Mineralogical Journal
Online ISSN : 1881-4174
Print ISSN : 0544-2540
ISSN-L : 0544-2540
14 巻, 3 号
選択された号の論文の3件中1~3を表示しています
 
  • Himadri BANERJEE, Hiroyuki MIURA, Yu HARIYA
    1988 年 14 巻 3 号 p. 83-91
    発行日: 1988年
    公開日: 2007/03/31
    ジャーナル フリー
    Experimental investigation in the Mn-rich portion of the system MnO–MgO–FeO–SiO2–CO2 has been carried out to study the effect of XFe on the phase relation in the ternary system MnSiO3–MgSiO3–FeSiO3. The experiments were conducted with oxygen and/or graphite buffers in the system C–O–H at pressure-temperature conditions corresponding to normal crustal metamorphism to understand the evolution of mineral assemblages from Ca-poor Mn–Mg–Fe carbonates admixed with silica.
    Stability field of pyroxmangite solid solution containing Fe can appear at lower temperature than the MnSiO3 end member. The appearance of single phase pyroxmangitess is insensitive to variations in XMn of the bulk in the range ∼0.8 and above. With increasing XMg and XFe in the bulk composition, carbonatess+quartz react to produce pyroxmangitess+Mn-clinopyroxeness and Mn-clinopyroxeness successively. All the reaction boundaries are insensitive to pressure, at least up to 8 kb, and have gentle slope in temperature. These reactions are also independent of the XCO2 of the fluid phase in the region XCO2=0.21−0.53 above moderate temperatures. The slope of the lnXCO2−10−3/T K relationship of these reactions is similar to that of the pure pyroxmangite forming reaction. Mn-clinopyroxeness can be stabilized at a low temperature than pyroxmangitess from favourable bulk composition [X(Mg+Fe)=0.4]. With increasing Fe content, stability field of Mn-clinopyroxeness extends toward higher XMn in region as compared to that in Fe-free system.
  • Masaaki SHIMIZU, Akira KATO, Satoshi MATSUBARA
    1988 年 14 巻 3 号 p. 92-100
    発行日: 1988年
    公開日: 2007/03/31
    ジャーナル フリー
    Hemusite from the Ohsawa No. 4 vein, the Kawazu mine, Shizuoka Prefecture, Japan, has a face-centered cubic cell with a=10.800Å. Variable Fe, Sn, Bi and Te contents are given by two representative chemical analyses: Cu 43.80, 42.54; Ag 0.06, 0.24; Fe 0.60, 1.60; Zn 0.08, 0.04; Mn 0.03, 0.03; Cd 0.04, 0.00; Sn 12.09, 8.87; Bi 1.42, 4.18; Te 0.50, 1.21; Mo 10.38, 10.87, S 29.82, 28.96; Se 1.06, 1.09; totals 99.88, 99.63 wt. %. The valency-loaded ideal formula is Cu1+4Cu2+2Sn4+Mo4+S8 with substitutions of Fe for Cu, (Bi+Te) for Sn, and Se for S. It occurs as very minute blady aggregates composed of seriated grains in a banded hydrothermal quartz vein in close association with tellurian sulphurian paraguanajuatite and chalcopyrite, and less close with sphalerite, djurleite and covellite, the last two being probably of secondary origin. X-ray powder data for paraguanajuatite are indexed on a trigonal cell with a=4.166, c=28.742Å, and the most tellurium-rich analysis gives Bi 63.38, Se 27.53, Te 8.31, S 1.44, total 100.66 wt. %. Relatively higher sulphur activity is expected to favour the formation of hemusite in hydrothermal condition.
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