TY - JOUR
T1 - Lithium, magnesium and uranium isotope behaviour in the estuarine environment of basaltic islands
AU - Pogge von Strandmann, Philip A.E.
AU - James, Rachael H.
AU - van Calsteren, Peter
AU - Gíslason, Sigurdur R.
AU - Burton, Kevin W.
N1 - Funding Information: We would like to thank the Borganes Rescue Team for providing and crewing the boat used for sampling trips in Iceland. Furthermore, we thank Jason Harvey, Chris Pearce, Mabs Gilmour, Louise Thomas and Fatima Mokadem for assistance in the field and the lab. Finally, we would like to thank Başak Kısakürek and an anonymous reviewer for reviews which have greatly helped to improve this manuscript. This work was funded by grants from the NERC (NE/B502701/1) and the Open University (studentship of PPvS).
PY - 2008/10/15
Y1 - 2008/10/15
N2 - This study presents major and trace elements and uranium (U), lithium (Li) and magnesium (Mg) isotope data for dissolved and suspended particulate material from estuaries draining dominantly basaltic terrains in Iceland (Borgarfjör{eth}ur) and Sao Miguel (Povoação) in the Azores archipelago. The concentrations of dissolved sodium (Na), calcium (Ca), potassium (K), sulphate (SO4), Mg and Li, and 7Li/6Li and 26Mg/24Mg isotope ratios vary directly as a function of the dissolved chloride concentration [Cl], indicating that these species are non-reactive in these estuaries. However, U appears to be affected either by colloid flocculation or the formation of Fe-oxyhydroxides in Borgarfjör{eth}ur. The major element composition of suspended particulate material in the estuary at Borgarfjör{eth}ur shows that the detrital silicates delivered to the estuarine mixing zone are relatively unweathered. Accordingly, the δ26Mg isotope composition of the suspended material is indistinguishable from that of the parent basalts. However, the (234U/238U) activity ratios of the suspended material are significantly different from the parent basalt indicating rapid equilibration of the U isotopes between particles and seawater. The Li concentration and δ7Li isotope composition of the suspended load are also observed to increase with increasing [Cl], consistent with ongoing weathering of detrital material and the formation of secondary minerals in seawater. Depending on the particle residence time in the estuary, this process could remove as much as 15-25% of the global riverine input of Li to the ocean.
AB - This study presents major and trace elements and uranium (U), lithium (Li) and magnesium (Mg) isotope data for dissolved and suspended particulate material from estuaries draining dominantly basaltic terrains in Iceland (Borgarfjör{eth}ur) and Sao Miguel (Povoação) in the Azores archipelago. The concentrations of dissolved sodium (Na), calcium (Ca), potassium (K), sulphate (SO4), Mg and Li, and 7Li/6Li and 26Mg/24Mg isotope ratios vary directly as a function of the dissolved chloride concentration [Cl], indicating that these species are non-reactive in these estuaries. However, U appears to be affected either by colloid flocculation or the formation of Fe-oxyhydroxides in Borgarfjör{eth}ur. The major element composition of suspended particulate material in the estuary at Borgarfjör{eth}ur shows that the detrital silicates delivered to the estuarine mixing zone are relatively unweathered. Accordingly, the δ26Mg isotope composition of the suspended material is indistinguishable from that of the parent basalts. However, the (234U/238U) activity ratios of the suspended material are significantly different from the parent basalt indicating rapid equilibration of the U isotopes between particles and seawater. The Li concentration and δ7Li isotope composition of the suspended load are also observed to increase with increasing [Cl], consistent with ongoing weathering of detrital material and the formation of secondary minerals in seawater. Depending on the particle residence time in the estuary, this process could remove as much as 15-25% of the global riverine input of Li to the ocean.
KW - Azores
KW - Iceland
KW - estuarine mixing
KW - lithium isotopes
KW - magnesium isotopes
KW - uranium isotopes
UR - https://www.scopus.com/pages/publications/52749088121
U2 - 10.1016/j.epsl.2008.07.041
DO - 10.1016/j.epsl.2008.07.041
M3 - Article
SN - 0012-821X
VL - 274
SP - 462
EP - 471
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 3-4
ER -