Stable isotope geochemistry of sediment-hosted groundwater from a Late Paleozoic-Early Mesozoic section in central Europe

摘要

The boron isotopic composition, in combination with oxygen, hydrogen and sulfur isotopes and hydrochemical tracers, is utilized to investigate the evolution of groundwaters from a Late Paleozoic (Permian) to Early Mesozoic (Triassic) section of the sedimentary cover in central Europe (N Switzerland-SW Germany). Four distinct groundwater types have been identified: (a) saline groundwater from Permian (Rotliegend) sediments (delta(11)B = +13.7 to +33.0 parts per thousand, delta(18)O = -6.7 to -5.3 parts per thousand, delta D = -53.4 to -37.8 parts per thousand, delta(34)S = +16.4 to +17.1 parts per thousand); (b) brackish to saline groundwater from Lower Triassic (Buntsandstein) sediments (delta(11)B = +6.4 to +22.3 parts per thousand, delta(18)O = -10.3 to -6.9 parts per thousand, delta D = -71.8 to -60.5 parts per thousand, delta(34)S = +18.2 to +18.4 parts per thousand); (c) fresh to saline groundwater from Middle Triassic (Muschelkalk) sediments (delta(11)B = -10.2 to +7.7 parts per thousand, delta(18)O = -11.8 to -8.8 parts per thousand, delta D = -86.6 to -63.0 parts per thousand, delta(34)S = +15.8 to +21.4 parts per thousand); and (d) saline groundwater from Upper Triassic (Keuper) sediments (delta(11)B = +26.3 parts per thousand, delta(18)O = -6.4 parts per thousand, delta D = -41.2 parts per thousand, delta(34)S = +16.1 parts per thousand). AS evidenced by B-O-H-S stable isotope and hydrochemical (e.g. Na/Cl, Br/Cl, Ca/SO4, (Ca + Mg)/SO4, K/B, and Li/B) constraints, interactions with sedimentary host rocks and inter-aquifer mixing have contributed to the evolution of the investigated groundwaters. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 39]