Salt Waters of the Northern Apennine Foredeep Basin (Italy): Origin and Evolution

Abstract

The salt waters from the Emilia-Romagna sector of the Northern Apennine Foredeep have been investigated using major and trace element and stable isotope (d 2 H, d 18 O, d 37 Cl, d 81 Br and 87 Sr/ 86 Sr ratio). Ca, Mg, Na, K, Sr, Li, B, I, Br and SO 4 vs. Cl diagrams suggest the subaerial evaporation of seawater beyond gypsum and before halite precipitation as primary process to explain the brine's salinity, whereas saline to brackish waters were formed by mixing of evaporated seawater and water of meteoric origin. A diagenetic end-member may be a third component for mud volcanoes and some brackish waters. Salinization by dissolution of (Triassic) evaporites has been detected only in samples from the Tuscan side of the Apennines and/or interacting with the Tuscan Nappe. In comparison with the seawater evaporation path, Ca-Sr enrichment and Na-K-Mg depletion of the foredeep waters reveal the presence of secondary processes such as dolomitization-chloritization, zeolitization-albitization and illitization. Sulfate concentration, formerly buffered by gypsum-anhydrite deposition, is heavily lowered by bacterial and locally by thermochemical reduction during burial diagenesis. From an isotopic point of view, data of the water molecule confirm mixing between seawater and meteoric endmembers. Local 18 O-shift up to ?11% at Salsomaggiore is related to water-rock interaction at high temperature (&150°C) as confirmed by chemical (Mg, Li, Ca distribution) and isotopic (SO 4 -H 2 O) geothermometers. 37 Cl/ 35 Cl and 81 Br/ 79 Br ratios corroborate the Electronic supplementary material The online version of this article (marine origin of the brines and evidence the diffusion of halogens from the deepest and most saline aquifers toward the surface. The 87 Sr/ 86 Sr ratio suggests a Miocene origin of Sr and rule out the hypothesis of a Triassic provenance of the dissolved components for the analyzed waters issuing from the Emilia-Romagna sector of the foredeep. Waters issuing from the Tuscan side of the Apennines and from the Marche sector of the foredeep show higher 87 Sr/ 86 Sr ratios because of the interaction with siliciclastic rocks.

Origin and assessment of deep groundwater inflow in the Ca' Lita landslide using hydrochemistry and in situ monitoring

“…3a, b in Fig. 1a) (Martinelli et al, 1989) as well as in other springs flowing out of TU flysch formations (i.e., Well SalsMag1 in Boschetti et al, 2010) or from LU-TU formations in the middle-frontal part of the Apennine chain (i.e., Regnano site point 3c in Fig. 1a; Capozzi and Picotti, 2010).…”

“…Stable isotopes ( 18 O and 2 H) are sometimes highly positive (δ 18 O up to +5 ‰ and δ 2 H equal to 0 ‰) while pCO 2 varies widely (0.03-0.9 kPa). B tot and Sr 2+ can be as high as 300 mg l −1 (Boschetti et al, 2010).…”

Tracing groundwater salinization processes in coastal aquifers: a hydrogeochemical and isotopic approach in the Na-Cl brackish waters of northwestern Sardinia, Italy

“…Boschetti et al, 2011). In the plot of I vs. Cl, the water samples have a scattered distribution, and most are characterized by a high I / Cl ratio, which departs significantly from the RSML.…”

Natural Variations of Stable Chlorine and Bromine Isotopes on Earth

“…Already in the first study reporting natural bromine isotope measurements (Eggenkamp and Coleman 2000) it was shown that this was definitely not the case. Figure 10.4 shows a histogram of the 128 bromine isotope measurements published in Eggenkamp and Coleman (2000), Shouakar-Stash et al (2007), Stotler et al (2010) and Boschetti et al (2011). In this histogram it is clearly shown that bromine isotopes tend to have mostly positive values in pore waters.…”

“…After Shouakar-Stash et al (2005) published their method to analyse bromine isotopes using an on-line technique they analysed the bromine isotope composition in several studies on formation waters from Precambrian shields in Siberia (Shouakar-Stash et al 2007) and Canada and Fennoscandia (Stotler et al 2010). The combination of chlorine and bromine isotopes was also determined in a set of Italian formation waters from the Northern Apennine Foredeep Basin in northern Italy (Boschetti et al 2011), the Williston Basin in North Dakota (Shouakar-Stash et al 2006), the Kangan gas field in Iran (Bagheri 2013;Bagheri et al 2014b) and from groundwater from the Great Artesian Basin in Australia (Gwynne et al 2013). Figure 10.6 shows the chloride and bromide concentrations of the samples from which these data are provided by the respective studies and Fig.…”