FN Archimer Export Format
PT J
TI Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland
BT 
AF Baronas, J. Jotautas
   Hammond, Douglas E.
   Bennett, Mia M.
   Rouxel, Olivier
   Pitcher, Lincoln H.
   Smith, Laurence C.
AS 1:1,2;2:1;3:3,4;4:5;5:3;6:3;
FF 1:;2:;3:;4:PDG-REM-GM;5:;6:;
C1 Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
   Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom
   Department of Geography, University of California Los Angeles, Los Angeles, CA, United States
   Department of Geography, The University of Hong Kong, Hong Kong, China
   IFREMER, Centre De Brest, Unité Géosciences Marines, Plouzané, France
C2 UNIV SOUTHERN CALIF, USA
   UNIV CAMBRIDGE, UK
   UNIV CALIF LOS ANGELES, USA
   UNIV HONG KONG, CHINA
   IFREMER, FRANCE
SI BREST
SE PDG-REM-GM
IN WOS Ifremer UPR
   DOAJ
   copubli-europe
   copubli-int-hors-europe
   copubli-sud
IF 3.661
TC 0
UR https://archimer.ifremer.fr/doc/00684/79577/82249.pdf
   https://archimer.ifremer.fr/doc/00684/79577/82250.xlsx
   https://archimer.ifremer.fr/doc/00684/79577/82251.zip
LA English
DT Article
DE ;glacial weathering;germanium;isotope fractionation;Amorphous silica;experimental dissolution
AB Glacial environments offer the opportunity to study the incipient stages of chemical weathering due to the high availability of finely ground sediments, low water temperatures, and typically short rock-water interaction times. In this study we focused on the geochemical behavior of germanium (Ge) in west Greenland, both during subglacial weathering by investigating glacier-fed streams, as well as during a batch reactor experiment by allowing water-sediment interaction for up to 2 years in the laboratory. Sampled in late August 2014, glacial stream Ge and Si concentrations were low, ranging between 12–55 pmol/L and 7–33 µmol/L, respectively (Ge/Si = 0.9–2.2 µmol/mol, similar to parent rock). As reported previously, the dissolved stable Ge isotope ratio (δ74Ge) of the Watson River was 0.86 ± 0.24‰, the lowest among global rivers and streams measured to date. This value was only slightly heavier than the suspended load (0.48 ± 0.23‰), which is likely representative of the bulk parent rock composition. Despite limited Ge/Si and δ74GeGe fractionation, both Ge and Si appear depleted relative to Na during subglacial weathering, which we interpret as the relatively congruent uptake of both phases by amorphous silica (aSi). Continued sediment-water interaction over 470–785 days in the lab produced a large increase in dissolved Si concentrations (up to 130–230 µmol/L), a much smaller increase in dissolved Ge (up to ∼70 pmol/L), resulting in a Ge/Si decrease (to 0.4–0.5 µmol/mol) and a significant increase in δ74Ge (to 1.9–2.2‰). We argue that during the experiment, both Si and Ge are released by the dissolution of previously subglacially formed aSi, and Ge is then incorporated into secondary phases (likely adsorbed to Fe oxyhydroxides), with an associated Δ74Gesecondary−dissolved fractionation factor of −2.15 ± 0.46‰. In summary, we directly demonstrate Ge isotope fractionation during the dissolution-precipitation weathering reactions of natural sediments in the absence of biological Ge and Si uptake, and highlight the significant differences in Ge behavior during subglacial and non-glacial weathering. 
PY 2021
PD MAR
SO Frontiers In Earth Science
SN 2296-6463
PU Frontiers Media SA
VL 9
UT 000634268400001
DI 10.3389/feart.2021.551900
ID 79577
ER

EF