Diatoms spread a high epsilon(Nd)-signature in the North Pacific Ocean

作者：Akagi Tasuku^*; Yasuda Saki; Asahara Yoshihiro; Emoto Mariko; Takahashi Kozo

来源：Geochemical Journal, 2014, 48(2): 121-131.

DOI：10.2343/geochemj.2.0292

• diatom silica frustules
• neodymium isotope
• seawater
• island arc
• loess

The Nd and Sr isotopes of the acetic-acid-soluble, hydrochloric-acid-soluble, hydrofluoric-acid-soluble (siliceous) fractions of settling particles collected in the highly diatom productive Bering Sea were measured. The siliceous fraction exhibits epsilon(Nd) values higher than that of the acetic acid extractable fraction or that dissolved in North Pacific seawater. Recent studies concluded that the siliceous fraction of settling particles collected in an area of extremely high diatom production consists almost exclusively of diatom frustules, that diatom frustules are a major Nd transporter in the ocean water column, and that half the Nd in diatom frustules should be supplied from an unknown input other than that diffused/advected from the deep seawater. The Nd isotope system of the siliceous fraction provides the first evidence that diatoms transport the high epsilon(Nd) signature to the oceanic system. The unknown input is the dissolution of silicate rocks which are somehow supplied to the sea surface. In the Bering Sea one of the sources of the high Nd values was identified to be island arcs. This diatom-mediated dissolution of silicate particles may be a mechanism to explain the rather pervasive island arc Nd isotope signature in the Pacific Ocean where there are surrounding island arcs.

• 出版日期2014