TY - JOUR
T1 - Evidence for stable Sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern Taiwan
AU - Chao, Hung Chun
AU - You, Chen Feng
AU - Liu, Hou Chun
AU - Chung, Chuan-Hsiung
N1 - Funding Information:
This study was supported by MOST and MOE grants to C.F.Y. Constructive comments by Dr. Edward Tipper and two anonymous reviewers are greatly appreciated, as well as the Executive Editor, Dr. Norman, and the associate editor, Dr. Gaillardet, for their effective handling of this manuscript. The authors wish to thank Prof. H.J. Yang of NCKU who kindly provided the international reference material, JB-2, for the leaching experiment.
Publisher Copyright:
© 2015 Elsevier Ltd.
PY - 2015/9/5
Y1 - 2015/9/5
N2 - Radiogenic Sr isotopes (87Sr/86Sr) are robust for provenance identification in hydrology, affected mainly by the age of background lithologies and the degree of chemical weathering. However, there is limited knowledge concerning the fractionation mechanism of stable Sr isotopes (88Sr/86Sr) in rivers. In this study, river water was collected on a weekly to monthly basis throughout dry and wet seasons. Furthermore, to study the variations of radiogenic and stable Sr isotopes during intense weathering, a major flooding event (2000mm precipitation in three days, Typhoon Morakot), water was captured within a small drainage catchment system (161km2) along the Hou-ku River in southwestern Taiwan. For a better constraint on the end member compositions, bedload sediments, suspended particles, and several host rocks were sampled for a systematic investigation. The carbonate and silicate phases of these solids were chemically separated. Dissolved major elements indicate that the watersheds were predominated by silicate weathering. Stable Sr isotopes show no significant variation (δ88Sr=0.24-0.31‰) temporally and spatially with an average of 0.28‰. Additionally, all solids showed lower δ88Sr values than the river water while the host rocks had higher δ88Sr values (δ88Sr=0.20-0.26‰) than the residual weathering products (δ88Sr=0.08-0.22‰), indicating preferential leaching of heavy Sr into the hydrosphere and leaving light Sr in the residual solids. Results of laboratory acid leaching experiments reveal that dissolution of high δ88Sr value minerals occurred at an early stage of weathering. The variation of weathering intensity does not alter stable Sr isotopes in silicate weathering dominated river water, which contains higher stable Sr isotopes than the associated sediments. The silicatic sedimentary rocks preferentially released higher stable Sr isotopes into the hydrosphere during chemical weathering, thus leaving lower stable Sr isotopes in the residual solids.
AB - Radiogenic Sr isotopes (87Sr/86Sr) are robust for provenance identification in hydrology, affected mainly by the age of background lithologies and the degree of chemical weathering. However, there is limited knowledge concerning the fractionation mechanism of stable Sr isotopes (88Sr/86Sr) in rivers. In this study, river water was collected on a weekly to monthly basis throughout dry and wet seasons. Furthermore, to study the variations of radiogenic and stable Sr isotopes during intense weathering, a major flooding event (2000mm precipitation in three days, Typhoon Morakot), water was captured within a small drainage catchment system (161km2) along the Hou-ku River in southwestern Taiwan. For a better constraint on the end member compositions, bedload sediments, suspended particles, and several host rocks were sampled for a systematic investigation. The carbonate and silicate phases of these solids were chemically separated. Dissolved major elements indicate that the watersheds were predominated by silicate weathering. Stable Sr isotopes show no significant variation (δ88Sr=0.24-0.31‰) temporally and spatially with an average of 0.28‰. Additionally, all solids showed lower δ88Sr values than the river water while the host rocks had higher δ88Sr values (δ88Sr=0.20-0.26‰) than the residual weathering products (δ88Sr=0.08-0.22‰), indicating preferential leaching of heavy Sr into the hydrosphere and leaving light Sr in the residual solids. Results of laboratory acid leaching experiments reveal that dissolution of high δ88Sr value minerals occurred at an early stage of weathering. The variation of weathering intensity does not alter stable Sr isotopes in silicate weathering dominated river water, which contains higher stable Sr isotopes than the associated sediments. The silicatic sedimentary rocks preferentially released higher stable Sr isotopes into the hydrosphere during chemical weathering, thus leaving lower stable Sr isotopes in the residual solids.
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U2 - 10.1016/j.gca.2015.06.006
DO - 10.1016/j.gca.2015.06.006
M3 - Article
AN - SCOPUS:84934325379
VL - 165
SP - 324
EP - 341
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
ER -