Chemical composition of manganese nodules from the Southern Pacific

Deep sea manganese nodules from the Southern Ocean have been studied using chemical analysis, X-ray diffraction, optical mineragraphic and electron probe microanalysis techniques. The nodules were lower in manganese, iron and associated elements than the average grade of manganese nodules from other localities. A number of chemical relationships have been observed. Nickel, copper, cobalt, barium, zinc, molybdenum, strontium, sulphur and phosphorus are associated with the manganese rich phases and titanium with the iron rich phases. X-ray diffraction analysis and electron probe microanalysis results indicate that the manganese phases are similar to the disordered delta-MnO2 and "manganite" phases reported by other workers.

Table 2. The element content of manganese crust

The terrains in the South China Sea were apart of the Southeast China continent, and their rift-departing process dominated the formation and evolution of the South China Sea. The survey results of topography and paleoenvironment of the northern South China Sea during SO-49 cruise demonstrate that the terrains rift-departed from the South China continent before early Eocene.

Description and chemical composition of manganese deposits during the deep-sea expedition of the streamer Valdivia in 1898-1899

This monograph forms the fourth part of the tenth volume of the scientific results of the voyage of the German exploring ship Valdivia in the Atlantic and Indian Oceans, made during the years 1898-1899. These volumes are published under the editorship of Prof. Chun, the zoologist of Leipzig, who was leader of the expedition ; and Prof. E. Philippi with the cooperation of Sir John Murray. The nature of the materials brought up at various points during the voyage is well illustrated by a series of plates, similar to those accompanying the Challenger volumes. Among the concretions from the Agulhas Bank were found phosphatic nodules containing 33 per cent, of calcium carbonate, 28 of calcium phosphate, 14.6 of calcium sulphate, and 4.8 of magnesium carbonate, with some ferric oxide, alumina, and silica. These nodules were dredged at a depth of 155 metres. Off the coast of Namibia, a large quantity of manganese nodules were also dredged. Their chemical analysis performed at the Mineralogical Institute of the University Jena show similar composition as the nodules recovered by the "Challenger" at station 253 in the Pacific Ocean.

Major and minor elements in hydrothermal and pelagic sediments at DSDP Leg 70 Holes

Interaction between young basaltic crust and seawater near the oceanic speading centers is one of the important processes affecting the chemical composition of the oceanic layer. The formation of metalliferous hydrothermal sediments results from this interaction. The importance of the interaction between seawater and basalt in determining the chemical composition of pore waters from sediments is well known. The influence of mineral solutions derived from this interaction on ocean water composition and the significant flux of some elements (e.g., Mn) are reported by Lyle (1976), Bogdanov et al. (1979), and others. Metal-rich sediments found in active zones of the ocean basins illustrate the influence of seawater-basalt interaction and its effect on the sedimentary cover in such areas. The role of hydrothermal activity and seawater circulation in basalts with regard to global geochemistry cycles has recently been demonstrated by Edmond, Measures, McDuff, McDuff et al. (1979), and Edmond, Measures, Mangum (1979). In the area of the Galapagos Spreading Center the interaction of sediments and solutions derived from interaction of seawater and basalt has resulted in the formation of hydrothermal mounds. The mounds are composed of manganese crusts and green clay interbedded and mixed with pelagic nannofossil ooze. These mounds are observed only in areas characterized by high heat flow (Honnorez, et al., 1981) and high hydrothermal activity.

Geochemistry at DSDP Leg 70 Holes

A total of 32 holes at five sites near 1°N, 86°W drilled on Deep Sea Drilling Project (DSDP) Leg 70 (November- December 1979) provide unique data on the origin of the hydrothermal mounds on the southern flank of the Galapagos Spreading Center. Hydrothermal sediments, primarily Mn-oxide and nontronite, are restricted to the immediate vicinity of the mounds (< 100 m) and are probably formed by the interaction of upward-percolating hydrothermal solutions with seawater and pelagic sediments above locally permeable zones of ocean crust. Mounds as high as 25 meters form in less than a few hundred thousand years, and geothermal and geochemical gradients indicate that they are actively forming today. The lack of alteration of upper basement rocks directly below the mounds and throughout the Galapagos region indicates that the source of the hydrothermal solutions is deeper in the crust.

Composition of sedimentary rocks from the Mountainous Crimea and the Northwestern Caucasus

Detailed data obtained on chemistry of sedimentary rocks from the Mountainous Crimea and the Northwestern Caucasus that were dated at the Cenomanian/Turonian boundary and formed during Oceanic Anoxic Event 2 make it possible to calculate dissolved oxygen concentration in bottom waters of the sedimentation basin. Enrichment factors of trace elements in black shales are revised and an explanation is suggested for genesis of the rocks with regard for unusual climatic changes.

Documentation of manganese nodules form the northwest Indian Ocean

Microscopic and electron probe examination of some manganese nodules show that they consist of segregations of manganese-iron oxides in an interstitial material almost free of manganese but rich in iron and silicates. The segregations are widely spaced in the volcanic cores of the nodules but become more abundant towards their outer crusts where they form the centres of linked polygons of interstitial materials. Most of the minor elements are concentrated in the segregations compared to the interstitial materials. It is suggested that the structures observed result partly from solution and reprecipitation of elements in the original volcanic cores of the nodules and partly from the replacement and coating of these cores by manganese-iron oxides precipitated from sea water.

Analysis of ferromanganiferous sedimentary rocks from Timor

Seven manganese nodules, eight ferromanganiferous shales from the Cretaceous Wai Bua Formation of Timor, and a pelagic limestone with four ferromanganese enriched layers from the Middle Eocene of Timor have been analysed. The nodules are compared with modern deep-sea nodules, and the ferromanganiferous shales are contrasted with relatively shallow marine manganiferous shales. The conclusion is reached that these rocks from Timor were probably deposited in a bathypelagic environment. There is a total absence of any indication that volcanic material has contributed to these deposits. The chemical composition of the ferromanganiferous rocks are discussed and some indications of biogenic influences are noted. The Middle Eocene pelagic limestone is compared with a similar modern sediment described from the Easter Island Rise in the Pacific.

Manganese nodules mesozoic deep-sea deposits off some Indonesian Islands

Concretions of manganese have been discovered by the geological expedition to the islands of the Timor group in 1910-1912 in triassic and jurassic deep-sea deposits, on the Island of Timor, and also well developed in similar jurassic deposits on the island of Rotti, and previously, in 1894, the author noticed them in abysmal deposits of the pre-cretaceous probably jurassic Danau formation, occurring in West and East Borneo. On the island of Rotti nodules of manganese were found in several localities in siliceous limestones, marls, siliceous and calcareous clayshales along with concretions and nodules of chert of jurassic age, full of tests of radiolaria.