Impact of authigenic clay formation on marine trace element cycling.

Abstract

The impact of marine authigenic clay formation on oceanic trace element cycling remains poorly constrained. Here we report a comprehensive trace and major element dataset for authigenic green clays (Fe-smectite and glauconite series). Our results show that these clays are consistently depleted in Cu, Ba, REEs, Nb, Ti and Al compared to detrital precursor phases, suggesting that systematic exclusion during authigenic clay formation provides a source of these elements to seawater via the porewater. Furthermore, authigenic clays inherit both their REE pattern and Nd isotope composition from their detrital precursor, demonstrating that dissolution-reprecipitation processes control porewater REE chemistry. B, Fe, Cs, K, Mg, Rb, Be, Cr, V, Zn, Co, Sc and Ga are consistently enriched in authigenic clays, requiring uptake from porewater. Global flux estimates constrained by these results confirm that clay authigenesis represents an important sink or source term in the oceanic cycles of many more trace elements than previously recognized.