Magnetite and Barite

Besides the precipitation of mineral phases, dissolution of numerous minerals initially supplied to the seafloor can occur in sediments that experience sulfate reduction and/or sulfate-depleted conditions. Iron (oxyhydr)oxides and barite (BaSO ) are two examples with particular relevance for paleoceanographic research. 

A second sedimentary component important for paleoceanographic reconstructions, which is prone to dissolution under conditions of sulfate reduction - or more precisely in srrlfate-depleted sediments - is the barium sulfate mineral, barite (BaSO ). Since a correlation has been detected between barite deposition and the flux of organic matter through the water column, the concentration of barite in sediments has been proposed and applied as a geochemical tracer to reconstruct past changes in ocean productivity (e.g.. Bishop 

Effects of Sulfate Reduction on Sedimentary Solid Phases 

In a novel approach, Dickens (2001) used sedimentary Ba records to assess temporal changes during the Late Pleistocene in the upward flux of methane within sediments of the Blake Ridge that are rich in sub-surface gas hydrates. Due to a lack of Ba enrichment above the present 

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Weighting agents (Table 10-10) are added to increase the density of the cement. They are typically used to combat high bottom-hole pressures. Common additives are powdered iron, ferromat, powdered magnetite, and barite. Hematite ean be used to increase the density of a mixture up to 2200 kg/m (19 Ib/gal). Hematite requires the addition of some water. 

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