The hydrothermal component in ferromanganese nodules from the southeast Pacific Ocean

Abstract

Statistical analyses of geochemical data from ferromanganese nodule samples representing a broad area of the southeast Pacific Ocean indicate nodule compositions are controlled by four factors: (1) suboxic diagenesis; (2) oxic diagenesis; (3) hydrogenous precipitation; and (4) hydrothermal precipitation. The first three are identical to those identified in studies of nodules from the North Pacific; the fourth factor represents the first quantitative determination of a significant hydrothermal end-member in ferromanganese nodules. Nodules apparently acquire a hydrothermal component through the accretion of colloidal-sized hydrothermal precipitates which are widely dispersed from their origin at vents along the East Pacific Rise (EPR). Nodules recovered from beneath the "shadow" of the present-day hydrothermal plumes emanating from the EPR contain significantly higher amounts of hydrothermal material relative to nodules from other areas.