All issues
Successor
Volume 71, Issue 12
Displaying 1-4 of 4 articles from this issue
- |<
- <
- 1
- >
- >|
-
YUZO KATO, SATOSHI HAMA1976 Volume 71 Issue 12 Pages 363-373
Published: December 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSSakainokami plutonic body is one of the many Cretaceous intrusive bodies in the northern Kitakami mountains. The present study revealed that the plutonic body is composed of three rock types, namely: type A, type B and type C, which have been emplaced successively in that order. Types A and C are further subdivided into three and two subtypes, respectively, as follows:
Type A
Subtype A-1: Biotite-bearing olivine augite hornblende gabbro
Subtype A-2: Biotite, hypersthene-bearing augite hornblende gabbro
Subtype A-3: Augite-bearing biotite hornblende gabbro
Type B: Augite-bearing biotite hornblende gabbro—diorite
Type C
Subtype C-1: Biotite hornblende monzodiorite—granodiorite
Subtype C-2: Biotite hornblende granodiorite.
Within subtypes A-2 and A-3, two groups differing in the crystallization sequence of plagioclase and hornblende are identified. In one group, hornblende has crystallized earlier than plagioclase and there is an accumulation of more hornblende than normally. In the other group, plagioclase has crystallized earlier than hornblende and there is an accumulation of opaque minerals in certain portions. The former group is designated as group h and the latter is designated as group p.
Without considering the presence of these groups the plots of type A rocks are segregated in accordance with these groupings three different trends emerge. These trends are designated as trend I, trend II and trend III. Trend I represents the case where there is accumulation of hornblende; trend II, where there is accumulation of opaque mineral; and trend III, representing the calc-alkaline trend.View full abstractDownload PDF (445K) -
SUSUMU NISHIMURA, TAKESHI IKEDA, SHIGEHARU MORISHITA1976 Volume 71 Issue 12 Pages 374-378
Published: December 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSSeven rare-earth elements (La, Ce, Sm, Eu, Tb, Yb and Lu), Ba, Co, Cr, Hf, Sc and Th have been determined by nondestractive neutron activation analysis and U by fissiontrack method on the basaltic rocks of meso-volcanic complex in Ikuno group, Hyogo Prefecture, Japan. The trace element abundances are discussed in terms of the petrological problems, especially, the origin of magma. The volcanic complex of Ikuno group consists of rhyolite, andesite, alteration of black shale and tuff, and dellenite. The basaltic rocks are found in the Ikuno group as sheet and dykes which intruded into Ikuno group. The basaltic sheet is alkalic rock and these dykes are high alumina basalt series.View full abstractDownload PDF (170K) -
TETSUYA SHOJI1976 Volume 71 Issue 12 Pages 379-388
Published: December 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSBased on the previously reported equilibrium data concerning the following reactions:
(1) CaCO3+SiO2=CaSiO3+CO2
(2) Ca6Si6O17(OH)2=6CaSiO3+H2O,
the equilibrium boundary for the reaction,
(3) 6CaCO3+6SiO2+H2O=Ca6Si6O17(OH)2+6CO2
has been determined at fluid pressures of 1000 bars and 2000 bars by the thermodynamic calculation.
Although Buckner et al. (1960) and Gustafson (1974) gave two different results for the temperature at which Reaction (2) takes place, the stability field of the assemblage calcitequartz in H2O-CO2 mixtures is almost independent of both of the results. The assemblage calcite-quartz is stable where the content of carbon dioxide in H2O-CO2 fluids is richer than 0.6 mole % at 400°C, and 0.03 mole % at 300°C, but changes to wollastonite or xonotlite where carbon dioxide is poorer. These values seem to indicate the lower limit of carbon dioxide content in H2O-CO2 mixtures, in which ore-bearing skarns are formed, because it is very rare that ore minerals, such as chalcopyrite and sphalerite, are accompanied with wollastonite and/or xonotlite.View full abstractDownload PDF (595K) -
OSAMU UJIKE, HITOSHI ONUKI1976 Volume 71 Issue 12 Pages 389-399
Published: December 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSStudies on volcanic hornblendes have been carried out with special reference to the relationship in chemistry to their host rocks from Kagawa Prefecture, Japan. The quantity of Si and AlIV in the hornblende seems to depend to a considerable extent on that of free silica in a magma represented by the rock. The groundmass contains about 4 times as much K2O as the hornblende does, and the coefficient of partition of K and Na between the groundmass and the hornblende is 2.2 on an average. It is deduced from considerations of phase relations in the rocks, two-pyroxene geothermometer and the chemistry of hornblendes that the hornblendes ware crystallized at temperatures above 900°C from magmas probably undersaturated with water. A precipitation of some iron-rich phases together with the hornblende must be required to produce a typical cale-alkaline trend. Hornblende-controlled fractionation at a phenocrystic stage of magmatic crystallization must change the residual melt into a peraluminous composition.View full abstractDownload PDF (463K)
- |<
- <
- 1
- >
- >|