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Title: Using 81Kr and noble gases to characterize and date groundwater and brines in the Baltic Artesian Basin on the one-million-year timescale

Analyses for 81Kr and noble gases on groundwater from the deepest aquifer system of the Baltic Artesian Basin (BAB) were performed to determine groundwater ages and uncover the flow dynamics of the system on a timescale of several hundred thousand years. We find that the system is controlled by mixing of three distinct water masses: Interglacial or recent meteoric water (δ 18O ≈ –10.4‰) with a poorly evolved chemical and noble gas signature, glacial meltwater (δ 18O ≤ –18‰) with elevated noble gas concentrations, and an old, high-salinity brine component (δ 18O ≥ –4.5‰, ≥ 90 g Cl /L) with strongly depleted atmospheric noble gas concentrations. The 81Kr measurements are interpreted within this mixing framework to estimate the age of the end-members. Deconvoluted 81Kr ages range from 300 ka to 1.3 Ma for interglacial or recent meteoric water and glacial meltwater. For the brine component, ages exceed the dating range of the ATTA-3 instrument of 1.3 Ma. The radiogenic noble gas components 4He* and 40Ar* are less conclusive but also support an age of > 1 Ma for the brine. Based on the chemical and noble gas concentrations and the dating results, we conclude that the brine originates from evaporatedmore » seawater that has been modified by later water–rock interaction. Furthermore, as the obtained tracer ages cover several glacial cycles, we discuss the impact of the glacial cycles on flow patterns in the studied aquifer system.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [6] ;  [7] ;  [8] ;  [2] ;  [4] ;  [1] ;  [3] ;  [9] ;  [1]
  1. Univ. of Bern, Bern (Switzerland)
  2. Tallinn Univ. of Technology, Tallinn (Estonia)
  3. Univ. of Heidelberg, Heidelberg (Germany)
  4. Univ. of Latvia, Riga (Latvia)
  5. Argonne National Lab. (ANL), Argonne, IL (United States); The Univ. of Science and Technology of China, Anhui (China)
  6. Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Chicago, Chicago, IL (United States); The Univ. of Science and Technology of China, Anhui (China)
  7. Vilnius Univ., Vilnius (Lithuania)
  8. Argonne National Lab. (ANL), Argonne, IL (United States)
  9. Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Chicago, Chicago, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 205; Journal Issue: C; Journal ID: ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); Swiss National Science Foundation (SNSF)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; Brine; Cambrian-Vendian aquifer system; Degassing; Environmental tracers; Glacial meltwater; Groundwater dating; Krypton-81; Mixing analysis; Paleoclimate
OSTI Identifier:
1377069
Alternate Identifier(s):
OSTI ID: 1415306