Petrographic and electron microprobe investigation of some deep- and shallow-water manganese nodules

Abstract

Manganese·rich nodules from the flanks of the Carlsberg Ridge in the Indian Ocean, the Jervis Inlet on the Pacific Coast of Canada, and Loch Fyne, western Scotland have been examined by petrographic, X-ray diffraction, bulk chemical, and electron microprobe methods. The deep·water nodule from the Carlsberg Ridge is typical of oceanic nodules and is characterised by well developed concentric structures, a high content of Cu, Ni, Co, and Pb and a low Mn/Fe ratio (1· 3). The trace elements show associations found in previous studies, although they are less regular. The shallowwater nodules (Jervis Inlet and Loch Fyne) do not show the concentric structures to the same extent, are much poorer in trace elements, and have much higher Mn/Fe ratios (8'8 and 14'9, respectively) than the Carlsberg Ridge nodule. 8-MnO:! is the principal mineral in the deep-sea nodule but lOA manganite (todorokite) is the principal phase in the shallow-water nodules. Angular detrital quartz and feldspar are common in the shallow-water types but much rarer in the deep·sea nodule. The differences between the nodules are attributed to differences in nucleation and growth rates attendant upon the different concentrations of Mn in the water from which the nodules formed. Other mechanisms of growth are briefly reviewed.

Manganiferous garnet underlying the Bousquet gold orebody, Quebec: metamorphosed manganese sediment as a guide to gold ore

“…The most common of these accessory minerals are goethite, quartz, feldspar, montmorillonite, illite, and zeolites. Dunham and Glasby (1974) have proposed that manganese nodules grow as concentrically banded cusps, each with a nucleation point. These cusps grow upward and outward with clay minerals and other detrital material collected between cusps and in voids formed where cusps coalesce.…”

Manganese nodules in the South Pacific: A review

“…This reflects the fact that the authigenic phase of manganese nodules represents an intermediate between Mn-rich and Fe-rich end members. Because of the cryptocrystalline nature of the oxide phase of manganese nodules, the end members never form discrete phases, but can be observed in individual nodules under the electron microprobe (Dunham & Glasby 1974). The gross relationship between Mn and Fe is, however, complicated by the fact that nodules represent a three-component system consisting of a manganese oxide phase, an iron oxide phase, and a detrital mineral phase.…”

Minerals, Metal Contents, and Mechanism of Formation of Manganese Nodules from the Central Pacific Basin (GH76-1 and GH77-1 Areas)

“…Chemical heterogeneity, which has been characterized by the laminations of manganese-rich and iron-rich zones observed in the interior of nodules and by similar variations in the abundance of copper, nickel and zinc relative to manganese (Burns and Fuerstenau, 1966;Friedrich et al, 1969;Sa no and Matsubara, 1970;Sorem and Foster, 1973;Dunham and Glasby, 1974) are related to the laminations of the 10~ manganite and the 6-Mn0 2 phases. It is also suggested, from the present studies, that the strong positive correlations between Mn and Ni and Mn and Cu as determined by the bulk composition of nodules from various environments, are not due to the crystallographic property of a single mineral, but due rather to the relative abundance of lO~ manganite which contains a large amount of nickel and copper.…”