Environmental Isotopes and Geochemistry of Bañado Carilauquen. Mendoza, Argentina

OSTERA, HECTOR; DAPEÑA, CRISTINA

Salvador-BA, Brazil

Simposio; IV South American Symposium on Isotope Geology; 2003

Comité SSAGI Brazil

The environmental impact of the industrial activities leads to a great concern about the conservation of natural pristine resources. This objective confronts with a big challenge: How we can determine the original environmental parameters before the anthropic influence? Moreover, in petroleum fields the base levels of hydrocarbon concentration in waters and soils have natural anomalies related to existence of oil reservoirs themselves. Consequently, it is very complex to quantify the environmental impact of petroleum exploitation and the influence of possible spills if previous base studies were not made. Since 1930, the Llancanelo oil field, located at Malargüe, Mendoza province, has been exploited and explored. Sulfurous waters and gas manifestations were found near the mouth of the arroyo Carilauquen. The aim of this study is to characterize the natural pristine conditions of the system by means of geochemistry and environmental stable isotopes (2H and 18O) and also, a first approach for the origin and circulation pattern of water. Geochemistry and isotope baseline study of Bañado Carilauquen indicate that there are two main types of water in the area: sulfate-chloride-calcium type and subordinate chloride-sulfate-sodium type. The sulfate contents are higher than limits proposed by OMS. Hydrocarbon pollution was not detected. The main sources of recharge for Carilauquen springs could be related to the Malargüe River infiltration westwards owing the similarities on isotope composition. However, it cannot discard some local meteoric recharge detected in groundwater. Mixing processes due overexploitation are detected by geochemical modeling, but are masked in the isotope signal. Lake waters show a marked isotope enrichment, linked with evaporation processes. These environmental parameters establish the natural geochemical and isotope background of this area, which fragile equilibrium could be endangered by human activities.