Bulletin of the Geological Survey of Japan Top Page

Bulletin of the Geological Survey of Japan Vol.59 No.3/4 (2008)

Cover photograph | Table of Contents | Abstract

Cover photograph

Giant Chimney of the Hitachi mine.

   Hitachi mine, located at the southernmost edge of the famed Abukuma metamorphic terrain, was a large copper producer from the Besshi-type chalcopyrite-pyrite deposits. Sulfurous acid gases exhausted during the smelting caused air-pollution to the local inhabitants, and the famed giant chimney (156 m high) was constructed in1914 on a mountainous hill with 300 m elevation above sea level. It is now broken into 1/3 of the height by storm. Electric section of the mine became the gigantic Hitachi Co. with many other Hitachi-group subsidiaries.

(Shunso Ishihara)

Table of Contents

Title	Author	PDF
Article
>Sedimentary facies and radiocarbon dates of two sediment cores from the eastern margin of the Tokyo Lowland: MZ (Mizumoto Park, Katsushika-ku) and SZ (Shinozaki Park, Edogawa-ku) cores.	Susumu Tanabe, Yoshiro Ishihara, Rei Nakashima, Katsumi Kimura and Toshio Nakayama (135-149)	59_03_01.pdf [3.9 MB]
Chemical compositions of the late Cretaceous granitoids across the central part of the Abukuma Highland, Japan - Revisited.	Shunso Ishihara and Bruce W. Chappell (151-170)	59_03_02.pdf [1.3 MB]
Report
Variance of magnetic properties of the marginal part of Miocene volcanic conduits in northwest of Ehime Prefecture, Shikoku District, Japan.	Rie Morijiri, Mitsuru Nakagawa, and Masahiko Makino (171-189)	59_03_03.pdf [2.6 MB]
Fission-track age of the Murasho granite porphyry in Nishimera Village, Miyazaki, Southwest Japan.	Toshimitsu Iwaya and Kazuki Naito (191-196)	59_03_04.pdf [2 MB]
Kogajajima Volcano in Tokara Islands, Kagoshima Prefecture, Japan.	Shun Nakano and Nobuo Geshi (197-201)	59_03_05.pdf [2.4 MB]

 

Abstract

Sedimentary facies and radiocarbon dates of two sediment cores from the eastern margin of the Tokyo Lowland: MZ (Mizumoto Park, Katsushika-ku) and SZ (Shinozaki Park, Edogawa-ku) cores.

Susumu Tanabe, Yoshiro Ishihara, Rei Nakashima, Katsumi Kimura and Toshio Nakayama

   We examined time and spatial distributions of sedimentary facies surrounding the spit sediments in the bay-mouth portion of the Paleo-Okutokyo Bay by using sedimentary facies and radiocarbon dates obtained from two sediment cores (MZ and SZ cores) from the eastern margin of the Tokyo Lowland. Latest Pleistocene to Holocene incised-valley fills (the Chuseki-so) which unconformably overlie Middle to Late Pleistocene deposits (Shimosa Group) consist of braided river, meandering river, estuary, spit and delta sediments in MZ core in ascending order. The Chuseki-so consists of delta sediments in SZ core. MZ and SZ cores yields radiocarbon dates ranging from 13150 to 3160 cal BP and from 3930 to 730 cal BP, respectively. Sand shoal sediments constituting part of the spit sediments in MZ core forms a sand body which elongates northeastward from the spit sediments. And this sand body seems to have deposited in a bay-mouth channel which existed behind the spit between 4500 and 3500 cal BP.

Chemical compositions of the late Cretaceous granitoids across the central part of the Abukuma Highland, Japan - Revisited.

Shunso Ishihara and Bruce W. Chappell

    Late Cretaceous granitoids of central area in the Abukuma terrain were analyzed by polarized XRF method and compared with the Ryoke granitoids of Chubu district. The Abukuma granitoids are mostly composed of hornblende and/or biotite granodiorite to granite and less in amount of muscovite-biotite granites, and are higher in Na₂O and Al₂O₃, lower in K₂O, Rb, Pb and Ba than the Ryoke granitoids on the Harker diagrams. The Abukuma granitoids appear to be generated within the continental crust of inmatured island-arcs, having mafic magmas and heat from the upper mantle.
   The Abukuma granitoids are generally reduced type accepting sedimentary carbon from the continental crust, similarly to the Ryoke granitoids, but an intermediate series occurs in the eastern-end zone. Zone II granitoids, which are rich in CaO and poor in K₂O and lithophile components such as Rb, Pb, Y, Ce and La, have weak signature of high Sr/Y ratio for adakite. An adakitic magma may have brought up from the subducting slab, but extremely modified within the continental crust.

Variance of magnetic properties of the marginal part of Miocene volcanic conduits in northwest of Ehime Prefecture, Shikoku District, Japan.

Rie Morijiri, Mitsuru Nakagawa, and Masahiko Makino

   High susceptibility bands of about a few meters were shown at contact zones between ilmeniteseries granite and andesite of Miocene volcanic conduits in northern part of Ehime Prefecture, southwest Japan. A profile of susceptibilities across the Senohana volcanic conduit in Nakajima, Matsuyama City clearly shows high susceptibility bands. Thirty-nine andesite and contacted granite samples were obtained from 11 sites of the Miocene volcanic conduits. Susceptibility, natural remnant magnetization and density were measured of 42 samples. Thermomagnetic and hysteresis measurements were carried out 15 samples of them. Natural remanent magnetization and susceptibility of marginal parts of volcanic conduits tend to be stronger than those of the inner part. Hysteresis parameters suggest that magnetites of marginal parts are smaller than those of inner parts. The granite in contact with andesites exceptionally had high susceptibility and natural remnant magnetization, although ilmenite-series granite had quite low susceptibility and natural remanent magnetization. A lot of fine magnetites were recognized in the granite in contact with andesite by microscope observation. They seem to be formed from biotites in the granite by contact metamorphism with intrusion of volcanic conduits.

Fission-track age of the Murasho granite porphyry in Nishimera Village, Miyazaki, Southwest Japan.

Toshimitsu Iwaya and Kazuki Naito

   Fission track dating was performed for the Murasho granite porphyry in the Outer Zone of Kyushu, Southwest Japan. A zircon fission track age was determined to be 14.3 ± 0.5Ma(1σ). This result is similar to those reported for the zircon fission track ages of the felsic rocks of Outer Zone of Kyushu.

Kogajajima Volcano in Tokara Islands, Kagoshima Prefecture, Japan.

Shun Nakano and Nobuo Geshi

   Kogajajima, composed of hornblende andesite and dacite lavas, is a small volcanic island 0.5 by 1 km in diameter and is at the summit of a seamount 5 by 10 km in diameter and more than 800 m high. The eastern half of the island is hydrothermally altered. Several active fumalores and hot springs were recognized in our survey in 2005 and 2006. In addition to the young K-Ar age suggesting late Pleistocene in age, the fumarolic activities implies that the volcano is still active in recent years.