@article{fdi:010064818,
  title = {{R}iverine {L}i isotope fractionation in the {A}mazon {R}iver basin controlled by the weathering regimes},
  author = {{D}ellinger, {M}. and {G}aillardet, {J}. and {B}ouchez, {J}. and {C}almels, {D}. and {L}ouvat, {P}. and {D}osseto, {A}. and {G}orge, {C}. and {A}lanoca, {L}. and {M}aurice, {L}aurence},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e report {L}i isotope composition (delta {L}i-7) of river-borne dissolved and solid material in the largest {R}iver system on {E}arth, the {A}mazon {R}iver basin, to characterize {L}i isotope fractionation at a continental scale. {T}he delta {L}i-7 in the dissolved load (+1.2 parts per thousand to +32 parts per thousand) is fractionated toward heavy values compared to the inferred bedrock (-1 parts per thousand to 5 parts per thousand) and the suspended sediments (-6.8 parts per thousand to -0.5 parts per thousand) as a result of the preferential incorporation of {L}i-6 into secondary minerals during weathering. {D}espite having very contrasted weathering and erosion regimes, both {A}ndean headwaters and lowland rivers share similar ranges of dissolved delta {L}i-7 (+1.2 parts per thousand to +18 parts per thousand). {C}orrelations between dissolved delta {L}i-7 and {L}i/{N}a and {L}i/{M}g ratios suggest that the proportion of {L}i incorporated in secondary minerals during weathering act as the main control on the delta {L}i-7(diss) across the entire {A}mazon basin. {A} "batch" steady-state fractionation model for {A}ndean and lowland rivers satisfactorily reproduces these variations, with a fractionation factor between weathering products and dissolved load (alpha(sec-dis)) of 0.983 +/- 0.002. {T}wo types of supply-limited weathering regimes can be identified for the lowlands: "clearwaters" with dominant incorporation of {L}i in secondary minerals, and "black waters" (e.g., {R}io {N}egro) where dissolution of secondary minerals enhanced by organic matter produces low delta {L}i-7. {A}part from the black waters, the delta {L}i-7 of {A}ndean and lowland rivers is negatively correlated to the denudation rates with the lowest delta {L}i-7 corresponding to the rivers having the highest denudation rates. {I}n contrast, the main tributaries draining both the {A}ndes and the lowlands have higher delta {L}i-7 compared to other rivers. {W}e propose that part of the dissolved {L}i derived from weathering in the {A}ndes is re-incorporated in sediments during transfer of water and sediments in floodplains and that this results in an increase of the dissolved delta {L}i-7 along the course of these rivers. {U}nlike other rivers, the dissolved delta {L}i-7 in the main tributaries is best described by a {R}ayleigh fractionation model with a fractionation factor alpha(sec-dis) of 0.991. {A}ltogether, the control imposed by residence time in the weathering zone and floodplain processes results in (i) a non-linear correlation between dissolved delta {L}i-7 and the weathering intensity (defined as {W}/{D}) and (ii) a positive relationship between the dissolved {L}i flux and the denudation rate. {T}hese results have important implications for the understanding of past ocean delta {L}i-7 and its use as a paleo weathering proxy.},
  keywords = {{ANDES} ; {PEROU} ; {BOLIVIE} ; {BRESIL} ; {AMAZONE} {BASSIN}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {164},
  numero = {},
  pages = {71--93},
  ISSN = {0016-7037},
  year = {2015},
  DOI = {10.1016/j.gca.2015.04.042},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064818},
}