Origin Of Saline Waters Research Articles

Chemical and isotopic constraints on the origin of saline waters from a hot spring in the eastern coastal area of China

The Jimo hot spring in Shandong Peninsula, China, is a typical coastal geothermal system. The geothermal water has a very high salinity (10.8 g/L) and the origin of the salt is key to utilization of this geothermal resource. A systematic investigation of the hydrochemistry and isotopes (δ11B, 87Sr/86Sr, δ18O, δD, 13CDIC and 14CDIC) of water from 14 geothermal wells was conducted. The results show that the geothermal waters from the high-temperature center and eastern part of the geothermal field are Cl-Na·Ca-type waters with Br/Cl (8 × 10−4–1.0 × 10−3), Na/Cl (0.63–0.70) and δ11B values (15.9–17.2‰) that are lower than those of seawater. The western geothermal waters are dominated by Cl-Na-type waters with Br/Cl and Na/Cl values similar to those of seawater. The depleted δD and δ18O compositions and the corrected 14CDIC age suggest that Jimo geothermal waters are mixtures of late Pleistocene to early Holocene and younger meteoric waters. An improved Br/Cl-Na/Cl diagram, ion mass balance calculations and δ11B values indicate that halite and K-salt dissolution and subsequent cation exchange formed the dominant Cl-Na·Ca-type geothermal water, and this was then modified into a small amount of Cl-Na-type water in the western area by mixing with minor seawater entrapped in the unconsolidated sediments. The 87Sr/86Sr ratios (0.710613–0.710726) of the geothermal waters reflect water–rock reactions in the sandstone. The improved Br/Cl-Na/Cl diagram, Piper plot and boron isotopic dataset containing saline waters from coastal geothermal systems worldwide further confirm that the salinity in the Jimo geothermal water originated from dissolution of marine evaporites.

A Multidisciplinary Approach for Clarifying the Recharge Processes and Origin of Saline Water in the Semi-Arid Punata Alluvial fan in Bolivia

The analysis of stable isotopes assisted in identifying that groundwater in the Punata alluvial fan is mainly recharged by heavy flash floods, and the recharge from rainfall is of less importance. In addition, the hydrochemical analysis identified the Pucara River as the main source of recharge. Other streams in the north and northwest of the fan do not seem to contribute to the recharge. The hydrochemistry also shows that there is an increase of the Na+ and Cl− concentrations in the middle and distal part of the fan. The salinization of groundwater is most likely a result of the mixing of fresh water with residual saline pore water in the lacustrine deposits and/or ion exchange within these layers. Geophysical surveys assisted in describing the aquifer system layering, and indicated a fine-grained bottom layer where ion exchange might occur. This study demonstrates that the integration of several methods (e.g., hydrochemistry, hydrogeophysics, and stable isotopes) is valuable for clarifying ambiguities during the interpretation process and for characterizing hydrogeological processes in alluvial fans in general.

中央構造線沿いに湧出する高塩分泉の起源

中央構造線沿いに湧出する高塩分泉の起源

Br/Cl ratios and O, H, C, and B isotopic constraints on the origin of saline waters from eastern Canada

Saline groundwaters were recovered from undisturbed (Restigouche deposit) and active (Brunswick #12 mine) Zn–Pb volcanogenic massive sulfide deposits in the Bathurst Mining Camp (BMC), northern New Brunswick, Canada. These groundwaters, along with fresh to brackish meteoric ground and surface waters from the BMC, have been analyzed to determine their major, trace element and stable isotopic (O, H, C, and B) compositions. Saline groundwaters (total dissolved solids = 22–45 g/L) are characterized by relatively high Na/Ca ratios compared to brines from the Canadian Shield and low Na/Cl molar and δ 11B isotopic compositions (−2.5‰ to 11.1‰) compared to seawater. Although saline waters from the Canadian Shield commonly have oxygen and hydrogen isotopic compositions that plot to the left of the global meteoric water line, those from the BMC fall close to the water line. Fracture and vein carbonate minerals at the Restigouche deposit have restricted carbon isotopic compositions of around −5‰ to −6‰. The carbon isotopic compositions of the saline waters at the Restigouche deposit (+12‰ δ 13C DIC) are the result of fractionation of dissolved inorganic carbon by methanogenesis. We suggest that, unlike previous models for shield brines, the composition of saline waters in the BMC is best explained by prolonged water–rock reaction, with no requirement of precursor seawater. We suggest that elevated Br/Cl ratios of saline waters compared to seawater may be explained by differential uptake of Br and Cl during groundwater evolution through water–rock reaction.

Stable isotope conservation and origin of saline waters from the Middle Jurassic aquifer of the Paris Basin, France

Seventy-nine samples of formation water from geothermal boreholes, oil-field and ground-water wells, tapping the Dogger (Middle Jurassic) limestone reservoir of the Paris Basin, have been analyzed for their 2H, 18O, TDS, bromide and chloride contents. Geostatistical mapping of 2H and of 18O contents and their variations with chloride content indicate that both isotopes have a common origin and a similar behaviour within the aquifer. The σ 2H and σ 18O values increase progressively from the outcrops toward a zone where temperature, Cl − and TDS values are high. The σ 2H and σ 18O values are very uniform in this zone and do not show any relation with formation temperature, in contrast to what is generally observed in other sedimentary basins. A discussion of isotopes exchange with the carbonate matrix for oxygen, and with H 2S for deuterium, shows that such processes are not controlling the heavy isotope contents of groundwaters. This is attributed to the relatively short residence time of groundwaters in the aquifer. Both 2H and 18O contents of groundwater may thus be considered as conservative tracers in the Dogger aquifer of the Paris Basin and their initial contents are modified only by fluid mixings. Complex mixing processes account for stable isotope composition, TDS, Cl − and Br − values of the Dogger fluids. All mixtures include a brine component. Meteoric water percolated and dissolved halite in the Triassic aquifer (secondary brine). This saline solution mixed with some residual primary brine, then migrated via vertical faults into the Dogger aquifer. Such migration is found to be in agreement with data from fluid inclusions in late carbonate cements from the Liassic and Dogger strata. The requirement that these units were exposed implies that meteoric invasion could not have occurred before the Tertiary. Successive mixings of the brine with several types of meteoric waters depleted in heavy isotopes account for the present isotope and chemical compositions of the Dogger fluids.

Saline waters and residual brines in the Shiraz-Sarvistan basin, Iran

Origin of saline waters in the Shiraz-Sarvistan area, Iran, is determined by a combined isotopic (18O and D) and chemical characterization. Four types are recognized: (a) fresh water of the anticlinal carbonatic aquifer; (b) fresh and brackish runoff in the synclinal basins; (c) salt springs originating through dissolution of rock salt by type (a) fresh water; and (d) residual brines formed in synclinal closed drainage basins, through evaporation of former water types and loss of the relatively less-soluble salts.

Relation of carbon 14 concentrations to saline water contamination of coastal aquifers

Naturally occurring stable or radioactive isotopes may be used in some places to identify the origin of saline water that contaminates some coastal aquifers. In a recent study to determine the origin of saline water in the Ocala Limestone aquifer near Brunswick, Georgia, the following sources were analyzed for C14 and deuterium concentrations: potable water from the Ocala Limestone, contaminated water from the Ocala Limestone, saune water from the underlying Claiborne Group, and nearby ocean water. The chloride concentration of the groundwater ranges from about 25 ppm in the potable water to more than 2000 ppm in the deeper part of the Claiborne Group. From an interpretation of piezometric maps and other hydrologic data, previous investigators had concluded that the source of the contaminating water was the Claiborne Group and not the nearby ocean. The essentially uniform range of low values of −965 to −987‰ of the modern standard (National Bureau Standard C14 oxalic acid) for the C14 activity of the groundwater samples (regardless of the degree of contamination) is in agreement with this conclusion. If recent ocean water, which had a C14 value of +285‰, were the source of contamination, the contaminated water would have had a C14 activity higher than the activity of the fresh water. Deuterium analyses are not inconsistent with the interpretation that water from the Claiborne Group, rather than recent ocean water, is the source of the contaminating water. The concurrence of the hydrologic and the isotopic data in this area where the hydrology is well known suggests that isotopic analysis may be used to identify the origin of water in different portions of a hydrologic environment.