Tracing the origin of salts in groundwater by Sr isotopic composition (the Crystalline Complex of the southern Sinai, Egypt)

A. Starinsky*, M. Bielski, A. Ecker, G. Steinitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The source of the salts in the groundwater from the arid crystalline complex of the southern Sinai has been traced by the Sr isotopic composition of the waters and their major chemical components. Twelve water sources with salinity ranging between 200 and 450 mg l−1 were analyzed. The salts are composed of ≈ 30% Na, (K), and CI and ≈ 70% Ca, (Sr), Mg, SO4 and HCO3. The 87Sr/86Sr ratio of the waters is in the range of 0.7087–0.7100 with an average of 0.7090 ± 0.0003. The 87Sr/86Sr ratio in the basement rocks (acid igneous and metamorphic) is generally higher than 0.71; even low Rb/Sr minerals have values of 0.72. Assuming Sr in the water genetically accompanies Ca (the major constituent of the carbonate fraction), the low 87Sr/86Sr ratio excludes the possibility that this fraction originated from dissolution of country rock. A mixing model between ancient carbonates and the crystalline country rock for Sr in the groundwater is rejected. It is suggested that the chemical composition of the water is mainly controlled by aerosols originating from beach sands (aragonite of recent reef debris) and sabkha sediments (halite, gypsum, anhydrite, aragonite and Mg-calcite) from the coastal plains of the Sinai. Thus under the present conditions chemical weathering is a process practically negligible. The Sr isotopic composition of the waters rejects the possibility that the air-borne dust in the region is derived from Cretaceous—Tertiary marine sediments in Egypt and Lybia.

Original languageEnglish
Pages (from-to)257-267
Number of pages11
JournalChemical Geology
Volume41
DOIs
StatePublished - 1983

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