All issues
Successor
Volume 38, Issue 207
Displaying 1-8 of 8 articles from this issue
- |<
- <
- 1
- >
- >|
-
An example of the Nupun-Tomuraushi area, Hidaka Belt, central HokkaidoYasushi WATANABE, Sumio MIYASHITA1988 Volume 38 Issue 207 Pages 1-13
Published: March 31, 1988
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe Hidaka Supergroup exposed in the Nupun-Tomuraushi area, central part of the Hidaka Belt, shows repeating cycles of black shale, meta-basalt, red shale, green shale and gray shale in ascending order. Fine-grained sandstone and siliceous gray shale are intercalated with the black shale which is broadly distributed in the studied area. The black shale contains higher amount of clastic grains of quartz, feldspar and opaque minerals than the other shales do. The meta-basalt consists of pillow lava, massive lava and hyaloclastite, and is regarded to have extruded on a deep seafloor of black mud.
The green and red shales are richer in Mn, Fe, Mg, Ba, Co, Zn, Cu and Pb, and poorer in Ti, Al, V and Cr than the black shale. The gray shale has an intermediate average composition between the black shale and the red and green shales. Assuming that the black shale represents terrigenous material, it is inferred that heavy metal elements such as Mn, Fe and Co supplied by hydrothermal activity were added to the material to have produced the green and red shales. On the basis of the geology and chemistry of the rocks, we conclude that the submarine volcanism generated the hydrothermal system and played an important role in the formation of red and green shales, and of associated ore deposits such as bedded hematite and bedded manganese.View full abstractDownload PDF (857K) -
Guillermo ALFARO, José FRUTOS1988 Volume 38 Issue 207 Pages 15-25
Published: March 31, 1988
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe geochemistry of the massive sulfides and their country rocks from the Coastal Range of southern Chile (between latitudes 39° and 42°S) is discussed.
The FeS content in sphalerite which is in equilibrium with pyrite and pyrrhotite allows to get 2.5 kbar as the equilibrium pressure for the last metamorphic event. Preliminary sulfur isotope analysis of pyrite gives the average value of δ34S=+2.5 per mil.
Based on the geochemical study on the sulfides (Cu, Zn, Mn, Co, Ag, Cd, etc.) and major and rare earth elements of their country rocks, it is concluded that the massive sulfide deposits are similar to either.Besshi-type ore deposits in Japan or those in the Norwegian Caledonian Mountains(e.g. Løkken).View full abstractDownload PDF (675K) -
Masahiro SAWADA1988 Volume 38 Issue 207 Pages 27-37
Published: March 31, 1988
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe abundance, mineralogy, internal texture and chemical composition of manganese micronodules in deep sea sediments from six areas in the Central Pacific Basin were studied by means of ore microscopy, X-ray diffraction and EPMA.
(1) Abundance of micronodules ranging from 50 to 500 mesh sieve tends to decrease with increasing grain size. Micronodules were not found in the size fraction greater than 50 mesh sieve.
(2) Constituent ferromanganese minerals of micronodules may be 10 Å-manganate and δ-MnO2.
(3) Based on internal texture of micronodules, they are classified into two types; Type-I with dendritic or cuspate textures and Type-II with stratified or columnar textures.
(4) Type-I micronodules are characterized by high contents of Mn, Ni and Cu, while Type-II are characteriz-ed by high contents of Fe and Si.
(5) Type-I and Type-II micronodules are resemble to r-type and s-type of manganese nodules with respect to internal texture, chemical composition, constituent minerals, and probably depositional environments.View full abstractDownload PDF (3541K) -
H.A. HUSSEIN, F.S. BAKHIT1988 Volume 38 Issue 207 Pages 39-48
Published: March 31, 1988
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe present study deals with the uranium mineralization found in bostonite of north Wadi Kariem and the surrounding areas, Central Eastern Desert. The structure and geology of the host rock and the relationship between the uranium mineralization and the country rock are also described.
The radioactive minerals in north Wadi Kariem and the surrounding areas occur in cracks and fissures of alkaline volcanics mostly of Carboniferous age. The mineralized structural features are caused by a deformation phase that created openings for solutions. Primary uranium minerals are coffinite and sooty pitchblende. These are found with sulfide minerals like pyrite, chalcopyrite, sphalerite, molybdenite, and galena. Hematite, quartz, calcite, psilomelane, and chlorite are the most common gangue minerals in the studied area.
It is suggested that the precipitation of uranium was more favoured by the existance of structural traps rather than the chemical composition of the host rock. The deposition of uranium had been repeated during the latest stage of tectonic activity probably in the Carboniferous-Permian period.View full abstractDownload PDF (664K) -
Koichi TAKEUCHI1988 Volume 38 Issue 207 Pages 49-56
Published: March 31, 1988
Released on J-STAGE: December 14, 2009
JOURNAL FREE ACCESSTellurium-bearing ore has been produced from the Arakawa No.5 vein of the Kushikino mine. The mine consists of many epithermal gold-silver vein type deposits which are related to the late Miocene to early Pliocene volcanism. It is rare in this mining district to have Te-mineral widely distributed in almost all part of the vein. Although the vein shows limited extent, it has some different characteristics from other veins in this mine.
The main features of the Arakawa No.5 vein are summarized as follows,
(1) The vein dips steeply (70°-80°S) in contrast with the general dip of 45°-60°S of the leading veins in this mine.
(2) Maximum Ag/Au ratio of the tellurium-bearing ore is about 100. The value is unusually higher than the average ratio of 8 for rest of this mine.
(3) Simple and symmetrical structure of the vein implies monoascendant mineralization.
(4) Ore minerals constituting the "ginguro" (silver-bearing sulfide-sulfosalts band) ore are galena, hessite, sphalerite, chalcopyrite, pyrite and electrum. Other Ag-minerals such as naumannite and polybasite which appear com-monly in this mine are not found.
(5) Sphalerite in the "ginguro" ore contains about 50 mol%CdS at its maximum.
(6) The homogenization temperatures of fluid inclusions are relatively high, ranging from 260°to 310°C.View full abstractDownload PDF (2999K) -
Hiroyuki MAEDA1988 Volume 38 Issue 207 Pages 57-62
Published: March 31, 1988
Released on J-STAGE: December 14, 2009
JOURNAL FREE ACCESSIn the Inakuraishi-Ohe mining district, there are successive mineralizations from the kuroko-type to polymetallic and iron sulfide vein-type deposits. These sequence can be estimated based on the stratigraphic horizons of their host rocks, the extent of the hydrothermal alteration haloes, and the whole-rock K-Ar dating of the alteration zone. The mineralization ages of the Inakuraishi and Ohe polymetallic vein-type deposits were determined by the K-Ar dating on the sericitized host rocks juxtaposed with these veins. The whole-rock K-Ar ages of the sericitized andesitic rocks of the early Miocene Lower Furubira Formation from the Inakuraishi mine were 4.9±0.2 to 2.7±0.2Ma. On the other hand, the sericitized quartz diorite of probably late Miocene age from the Ohe mine gave the K-Ar age of 3.4±0.3Ma. This quartz diorite is considered to be related to the mineralizations of the Inakuraishi and Ohe deposits. It is suggested that the mineralizations of the Inakuraishi and Ohe deposits had taken place in late Miocene to Pliocene time after the intrusion of quartz diorite. Especially the main mineralizations of both deposits appear to have occurred in Pliocene time.View full abstractDownload PDF (449K) -
1988 Volume 38 Issue 207 Pages 63-84
Published: March 31, 1988
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (1876K) -
1988 Volume 38 Issue 207 Pages 84-89
Published: March 31, 1988
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (507K)
- |<
- <
- 1
- >
- >|