Org. matter from living algal mats and their decay products from mud pools of the geothermal areas at Rotokawa and Waimangu, New Zealand, was sepd. into a solvent-extractable and a protokerogen fraction. Fourteen elements were detd. in the bulk samples and the solvent-extractable fractions by optical emission spectroscopy, and 15 elements (including some rare earth elements) in the protokerogen concs. by instrumental neutron activation anal. Many elements were strongly enriched in the org. fractions as compared to the bulk sample: concns. in the exts. are of the order of g/kg for P, Zn and Sb, and 10 g/kg for As; those in protokerogens are 10 g/kg for Fe and Sb, and 100 mg/kg for La and Ce. The results demonstrate that in contact with metal-rich geothermal waters, biogenic material is able to incorporate high amts. of metals into the org. matrix. While inorg. contributions to the solvent-extractable fractions are shown to be minimal, the presence of inorg. microinclusions in protokerogen concs. cannot be excluded.