Metal-organic associations in sediments--2. Algal mats in contact with geothermal waters

Organic matter from living algal mats and their decay products from mud pools of the geothermal areas at Rotokawa and Waimangu, New Zealand, was separated into a solvent-extractable and a protokerogen fraction. Fourteen elements were determined in the bulk samples and the solvent-extractable fractions by optical emission spectroscopy, and 15 elements (including some rare earth elements) in the protokerogen concentrates by instrumental neutron activation analysis. The results demonstrate that in contact with metal-rich geothermal waters, biogenic material is able to incorporate high amounts of metals into the organic matrix. While inorganic contributions to the solvent-extractable fractions are shown to be minimal, the presence of inorganic microinclusions in protokerogen concentrates cannot be excluded.