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Large sulfur isotope fractionations associated with Neoarchean microbial sulfate reduction.

Large sulfur isotope fractionations associated with Neoarchean microbial sulfate reduction.

Science (New York, N.Y.) (2014-11-08)

Iadviga Zhelezinskaia, Alan J Kaufman, James Farquhar, John Cliff

ABSTRACT

The minor extent of sulfur isotope fractionation preserved in many Neoarchean sedimentary successions suggests that sulfate-reducing microorganisms played an insignificant role in ancient marine environments, despite evidence that these organisms evolved much earlier. We present bulk, microdrilled, and ion probe sulfur isotope data from carbonate-associated pyrite in the ~2.5-billion-year-old Batatal Formation of Brazil, revealing large mass-dependent fractionations (approaching 50 per mil) associated with microbial sulfate reduction, as well as consistently negative Δ(33)S values (~ -2 per mil) indicative of atmospheric photochemical reactions. Persistent (33)S depletion through ~60 meters of shallow marine carbonate implies long-term stability of seawater sulfate abundance and isotope composition. In contrast, a negative Δ(33)S excursion in lower Batatal strata indicates a response time of ~40,000 to 150,000 years, suggesting Neoarchean sulfate concentrations between ~1 and 10 μM.

MATERIALS

Product Number

Brand

Product Description

Sigma-Aldrich

Iron, powder, −325 mesh, 97%

Iron, IRMM^®, certified reference material, 0.5 mm wire

Sigma-Aldrich

Iron, chips, 99.98% trace metals basis

Sigma-Aldrich

Iron, foil, thickness 0.1 mm, ≥99.9% trace metals basis

Sigma-Aldrich

Iron, puriss. p.a., carbonyl-Iron powder, low in magnesium and manganese compounds, ≥99.5% (RT)

Iron, foil, 1m coil, thickness 0.05mm, hard, 99.5%

Iron, foil, 20m coil, thickness 0.038mm, hard, 99.5%

Iron, foil, 25mm disks, thickness 0.05mm, hard, 99.5%

Iron, foil, 8mm disks, thickness 0.05mm, hard, 99.5%

Iron, rod, 100mm, diameter 2.0mm, as drawn, 99.99+%

Iron, foil, light tested, 100x100mm, thickness 0.025mm, hard, 99.5%

Iron, foil, 6mm disks, thickness 0.25mm, as rolled, 99.99+%

Iron, foil, light tested, 100x100mm, thickness 0.038mm, hard, 99.5%

Iron, foil, not light tested, 100x100mm, thickness 0.015mm, 99.99+%

Iron, foil, not light tested, 100x100mm, thickness 0.003mm, 99.85%

Iron, foil, not light tested, 50x50mm, thickness 0.0025mm, 99.85%

Iron, rod, 1000mm, diameter 2.0mm, as drawn, 99.99+%

Iron, foil, not light tested, 50x50mm, thickness 0.01mm, 99.99+%

Iron, microfoil, disks, 10mm, thinness 0.25μm, specific density 176.7μg/cm², permanent mylar 3.5μm support, 99.99+%

Iron, foil, light tested, 100x100mm, thickness 0.075mm, as rolled, 99.99+%

Iron, foil, 8mm disks, thickness 0.125mm, hard, 99.5%

Iron, microfoil, disks, 25mm, thinness 0.05μm, specific density 40.44μg/cm², permanent mylar 3.5μm support, 99.99+%

Iron, foil, light tested, 25x25mm, thickness 0.075mm, hard, 99.5%

Iron, rod, 100mm, diameter 25mm, as drawn, 98+%

Iron, foil, not light tested, 50x50mm, thickness 0.003mm, 99.85%

Iron, rod, 100mm, diameter 50mm, as drawn, armcO« soft ingot 99.8%

Iron, foil, not light tested, 100x100mm, thickness 0.007mm, 99.85%

Iron, foil, not light tested, 100x100mm, thickness 0.008mm, 99.85%

Iron, rod, 500mm, diameter 50mm, as drawn, 98+%

Iron, foil, not light tested, 100x100mm, thickness 0.009mm, 99.85%