Geochemical Journal, Vol. 23, pp. 339 to 347, 1989

Experimental studies on ion exchange equilibria between minerals and aqueous chloride solution in the system CaWO4-FeWO4-MnWO4 under supercritical condition

ETSUO UCHIDA, MASATAKA GIMA and NAOYA IMAI

Department of Mineral Resources Engineering, School of Science and Engineering, Waseda University, Ohkubo 3-4-1, Shinjuku-ku, Tokyo 169, Japan

(Received December 1, 1989; Accepted February 16, 1990)

Ion exchange experiments in the system CaWO4-FeWO4-MnWO4-(Ca, Fe", Mn2+)C12-H20, cor responding to scheelite-ferberite-huebnerite series mineral as solid phase, were carried out at 400 and 600°C under 1000 kg/cm2. Ferberite and huebnerite form a continuous solid solution (wolframite ss), which may exhibit ther modynamically ideal behavior. Also, ferrous ion tends to concentrate preferably into wolframite ss than into aqueous chloride solution. This tendency becomes more pronounced with decreasing temperature. Scheelite and wolframite ss do not dissolve into each other essentially, but form a wide miscibility gap. The Ca /(Ca+Fe2++Mn2+) mole ratios of aqueous chloride solution coexisting with both minerals are about 0.65 at 400°C and 0.3 at 600°C. Temperature has a significant effect on the mole ratio, although a slight variation due to the compositional change of wolframite ss is recognized. The present experimental results cast a doubt on "wolframite geothermometer".

series mineral, which belong to R"W04-type INTRODUCTION compound, represent the major source of Experimental studies of ion exchange tungsten in nature. However, such data for the equilibria between minerals and aqueous tungsten-bearing minerals have not been furnish chloride solution provide us with information on ed except for a preliminary work by Baumer et thermodynamic properties of minerals and al. (1985). In the present study, therefore, we car aqueous species, which are also important basic ried out ion exchange experiments in the system data for estimating the chemical compositions of CaWO4-FeWO4-MnWO4-(Ca, Fe e+, Mn2+ )C12 ore-forming fluids. This is partly the reason why H20 under supercritical condition. We deter experimental studies on ion exchange equilibria mined relative concentrations of calcium, fer have been carried out by many workers; e.g., rous, and divalent manganese ions in the Wyart and Sabatier(1956), Orville(1963), and aqueous chloride solution which coexists with Iiyama(1966) for alkali feldspars; Iiyama(1966), these solid phases in equilibrium. An attempt and Orville(1972) for plagioclase; Roux(1974) was also made to clarify the thermodynamic for nepheline, Schulien et al.(1970) and Bar properties of wolframite ss series. tholomew(1989) for olivine, Iiyama(1964), Schulien(1980), Pascal and Roux(1985), and ABBREVIATIONS, SYMBOLS AND CONSTANT Flux and Chatterjee(1986) for micas, Uchida(1982) for clinopyroxene, and Lehmann aq: in aqueous solution and Roux(1986) for spinel. fer: ferberite Scheelite and wolframite solid solution(ss) hue: huebnerite

339 340 E. Uchida et al.

sch: scheelite periments. Wolframite ss is known to be stable wol: wolframite solid solution (ss) under these conditions of oxygen fugacities A G: Gibbs energy of reaction (Hsu, 1976). A G°: standard Gibbs energy of reaction After welding, the charged capsules were put A GEX: excess Gibbs energy of reaction into the pressure reactor of cold seal-type made Ga,EM: excess Gibbs energy of mixing for of Stellite-25 alloy. Pressure was measured by a phase a Heise gage (scale interval of 5 kg/cm2) with the Kd: distribution coefficient range of 0 to 2000 kg /cm', and was kept at 1000 m,: molality of component i kg/cm2 for every run of the present experiments. R: gas constant The uncertainty was within ± 10 kg/cm2. The T: temperature in Kelvin temperatures were measured with chromel W: interaction parameter in regular s olu alumel thermocouple, attached to the outside tion model wall of the reactor. In the present experiments, X7 a, mole fraction of component i in phase the temperatures of furnace were kept at 400°C a or 600°C, and controlled within ±5°C. Run Pa: chemical potential of component i in duration varied from 7 to 11 days at 400°C and phase a from 4 to 8 days at 600°C. The achievement of ?,a. ,ui standard chemical potential of compo equilibrium in the experiments was examined us nent i in phase a ing an internal consistency of Gibbs energy of a,EX: I excess chemical potential of component reaction as described later. i in phase a After the run, the charge was quenched by removing the reactor from the furnace and imme diately placing it in cold water. After the check EXPERIMENTAL PROCEDURES for leakage, gold capsules were opened and the A stoichimetric mixture of reagent-grade run products were washed away into a beaker calcium hydroxide and tungsten trioxide was with distilled water. Solid products were heated at 800°C for one day. The burned cake separated from aqueous chloride solution with thus obtained and ground was used as a starting membrane filter of 0.45,um pore size made by material for scheelite. Reagent-grade metallic Millipore Co. Solid phases were identified with a iron powder and metallic manganese powder polarization microscope, an X-ray diffrac were stoichiometrically mixed with tungsten tometer and a scanning electron microscope. In trioxide and used for ferberite and huebnerite, re order to avoid the effects of zoning and inclusion spectively. of starting material in synthesized minerals, Twenty to 50 milligrams of the starting chemical analysis on the grain surface was done materials and 10 to 50 milliliters of aqueous (Ca, using a JEOL 733 microprobe with EDS TN Fe", Mn2+)C12solution with 1 molar concentra 5400. In this study, surface equilibrium of tion* (1 mol/1) were sealed in gold capsules with minerals with aqueous chloride solution was a 3.0 mm outer diameter, a 0.15 mm wall assumed. The analytical precision of minerals is thickness, and a length of 30 to 35 mm. A few considered to be within ±2 mole%. The milligrams of anthracene were added as a reduc chemical composition of liquid phase was deter ing agent to keep iron and manganese ions in a mined by means of atomic absorption spec divalent state. The oxygen fugacity is considered trophotometry. to be controlled between FMQ and IM buffers or between FMQ and MW buffers during the ex

*The difference between molarity(M) and molality(m) in aqueous chloride solution is not so large in this work. Accordingly, we assume in this study that molarity is equal to molality.

. Ion exchange equilibria between tungstates and chloride solution 341

other phase. The degree of crystallinity of these EXPERIMENTALRESULTS synthesized minerals is similar to the case of the The system CaW04-FeW04-(Ca, Fe2+)Cl2-H20 system CaWO4-FeWO4-(Ca, Fe 2+ )C12-H20 The experimental results of this system are The Ca /(Ca+Mn) mole ratio of the aqueous summarized in Fig. 1. Solid products consist of chloride solution coexisting with both scheelite scheelite and ferberite in every run. Under the and huebnerite is 0.644 at 400°C and 0.319 at present experimental conditions, scheelite and 600°C. These results are similar to those of the ferberite show extremely limited solubility in system CaWO4-FeWO4-(Ca, Fe 2+)C12-H2O. Ac each other phase. Both scheelite and ferberite cordingly, the thermodynamic behavior of formed at 600°C are well-crystallized and their ferberite is expected to be analogous to that of grain size reaches up to 20 ym (Fig. 2B). On the huebnerite. other hand, these minerals formed at 400°C show poor crystallinity and are accompanied by The system Ca WO4-FeWO4-(Fe2+, Mn2+)Cl2 fine particles of the same minerals (Fig. 2A). H20 The Ca/(Ca+Fe) mole ratio of the aqueous The experimental results of this system are chloride solution coexisting with both scheelite summarized diagrammatically in Fig. 4. Under and ferberite is 0.657 at 400°C and 0.381 at the present experimental conditions, ferberite 600°C, indicating that a temperature and huebnerite form a continuous solid solution dependence of the values is conspicuous. series; i.e., wolframite ss series. Under the polarization microscope, the synthesized The system CaWO4-Mn W04-(Ca, Mn2+)Cl2 wolframite ss is opaque near the end member H20 composition of ferberite, and with increasing The experimental results are summarized in huebnerite component, it becomes transparent Fig. 3. Solid products consist of scheelite and gradually with a colour of reddish brown. The huebnerite in every run. Scheelite and huebnerite crystallinity of wolframite ss is poor at 400°C also show extremely limited solubility in each (Fig. 2E). Ferrous ion tends to be concentrated into wolframite ss as compared with aqueous chloride solution at 600°C. This tendency 1.0 becomes more pronounced at 400°C.

0.8 The system CaWO4-FeWO4-Mn W04-(Ca, 00 Fe2+, Mn2+)CI2-H20 0 for 4000C sch 0 The experimental results of this system are 0.6 0 summarized diagrammatically in Figs. 5 and 6. U, Solid products consist of scheelite and 600°C wolframite in every run. 0.4 Figure 5 shows the relationship between Fe / (Fe + Mn) mole ratio of wolframite ss and

0.2 that of the coexisting aqueous chloride solution. The results are consistent with those obtained in the system FeWO4-MnWO4-(Fe2+, Mn2+ )C12 0 0.2 0.4 0.6 0.8 1.0 H20.

Ca/(Ca+Fe) solid Figure 6 shows the relationship between Fig. 1. Ion exchange isotherms in the system Fe/(Fe+Mn) mole ratio of wolframite ss coex CaWO4-FeW04-(Ca, Fe2+)Cl2-H20 at 400°C(circle) isting with scheelite and Ca / (Ca + Fe - Mn) and 600°C(square) under 1000 kg/cm2. mole ratio of the aqueous chloride solution. The 342 E. Uchida et at.

~~ x~

.~ ~.

k K

e

,.y ->...... ~~%i ~.

C

x

Pet

3 8 r

3 t r' S

C n K i) 15

E

A

t 1 i ,

Fig. 2. SEM images. A: Scheelite and ferberite synthesized at 400°C and 1000 kg/cm2 . Run No. 177. B: Scheelite and ferberite synthesized at 600°C and 1000 kg/ cm2. Run No. 185. C: Scheelite and huebnerite syn thesized at 400°C and 1000 kg/cm2. Run No. 122. D: Scheelite and huebnerite synthesized at 600°C and 1000 kg/cm2. Run No. 104. E: Wolframite with 86.5 mole% of ferberite component synthesized at 400°C and 1000 kg/cm2. Run No. 331. F.• Wolframite with 85.2 mole% of ferberite component synthesized at 600°C and 1000 kg/cm2. Run No. 3.

Ion exchange equilibria between tungstates and chloride solution 343

1.0 1.0

0.8 0.8

We 400 $c L g ----1C------0 0.6 i}' 0.6 0 0 V) y 6000 •

4000C • • • 0.4 °' 0.4 w 600°C

0.2 0.2

0 0.2 0.4 0.6 0.8 1.0 0 Q2 0.4 0.6 0.8 1.0 Ca/(Ca+Yn) solid Fe/(Fe+Yn) solid Fig. 5. Ion exchange isotherms for wolframite coex Fig. 3. Ion exchange isotherms in the system Ca W04-Mn W04-(Ca, Mn2+)Cl2-H20 at isting with scheelite in the system CaWO4-FeWO4 400°C Mn W04-(Ca, Fee+, Mn2+ )C12-H20 at 400'C(circle) (circle) and 600°C(square) under 1000 kg/cm2. and 600°C(square) under 1000 kg/cm2.

1.0

1.0

0.8

0 0.8 a . 0.6 0 400°C a . 0 U) 600`C a . . 0 0.6 a 4000 + a) w 0.4 0 • a) w

0.4 c.) 6000

0.2 Ca U •

0.2

0 0.2 0.4 0.6 0.8 1.0 Fe/(Fe+Mn) solid 0 0.2 0.4 0.6 0.8 1.0 Fig. 4. Ion exchange isotherms in the system Fe WO4-MnWO4-(Fe2+, Mn2+)C12-H20 at 400°C(cir Fe/(Fe+Mn) solid cle) and 600°C(square) under 1000 kg/cm2. Fig. 6. Plot of Ca/(Ca+Fe+Mn) mole ratio of aqueous chloride solution coexisting with both scheelite and wolframite versus chemical composition of wolframite at 400°C(circle) and 600°(square) under 1000 kgl cm2. Experimental results in the systems Ca WO4-Fe W04 and Ca W04-Mn WO4 are also plotted in this figure. Solid lines were drawn using the ex perimental results in the system Ca W04-Fe W04 Mn W04-(Ca, Fee+, Mn2+)C12-H2O.

• 344 E. Uchida et al. experimental results of this system are consistent When scheelite coexists with huebnerite in with those of the system CaW04-MnWO4-(Ca, equilibrium with aqueous chloride solution, the Mn2+ )C12-H20 at 400 and 600°C, and with those ion exchange reaction is written as follows: of the system CaWO4-FeWO4-(Ca, Fe 2+ )C12 CaWO4+MnC12=MnW04+CaC12. (4) H20 at 400°C, but not so at 600°C. (sch) (aq) (fer) (aq) As in the case of reaction (1), we can obtain THERMODYNAMIC CONSIDERATION OF THE the following equation: EXPERIMENTAL RESULTS d G°(4)+RT In (mcaC12/mMnC12)=0. (5) The system Ca W04-FeWO4-(Ca, Fe2+)Cl2-H20 Using the eq. (5) and experimental results, When scheelite coexists with ferberite in d G°(4) is estimated to be -0.79--L0.17 aqueous chloride solution, the ion exchange reac kcal /mole at 400'C and 1.32 ± 0.20 kcal/ mole tion is written as, at 600°C. CaWO4 + FeC12= FeWO4 + CaC12. (1) (sch) (aq) (fer) (aq) The system FeWO4-MnWO4-(Fe2+, Mn2+)C12 Here, we assume that neutral aqueous H20 chloride complexes, FeCl2, CaCl2 and MnClo are In this system, the ion exchange reaction is dominant species in the present experimental con written as follows: ditions (Boctor et al., 1980; Popp and Frantz, FeWO4+MnC12=MnWO4+FeC12. (6) 1979; Boctor et al., 1980). At equilibrium, (fer) (aq) (hue) (aq) d G(1) =,u Fewo4+,u CaC12-lu CaWO4-,u FeCl2 At equilibrium, =d G°(1)+RT In Kd(1)+d GEx(1)=0, A G(6) =,u Mwoo +,u Fec,2 /A /O4 /4MnC12 (2) =d G°(6) +R T In Kd(6) + d GEX(6)= 0,

where (7) d G 0 (1)=,uFewo4+~udaC12-,udaWo4-µFeC12 o,fer o aq o sch o,aq where dG EX (1)=µFe~WO4+/4CaC1zfer EX aq,EX /2CawO4 sch EX _ /1FeC12, aq,EX d GO(6)=,uMnWO a +/2Fe~1 z-iuFeW04-iul o,wol o naq 12 and Kd(1)=(XF wo4'mcaC12)/(XcWo4'mFecl2). A G`(6) =µMn~V04+1uwol EX aq,EX FeC12 _ /2FeV~04 wol EX _ ~1 aq mnC12 EX Since X"' oo=1 and X Fewo4-1, we can and Kd(6)=(XMri 04'mFeC12)/(XFeWO4'mMnC12). assume that 2CaWO4-OruFeV~04-O. There is a following thermodynamic relation Though there is a question about ideality of ship: aqueous chloride solution(Bartholomew, 1989), we assume here that aqueous chloride solution (aGwol,EX/aXFeW04)=/FeV/O4-PMn~TVO4. (8) behaves as an ideal solution, namely, uCc12= Here, aqueous chloride solution is assumed ,uFe 12=0. Therefore, the eq. (2) is rewritten as, to behave as an ideal solution, namely, pFeclx d G°(1)+RT In (mcacl2/mFeC12)=0. (3) =pV ci =0. Accordingly, the eq. (7) is rewritten A G°(1) will be calculated from the experimen as tal results using eq. (3). A G°(1) is estimated to be d G°(6) _ (aGwo1,EX/aXFeW04) -0 .87±0.32 kcal/mole at 400°C and +RTIn Kd(6)=0. (9) 0.84±0.34 kcal/mole at 600°C. Also, we assume that excess Gibbs energy of The system Ca W04-MnW04-(Ca, Mn2+)C12 mixing for wolframite ss is expressed by an asym H20 metric regular solution model (Thompson, 1967): Ion exchange equilibria between tungstates and chloride solution 345

Gwol,EX=Xwol FeWO4'XMnWO4(Whue wo1 XwolFeW04 and at 600°C, + Wfer'XMWO). (10) d G °(6) = 0.30 ± 0.27 kcal /mole Differentiating both sides of eq. (10) with Wfer= 0.24 respect to XFewo4, then we obtain, Whue= 0.30. (a G wo1,EX/ adFeWO4) As described before, eq. (3) was derived from Wfer[1-4XFeWO4+3(XFeWO4)2] eq. (2) on the assumptions that XF wo4-1 and wolEX wol wolEX µ + Whue[2XFeWO4 3(XFeW04)21• (11) Fe~o4 ,. If XFewo, 1 and ,uFev~o4 ;6 0, we have the following equations: From the above relationship, eq. (9) can be rewritten as dG°(1)+RT In (XFewo4'mcacl2/InFeCl)+,uFe\,1O4 =0, (13) d G°(6) [ Wfer(1 4XFew04+(XFeW04)2] where Whue[(2'XFeW04 3 (XFeWO4)2J wolEX= Xwol 2Xwol ~ +RTIn Kd(6)=0. (12) Fe%$O4( MnWO4)2.[( FeW04'Whue) +(1-2XFeW04)' Wfer] (14) The values of d G°(6), Wfer and Wh1e can be calculated from the experimental data using Using eq. (13), the values for J G°(1) were es a least-square fit method. The results are as timated to be -1.17 ± 0.19 kcal / mole at 400°C follows: at 400°C, and 1.39±0.31 kcal/mole at 600°C. In the same way, we can obtain the values for AGO(6)=0.69±0.07 kcal /mole dG°(4) as -0.58±0.15 kcal/mole at 400°C and Wfer=0.33 1.69 ± 0.28 kcal / mole at 600'C. Whue= 0.46, Internal consistency of the results and at 600°C, Theoretically,thereisa following) relation ship: I dG°(6)=0.42±0.27 kcal/mole EG=dG°(1)-dG°(4)+AG°(6)=0. (15) Wfer=0.15 Whue=0.25. For the experimental results of the ternary system CaWO4-FeWO4-MnWO4, the EG value If we take the experimental errors into con must be zero, because dG°(1), dG°(4) and sideration, it can be stated that wolframite ss ex d G°(6) are mutually dependent. However, as for hibits nearly ideal behavior under the present ex the binary systems CaWO4-FeWO4, CaWO4 perimental conditions. MnWO4 and FeWO4-MnWO4, they are indepen dent estimates. Accordingly, we can examine in The system Ca WO4-Fe W04-Mn W04-(Ca, ternal consistency of the experimental results for Fe e+, Mn2+)Cl2-H20 the binary systems using eq. (15). The calculated Using the present experimental data in this EG values are 0.60 kcal/mole at 400°C and 0.06 system, the values for d G°(6), Wfer and Whuecan kcal/mole at 600°C. also be calculated by the same method as de The internal consistency of the results is ex scribed in the preceeding section. The results are cellent for the experiments at 600°C, and is also as follows: at 400°C, good even at 400°C. Although formal reversal dG°(6)=0.59±0.21 kcal/mole of the equilibria as discussed in Flux and Chatter jee(1986) has not been done, it seems reasonable Wfer=0.21 to assume that a good approximation of Whue=0.59, equilibrium has been achieved in these ex 346 E. Uchida et al.

periments. doubt or denial upon the Mn / Fe ratio of the mineral as a geothermometer (e.g., Moor and

GEOLOGICAL CONSIDERATION AND CONCLUSIONS Howie, 1978; Amosse, 1978; Nakashima et al., 1986). The present results indicate that the Scheelite and wolframite ss represent the Mn/Fe ratio of wolframite ss increases with in most common tungsten-bearing minerals in creasing temperature of formation, although the nature. Among them, scheelite occurs mainly in variation of the ratio is small. However, the skarn-type deposits, whereas wolframite ss oc Mn / Fe ratio also varies sensitively depending curs largely in vein-type deposits. Judging from upon the compositional change of coexisting the present results, the Ca / (Ca +Fe2+ +Mn2+ ) aqueous chloride solution. Consequently, it is mole ratios of the ore-forming fluids of skarn not safe to estimate formation temperatures of type deposits should be higher than that of wolframite ss based on its compositional change vein-type deposits. Clinopyroxene occurs in alone. skarn-type deposits as a major skarn-forming constituent. Uchida(1982), based on his ex Acknowledgments-We like to express our sincere perimental study of ion exchange equilibria be thanks to Professors R. Otsuka and S. Tsutsumi of tween clinopyroxene and aqueous chloride solu Waseda University for access to their facilities of tion, revealed that the Ca / (Ca +Fe2+ +Mn2+ ) hydrothermal apparatus. We wish to acknowledge the ratio of the fluid in equilibrium with clinopyrox financial supports in part by a Grant-in-Aid for Scien tific Research from the Ministry of Education, Science ene is larger than 0.61 at 600°C under 1 kbar. and Culture of Japan (Project No. 63740472, E. This is concordant with the present experimental Uchida) and by a Grant-in-Aid for Specified Research results. Project from Waseda University (Project No. 6313-9, The ferberite pseudomorph after scheelite is N. Imai). Three anonymous reviewers' comments are well known as "reinite" (Luedecke, 1879). greatly appreciated. Recently, replacement texture of scheelite by wolframite ss has been reported in several skarn REFERENCES type deposits; e.g., at MacTung(Dick and Hodgson, 1982) and Kiwada, Japan(Sato, 1977). Amosse, J. (1978) Physicochemical study of the huebnerite-ferberite (MnWO4-FeWO4) zonal The formation of the replacement texture may distribution in wolframite (Mn,,Fe(,-, )W04) be explained by a compositional variation of deposits. Phys. Chem. Minerals 3, 331-341. ore-forming fluid with time, i.e., the Bartholomew, P. R. (1989) Interpretation of the solu Ca/ (Ca + Fe 2++Mn2+) mole ratio decreased in a tion properties of Fe-Mg olivines and aqueous Fe later stage. An alternative is the formation of Mg chlorides from ion-exchange experiments. Amer. Mineralogist 74, 37-49. this texture by a decrease of temperature, since Baumer, A., Caruba, R. and Guy, B. (1985) Ex the stability field of wolframite ss is enlarged perimental study of hydrothermal transformations with decreasing temperature. scheelite=ferberite: preliminary results. Bull. With reference to the relationship between Miner. 108, 15-20. MnWO4/FeWO4 mole ratio (Mn/Fe ratio) of Boctor, N. Z. (1985) Rhodonite solubility and ther wolframite ss and the formation temperature, modynamic properties of aqueous MnC12 in the system MnO-SiO2-HCl-H20. Geochim. i.e., the significance of the Mn/Fe ratio as a Cosmochim. Acta 49, 565-575. geothermometer, previous researchers have Boctor, N. Z., Popp, R. K. and Frantz, J. D. (1980) made opposite conclusions: the increase in Mineral-solution equilibria. IV. Solubilities and the Mn / Fe ratio of wolframite ss with increasing thermodynamic properties of FeC19 in the system temperature of formation (e.g., Oelsner, 1944, Fe2-H2-H20-HCI. Geochim. Cosmochim. Acta 44, 1952; Lawrence, 1961), and the reverse relation 1509-1518. Dick, L. A. and Hodgson, C. J. (1982) The MacTung ship (e.g., Ganeev and Sechina, 1960). However, W-Cu(Zn) contact metasomatic and related recent investigations on wolframite ss have cast a deposits of the Northeastern Canadian Cordillera. Ion exchange equilibria between tungstates and chloride solution 347

Econ. Geol. 77, 845-867. Oelsner, O. (1952) Die pegmatitisch Flux, S. and Chatterjee, N. D. (1986) Experimental pneumatolytischen Lagerstatten des Erzgebirges reversal of the Na-K exchange reaction between mit Ausnahme der Kontaktlagerstatten. Freiberger muscovite-paragonite crystalline solutions and a Forschungsh. C4, 3-80. 2molal aqueous (Na, K)Cl fluid. Jour. Petrol. 27, Orville, P. M. (1963) Alkali ion exchange between 665-676. vapor and feldspar phases. Am. J. Sci. 261, 201 Ganeev, I. G. and Sechina, N. P. (1960) Geochemical 237. peculiarities of wolframite. Geochim. Internat. 6, Orville, P. M. (1972) Plagioclase cation exchange 617-623. equilibria with aqueous chloride solution: Results Hsu, L. C. (1976) The stability relations of the at 700°C and 2000 bars in the presence of quartz. wolframite series. Amer Mineralogist 61, 944-955. Am. J. Sci. 272, 234-272. Iiyama, J. T. (1964) Etude des reactions d'echange Pascal, M. L. and Roux, J. (1985) Na-K exchange d'ions Na-K dans la serie muscovite-paragonite. equilibria between muscovite-paragonite solid solu Bull. Soc. Franc. Miner. Crist. 87, 532-541. tion and hydrothermal chloride solution. Miner. Iiyama, J. T. (1965) Contribution a 1'etude des Mag. 49, 515-521. equilibres sub-solidus du systeme ternaire orthose Popp, R. K. and Frantz, J. D. (1979) Mineral-solution albite-anorthite a l'aide des reactions d'echange equilibria-II. An experimental study of complexing d'ions Na-K au contact d'une solution hydrother and thermodynamic properties of aqueous CaC12 in male. Bull. Soc. Franc. Miner. Crist. 88, 618-622. the system CaO-SiO2-H20-HCI. Geochim. Iiyama, J. T. (1966) Influence des anions sur les Cosmochim. Acta 43, 1777-1790. equilibres d'echange d'ions Na-K dans les Roux, J. (1974) Etude des solutions solides des feldspaths alcalins a 600°C sous une pression de nephelines (Na, K)A1SiO4. Geochim. Cosmochim. 1000 bars. Bull. Soc. Franc. Miner. Crist. 89, 442 Acta 38, 1213-1244. 454. Sato, K. (1977) Wolframite from the contact Lawrence, L. J. (1961) Crystal habit of wolframite as metasomatic scheelite deposits of the Kiwada, Fu an indication of relative temperature of formation. jigatani and Kuga mines, Yamaguchi Prefecture, Neues Jahrb. Miner. Monatsh. 1961, 241-247. Japan. Mining Geology 27, 31-37 (Japanese). Lehmann, J. and Roux, J. (1986) Experimental and Schulien, S. (1980) Mg-Fe partitioning between theoretical study of (Fe2+, Mg)(Al, Fe3+)2O4 biotite and a supercritical chloride solution. Con spinels: Activity-composition relationships, trib. Mineral. Petrol. 74, 85-93. miscibility gaps, vacancy contents. Geochim. Schulien, S., Friedrischen, H. and Hellner, E. (1970) Cosmochim. Acta 50, 1765-1783. Das Mischkristallverhalten des Olivins zwischen Luedecke, O. (1879) Uber Reinit, K. V. Fritsch, ein 450°C and 650°C bei 1 kb Druck. Neues Jahrb. neues wolframsaures Eisen oxydul. Neues Jahrb. Miner. Minatsh. 4, 141-147. Miner. Geol. Palaeont. 1879, 286-291. Thompson, J. B., Jr. (1967) Thermodynamic proper Moore, F. and Howie, R. A. (1978) On the applica-, ties of simple solution. Researches in geochemistry, tion of the hiibnerite: ferberite ratio as a geother vol. 2, ed. P. H. Abelton, 340-361, Wiley. mometer. Miner. Deposita 6, 391-397. Uchida, E. (1982) Skarnization in the Kamaishi mine Nakashima, K., Watanabe, M. and Soeda, A. (1986) and experimental studies on ion exchange Regional and local variations in the composition of equilibria. Unpublished Ph. D. thesis, University of the wolframite series from SW Japan and possible Tokyo. factors controlling compositional variations. Wyart, J. and Sabatier, G. (1956) Transformations Miner. Deposita 21, 200-206. mutuelles des feldspaths alkalins. Reproduction du Oelsner, O. (1944) Uber erzgebirgische Wolframite. microcline et de 1'albite. Bull. Soc. Franc. Miner. Ber. Freiberger Geol. Ges. 20, 44-49. Crist. 79, 444-448.