Hydrothermal manganese minerals in Leg 126 cores

Abstract

Three substantial manganese deposits were recovered from deep stratigraphic levels. The characteristics of the fossil manganese deposits are similar to those of modern submarine hydrothermal manganese deposits occurring on the seafloor in this area. Two are clearly hydrothermal. They have high Mn/Fe ratios, lack divalent stabilizing interlayer cations, have large crystal sizes, and have 10A d-spacings that are resistent to heating. The third deposit consists of manganese minerals in semiconsolidated Miocene claystones at Site 793. This deposit may be the result of primary early-diagenetic manganese deposits that evolved into more stable hydrothermal-like minerals during later diagenesis after burial. -from Author