巻号一覧
82 巻, 9 号
選択された号の論文の3件中1～3を表示しています
- |<
- <
- 1
- >
- >|
-
横山 一己1987 年 82 巻 9 号 p. 319-335
発行日: 1987/09/05
公開日: 2008/08/07
ジャーナル フリー黒瀬川帯の超苦鉄質岩中には異なった時期を示す2種類の形態と化学組成をもつかんらん石と単斜輝石がある。超苦鉄質岩の源岩は主にハルツバージャイトかレルゾライトで角閃岩相程度の条件で平衡にあった。その後これらの岩石は約400°Cで変成された。紀伊半島東部から関東山地にかけて秩父帯中にある超苦鉄質岩は黒瀬川帯のものと同じ形態と化学組成を示し黒瀬川帯の延長と考えられる。超苦鉄質岩と黒瀬川帯を構成する他の岩石は,元来は,現在の位置より西方にあり,白亜紀前期の左横ずれ断層により破砕され東方に運ばれた。その際滑りやすい蛇紋岩化した超苦鉄質岩は関東山地まで達したが,滑りにくい花崗岩等は西方に残された。抄録全体を表示PDF形式でダウンロード (2860K) -
他の環伊豆地塊蛇紋岩類との比較荒井 章司, 石田 高1987 年 82 巻 9 号 p. 336-344
発行日: 1987/09/05
公開日: 2008/08/07
ジャーナル フリーSerpentinized peridotites with or without plagioclase are distributed in the Setogawa, Kobotoke, Hayama and Mineoka Groups, the eastern extension of the Shimanto belt, encircling the northern end of the Izu Massif. They can be collectively named, therefore, “the Circum-Izu Massif serpentinites”.
Serpentinites in the Kobotoke Group of the Sasago area are derived from harzburgite and lherzolite with or without plagioclase. Olivine, orthopyroxene and plagioclase were almost completely altered. Chemical compositions of chromian diopside, chromian spinel and Ca-rich amphibole are equivalent to those in peridotites from the Mineoka belt, and are slightly but distinctly different from those in peridotites from the Setogawa belt and the Hayama belt. Ca/(Ca+Mg+Fe*) (Fe*, total iron) atomic ratio of chromian diopside in the Kobotoke-Mineoka peridotites is lower by 0.01 on average than that in the Setogawa-Hayama peridotites. Ca-amphiboles of the former peridotites are more enriched in Al and Na than those of the latter peridotites. Peridotites of the Setogawa and the Hayama belts are also characterized by a higher abundance of Ca-rich amphiboles than the Kobotoke-Mineoka ones. These petrographical differences are due to the lower equilibrium temperature and higher H2O availability of the upper mantle from which peridotites in the Setogawa and the Hayama belts were derived.抄録全体を表示PDF形式でダウンロード (1411K) -
今田 正, 大場 与志男, 土肥 浩巳, 玉井 ます美1987 年 82 巻 9 号 p. 345-351
発行日: 1987/09/05
公開日: 2008/08/07
ジャーナル フリーMt. Ryuzan (elevation 1, 362m) represents the oldest edifice in the Zao volcanic group of NE Japan. It consists of thick piles of lavas and pyroclastic rocks, and has been subjected to volcanic eruption or land slide activity which produced mud-flow (debris flow) deposits.
Both K-Ar ages and paleomagnetic data of these lavas indicate that the volcano formed at about 1 million years ago.
The analyzed rocks from Mt. Ryuzan fall within the SiO2 range of 47.4-60.3% (water free basis) and basalt is the predominant rock type. Alkali contents, especially K2O, are very low in those basalts, compared with rocks forming the main (Central) Zao volcano. Chemically, rocks of Mt. Ryuzan belong to the tholeiitic series (TH) of Miyashiro (1974).
It is noteworthy that low-K tholeiitic basalts occur at the early stage of the formation of Zao volcano.抄録全体を表示PDF形式でダウンロード (553K)
- |<
- <
- 1
- >
- >|