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Volume 77, Issue 5
Displaying 1-3 of 3 articles from this issue
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KEITARO KUNUGIZA1982 Volume 77 Issue 5 Pages 157-170
Published: May 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSOlivine formed by the reaction antigorite+brucite=2 olivine+3 water from the Ryumon peridotite body, a regionally metamorphosed serpentinite of the Sanbagawa metamorphic belt, exhibits zoning with Fe, Mn and Ni-rich core and Mg-rich rim. From the core to the rim, XMn decreases at much higher rate than XNi does. The chemical relations between olivine and coexisting antigorite and brucite suggest that the zoning was formed by fractional crystallization of olivine from antigorite and brucite at the time of progressive metamorphism. The higher decreasing rate of XMn than XNi can be explained by the smaller values of KDanti-ol Mn-Mg and KD bru-ol Mn-Mg than KDanti-ol Ni-Mg and KDbru-ol Ni-Mg, respectively. This type of zoning may be characteristic of the zoning of olivine crystallized from serpentine. The zoned olivine suggests that local equilibrium was maintained even at low-grade in metamorphosed serpentinite.View full abstractDownload PDF (1002K) -
Part 2. petrography and modal compositionYoon Jong Lee1982 Volume 77 Issue 5 Pages 171-180
Published: May 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSGranitic rocks, from the southern Gyeongsang basin are of Cretaceous to early Tertiary age and have been divided into seven groups, A-G, as described in the previous paper (Lee, 1980). Recently, they were studied from the petrographic point of view.
These granitic rocks are described in terms of their rock forming minerals, mineral interrelationships, and average modal composition of each group. Seventy six new modal analyses have been measured and the petrographic characteristics of these rocks are discussed briefly. Some granodiorites of groups B, C and D are distinguished from other groups by containing hypersthene and augite. The Color Index of Outer zone granitic rocks (groups B-E) is clearly higher than that of Inner zone granitic rocks (group F). The Color Index of Tertiary granitic rocks (group G) is a little higher than that of Inner zone granitic rocks.
In modal composition, these granitic rocks contain relatively smaller amounts of K-feldspar and quartz, and more plagioclase and mafic minerals than those of the younger granites of the middle Ogcheon geosynclinal zone (Lee, 1971). In Qz-F-Mf triangular diagrams, acidic rocks in groups A2, B, D, E, F and G plot in apparently the same area as the younger granitic rocks in the Ogcheon geosynclinal zone but group C does not. Generally, the younger granitic rocks of the Ogcheon geosynclinal zone are abundant in quartz and contain smaller amounts of mafic minerals and feldspar. In (Qz+K-f)-P1-Wf triangular diagrams, acidic rocks of groups B, D, E, F and G plot in the same area as the younger granitic rocks of the Ogcheon geosynclinal zone but groups A and C do not. This means, the southern Gyeongsang basin granitic rocks are generally more basic and contain smaller amounts of quartz and K-feldspar.View full abstractDownload PDF (763K) -
Fluid inclusions in the Shinyama pyrometasomatic ore depositYôichi Muramatsu, Matsuo Nambu1982 Volume 77 Issue 5 Pages 181-190
Published: May 05, 1982
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSFilling temperatures and salinities of fluid inclusions in quartz and calcite collected from the Shinyama pyrometasomatic iron and copper ore deposit of the Kamaishi mine, Iwate prefecture, Japan, were measured by means of the heating- and freezing- stage microscope.
Fluid inclusions are generally several microns in size. Most inclusions are liquid inclusions, but some of them are gaseous inclusions. Polyphase inclusions are not recognized.
Most of filling temperatures of liquid inclusions in quartz and calcite which are considered to have been formed at the main stage of sulfide mineralization, range from 290 to 334°C. The filling temperature has a tendency to increase from the upper level to the lower, but no tendency is recognized laterally, that is, from the igneous rock side to the limestone side. Salinities of liquid inclusions in quartz range from 4.2 to 15.0 weight percent NaCl equivalent concentration. No relationship is recognized between the filling temperature and the salinity.
On the other hand, most of the filling temperatures and salinities of liquid inclusions in vein quartz range from 284 to 310°C, and from 5.5 to 7.9 weight percent, respectively.
From the result of the present inclusion study, it is inferred that the ore-forming fluids had relatively high salinities, and that the densities of fluids varied remarkably from the main stage of sulfide mineralization to the post-ore vein quartz.View full abstractDownload PDF (1870K)
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