1988 Fiscal Year Final Research Report Summary
Diffusion in sulfide minerals and its application to ore deposits
| Project/Area Number |
61540596
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
鉱物学(含岩石・鉱床学)
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| Research Institution | Kumamoto University |
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Principal Investigator |
OZAKI Masaharu Department of Geology, Kumamoto University, 理学部, 助教授 (50040118)
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| Co-Investigator(Kenkyū-buntansha) |
MIZUTA Toshio Department of Geology, Kumamoto University, 理学部, 助手 (80094051)
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| Project Period (FY) |
1986 – 1987
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| Keywords | sulfide mineral / sphalerite / diffusion / tracer / transition element / 硫黄分圧 / bementite / Mn-clinopyroxene / tephroite |
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| Research Abstract |
DIFFUSION IN SULFIDE MINERALS AND ITS APPLICATION TO ONEDEPOSITS
Diffusion coefficients for transition elements in natural sphalerite were determined experimentally as a function of temperature and aS_2 using radioacive ^<54>Mn, ^<59>Fe, ^<60>Co, ^<63>Ni and ^<65>Zn. The tracer was deposited on a polished surface of natural sphalerite as a 1 1 drop of aqueous chloride solution. The doped sphalerite was then heated in sealed silica tubes together with an iron and/or synthesized pyrrhotite and/or pyrite aS2 buller, The tracer distribution was determined by measuring and emissions of powder sampled from successive 4 - 8 m thick layers of the sphalerite chip. Results of diffusivity measurements are as follows.
1.Logarithms of diffusion rates for ^<59>Fe(D_<Fe> cm^2s^<-1>) normal to the cleavage (110) under Fe-FeS aS_2 buffer are -11.0 0.3 at 800゜C and -11.7 0.2 at 700゜C. Log(D_<Co>) are -10.7 0.2 and -11.5 0.3, respecively. Log(D_Zn_< cm^2s^<-1>) normal to the cleavage (110) under Fe-FeS aS_<2> buffer are -10.9 0.2 at 800゜C and -11.8 0.3 at 700゜C. Log(D<_Ni>) are -10.9 0.3 and -12.0 0.3, respectively.
2. The dependence of ^<59>Fe diffusivity on aS_2 is clearly observed in the 800゜C and 700゜C experiments. ^<59>Fe diffusion rates are lower at higher aS_2 conditions (aS_2=10^<-2.9>, Fe_<1-x^S-S_<liq>. buffer; D_<Fe>=10^<-11.0 0.3> at 800゜C) and higher at lower aS_<2>(aS_<2> = 10^<-9.0>, Fe-FeS buffer; D<_Fe> = 10^<-11.3 0.2> at 800゜C).
3. Diffusion rates for ^<60>Co parallel to the (110) plane of sphalerite at 800゜C approximately twice that normal to (110). Sphalerites from metamorphosed Besshi-type deposits in Japan have different element abundances but are characterized by a distinct lack of compositional zoning. It is suggested that sphalerites were homogenized by diffusion processes during regional metamorphism. Calculated annealing times are 16 m.y. at 350゜C and 240 m.y. at 300゜C, assuming 1 millimeter mean displacement of zinc atoms in sphalerite.
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Research Products
(10 results)
