Abstract
To constrain Trinidad mud volcanoes hydraulic behavior, both cosmogenic 10Be (t1/2=1.5 Myr) and 9Be concentrations have been measured in fluid and associated expelled mud. As previously evidenced [A.N. Dia, M. Castrec, J. Boulègue, P. Comeau, Trinidad Mud Volcanoes: where do the expelled fluids come from? Geochim. Cosmochim. Acta 63 (1999) 1023–1038] from δ18O values and Cl concentrations, 9Be concentrations in the fluids mostly reflect the mixing of two deep components: REM I and REM II. REM I (δ18O=10.5‰, Cl≈275 mM and 9Be≈0.05 nM) has characteristics of a continental fluid while REM II (δ18O=3‰, Cl≈350 mM and 9Be≈1 nM) results from seawater–volcanogenic derived sediment interaction. Although 10Be concentrations in the fluid samples are close to the detection limit, the distribution of both beryllium isotopes between the hydroxylamine leachable and residual phases indicates exchange reaction with fluid younger than 15 Myr. Comparison between the lowest REM I 10Be/9Be ratio in fluid recorded by the hydroxylamine leachable phase (TD5 mud sample) and the 10Be/9Be ratio representative of meteoric contribution in the recharge area (TD8 fluid sample) yields a circulation rate of REM I fluid in the Trinidad mud volcanoes of several 10−1 m/yr.
Published Version
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