Groundwater age and hydrothermalism of confined aquifers in the Argentine Pampean plain

Abstract

The Pampean plain of Cordoba province (Argentina) has hydrothermal manifestations linked to Cretaceous depocenters. However, they are in general neither well known nor carefully used, and, in numerous cases, they are unjustifiably wasted. The objective of this work is to show the most outstanding hydrogeological features and the geologic setting that control the low enthalpy hydrothermal deep systems and groundwater age in the Pampean plain of Cordoba province. To perform the study, conventional geological and hydrogeological methodologies were used. Isotopic ( C and 14 C) and geochemical studies (Cl-SO 4 -HCO 3 and Na-K-Mg ternary diagrams) were made to evaluate groundwater age and hydraulic and geochemical features of the aquifer system. The confined aquifer systems (CASs), located at 120-350 m depth, are multilayered and linked to fluvial Neogene paleosystems. The isotopic analysis for these hydrothermal systems shows that groundwater is not related to magmatic waters and it has a meteoric origin being recharged in the mountain and piedmont western areas (Comechingones Mountains). The 14 C ages obtained for A1 and A2 CASs indicate waters recharged during Holocene cold periods, between the "Little Ice Age" and the ending of "Holocene Climatic Optimum, " and during the last glaciation, respectively. The groundwater temperatures in the discharge points are between 24 and 38 °C, which exceeds 4-12 °C the expected value for that depth, if normal gradients are considered. The analysis using geothermometers showed that the groundwater samples were located in the immature water field near the boundary of the partially equilibrated waters. The thermal anomaly is linked to the Cretaceous depocenters of General Levalle, especially associated to the low block of the Tigre Muerto regional fault. This geothermal anomaly shows agreement with the regional geotectonic setting and it should be the result of the continental crustal thinning and the geological regional faults that make easy groundwater circulation to several depths. The groundwater flowing from recharge areas, favored by the structure of dipping regional blocks, would be reached higher temperatures (the order of 79 °C) explaining the present oversaturation in SiO 2 , what implies maximum depths of up to 1500 m and the observed thermodynamic behavior of such mineralogical phases. This general framework is in agreement with the Cl-SO 4 -HCO 3 ternary diagram which indicates steam-heated waters.

Isotope and Geochemistry Characterization of Hot Springs and Cold Springs of Sembalun – Rinjani Area, East Lombok, West Nusa Tenggara – Indonesia

“…The aim of this current study is to determine the characteristics of hot springs and cold springs and asses its geothermal potential using isotopes and geochemistry data in the hydrogeological framework. The study utilized stable isotopes of water, i.e., 2 H and 18 O, to investigate the origin of fluids and its interaction with surrounding rocks [2][3], while 14 C radioisotope is used to determine groundwater age [4][5]. In addition, a fluid geochemistry approach is used to determine the characteristics and temperature of the reservoir [6].…”

Hydrogeochemical features and groundwater renewal rate estimates from deep aquifers in the Pampean plain, Córdoba province, Argentina

“…All samples were conditioned, properly cooled and sent to the laboratory to carry out chemical and stable isotope analyses. The local meteoric line for the 2007-2014 rainfall cycle in Río Cuarto city (Cabrera et al, 2017), was updated following the International Atomic Energy Agency guidelines (IAEA/GNIP, 2014). In addition, monthly precipitation data for the period 2015-2017 from the Alpa Corral station, located in the Comechingones Mountains are available (Fig.…”

Vanadium for Green Energy: Increasing Demand but With Health Implications in Volcanic Terrains

“…Extraction from groundwater would be more economic if the large scale was not essential. Groundwater with a V content of 100 μg V/L in 10% aquifer porosity would contain 10 4 kg V. Given the rate at which groundwaters move in Argentina, estimated as 0.01–0.42 m/day and more specifically in one study as 0.07 m/day (Cabrera et al., 2010 , 2017 ; Maldonado et al., 2016 ), groundwaters with 100 μg V/L in 10% aquifer porosity would be replenished within 40 years. Less conservative values of 20% porosity and 200 μg V/L would see replenishment of all the groundwater V within 10 years.…”