Pelagic clays as archives of marine iron isotope chemistry

Slowly accumulating pelagic clays are enriched in metals that were formerly seawater, including iron, an important micronutrient. Because the minimally remobilized oxygenated porewater, may be a potential archive for records of past marine micronutrient cycling. Here, we present record changes hydrogenous iron (Fe) isotopes since late Cretaceous derived from dated with osmium isotope chronostratigraphy. To optimize separation metal (oxy)hydroxides bulk sediment, repeatedly leached oxic clay sample under variable conditions (HCl molarity, temperature, time) and measured element concentrations, Fe isotopes, Os isotopes. The common behavior elements amidst permutations leach experiment offers insight into which components dissolved defined range successful leaches. We applied our optimal (1 M HCl, 24 h at 20 °C) to 45 samples Site U1366 South Pacific Gyre. resulting suggests dynamic cycle water column overlying over 95 million years. Early site's history, trends interpreted as reflecting hydrothermal distance ridge. Contributions background source identified well transition dust-like after 50 Ma until present. Constructing similar multiple sites will provide basin-wide perspective on how has changed million-year timescales.