The fact that the mineral barite, a very insoluble and crystalline form of barium sulfate, is found in marine waters around the world is one of the mysteries of modern chemical oceanography. Although the microcrystals usually have the appearance of crystals precipitated directly from solution, the concentration of barium is too low to provide the saturated-to-supersaturated solution chemistry to cause direct precipitation. In this study, geochemists from the Woods Hole Oceanographic Institution will tackle this problem by studying several of the most promising candidate mechanisms for barite formation. They believe that the most likely mechanism would involved the generation of supersaturated conditions in the microenvironment around sinking, decomposing biogenic particle, but other possibilities (such as catalytic effects of opal surfaces and dissolution of celestite, abarium-rich mineral) will also be considered. Because barite is relatively well preserved in marine sediments, its rate of accumulation could potentially provide quantitative information on past changes in oceanic export productivity (a measure of the ability of the ability of the phytoplankton to fix carbon dioxide and deliver it to depth).
