Estimation of sulfur, fluorine, chlorine and bromine fluxes at Mid Ocean Ridges using a new experimental crushing and extraction method

Abstract

We measured helium-3 (3He), sulfur (S), fluorine (F), chlorine (Cl) and bromine (Br) concentrations in vesicles of Mid Ocean Ridge Basalts (MORBs) and Back-Arc Basin Basalts (BABBs). The aim of this study was to characterize the MORB-source composition and to estimate the fluxes of S, F, Cl and Br from the mantle. A newly developed gas extraction method called the “Frozen Crushing Method” was applied. Measured concentrations in vesicles were (4-31) × 10-15 mol/g of 3He, (20-420) × 10-9 mol/g of S, (60-5000) × 10-9 mol/g of F, (160-450) × 10-9 mol/g of Cl and (10-1300) × 10-9 mol/g of Br. We estimated global fluxes of S, F, Cl and Br at Mid Ocean Ridges using the molar ratio of each element on the 3He in the samples and the known mantle 3He flux of 527 mol/yr. Estimated fluxes using element concentrations measured in vesicles are (1.2 ± 0.7) × 1010 mol/yr of S, (1.4 ± 1.0) × 1011 mol/yr of F, (1.4 ± 0.5) × 1010 mol/yr of Cl and (3.1 ± 2.8) × 1010 mol/yr of Br. In addition, fluxes calculated on the basis of estimated concentrations in the bulk basalts are (1-26) × 1010 mol/yr of S, (2-120) × 1011 mol/yr of F, less than (2-120) × 1010 mol/yr of Cl and (4-240) × 1010 mol/yr of Br. © 2012, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.