TY - JOUR
T1 - Sn-isotope fractionation as a record of hydrothermal redox reactions
AU - Yao, Junming
AU - Mathur, Ryan
AU - Powell, Wayne
AU - Lehmann, Bernd
AU - Tornos, Fernando
AU - Wilson, Marc
AU - Ruiz, Joaquin
N1 - Funding Information:
This work is supported by the National Key R&D Program of China (2016YFC0600405), the GIGCAS No.IS-2547, the National Natural Science Foundation of China (nos. 41672079 and 41372085), and Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB1803206).
Publisher Copyright:
© 2018 Walter de Gruyter GmbH, Berlin/Boston.
PY - 2018/10/25
Y1 - 2018/10/25
N2 - A redox reaction in which Sn2+ oxidizes to Sn4+ is thought to occur during the precipitation of cassiterite (SnO2) and stannite (Cu2FeSnS4) from high-temperature hydrothermal solutions. In four stanniferous regions with differing mineralization environments (South Dakota, U.S.A.; Cornwall, England; Erzgebirge, Germany/Czech Republic; Andean tin belt, Bolivia), the tin isotope composition in stannite (mean value δ124Sn = -1.47 ± 0.54‰, n = 21) is consistently more fractionated toward negative values than that of paragenetically earlier cassiterite (mean value δ124Sn = 0.48 ± 0.62‰, n = 50). Given the oxidation-dependent mechanism for cassiterite precipitation, this isotopic shift is most likely attributable to the oxidation of Sn in solution; precipitation of heavy-Sn-enriched cassiterite results in residual dissolved Sn with lighter isotopic composition, which is expressed in the negative δ124Sn values of later-formed stannite. Equally important is that the mean values for the cassiterite from the various deposits are slightly different and may indicate that the initial Sn isotope composition in early-formed cassiterite relates to variations in the source or magmatic processes. Therefore, the Sn isotopes may provide information on both redox reactions and petrologic sources and processes.
AB - A redox reaction in which Sn2+ oxidizes to Sn4+ is thought to occur during the precipitation of cassiterite (SnO2) and stannite (Cu2FeSnS4) from high-temperature hydrothermal solutions. In four stanniferous regions with differing mineralization environments (South Dakota, U.S.A.; Cornwall, England; Erzgebirge, Germany/Czech Republic; Andean tin belt, Bolivia), the tin isotope composition in stannite (mean value δ124Sn = -1.47 ± 0.54‰, n = 21) is consistently more fractionated toward negative values than that of paragenetically earlier cassiterite (mean value δ124Sn = 0.48 ± 0.62‰, n = 50). Given the oxidation-dependent mechanism for cassiterite precipitation, this isotopic shift is most likely attributable to the oxidation of Sn in solution; precipitation of heavy-Sn-enriched cassiterite results in residual dissolved Sn with lighter isotopic composition, which is expressed in the negative δ124Sn values of later-formed stannite. Equally important is that the mean values for the cassiterite from the various deposits are slightly different and may indicate that the initial Sn isotope composition in early-formed cassiterite relates to variations in the source or magmatic processes. Therefore, the Sn isotopes may provide information on both redox reactions and petrologic sources and processes.
KW - Tin isotopes
KW - cassiterite
KW - metal isotope fractionation
KW - redox
KW - stannite
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U2 - 10.2138/am-2018-6524
DO - 10.2138/am-2018-6524
M3 - Article
AN - SCOPUS:85054562531
SN - 0003-004X
VL - 103
SP - 1591
EP - 1598
JO - American Mineralogist
JF - American Mineralogist
IS - 10
ER -