巻号一覧
81 巻, 9 号
選択された号の論文の5件中1～5を表示しています
- |<
- <
- 1
- >
- >|
-
WATCHARAPORN KEANKEO, 北村 強, 谷田 勝俊1986 年 81 巻 9 号 p. 341-347
発行日: 1986/09/05
公開日: 2008/08/07
ジャーナル フリー肘葛鉱山の層状マンガン鉱床は宮古花崗岩体の迸入によって高度の接触変成を蒙り,多種多様の鉱物を産出する。主要鉱石鉱物はバラ輝石とテフロかんらん石であって,バラ輝石には鉄に乏しい種と,かなりの鉄を含む種とが知られているが,テフロかんらん石は端成分Mn2SiO4に近い組成のものしか知られていなかった。今回,本鉱山より採取した試料の再検討を行なったところ,かなり鉄の含有量の高いクネベルかんらん石も産することが明らかとなった。なお, Fe2SiO4-Mn2SiO4系かんらん石の分類はHenriques (1956)の方法に従がっている。
テフロかんらん石はMn2SiO4 97.30, Mg2SiO4 1.47, Ca2SiO4 1.23mol.%の組成を有し,端成分Mn2SiO4に極めて近く,これに伴なうピンク色のバラ輝石も鉄に乏しい。これに対し,クネベルかんらん石はFe2SiO4 30.47, Mn2SiO4 66.24, Mg2SiO4 3.29mol.%とかなり鉄に富み,共生する赤褐色バラ輝石および桃色バスタム石は共に高い鉄の含有量を示す。抄録全体を表示PDF形式でダウンロード (360K) -
砂川 一郎, 杉渕 史子1986 年 81 巻 9 号 p. 348-358
発行日: 1986/09/05
公開日: 2008/08/07
ジャーナル フリー仙台市郷六産両錐石英の{10_??_1}面上には, 622の対称に従う丸味をもった三角形のエッチピットが観察される。本試料を実験室的にエッチすると32の対称に支配されたエッチピットができる。両者の対応関係,比較から,本両錐石英は渦巻成長機講により成長し,成長中に結晶の合体,微弱なソ性変形を経験し,また転移温度以上で非平衡条件に遭遇して溶解作用をうけ,その直後に急冷により転移し,転移に伴なう体積変化で転位が増殖し,かつドフィーネ双晶が形成されたと解析された。断熱膨張により急冷された凝灰岩中の石英は,上記全履歴をよく保存しているが,より除冷された溶岩中の斑晶石英では,溶解がはるかに進行している。抄録全体を表示PDF形式でダウンロード (5613K) -
林 歳彦1986 年 81 巻 9 号 p. 359-369
発行日: 1986/09/05
公開日: 2008/08/07
ジャーナル フリーGeological and petrographical studies were carried out on the rocks from Early Cretaceous granitoids (112-122Ma) in the Tanohata area, northeastern Japan. It was revealed that the granitic complex called the Tanohata pluton consists of six granitic intrusives, which are different in lithology and intruded at the different stages. The largest body is a concentric texturally and compositionally zoned pluton. This body is definede as the Tanohata aoned pluton. Other five smaller bodies are distrbuted aroud the zoned pluton.
The granitoids that make up the Tanohata zoned pluton are progressively more felsic inward; from biotite hornblede quartz diorite_??_tonalite (A-2 type) at the margin to biotite leucogranodiorite (A-7 type) in the center through biotite hornblende tonalite_??_granodiorite (A-3, 4 type), hornblende biotite granodiorite (A-5 type) and biotite granodiorite (A-6 type). The mineral assemblages of these rock types are as follows: pl+opx+cpx+ho+bio+qz+K-f (A-2 type), pl+cpx+ho+bio+qz+K-f (A-3 type), pl+ho+bio+qz+K-f (A-4, 5 type), pl±ho+bio+qz+K-f (A-6 type), and pl+bio+qz+K-f (A-7 type, pl+opx+cpx+ho+bio) is foud with the A-2 and A-3 types. The zoned pluton is generally fine-grained and well-foliated at the margin and becomes progressively coarse-grained and poorly-foliated towards center. Mafic minerals decrease and quartz and K-feldspar slightly increase from the margin to the center (from 27-21 to 7-4 in the color index). The anorthite content of plagioclase core decrease from 60-52 at the margin to 35-28 in the center.
Continuous geological and petrographical changes of these rocks (at least the A-2_??_A-7 types) suggest that this zoned pluton formed by differentiation of a single magma, and that the crystallization sequences of principal minerals is plagioclase, orthopyroxene, clinopyroxene, hornblende, biotite, quartz, and K-feldspar.抄録全体を表示PDF形式でダウンロード (998K) -
微量元素組成および岩石成因論林信 太郎1986 年 81 巻 9 号 p. 370-383
発行日: 1986/09/05
公開日: 2008/08/07
ジャーナル フリーTwenty-seven representative volcanic rocks from Chokai volcano, Northeast Japan, were analysed for Co, Sc, Sr, Ce, Y, Zr, Nb, Rb, Cs, and Ba to discuss the origin of the rocks in combination with the previously reported geochemical and mineralogical data. The major and trace element variations are indicative of a considerable difference in the origin between olivinefree rock (OLF) suite and olivine-bearing rock (OLB) suite.
The OLF sequence was formed by crystallization differentiation from the associated olivinefree mafic andesite. The most evolved andesite of the OLF suite can be produced after approximately 31% fractionation of the phenocryst minerals from the parental mafic andesite magma. Their mineralogical features are consistent with this model.
The OLB suite has two sets of mineral group as apparent phenocrysts but neither can be in equilibrium with another. They make straight variation trend in MgO-K2O diagram; crystallization differentiation cannot account for. An internal magma mixing model was proposed to solve all the conflicts. Basaltic melts mixed with felsic andesitic magma and a series of the OLB suite was produced. Before the mixing, the basaltic melts contained phenocrysts of Mg-rich olivine, augite, spinel and Ca-rich plagioclase, while less Mg-rich augite, hypersthene, and Na-rich plagioclase were crystallizing with magnetite and ilmenite in the felsic ones. Consequently, the mixtures included the disequilibrated sets of the mineral group. All the elemental variation trends should make simple lines between the end members. Mineralogical and geochemical consanguinitie indicate that the felsic end members were the differentiation products of the OLF suite. The basaltic end component cannot be the parental magma of OLF suite, because the Zr/Rb ratio of the latter is larger than that of the former.抄録全体を表示PDF形式でダウンロード (973K) -
一ノ瀬 丁己, 周藤 賢治, 八島 隆一1986 年 81 巻 9 号 p. 384-391
発行日: 1986/09/05
公開日: 2008/08/07
ジャーナル フリーUltramafic and mafic inclusions, including intermediate ones, up to 3 cm in size found in high magnesian tholeiitic basalts are divided into the following three groups based on the mineral assembalge and texture: 1) poikilitic peridotite and pyroxenite, 2) pyroxenite including webster-ite, clinopyroxenite and orthopyroxenite, and 3) gabbro and diorite. The 1st group consists of euhedral olivine chadacrysts with chrome spinel inclusions, and clinopyroxene and/or orthopyrox-ene oikocrysts. The 2nd one shows equigranular in texture, but the last one does poikilitic and equigranular. Most of them contain interstitial patches composed of plagioclase, magnetite, clinopyroxene and glass. Petrographic features suggest that these inclusions are cumulates derived from the host magma.抄録全体を表示PDF形式でダウンロード (2089K)
- |<
- <
- 1
- >
- >|