Hidroquímica de ríos de monta？a (Sierras de Córdoba, Argentina): elementos mayoritarios disueltos

the sierras pampeanas of córdoba, argentina, is an interesting locality to study the geochemistry of mountainous river systems, both for their socio-economic and cultural significance and for the diversity of streams and rivers that drain its slopes. several important drainage networks in córdoba province have their headwaters in these ranges. in this work, the major chemical composition of water collected from four hydrological catchments is analyzed, with the aim of determining the sources of solutes, the geochemical processes that control their basin's dynamics and the influence of climatic conditions on the seasonal variation of elemental concentrations. four drainage basins were selected for this study. all basins are classified as 5th order in horton's classification (1945) (modified by stralher, 1987) and their mean slopes vary between ~5%, in the eastern flank, and more than 9% on the range's western side. the study area is located between 31° 30' - 32° 00's and between 64° 30' and 65° 10'w. maximum altitude is about 2,400 m a.s.l. (fig. 1). dominant rocks are granitoids of the achala batholith that crop out in the upper and middle parts of the study basins, while gneisses and modern sediments dominate in the lower reaches. climate is semiarid; mean rainfall reaches about 750 mm per year. the atmospheric input chemical signature (pluvial and snow precipitation) was analyzed and compared with that of springs and 1st order streams (fig. 3) using an upper continental crust (ucc, mclennan, 2001) normalized diagram. the concentration of dissolved major and trace elements is of the order of 103 to 107 times lower than the mean upper continental crust. according to the observed patterns, atmospheric and spring chemical signals are very similar; however, elements such as si, na+ and in less importance al+3 and mg+2 are more enriched in springs and 1st order streams than in precipitations. the latter suggests an important contribution to water discharges in these sma