Based on to the method of so-called "Matched Filter" by SPECTOR and GRANT (1970), the authors designed a manual process for the bandpass filtering operation. The manual process was applied to the interpretation of airborne magnetic data of the Tsushima islands in order to discriminate composite anomalies consisting of different bands. Then, the authors carried out the two dimenstional analysis, and tried to re-examine the magnetic strcuture of the Tsushima islands. The result of the analysis is quite harmonic with geologic data of the Tsushima islands. Although the manual process is very arbitrary in terms of data-processing, it is considered to be sufficiently helpful for the practical application.

View full abstract

Petrological, mineralogical and chemical investigations of marine manganese nodules from the West Pacific revealed the intimate relation between the chemical and mineral compositions and the remarkable preferential partitioning of metal elements in the ferromanganese minerals. The microscopic observations of textures of manganese nodules tell the growth history of manganese nodules and the formation conditions of ferromanganese minerals.
Chemical compositions of nodules from Komahashi-Daini Seamount are very similar to those of the nodules from marginal banks and seamounts. Compositional variations in the bulk composition of nodules collected from the same dredge haul are considerably small, suggesting the similarity of the growth history of individual nodules, although the contents of metal elements vary remarkably from layer to layer in a single nodule.
Such variations and inter-element relationships are generally controlled by the mineral compositions and the chemical properties of costituent ferromanganese minerals, especially of 10 Å manganite. Most of Cu and Ni are concentrated in 10 Å manganite and Mn/Ni ratios of 10 Å manganite are fairly constant. High Fe contents in the nodules analysed in the present work are attributed to δ-MnO₂, which is composed of cryptocrystalline aggregates of Mn oxide and amorphous Fe hydroxide.
Microscopic observations and electron microprobe analyses of ferromanganese minerals revealed that the formation mechanisms of the two major constituent ferromanganese minerals are evidently different from each other. Optical and chemical homogeneity and characteristic textures, such as veinlets and clastic structures of 10 Å manganite suggest that it was rapidly formed in a short period as compared to δ-MnO₂, probably due to the supply of metal elements from interstitial waters of associated sediments. On the other hand, it is inferred that δ-MnO₂ was formed through slow accumulation of colloidal Mn- and Fe-hydroxide, incorporating many detrital materials. Therefore it is presumed from the present results that the growth of manganese nodules was not uniform during their formation but variable and intermittent in accordance with the environmental variation of the sea bottom.

View full abstract

The copper deposits of the Qaleh-Zari mine are situated at the central part of eastern Iran, and they are represented by the quartz-copper veins of fissure-filling type. The ores of the mine usually contain bismuth, gold and silver. Maximum contents of those metals are as follows: Bi 0.28%, Au 180 g/t and Ag 600 g/t.
In the present paper, the ores are investigated by means of ore microscopy and X-ray spectroscopic qualitative analyses using electron microprobe. The following results were obtained.
1) The ores consist mainly of specular hematite and chalcopyrite with some galena, sphalerite and electrum.
2) It is noticeable fact that aikinite usually occurs as minor minerals in the ores.
3) In addition to aikinite, the existence of the following Bi-bearing minerals was inferred. Galenobismuthite, cosalite, emplectite, wittichenite, bismuthinite and matildite.
4) It is supposed that bismuth in the ores presents as aikinite and other Bi-bearing minerals as mentioned above.
5) In these ores, gold presents as electrum, but almost all silver may be contained in the Bi-bearing minerals and a part of silver may present in galena as iso-marphous substitution of lead by silver.

View full abstract

Hydrogen peroxide formed in the silica-gold solution with excess silica gel at room temperature and pressure was confirmed by sensitive indicators (e.g., mercury grains and TiO⁺⁺ sulfuric acid solution). Gold (III) is reduced by hydrogen peroxide to gold (0) sols.

View full abstract

Small gold nuggets are grown experimentally in the system of Au-SiO₂-H₂O. Based on the experimental results, some consideration is presented on the growth of gold nugget.

View full abstract