ALBERT

Description: Conglomerates and sandstones in lithologic unit V at DSDP Site 445 comprise lithic clasts, detrital minerals, bioclasts, and authigenic minerals. The lithic clasts are dominantly plagioclase-phyric basalt and microdolerite, followed by plagioclase-clinopyroxene-phyric basalt, aphyric basalt, chert, and limestone. A small amount of hornblende schist occurs. Detrital minerals are dominantly plagioclase, augite, titaniferous augite, olivine, green to pale-brown hornblende, and dark-brown hornblende, with subordinate chromian spinel, epidote, ilmenite, and magnetite, and minor amounts of diopside, enstatite, actinolite, and aegirine-augite. Bioclasts are Nummulites boninensis, Asterocyclina sp. cf. A. penuria, and some other larger foraminifers. Correlation of cored and dredged samples indicates that the Daito Ridge is mainly composed of igneous, metamorphic, ultramafic, and sedimentary rocks. The igneous rocks are mafic (probably tholeiitic) and alkalic. The metamorphic rocks are hornblende schist, tremolite schist, and diopside-chlorite schist. The ultramafic rocks are alpinetype peridotites. Mineralogical data suggest that there were two metamorphic events in the Daito Ridge. The older one was intermediate- to high-pressure metamorphism. The younger one was contact metamorphism caused by a Paleocene volcanic event, possibly related to the beginning of spreading of the west Philippine Basin. The ultramafic rocks suffered from the same contact metamorphism. During the Eocene, exposed volcanic and metamorphic rocks on the uplifted Daito Ridge may have supplied pebble clasts to the surrounding coast and shallow sea bottom. The steep slope offshore may have caused frequent slumping and transportation of the pebble clasts and shallow-water benthic organisms into deeper water, forming the conglomerates and sandstones treated here.

Description: Fifty-seven samples of manganese nodules from the GH78-1 area were analysed in bulk rock for major and some minor metal elements to provide the data for the evaluation of the chemical features of the nodules. Air-dried sample of 0.1 g was decomposed with a mixture of 5 ml of hydrochloric acid and 5 ml of nitric acid in a covered 50 ml beaker on a boiling bath for about 30 minutes. After cooling, the solution was filtered into a 100 ml calibrated flask and diluted to the mark with water. The analyses for Mn, Fe, Co, Ni, Cu, Zn and Pb were done by atomic absorption spectrometry. The total water was analyzed gravimetrically.

Description: Seventeen chemical elements were determined for 49 samples taken from the GH78-1 cruise of the R/V Hakurei-Maru northern Central Pacific Basin. Thirty-one samples of them are from surface of grabbed sediments and others are ones resampled in core from the same grabbed sediment samples by plastic tube. Sediments containing sea water were stirred and dispersed in distilled water, were separated from water in the centrifuge, and the water was decanted. This cleansing process was repeated four or five times until no chloride ion was admitted. Then the sediments were dried, ground under the size of 200 mesh (74 micrometer), and contained in a desiccator as the sample for analysis. Bound water (H2O+) and carbon dioxide (CO2) were determined by heating the sample at 1000 °C. All oxide components were determined by wet chemistry. The other minor ekements were measured using atomic absorption spectrophotometry.

Description: The GH72-2 shipborne survey was carried out in the northwest Pacific during 31 days under the 'Basic investigations for exploration of deep sea mineral resources' program. The sediments encountered could be classified as follows: 1) Most of the brown clays occur on the abyssal plain of the basins at depth over 4500m. 2) Calcareous oozes are predominant at the top, slope and foot of seamounts and guyots. 3) Terrigeneous sediments are distributed near islands. The concentrated zone of ferromanganese nodules was located in the Magellan seamounts area. However, the metal contents in Mn, Cu, Ni and Co for these nodules are relatively poor, and these ferromanganese deposits occur at a depth over 5000m. It is interesting to note that the shape of the nodules is sometimes nearly spherical, and that the chemical composition of the nodules is characterized by the low ratio Mn/Fe and Co/Ni.