The fundamental role of island arc weathering in the oceanic Sr isotope budget

Claude-Jean Allegre (1) , Pascale Louvat (1) , Jérôme Gaillardet (1) , Laure Meynadier (1) , Sétareh Rad , Françoise Capmas (1)

1 IPGP - Institut de Physique du Globe de Paris

We have re-assessed the Sr isotopic budget of the modern ocean taking into account the high erosion rates of volcanic islands, and especially of island arcs, emphasizing important contribution from subsurface weathering to global budgeting. We propose that intensive weathering on volcanic islands, island arcs and oceanic islands, coupled with large surface and subsurface water fluxes is the missing source of mantlederived 87Sr/86Sr (0.703) in seawater Sr isotope balance. In our approach, it represents 60% of the actual mantle-like input of Sr to the oceans, the remaining 40% supplied by ridge-crest hydrothermal activity and sea-floor low-temperature alteration of basalts. The seawater Nd isotopic budget is consistent with this interpretation and explains well the regional contributions from ridge crest and island arc activity among the oceans.

Mots clés: strontium isotopes; ocean water; arc volcanism; rivers; erosion

Domaines: Géochimie; Milieux et Changements globaux

Claude-Jean Allegre, Pascale Louvat, Jérôme Gaillardet, Laure Meynadier, Sétareh Rad, et al.. The fundamental role of island arc weathering in the oceanic Sr isotope budget. Earth and Planetary Science Letters, 2010, 292 (1-2), pp.51-56. ⟨10.1016/j.epsl.2010.01.019⟩. ⟨hal-00755703⟩