Degree of trace metal pyritization in sediments from the Pacific coast of Baja California, Mexico

We analyzed sediments from a core collected on the Pacific coast of Baja California, similar to 45 km off the city of Tijuana and at 1257 m water depth (32 degrees 29.5 'N, 117 degrees 28.3 'W), for trace metal content in two operationally-defined fractions, HCl and pyrite. Our results indicate a transference of Cu > Ni > Zn much greater than Hg and Ag from the HCl to the pyrite fraction. Sediments have degrees of pyritization (DOP) that averaged 7.2 +/- 4.9%, with a maximum value of 18.5%. Average degrees of trace metal pyritization (DTMP) ranged from 6.2 +/- 2.1% to 83 +/- 18% for Mn and Hg, respectively, although maximum values for some metals were close to 100%. This transference is apparently a function of the solubility products of metal sulfides and the relative abundances of metals in the HCl fraction, as suggested by the significant correlation (p < 0.001) observed between these two parameters and the DTMP of a number of trace metals. A similar correlation was obtained from published data of two cores collected in the Gulf of Mexico.