Annotated record of the detailed examination of Mn deposits from DSDP Site 160, Leg 16 (Cores 16-160-1, 16-160-2 and 16-160-3)

DSDP 160 forms part of a series of sites in the eastern equatorial Pacific on the west flank of the East Pacific Rise. Earlier legs of the Deep Sea Drilling Project, in particular Legs 5 and 9, have reported sediments rich in oxides of iron and perhaps other transition metals just above basement in the eastern Pacific. These occurrences roughly define a broad zone on the west flank of the rise. Site DSDP 160 lies on this trend and were selected by the Pacific Site Selection Panel to test the extent of such deposits.

Annotated record and chemical composition of Mn deposits from R/V Mahi Cruise Abyssal Hills 69 stations

A University of Hawaii oceanographic cruise, Abyssal Hills 69, with the R/V Mahi, was carried out to study the association of manganese nodules with an abyssal hill. Manganese nodules from three dredge hauls on an abyssal hill located at 36°W and 157°W exhibited differences in morphology and composition between stations only three miles apart. The morphology of the nodules suggests that nodules from a single site have similar morphologies because they began growth at the same time, probably because of a volcanic event. Differences in morphology between stations indicate a local supply of elements. Atomic absorption analysis for manganese, iron, cobalt, nickel, and copper revealed that nodules nearest to a probable fault line and source of volcanism have a, lower manganese to iron ratio than nodules farther removed. This finding supports the theory that volcanism contributes to the formation of some nodules. Additional evidence showing association with volcanism consists of volcanic nuclei in nodules, crusts formed on layers of volcanic ash, and basalt encrusted to various degrees. The variation in cobalt, nickel, and copper contents Gt the nodules from a single dredge is two-to threefold, but iron content is more uniiorm. Four of the six cores from the area increased in manganese concentration with depth, suggesting that diffusion is concentrating manganese in the upper zone of the sediments or in nodules. The author concludes that volcanism is contributing to the formation of nodules by supplying nuclei and transition elements, but is not necessary for the formation of manganese nodules.

(Table, Appendix C) Metal content of nodules at Sea Scope stations based upon XRF analyses at the Ore Microscopy Laboratory, Washington State Unicersity, USA

New information on possible resource value of sea floor manganese nodule deposits in the eastern north Pacific has been obtained by a study of records and collections of the 1972 Sea Scope Expedition. Nodule abundance (percent of sea floor covered) varies greatly, according to photographs from eight stations and data from other sources. All estimates considered reliable are plotted on a map of the region. Similar maps show the average content of Ni, Cu, Mn and Co at 89 stations from which three or more nodules were analyzed. Variations in nodule metal content at each station are shown graphically in an appendix, where data on nodule sizes are also given. Results of new analyses of 420 nodules from 93 stations for mn, fe, ni, cu, CO, and zn are listed in another appendix. Relatively high Ni + Cu content is restricted chiefly to four groups of stations in the equatorial region, where group averages are 1.86, 1.99, 2.47, and 2.55 weight-percent. Prepared for United States Department of the Interior, Bureau of Mines. Grant no. GO284008-02-MAS. - NTIS PB82-142571.

(Table 8, page 38) Spectrographic analyses of deep sea manganese nodules from the Pacific and Indian Oceans

In an earlier paper by two of the authors the conclusion was reached that the 33 recognized species of oxides of Mn could be separated into 3 groups: 1) those which appeared to be persistently supergene in origin, 2) those which appeared to be persistently hypogene, and 3) those which were supergene in some localities and hypogene in other localities. When that paper was written, there were available about 250 X-ray diffraction analyses of mineral specimens, also 35 complete and about 150 partial chemical analyses. The conclusions of that paper were based upon the interpretation of the geologic conditions under which these specimens occurred. Late in the preparation of that paper, it seemed worthwhile to make numerous semiquantitative analyses of specimens, largely from 9 western [U.S.A] states, selected carefully from 5 groups of geologic environments, in the hope that the frequency and percentages of some elements might be distinctive of the several geologic groups. For this purpose, 95 specimens were selected from the 5 groups, as follows: 19 specimens interpreted as supergene oxides by the geologists who collected them, 35 specimens of hypogene vein oxides, 22 specimens of Mn-bearing hot spring aprons, 9 specimens of stratified oxides, and 10 specimens of deep-sea nodules. The spectrographic analyses here recorded indicate that a group of elements - W, Ba, Sr, Be, As, Sb, Tl, and Ge - are present more commonly, and largely in higher percentages, in the hypogene oxide than in the supergene oxides and thus serve to indicate different sources of the Mn. Also, the frequency and percentages of some of these elements indicate a genetic relation of the manganese oxides in hypogene veins, hot spring aprons, and stratified deposits. The analyses indicate a declining percentage of some elements from depth to the surface in these 3 related groups and increasing percentages of some other elements. It is concluded that some of the elements in deep-sea nodules indicate that sources other than rocks decomposed on the continents, probably vulcanism on the floors of the seas, have contributed to their formation.

Annotated record of the detailed examination of Mn deposits from DSDP Site 161, Leg 16 (Cores 16-161-1 and 16-161A-14)

DSDP 161 is located on the lower west flank of the East Pacific Rise about midway between the Clipperton and Clarion fracture zones which define the boundaries of a large structural block in the eastern Pacific. The site is about 4,000 km west of the present crest of the Rise. It is located near the northern edge of a zone of thick Cenozoic sediments which marks the general location of the equatorial zone of high biological productivity.

Description, geochemistry and growth rate of buried nodules from the Central Indian Basin

Buried nodules from siliceous sediments in the central Indian Basin are morphologically variable and mineralogically consist of d-MnO2 and incipient todorokite. Compositionally they are weakly diagenetic. The sediment coarse fractions (>63 µm) at different depths show variable abundances of micronodules, volcanic glass shards and biodebris. Dissolution of biodebris increases and abundance of micronodules decreases with increasing depth. Enrichment in Mn, Fe, Cu, Ni, Co, together with a decrease in organic carbon in the sediment column, may result from diagenetic metal remobilization. Diagenetically remobilized trace metals might have been utilized for the growth of micronodules over the buried nodules.

(Table 1, page 258) Chemical composition of 24 concentric layers inside manganese nodule DH9-9 from the Pacific Ocean

The minor-element composition of concentric layers within a single ferromanganese nodule from the eastern North Pacific exhibits strong correlations with Fe and Mn contents but appears to be independent of pronounced mineralogic variations. On the basis of these correlations, the elemental composition of individual layers apparently is controlled by the relative contribution of two sources: seawater, and interstitial water of associated sediment. In contrast, the mineralogy of the nodule, consisting of birnessite in the outer few layers and todorokite in the inner layers, is considered to be a function of nodule diagenesis.

Lithium concentration in manganese nodules of the Pacific Ocean (Hakurei Maru Cruise GH77-1, January-March, 1977)

Various manganese nodules donated to the Scripps Institution of Oceanography from the Hakurei Maru Cruise GH77-1, January-March, 1977, in the Central Pacific Basin have been analysed for their lithium content by J. Korkish from the Institute of Analytical Chemistry, Analysis of Nuclear Raw Materials Division, University of Vienna, Austria. The author has used a Perkin-Elmer atomic-absorption spectrometer 303 after speration by dissolution in hydrochloric acid.

(Table XIV-1, Page 137-139) Physical characteristics of manganese nodules collected in the Pacific Ocean during cruise GH76-1 of R/V Hakurei Maru

Nodule samples obtained were described and studied on board for 1) observation of occurrence and morphology in and outside samplers, size classification, measurement of weight and calculation of population density (kg/m2); 2) photographing whole nodules on the plate marked with the frames of unit areas of both 0cean-70 (0.50 m2) and freefall grab (0.13 m2), and that of typical samples on the plate with a 5 cm grid scale: 3) observation of internal structures of the nodules on cut section; and 4) determination of mineral composition by X-ray diffractometer. The relation between nodule types and geological environment or chemical composition was examined by referring to other data of related studies, such as sedimentology. acoustic survey, and chemical analysis.

(Table 2, page 156), The comparison of heavy elements in manganese nodules

The comparison of Mn/Fe, Co/Ni, Co/Fe, Ni/Mn, and Cu/Fe ratios is presented and it is noticed that Co/Ni and Ni/Mn ratios of nodules fairly coincide with those of coexisting sediments. This agreement suggests that Mn, Ni, and Co are accumulated in both nodules and sediments at about the same rates. According to the calculation of Somayajulu et al. similar consideration is also applicable to Cu. Results are, however, implying that Cu co-precipitates with Fe, rather than Mn.

Description of manganese nodules and crust collected from the Hakurei Maru Cruise GH76-1, January-March, 1976, in the Central Pacific Basin

This report of the GH76-1 cruise mainly includes the results of the on-board observations in the survey area of the medial-eastern part of Central Pacific Basin (5 degree -10 degree N, 170 degree -175 degree W) and partly of analytical work at the on-shore laboratory. In addition, the results of some on-board optical and geophysical works along the tracks of Japan-Ogasawara-survey area-Hawaii, are described in appendices. The GH76-1 cruise of the R/V Hakurei-maru was carried out from the 10th January to the 9th March, 1976 as the second phase field work of the Geological Survey of Japan five-year research program of study on the manganese nodule deposits of the Central Pacific Basin and also as a part of the National Research Institute for Pollution and Resources research program of technological study on the exploitation of deep sea mineral resources. The GSJ research program (F.Y. 1974-F.Y. 1978) aims at providing basic information on the manganese nodule distribution and their origin on the deep sea floor of the Central Pacific Basin bounded by the Marshall Ridge to the west, the Christmas Ridge to the east, and the Mid-Pacific Mountains to the north. The first phase of investigation was carried out during the GH74-5 cruise in the eastern part of the area (6 degree -10 degree 30'W, 164 degree 30'-171 degree 30'N)(Mizuno and Chujo, eds., 1975), and the present second phase covered an areas of 5 degree square, just west of the GH74-5 area.