Chemical Composition of Japanese Granites, Part 2.VARIATION Trends and Average Composition of 1200 Analyses

重雄, 荒牧; 久米子, 平山; 保, 野沢

doi:10.5575/geosoc.78.39

Cited by 68 publications

(20 citation statements)

References 4 publications

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“…6. It is clear from the diagrams that the chemical variation of rocks of the present study, especially CaO, SiO2, total FeO and TiO2 is nearly equal to the trend of the average Japanese granitic rocks (Aramaki et al, 1972). However, Al2O3, FeO and Na2O contents are higher and MgO and Fe2O3 are slightly lower than those of average Japanese granitic rocks.…”

Section: Chemical Characteristics Of Analysed Hornblende-bearing Rockssupporting

confidence: 49%

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Chemical composition of hornblendes of some Ryoke granites, central Japan.

Kanisawa

1975

J. Japan. Assoc. Min. Petr. Econ. Geol.

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Section: Chemical Characteristics Of Analysed Hornblende-bearing Rockssupporting

confidence: 49%

“…Oxidation ratio (mol. 2Fe2O3/2Fe2O3+FeO, Chinner, 1960) of granites in the Ryoke belt is commonly smaller than those of the Kita kami Mountains, and the relation between Aramaki et al (1972). thus their mg values are always smaller than those of the Kitakami Mountains as shown in Fig.…”

Section: Chemical Characteristics Of Analysed Hornblende-bearing Rocksmentioning

confidence: 95%

Chemical composition of hornblendes of some Ryoke granites, central Japan.

Kanisawa

1975

J. Japan. Assoc. Min. Petr. Econ. Geol.

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“…The final products were fused at 1,200øC in platinum crucibles for 30 minutes to get homogeneous glasses. The chemical compositions of these glasses were calculated by extracting normative percentages of quartz, albite, orthoclase, anorthite, and corumdum from average Japanese granites with a differentiation index of 85 (Aramaki et al, 1972). The chemical compositions of these glasses were calculated by extracting normative percentages of quartz, albite, orthoclase, anorthite, and corumdum from average Japanese granites with a differentiation index of 85 (Aramaki et al, 1972).…”

Section: Starting Materialsmentioning

confidence: 99%

Aluminous granite as a source magma of hydrothermal ore deposits; an experimental study

Urabe¹

1985

Economic Geology

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Partition ratios of zinc and lead between synthetic granitic melts and aqueous phase were determined at 800øC and under PH•o = 3.5 _ 0.25 kb. Two starting glasses in the system SiO2-A12Oa-CaO-Na20 were prepared. Their bulk chemical compositions are similar, i.e., SiO2 content of 75.65 percent in glass 1 and of 74.68 percent in glass 2. Glass 1 is prepared to be slightly alkaline with 1.89 percent normative wollastonite and glass 2 is slightly aluminous with 2.42 percent normative corundum. The partition ratio of sodium between aqueous fluid and melt, K•a, can be expressed by the following equation over the whole range of chloride concentrations in the aqueous solution m v (mole/kg), regardless of the c• normative composition of the melt: K•a = 0.468 X m v ci. However, the partition ratio of zinc, K •' for the aluminous melt is more than two orders zll, of magnitude larger than that for the alkaline melt. K•. varies with the square of the chloride concentration in the aqueous phase and is satisfied by the following two equations: K r = 0.0833 X (alkaline melt 1). z,, = 9.40 X (m•::•) '• (aluminous melt 2) and K •' •m' • Zu I, CI] A similar contrast was also observed in the partition ratios of lead between aqueous phase and melts: K]•, = 2.26 X (m•:O '• (aluminous melt 2) and K•, = 0.0474 X (m•:•) • (alkaline melt 1). The log of the partition ratio shows an excellent inversely proportional relation with the pH (at 25øC) of the aqueous solution which was equilibrated with granitic melts and quenched. A slope of -2 is obtained for alkaline melt and is reasonably explained by the equation, PbO,,,,4t + 2H•+• .... + 2C1• .... = PbCI• ....... + H,20. The slope for the aluminous melt, -V•, may be explained only by complex reactions involving silicate ligands in the melt.The results indicate that only aluminous granite is capable of producing hydrothermal fluids which would contain a significant amount of ore metals. In other words, aluminous granite can be "ore-bearing" by postmagmatic processes. This is likely to happen when a granitie magma which originally was slightly alkaline changed its composition to slightly aluminous during diapiric uplift by assimilation of pelitic sediments. If this compositional evolution happened, then granitic magma would tend to store up base metals during the early stages of its evolution and release them very efficiently in the later stages to form a hydrothermal ore solution. Introduction IN 1972, Holland published a milestone paper titled "Granites, solutions, and base metal deposits." In the paper, he proved that hydrothermal solutions in equilibrium with granitic magmas can contain (a high concentration of) ore metals. He concluded (p. 292), "the classic hypothesis of the derivation of post-magmatic hydrothermal ore deposits from granitic magma is found to be in excellent health." However, the problem of so-called ore-bearing and barren granites is left unexplained. The present study investigates experimentally the problem in terms of a slight difference in the chemistry of granitic m...

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“…Because all the data are plotted on near-linear trends in Figure 6, the granitoids cropped out in five areas would form a continuous granitic pluton below ground. Comparing to the general trend of Japanese granitoids after Aramaki et al (1972), FeO contents of the pluton are slightly higher and Al 2 O 3 contents are little lower (Fig. 6).…”

Section: Mineral and Whole-rock Compositions Of Granitoidsmentioning

confidence: 99%

Characterization of Magnetically Zoned Pluton, Tsushima, Japan

2000

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: Systematic measurements of magnetic susceptibility were carried out at the outcrops of the Uchiyama granitic pluton, Tsushima Islands. The pluton consists of hornblende‐biotite granodiorite and biotite granite. It intrudes concordantly along an anticline axis of the Taishu Group in middle Miocene (16. 10. 5 Ma), and crops out in five areas. The results show that the low magnetic susceptibility facies (LM–facies, <100A‐10‐6 emu/g) always occurs in the peripheral part of the pluton, while the high magnetic susceptibility facies (HM–facies, > 250 A 10‐6 emu/g) occupies the core through the medium magnetic susceptibility zone (MM–facies). It is pointed out that the pluton forms a magnetic zoning within a single plutonic body. Chemical compositions of the granitoids show no conspicuous differences in major elements among the LM–, MM–, and HM–facies. Biotites from the LM–, MM–, and HM‐facies also indicate uniform compositions with Fe/(Fe+Mg)=0. 6. The pluton is principally surrounded by black mudstones of the Lower Formation of the Taishu Group, which is deltaic to shallow sea sediments of the Eocene to early Miocene age, and the carbon contents in them were analyzed. The analyses show that carbon was mostly decomposed and lost in the hornfels zone, while mudstones in the non‐hornfels zone usually contain 0. 5 to 0. 7 % C. From these facts, it is concluded that the magnetically zoned pluton at Tsushima was formed by an external volatile buffer system such as CH4–CO2 during the solidifying magma process.

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Chemical Composition of Japanese Granites, Part 2.VARIATION Trends and Average Composition of 1200 Analyses

Cited by 68 publications

References 4 publications

Chemical composition of hornblendes of some Ryoke granites, central Japan.

Chemical composition of hornblendes of some Ryoke granites, central Japan.

Aluminous granite as a source magma of hydrothermal ore deposits; an experimental study

Characterization of Magnetically Zoned Pluton, Tsushima, Japan

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