巻号一覧
75 巻, 1 号
選択された号の論文の4件中1～4を表示しています
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氏家 治1980 年 75 巻 1 号 p. 1-9
発行日: 1980/01/05
公開日: 2008/08/07
ジャーナル フリーMinerals occurring as groundmass, phenocrysts and constituents of cumulates are systematically different in chemical composition in an andesite flow at Katadomari, Kuro-shima Volcano, Kagoshima. The groundmass plagioclase contains more ∑ Fe than the phenocryst, which in turn, is richer in ∑ Fe than plagioclase of the cumulates. The groundmass pyroxenes (orthopyroxene and augite) have the highest Al and Ti contents, whereas pyroxenes of the three distinct generations are nearly identical in Na+K content. Oxidation accompanied by the lava eruption might have contributed a little to the increase in ∑ Fe content in plagioclase. However, most observations can be explained rationally in terms of different growth rate of the minerals (groundmass _??_ phenocrysts _??_ cumulates) combined with differences of cations in diffusion coefficient and crystal/liquid partition coefficient in the magma.
A cation with a small diffusion coefficient tends to increase in concentration in portions of a liquid immediately adjacent to growing crystals if its partition coefficient is small; and it tends to decrease if the partition coefficient is large. This must result in that the more rapidly grown minerals contain the more amounts of cations with smaller partition coefficients and smaller diffusion coefficients among the exchangeable cations. For certain elements, the phenocryst/groundmass partition coefficient must be far from the equilibrium partition coefficient in magmatic processes.抄録全体を表示PDF形式でダウンロード (491K) -
石坂 恭一, 巽 好幸1980 年 75 巻 1 号 p. 10-13
発行日: 1980/01/05
公開日: 2008/08/07
ジャーナル フリーEleven trace element contents, including seven REE, were preliminary determined for eight samples of the Ryozen volcanic rocks of Miocene age, northeastern part of Fukushima Prefecture. The results revealed that some of the Ryozen volcanic rocks (ol-basalt_??_auol-basalt) are characterized by high Cr contents ranging from 868 to 355 ppm. Thus, Ryozen volcanic rocks make a marked contrast to the Quaternary volcanic (tholeiitic) rocks of the Nasu zone with low Cr contents. The basalts have REE patterns characteristic to “Northeast Japan Type island arc tholeiite” defined by Masuda and Aoki (1978). Relationship between the Ryozen volcanic rocks and the Setouchi volcanics is briefly discussed.抄録全体を表示PDF形式でダウンロード (192K) -
椚座 圭太郎1980 年 75 巻 1 号 p. 14-24
発行日: 1980/01/05
公開日: 2008/08/07
ジャーナル フリー三波川変成帯の横臥褶曲中軸部には,いくつかのダンかんらん岩-蛇紋岩岩体が見られる。それらのうち四国中央部の東赤石,白髪山岩体,紀伊半島の竜門岩体のかんらん石の組織及び組成を調べた所,本変成帯のダンかんらん岩には成因的に2つのタイプがあることがわかった。東赤石岩体のかんらん岩は,2回の変成作用を受けかんらん石に若干の組成変化が認められるが,初生的なかんらん岩である。一方,白髪山,竜門岩体のそれは,蛇紋岩の変成作用によって生じたかんらん石からなる。そのようなかんらん石は,磁鉄鉱など蛇紋岩に特有な鉱物を含有物として持ち, Fe/Fe+Mg)比NiOと含有量の関係は,結晶分化作用から期待されるものとは異なり正の相関を示すことがある。かんらん石+アンチゴライトの鉱物共生及びそれらが広く産することは,このようなかんらん石が三波川変成作用によって形成されたことを示している。三波川変成帯のダンかんらん岩蛇紋岩岩体は様々な熱史を経ており,東赤石岩体に代表されるような岩体の一部が欠けたものではない。抄録全体を表示PDF形式でダウンロード (2154K) -
宮久 三千年, 桃井 斉, 皆川 鉄雄, 野戸 繁利, 松枝 大治1980 年 75 巻 1 号 p. 25-29
発行日: 1980/01/05
公開日: 2008/08/07
ジャーナル フリーThe reinvestigation of the titaniferous pyroxene from Shisaka-jima in the Ryoke metamorphic zone has revealed that the mineral was identified with titanian fassaite by its color and chemistry. The fassaite bearing dark crystalline aggregate of lenticular or nodular form in saccharodial limestone is composed of fassaite, spinel, magnetite, and ilmenite, as accessory phlogopite, amphibole, pyrrhotite, apatite, and titanite. It has equigranular granoblastic texture.
Two samples of the purplish brown fassaite were analyzed with EPMA. The result shows that the aluminium contents replacing silicon in tetrahedral site are 0.173 and 0.188 atomic percents on the basis of 0=6.000, and the mineral contains 9 mole percents of Ca-tschermackite. The green spinel, magnetite, and ilmenite were also analyzed with EPMA, and the conditions of formation have been disccused.
The occurrence suggests that the spinel-fassaite rock was derived from an aluminium rich sediment like laterite through the metamorphism of the amphibolite facies.抄録全体を表示PDF形式でダウンロード (1006K)
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