Phase Equilibria in the System Fe Ni S at 500°C and 400°C
Journal of Mineralogical and Petrological Sciences,Volume 95,page 145 161,2000
Phase equilibria in the system Fe Ni S at 500°C and 400°C
Teiichi UENO,Shin ichiro ITO,Shinya NAKATSUKA, Kazuki NAKANO,Takayuki HARADA and Takeshi YAM AZAKI
Department of Earth Sciences,Fukuoka University of Education, 729-1 Akama,Munakata,Fukuoka 811 4192,Japan
Phase equilibria in the system Fe Ni S were investigated by dry synthesis at 500°C and 400°C using three
elements(Fe,Ni and S)and two synthetic sulfides(FeS and NiS).Phase diagrams of this ternary system
at these two temperatures were obtained.The extent of the monosulfide solid solution(mss)is complete
at 500°C and 400°C.The d(102)values of the mss are increasing with the increasing Fe/(Fe＋Ni)ratio and
are decreasing with the increasing sulfur content of the mss.Pentlandite has the solid solution areas ranging
from(Fe Ni ) S to(Fe Ni ) S at 500°C and from(Fe Ni ) S to(Fe Ni ) S at 400°C.Violarite has the solid solution area ranging from(Fe Ni ) S to(Fe Ni ) S at
400°C and does not exist at 500°C.Godlevskite is stable at 400°C and it transforms toα Ni S phase at
500°C run.Tie lines of pentlandite to godlevskite at 400°C and pentlandite toα Ni S phase at 500°C are
stable.On the Fe Ni join,two kinds of Fe Ni alloys(α iron andγ phase)and pure nickel are stable. Alfa iron has a body centered cubic str ucture and pure nickel has a face centered cubic structure. Gamma phase has a primitive tetragonal structure and the FeNi phase is included in theγ phase solid
solution.
Ni S solid solution(mss)at 600°C and 400°C.Nal- drett et al.(1967)investigated the central portion of the Introduction Fe Ni S system and applied for the interpretation of the
The information on the phase equilibrium in the Fe pentlandite exsolution in iron nickel sulfide ores.
Ni S system is very important for understanding of the They showed the relationship between d(102)values genesis of many ore deposits producing iron nickel and compositions of the mss.Craig et al.(1967) minerals,meteorites and core materials of the earth.A showed the 400°C isothermal diagram of this system,but large number of the phase equilibrium studies were quite different from the 400°C isothermal diagram performed by many authors and the phase diagrams of obtained by Kullerud(1963a).Main differences are(1) this ternary system were published from 1100°C to 300°C. the presence of the(Ni,Fe) S solid solution,(2)the
Kullerud(1963a)showed many phase diagrams of this continuity of the mss,(3)the presence of the tie line system throughout the temperature range 400°C 1100°C. between pentlandite and Ni S phase,(4)the solid
Kullerud(1963b)showed the thermal stability of pent- solution range of pentlandite.Shewman and Clark landite.Clark and Kullerud(1963)studied the sulfur (1970)studied the pentlandite phase relations in the Fe rich portion of this system. Craig(1966)studied the Ni S system and showed the phase diagrams of the pyrite pentlandite relations and Craig(1967)showed central portion of this system at 600°C,500°C and 400°C. the violarite stability relations.Naldrett(1966),and Their diagrams are quite different from the diagrams
Naldrett and Craig(1967)investigated the Fe S shown by Kullerud(1963a)and are similar to the
diagrams shown by Craig(1967),and Craig et al. T.Ueno，上野禎一， uenot＠fueipc.fukuoka edu.ac.jp Corre- (1967).Recently,Karup Mo/ller and M akovicky sponding author (1995)studied the phase equilibria in this system at
S.Ito，伊東伸一郎 725°C,and Sugaki and Kitakaze(1998)investigated the S.Nakatsuka，中務慎也 K.Nakano，中野一樹 high form of pentlandite and its thermal stability.But, the more important phase relations at 500°C and 400°C T.Harada，原田貴之 T.Yamazaki，山崎武 in the study of ore deposits are not completely cleared. Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 1. Experimental results for Phase equilibria in the system Fe Ni S at 500°C and 400°C
of the Fe-Ni-S system at 500°C
pn,pentlandite;mss,monosulfied solid solution;S,sulfur;py,pyrite;hz,heazlewoodite;vae,vaesite;γ,γ-phase; α-Ni S ,α-(Ni,Fe) S .
The present study was performed in order to prepare the and by X ray powder diffractometry(Ni filtered CuKα detailed phase diagrams of this system at 500°C and radiation,40 kV,100 mA),with Si as an internal stan-
400°C,and to show the relationship between d(102) dard.The d(102)values of the mss were precisely values and compositions of the mss. measured and cell parameters were calculated for some
phases by the least squares method.The chemical
compositions of the phases were determined by a JEOL Experimental 50A electron microprobe.Operating conditions for the
Elemental Fe(99.99%),Ni(99.99%)and S(99.999%)and microprobe were 25 kV and 20 nA(on MgO crystal). synthetic mono sulfides(FeS and NiS)were used for the Synthetic FeS,FeS ,NiS,NiS and Ni S and metallic phase equilibrium experiments.Tables 1 and 2 show Ni and Fe were used as standards.The analytical bulk compositions of the starting mixtures.They were results,each an average of several grains,are shown in sealed in evacuated pyrex tubes.The tubes were heated Tables 3 and 4.All analytical errors are within 0.1 in an electric furnace at 200°C for 1 day to transform wt.%.Chemical formulae were calculated for each starting mixtures into sulfides and were reheated at phase from normalized atomic proportions.
500°C or 400°C to obtain the equilibrium states.After reheating,the tubes were quenched in cold water and products were examined by reflected light microscopy Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 2. Experimental results for Phase equilibria in the system Fe Ni S at 500°C and 400°C
of the Fe-Ni-S system at 400°C
pn,pentlandite;mss,monosulfied solid solution;S,sulfur;py,pyrite;hz,heazlewoodite;vae,vaesite;god,godlevskite;γ,γ-phase; α,α-iron;vio,violarite. Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 3. Chemical compositions of Phase equilibria in the system Fe Ni S at 500°C and 400°C
phases in the Fe-Ni-S system at 500°C
Description of phases method.The upper line corresponds to the values of
relatively low sulfur contents.The middle line corre- Many phases are synthesized in this experiment,and they sponds to the values of mss inside.The lower line are described as follows. corresponds to the values of relatively high sulfur con- tents.The d(102)values are increasing with the
Monosulfide solid solution increasing Fe/(Fe＋Ni)mole ratio,reflecting the differ- ence in ionic radii of Fe and Ni.The d(102)values are
As reported previously by Naldrett et al.(1967),the decreasing with the increasing sulfur content of the mss. existence of a complete Fe S Ni S solid solution Decrease of the metal content with regard to the amount
(monosulfide solid solution＝mss)was first suggested by of sulfur means the increase of the vacancies of metal
Hawley et al.(1943)and was demonstrated by Lund- sites in the mss structure.Unit cell of mss decreases qvist(1947).The crystal structure of the mss obtained with the increase of the vacancies.The results obtained in the present study is the simple hexagonal NiAs type. at 400°C were similar to those at 500°C. The solid solution is continuous between Fe S and
Ni S at 500°C and 400°C isotherms.Microscopically, Pentlandite solid solution the Fe rich mss shows creamy pinkish brown and has very strong anisotropy from yellow gray to grayish blue, As reported previously by Shewman and Clark(1970), and the Ni rich mss shows creamy yellow and has and by Lindqvist et al.(1936)pentlandite was iso struc- strong anisotropy from lemon yellow to blue or violet. tural with synthetic Co S .They wrote its formula as Table 5 shows compositions and d(102)values of the (Fe,Ni) S .We obtained the pentlandite solid solu- mss at 500°C.The mss phases from run nos.P007 to tion areas ranging from(Fe Ni ) S (P019)to
P021 coexist with pentlandite orα Ni S and they show (Fe Ni ) S (P012)at 500°C and from relatively low sulfur contents.The mss phases from run (Fe Ni ) S (HA008)to(Fe Ni ) S nos.K011 to UT033 are mono phases.The mss (UT072)at 400°C.These solid solution ranges are phases from run nos.UT055 to UT063 coexist with larger than the areas shown by Kullerud(1963a)and pyrite or vaesite and show relatively high sulfur contents. similar to those of Shewman and Clark(1970),but with
Figure 1 shows the relation between compositions and a little shift rich in iron compared with the areas shown d(102)values of the mss at 500°C.The horizontal axis by Craig et al.(1967).Table 6 shows the X ray pow- shows the Fe/(Fe＋Ni)mole ratio and the vertical axis der diffraction data for the pentlandite solid solution. shows the d(102)values(Å).Three lines are deter- According to this Table,the cell dimension,a,decreases mined as the quadratic curve by the least squares with the increasing nickel content.As for the cell Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 4. Chemical compositions of Phase equilibria in the system Fe Ni S at 500°C and 400°C
phases in the Fe-Ni-S system at 400°C
dimension of the pentlandite solid solution,Shewman Craig(1967).Table 7 shows the X ray powder dif- and Clark(1970)showed the variation of the d(115) fraction data for violarite.Comparing with the data of ○ values of pentlandite for Fe/Ni atomic ratio＝1 in order Lundqvist(1947),cell dimension,a,is about 0.04 A to determine the solid solution with the sulfur content. larger.Microscopically the violarite solid solution
According to their results,the d(115)values increase shows yellowish gray in reflected light and has no with the increase of the Fe/Ni ratios and decrease with anisotropy.It occurs commonly in nature as an alter- the increasing sulfur contents.Microscopically,the nation product of pentlandite(Craig,1974).In our pentlandite solid solution shows light creamy yellow in 500°C experiment violarite was not obtained. reflected light and has no anisotropy.It is difficult, under the microscope,to distinguish between the Fe Pyrite rich pentlandite and the Ni rich one.Naturally,pent- landite is a common mineral in both massive and Pyrite contains maximum 2.8 at.%nickel(UT059)at disseminated sulfides which are associated with the 500°C and 2.4 at.%nickel(HA025)at 400°C.Micro- mafic rocks(Craig,1974).According to Kullerud scopically nickel bearing pyrite ressembles to pure
(1963b),pentlandite is stable below 610°C in the Fe Ni pyrite.In nature,it occurs in almost all types of ore
S system. deposits and in igneous,sedimentary and metamorphic
rocks. Violarite solid solution Vaesite Craig(1967,1971)studied the violarite stability relations and showed that it is stable below 461°C in the presence Vaesite contains maximum 1.5 at.%iron at 500°C of an equilibrium sulfur vapor.In the 400°C experi- (UT059)as well as at 400°C(HA025).Microscopically ment,the violarite forms a solid solution ranging from vaesite shows gray in reflected light and has no
(Fe Ni ) S (HA026)to(Fe Ni ) S anisotropy.Vaesite is the nickel analogue of pyrite and
(HA025).This area is similar to the one shown by was named by Kerr(1945).It occurs in association Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 5. Compositions and d(102)-value of the mono sulfide solid solution at 500°C
with pyrite. contains maximum 1.0 at.%iron(N027).Microscopi- cally godlevskite shows pale yellow with weak birefrin- Heazlewoodite gence in shades of yellow in reflected light and has
strong anisotropy from bluish to reddish.According to
Heazlewoodite contains maximum 0.3 at.%iron at 500°C Kullerud and Yund(1962),the upper limit of godlevs- (P020)as well as at 400°C(K032).Microscopically kite is 400°C.Godlevskite was found in bornite and heazlewoodite shows whitish yellow with brown tint in bornite chalcopyrite veins of the Noril’sk deposit and reflected light and has strong anisotropy of bluish gray, the Talnakh deposit by Kulagov et al.(1969),and also dark yellow and brown.Heazlewoodite was first de- Naldrett et al.(1972)found from the Texmont Mine, scribed by Petterd(1896)and was identified as a mineral Ontario where it is associated with pentlandite,millerite species by Peacock(1947). and heazlewoodite.
Godlevskite Alpha Ni S
In the 400°C experiment,godlevskite was obtained. In the 500°C experiment,α Ni S was obtained.Table
Table 8 shows the X ray powder diffraction data of 9 shows the X ray powder diffraction data forα Ni S . godlevskite.Comparing with the data of Kulagov et al. Comparing with the data of Fleet(1972),cell dimen- (1969),cell dimensions,a,b,and c are larger.It sions,a and c are smaller but b is larger.Maximum Phase equilibria in the system Fe Ni S at 500°C and 400°C
iron content inα Ni S phase is 3.3 at.%iron at 500°C (P026).Microscopically this phase shows creamy yel- low with pink tint in reflected light and has strong
anisotropy from orange to light gray.According to
Kullerud and Yund(1962),α Ni S is the high temper- ature form of Ni S (godlevskite)and is stable below
573°C.
Fe Ni alloys
In the phase diagrams by Kullerud(1963a)three kinds
of Fe Ni alloys were shown at 500°C and 400°C.They
areα iron,γ phase(taenite)and FeNi .According
to Kullerud(1963a),FeNi phase exists in the 500°C
isothermal section with the compositional limits of
about 74 and 75 weight%Ni.The field cuts the field
ofγ phase solid solution.The FeNi phase forms a
solid solution from 62 to 83 weight%of Ni in the 400° Figure 1. Relations between compositions and d(102)values C isothermal section.This area cuts theγ phase solid of the mss at 500°C. solution.Haworth(1938)showed the calculated X ray
Table 6. X-ray powder-diffraction data for pentlandite
1,JCPDS Card No.30-657(Calvert,1978);2,UT-066(Fe Ni S ,Fe-rich pentlandite);3,UT-069(Fe Ni S ); 4,UT-072(Fe Ni S ,Ni-rich pentlandite). Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 7. X-ray powder-diffraction data for violarite
1,JCPDS Card No.11-0095(Lundqvist,1947);2,HA-020(Fe Ni S ).
Table 8. X-ray powder-diffraction data for godlevskite
1,JCPDS Card No.22-1193(Kulagov et al.,1969);2,K-056(Ni S ). Phase equilibria in the system Fe Ni S at 500°C and 400°C
Table 9. X-ray powder-diffraction data forα-Ni S phase
1,JCPDS Card No.24-1021(Fleet,1972);2,K-045(Ni S ).
diffraction intensities of the FeNi phase for the reflec- has a body centered cubic structure and pure nickel has tions;(111),(200),(220),(311),(222)and(400),and for a face centered cubic structure.Theγ phase has been the super structure lines;(100),(110),(210),(211),(300), reported to have a face centered cubic structure and the
(221),(310),(320)and(321).In his experiment,he FeNi phase has been reported to have the super struc- could not get the superstructure in the FeNi phase. ture lines((100),(110),(210)and so on),which corre- Afterwards,Leech and Sykes(1939)reported the detec- sponds to totally primitive cubic structure.But as far as tion by X rays of superstructure in this phase in speci- the X ray powder data in our experiments are con- mens which had been heated at 490°C for 50 150 hours, cerned,theγ phase should have a primitive tetragonal and cooled down very slowly to 370°C.Hawarth structure as shown in Table 10.FeNi phase is includ- (1939)also obtained the FeNi superstructure phase by ed in theγ phase solid solution.Runs from UT103 to the experiment in which a specimen containing 73.8% UT108 were performed at 500°C and mono phase was nickel was heated at 490°C for six days and then cooled obtained.Although the cell dimension a is nearly down to 440°C in fourteen days.In our 500°C and constant,other dimension,c increases proportionally
400°C experiments,two kinds of Fe Ni alloys(α iron with the increasing iron content. andγ phase)and pure nickel are obtained.Alfa iron Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Table 10. X-ray powder-diffraction data for Fe-Ni alloys
1,UT096;2,UT103;3,UT104;4,UT105;5 UT106;6,UT107;7,UT108;8,Iron,syn JCPDS Card No.6-696.
the FeS direction as compared with the data shown by
Concluding remarks Shewman and Clark(1970).Alpha Ni S phase, high temperature form of Ni S (godlevskite),exists and
The 500°C isothermal section contains maximum 3.3 at.%iron(P026).The tie line of
pentlanditeα Ni S and two univariant assemblages Phase diagram of the ternary system Fe Ni S at 500°C (pentlandite＋α Ni S ＋mss and pentlandite＋α (Fig.2)has been constructed from the experimental Ni S ＋heazlewoodite)are stable.This interpretation results in Table 1.The chemical compositions of the is different from Kullerud(1963a)but is similar to phases are given in Table 3.The solid solution mss is Shewman and Clark(1970).Heazlewoodite contains complete between Fe S and Ni S at 500°C as shown maximum 0.3 at.%iron(P020)at 500°C.Around by Craig(1967),and Shewman and Clark(1970).The heazlewoodite two univariant assemblages(pentlan- complete solid solution of the mss also suggested by the dite＋α Ni S ＋heazlewoodite and pentlandite＋γ continuous variation of d(102)values(Fig.1)in the phase＋heazlewoodite)are stable.Gamma phase present study.Pentlandite is stable in the sulfur defi- forms a wide solid solution field from nearly Ni to cient area and forms a solid solution from Fe Ni (P018).This solid solution forms three
(Fe Ni ) S (P019)to(Fe Ni ) S univariant assemblages;pentlandite＋γ phase＋heazle- (P012).This range is wider than that shown by Kuller- woodite,pentlandite＋γ phase＋mss,and mss＋γ ud(1963a)and is similar but slightly rich in iron(about phase＋α iron.Pure nickel is not included in theγ
1 atomic%)compared with the one shown by Shewman phase solid solution.Because it shows a face centered and Clark(1970).Pyrite contains maximum 2.8 at.% cubic pattern in the X ray diffraction.On the other nickel(UT059)and vaesite contains maximum 1.5 at.% hand,theγ phase solid solution shows a primitive iron(UT059)at 500°C.The composition of the mss tetragonal pattern.Alpha iron contains maximum 6.2 coexisting with pyrite and vaesite is(Fe Ni ) S at.%nickel(HA040)at 500°C and its solid solution
(P024),which is quite different from the data shown by shows a body centered cubic pattern.
Kullerud(1963a).It is similar but about 2 at.%shifts to Phase equilibria in the system Fe Ni S at 500°C and 400°C
Figure 2. Phase relations in the system Fe Ni S at 500°C determined by dry synthesis.
The 400°C isothermal section (Fe Ni ) S (UT072).This area is larger than
the area shown by Kullerud(1963a)and is similar in size
Phase diagram of the ternary system Fe Ni S at 400°C but rich in iron(about 3 atomic%)compared with the
(Fig.3)has been constructed from the experimental one shown by Shewman and Clark(1970).Pyrite results in Table 2 and the chemical compositions of the contains maximum 2.4 at.%nickel(HA025)and vaesite phases are given in Table 4.The solid solution mss is contai ns maximum 1.5 at.%iron(HA025)at 400°C. complete between Fe S and Ni S at 400°C as shown Above the mss,violarite has the solid solution range by Craig(1967),and Shewman and Clark(1970).The f r o m (Fe Ni ) S (H A 0 2 6) t o complete solid solution of the mss also was suggested by (Fe Ni ) S (HA025).Around the violarite the continuous variation of d(102)values as the case at solid solution three univariant assemblages(pyrite＋
500°C.In the sulfur deficient area,pentlandite is stable violarite s.s.＋vaesite,pyrite＋violarite s.s.＋mss,and in the sulfur deficient area,forming the solid solution mss＋violarite s.s.＋vaesite)are stable.This interpreta- ranging from(Fe Ni ) S (HA008)to tion is the same as Craig(1967),and Shewman and Teiichi Ueno,Shin ichiro Ito,Shinya Nakatsuka,Kazuki Nakano,Takayuki Harada and Takeshi Yamazaki
Figure 3. Phase relations in the system Fe Ni S at 400°C determined by dry synthesis.
Clark(1970).The mss composition of the univariant (1967),and Shewman and Clark(1970).The mss assemblage of pyrite＋violarite s.s.＋mss is composition of the univariant assemblage of pentlan- (Fe Ni ) S (K025)and the mss composition dite＋godlevskite＋mss is(Fe Ni ) S of the univariant assemblage of vaesite＋violarite s.s.＋ (UT025),which is similar to the data by Shewman and mss is(Fe Ni ) S (HA026).These composi- Clark(1970).Heazlewoodite contains maximum 0.3 tions are similar to the data by Craig et al.(1967). at.%iron(K032)at 400°C.Around heazlewoodite two
Instead ofα Ni S ,godlevskite appears at 400°C and it univariant assemblages(pentlandite＋godlevskite＋heaz- contains maximum 1.0 at.%iron(N027).The tie line of lewoodite,and pentlandite＋γ phase＋heazlewoodite) pentlandite to godlevskite is stable and around godlevs- are stable.On the join Fe Ni,α iron,γ phase and kite,two univariant assemblages(pentlandite＋godlevs- pure nickel are stable.Alpha iron contains maximum kite＋mss,and pentlandite＋godlevskite＋heazl- 8.0 at.%nickel(N021 and K028)at 400°C.Gamma ewoodite)are stable.This interpretation is different phase forms the long range solid solution field from from Kullerud(1963a)but is similar to Craig et al. nearly Ni to Fe Ni (UT093)and the FeNi Phase equilibria in the system Fe Ni S at 500°C and 400°C phase is included in this solid solution.Pure nickel is from the Belgium Congo. American Mineralogist,30, not included in this solid solution,because it has a face 483 497. Kulagov,E.A.,Erstigneeva,T.L.and Yashko Zakharova centered cubic structure. (1969)The new nickel sulfide godlevskite.Geologi
Rudnykh Mestorozhdeni,11,115 121. Acknowledgements Kullerud,G.(1963a)The Fe Ni S system. Carnegie Insti- tution W ashington Year Book,62,175 189. The authors thank Prof.Gen ichiro Kura of Fukuoka Kullerud,G.(1963b)Thermal stability of pentlandite. Canadian Mineralogist,7,353 366. University of Education for use of the high energy X Kullerud,G.and Yund,R.A.(1962)The Ni S system and ray diffractometer(Mac Science)and Dr.Shoji Kojima related minerals.Journal of Petrology,3,126 175. of Universidad Catolica del Norte for his valuable Leech,P.and Sykes,C.(1939)The evidence for a superlattice suggestions.Our paper has benefitted from thorough in the nickel iron alloy Ni Fe.Philosophical Magazine, reviews by Prof.Hiroaki Kaneda of University of Tokyo 27,742 753. Lindqvist,M.,Lundqvist,D.and Westgren,A.(1936)The and two anonymous referees.This research was funded crystal structure of Co S and of pentlandite(Ni,Fe) S . by grants from the Ministry of Education,Science and Kemisk Tidskrift,48,no.156 160. Culture of Japan to Ueno. Lundqvist,D.(1947)X ray studies on the ternary system Fe
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