Degree of trace metal pyritization in sediments from the Pacific coast of baja california, mexico

Abstract

We analyzed sediments from a core collected on the Pacific coast of Baja California, ~45 km off the city of Tijuana and at 1257 m water depth (32º29.5′N, 117º28.3′W), for trace metal content in two operationally-defined fractions, HCl and pyrite. Our results indicate a transference of Cu > Ni > Zn >> 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.