TY - JOUR
T1 - Release of tephra-hosted iron during early diagenesis fingerprinted by iron isotopes
AU - Longman, Jack
AU - Dunlea, Ann G.
AU - Böning, Philipp
AU - Palmer, Martin R.
AU - Gernon, Thomas M.
AU - McManus, James
AU - Manners, Hayley R.
AU - Homoky, William B.
AU - Pahnke, Katharina
PY - 2023/3/1
Y1 - 2023/3/1
N2 - The micronutrient iron (Fe) plays a fundamental role controlling primary productivity in the upper ocean, with volcanic eruptions and deposition of airborne volcanic material (termed tephra) a potential source of Fe. Here, we investigate the geochemical and Fe isotopic (
Fe) composition of tephra layers, sediments, and mixed tephra-sediment samples from the Integrated Ocean Drilling Program (IODP) Hole 1396C, located offshore the volcanically active island of Montserrat in the Lesser Antilles, Caribbean Sea. We find that buried tephras, which have experienced diagenesis, exhibit lighter
Fe (relative to standard IRMM-524a) compositions (down to −0.26 ± 0.04‰, 2SD) than fresh tephra deposited in Montserrat (
Fe = 0.02 ± 0.02‰, 2SD). Such negative values suggest that isotopically heavier Fe has been lost from the originally deposited material. Using multivariate statistical modelling and mass balance constraints, we identify the outward Fe flux (with calculated
Fe of 0.21 ± 0.31‰, 2SD, n = 12) during non-reductive dissolution of tephra as the likely cause of the retention of these light
Fe compositions. Due to the widespread nature of tephra deposition, tephra diagenesis may provide an important source of isotopically heavy dissolved Fe (dFe) to the oceans. This process contrasts with more commonly considered reductive dissolution processes, which provide a source of dFe enriched in light isotopes to the oceans.
AB - The micronutrient iron (Fe) plays a fundamental role controlling primary productivity in the upper ocean, with volcanic eruptions and deposition of airborne volcanic material (termed tephra) a potential source of Fe. Here, we investigate the geochemical and Fe isotopic (
Fe) composition of tephra layers, sediments, and mixed tephra-sediment samples from the Integrated Ocean Drilling Program (IODP) Hole 1396C, located offshore the volcanically active island of Montserrat in the Lesser Antilles, Caribbean Sea. We find that buried tephras, which have experienced diagenesis, exhibit lighter
Fe (relative to standard IRMM-524a) compositions (down to −0.26 ± 0.04‰, 2SD) than fresh tephra deposited in Montserrat (
Fe = 0.02 ± 0.02‰, 2SD). Such negative values suggest that isotopically heavier Fe has been lost from the originally deposited material. Using multivariate statistical modelling and mass balance constraints, we identify the outward Fe flux (with calculated
Fe of 0.21 ± 0.31‰, 2SD, n = 12) during non-reductive dissolution of tephra as the likely cause of the retention of these light
Fe compositions. Due to the widespread nature of tephra deposition, tephra diagenesis may provide an important source of isotopically heavy dissolved Fe (dFe) to the oceans. This process contrasts with more commonly considered reductive dissolution processes, which provide a source of dFe enriched in light isotopes to the oceans.
U2 - 10.1016/j.epsl.2023.118016
DO - 10.1016/j.epsl.2023.118016
M3 - Article
SN - 0012-821X
VL - 605
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 0
ER -