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doi:10.2204/iodp.proc.331.106.2011

Geochemistry

Headspace gas analysis

Because most of the recovered core at Site C0016 was hard, solid rock, only a single sample was recovered for headspace analysis (from Section 331-C0016B-3L-1). This sample, from 37 mbsf, yielded a methane concentration (Tables T3, T4) estimated to be between 86 and 310 μM. This estimate used the water content measured on nearby hard rock, and so is likely to be revised downward once water content is determined on the actual material used for the headspace analysis.

A high concentration of hydrogen was observed in Section 331-C0016B-3L-1, which might be an artifact of hydrogen production caused by BHI rotary drilling into hard pyritic rock.

Sediment carbon, nitrogen, and sulfur composition

For the three samples investigated, calcium carbonate (CaCO₃) content calculated from inorganic carbon concentration is low, ranging from below detection (<0.001 wt%) to 0.055 wt% (Table T5). Total organic carbon is also low, ranging from 0.007 to 0.022 wt%. Total sulfur (TS) is high, ranging from 7.7 to 23.2 wt%. The shallowest sample (from Section 331-C0016B-1L-1), a massive black ore rich in sphalerite and pyrite, has a TS content of 21.2 wt%. The next deepest sample (331-C0016B-1L-CC) is a silicified volcanic rock with a low TS content of 7.7 wt%, likely reflecting a higher silica content and lower abundance of pyrite. The deepest sample (331-C0016B-2L-CC) is an anhydrite-sulfide vein with a high TS of 23.2 wt%.

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