waters towards the discharge zones near the Spas The discharge zones are mainly related to the intersection of major regional fault lineaments (and conjugate structures) responsible for creating the mineral waters ascent In some cases geochemical and isotopic data point out to the existence of anthropogenic contamination of some geothermal spring waters related to the intense use of fer tilizers in areas of widespread agricultural practices
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
20