synthetic fluid inclusions: xii. the system h20 … bodnar, gca 58.pdfexperimental determination of...

Gewhimica et Cosmochimica Acta, Vol. 58, No. 3, pp. 1053-1063, 1994

Pergamon Copyright 0 1994 Elsevier Science Ltd Printed in the USA. All rights reserved

0016-7037/94 $6.00 + .OO

Synthetic fluid inclusions: XII. The system H20-NaCI. Experimental determination of the halite liquidus and isochores for a 40 wt% NaCl solution*

R. J. BODNAR

Fluids Research Laboratory, Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 2406 I, USA

(Received October 27, 1992; accepted in revised form July 8, 1993)

Abstract-The slopes of the liquidus and lines of constant liquid-vapor homogenization temperature (iso-Th) in P-T space for a 40 wt% NaCl bulk composition in the H20-NaCl system were determined using synthetic fluid inclusions. Inclusions were synthesized in the one-phase field at 350”-800°C and l-6 kbar, and the temperatures of liquid-vapor homogenization and halite dissolution were determined on a heating/cooling stage. The pressure along the liquidus corresponding to a measured halite dissolution temperature [ Tm (halite)] was determined from the intersection of the inclusion iso-Th line in the one- phase field with the measured Tm (halite). The P-T position of the iso-Th line in the one-phase field was determined from the measured liquid-vapor homogenization temperature [ Th (L-V)] of a given inclusion and the known experimental formation temperature and pressure for that same inclusion.

The slope of the 40 wt% halite liquidus determined from synthetic fluid inclusions is -5S’C/ kbar. This value is in good agreement with an extrapolation of the data of GUNTER et al. ( 1983) and cooling data of KOSTER VAN GROOS ( 199 1) to lower salinities, but shows considerable disagreement with the extrapolated heating data of KOSTER VAN GROOS ( 199 1 ), Over the salinity range 27- 100 wt% NaCl, the slope of the halite liquidus predicted by the results from this study combined with data of MILNE ( 1978 ), GUNTER et al. ( 1983), and cooling data of KOSTER VAN GROOS ( 1991) is given by

dT/dP( “C/kbar) = -38.38 + 0.90s - O.O029S*,

where “S” is the salinity in wt% NaCl. Microthermometric data combined with the known temperatures and pressures of formation were

used to construct lines of constant liquid-vapor homogenization temperature (iso-Th) for fluid inclusions with a salinity of 40 wt% NaCl. The slopes of the iso-Th lines for inclusions which homogenize by vapor- bubble disappearance decrease smoothly with increasing Th, from 14.1 bars/“C for inclusions which homogenize at 323°C to 5.52 bars/“C for inclusions with homogenization temperatures of 650°C. For inclusions which homogenize by halite dissolution (Th < 323”C), the slopes of the iso-Th lines within the one-phase liquid field decrease with increasing Th (L-V) from 2 1.5 bars/ “C ( 1 SO’C) to 14.1 bars/ “C (323°C). The average slopes of the iso-Th lines within the liquid + halite field are much steeper than those in the one phase field, and decrease from 24.8 bars/ “C at 150°C to 20.3 bars/ “C at 300°C.

lNTRODUCTION

FLUID INCLUSIONS CONTAINING halite daughter minerals are common in many geologic environments and are a charac- teristic inclusion type in the porphyry copper deposits (NASH, 1976). Halite-bearing fluid inclusions may exhibit three different modes of homogenization, depending on the density of the inclusion, which is in turn dependent on the P-T conditions of formation. Figure 1 shows three different halite- bearing synthetic fluid inclusions (A, B, C), each containing 40 wt% NaCl but with different bulk densities, as reflected by the different relative vapor bubble volumes at room temperature (top photograph). Inclusion A contains a relatively large vapor bubble at room temperature, indicating a relatively low bulk density. When this inclusion is heated, the halite daughter mineral dissolves before the vapor disappearance temperature is reached. With continued heating

* Presented at the fourth biennial Pan-American Conference on Research on Fluid Inclusions (PACROFI IV), held May 22-24, 1992, at the UCLA Conference Center, Lake Arrowhead, California, USA.

beyond the temperature of halite dissolution, the inclusion follows a path through the 40 wt% two-phase (liquid + vapor) field and the vapor bubble disappears when this path intersects the 40 wt% liquid-vapor isopleth (L(40) + I’on Fig. 2). The P-T path followed by the inclusion following halite dissolution is easily calculated using PVTX data for coexisting liquids and vapors in the H20-NaCl system (cf. BISCHOFF, 1991) and mass and volume constraints imposed by the inclusion. The inclusion thus homogenizes along the 40 wt% liquid + vapor curve [ L( 40) + V] shown in Fig. 2. Any inclusion containing 40 wt% NaCl and trapped in Field A (Fig. 2), which is bounded by the 40 wt% NaCl liquid + vapor curve and the dashed isochore labeled B (described below), will exhibit a similar mode of homogenization. With continued heating beyond the temperature of homogenization, the inclusion will follow an isochoric P-T path (Isochore A, Fig. 2) in the one-phase field and through the inclusion formation conditions.

Inclusion C has a relatively high density compared to inclusion A, as indicated by the smaller relative proportion of vapor in inclusion C at room temperature (Fig. 1). When heated, the first phase to disappear is the vapor bubble. With

1053

1054

continued heating the inclusion follows a path (shown by

R. J. Bodnar

FIG. I Series of photomicrographs depicting the three different modes of homogenization possible for halite-bearing inclusions. All inclusions have a salinity of 40 wt% NaCl, and the scale bar represents 25 microns for each inclusion. The top photo of each inclusion sequence was taken at room temperature. The differing relative vapor bubble sizes reflect the different relative densities of the inclusions. When heated, the first phase to disappear in inclusion A is the halite, followed by vapor-bubble disappearance at some higher temperature. Inclusion C homogenizes by disappearance of the halite crystal after the vapor bubble has disappeared. The vapor bubble and the halite crystal both disappear at the same temperature in inclusion B.

the dot-dash line labeled Isochore C on Fig. 2) through the liquid + halite field until the halite dissolves at some higher temperature when the path intersects the liquidus. This in-

clusion thus homogenizes along the 40 wt% NaCl halite liquidus [ L( 40) + H; Fig. 21, and similar homogenization behavior would be displayed by any inclusion trapped in Field C. bounded by the halite liquidus and the dashed isochore (Isochore B, Fig. 2). With continued heating beyond the temperature of halite dissolution, i.e., beyond the temperature of homogenization, the inclusion follows an isochoric path through the one-phase field (solid line labeled Isochore C, Fig. 2).

The dashed isochore shown on Fig. 2 (Isochore B) represents the isochore that originates on the three-phase (liquid + vapor + halite) curve at a point defined by the intersection of the 40 wt% liquidus [L(40) + H] with the 40 wt% liquid + vapor curve [ L( 40) + V]. The dashed isochore thus sep- arates P-T space into two fields. Halite-bearing inclusions trapped in the P-T regions labeled Field A and Field C will

exhibit behavior as described above while inclusions trapped along isochore B, separating Fields A and C, will homogenize by the simultaneous disappearance of halite and vapor.

Natural halite-bearing fluid inclusions from porphyry copper deposits may exhibit any of the three modes of homogenization described above (cf. BODNAR and BEANE, 1980).

With limited data on the vapor pressures (BODNAR et al., 1985) and PVTproperties (BODNAR, 1985; URUSOVA, 1975) of high salinity fluids, it has been possible to approximate trapping conditions for inclusions exhibiting homogenization behavior similar to inclusions A and B shown on Fig. I (i.e., vapor bubble disappearance temperature 2 halite disappearance temperature). However, interpretation of microthermometric data from inclusions homogenizing by halite dissolution (inclusion C on Fig. 1) has not been possible, and attempts to interpret these inclusions have led to wide variation in estimated P-T formation conditions, as discussed by ROEDDER and BODNAR ( 1980). For example, the pressure at homogenization of a halite-bearing inclusion in which the vapor bubble disappears at 3 10°C and the halite disappears

Experimental determination of the halite liquidus and isochores for a 40 wt% NaCl solution 1055

200 400 600

Temperature 0

( C)

800

FIG. 2. Partially schematic diagram showing the relationship between the P-T formation conditions and the mode of homogenization of H20-NaCI fluid inclusions with a salinity of 40 wt%. The vapor-pressure curve for a 40 wt% NaCl liquid [L(40) + V] was calculated using equations in Bodnar ( 1992a). Inclusions trapped in Field A homogenize by disappearance of the halite followed by vapor-bubble disappearance at some higher temperature along the liquid- vapor curve [L (40) + V] . Inclusions trapped in Field C exhibit vapor-bubble homogenization first, followed by halite dissolution at some higher temperature along the liquidus [L(40) + H]. Inclusions trapped along the dashed isochore B homogenize by the simultaneous disappearance of halite and vapor at the temperature defined by the intersection of the liquidus [L(40) + H] and the liquid-vapor [L(40) + V] curves, represented by the dot.

at 400°C has been estimated as 650 bars, 1100 bars, and 5000 bars, using the ROEDDER and BODNAR ( 1980), LEMM- LEIN and KLEVSTOV ( 196 1 ), and LYAKHOV ( 1973) techniques, respectively (see ROEDDER and BODNAR, 1980). A rigorous evaluation of the validity of the three different techniques has not been possible owing to a lack of information on the P-T slopes of the liquidi and the isochores in the liquid

+ halite field in the H20-NaCl system. GUNTER et al. (1983) and KOSTER VAN GROOS (1991)

have determined the P-T slopes of the liquidi for high-salinity solutions (>50 wt% NaCl) using DTA techniques. GUNTER et al. ( 1983 ) obtained the positions of the liquidi by measuring the halite nucleation temperatures during cooling at different rates, and extrapolated these data to a zero cooling rate. KOS- TER VAN GROOS ( 199 1) determined the locations of the liquidi during both heating and cooling runs, but he reports the positions of the liquidi based on results of heating runs because he believes the cooling runs give incorrect temperatures that are too low owing to nucleation problems. The two studies are in close agreement concerning the slopes of halite liquidi determined from cooling runs, and also agree for pure NaCl and other very high salinity compositions. However, the slopes reported by GUNTER et al. ( 1983) and the preferred slopes of KOSTER VAN GROOS ( 199 1 ), i.e., those determined from heating runs, begin to diverge with decreasing salinity. Extrapolation of data from the two different studies into the salinity range corresponding to that of most natural inclusions

which homogenize by halite dissolution (30-50 wt%), results in predicted slopes which are significantly different in both magnitude and sign. Thus, at 2 kbars the liquidus temperature for a composition of 40 wt% NaCl predicted by the extrapolated data of GUNTER et al. ( 1983) and by a linear extrapolation of the heating data of KOSTER VAN GROOS ( 1991) would be 310.3”C and 336.3”C, respectively, or a difference of 26°C. This temperature difference corresponds to a salinity difference of 5 wt% NaCl (37.8 wt% predicted by GUNTER

et al., ( 1983); compared to 42.8 wt% predicted by KOSTER VAN GROOS, ( 199 1))) if solubility data along the vapor-saturated solubility curve are used to interpret the results, as is done in most fluid inclusion studies.

In order to accurately interpret microthermometric data for all three types of halite-bearing fluid inclusions described above, we must have information on ( 1) the solubility of halite as a function of temperature along the vapor-saturation curve; (2) the vapor pressure as a function of salinity and temperature; (3) the P-T slope of the halite liquidus as a function of salinity; and (4) the isochores in both the single- phase and two-phase (liquid + halite) fields. Recently, STER- NER et al. ( 1988) presented an equation, based on experimental results, for the vapor-saturated solubility of NaCl in water over the range O-801 “C, and BODNAR et al. ( 1985) presented data for the vapor pressures of H20-NaCl solutions having salinities I 90 wt% NaCl. These results have been summarized by BODNAR ( 1992a). In this study, the P-T

1056 R. J. Bodnar

position of the halite liquidus for a salinity of 40 wt% NaCl

has been determined using synthetic fluid inclusions. Addi-

tionally, the slopes of the constant liquid-vapor homogeni-

zation temperature (iso-Th) lines have been determined to

800°C and 6 kbar.

METHODOLOGY

Experimental Procedure

Experimental details for producing synthetic fluid inclusions have been described previously (STERNER and BODNAR, 1984; BODNAR and STERNER, 1987). and only those aspects which are specific to this study are discussed here. All synthetic fluid inclusions were made using pre-fractured quartz cores (see below), and the capsule material was platinum. Because the bulk salinity (40 wt% NaCI) ofinclusions used in this study was greater than the solubility of NaCl in water at room temperature (~26.4 wt%). it was necessary to load water and NaCl into the capsules separately to generate the desired composition. Sodium chloride was always loaded first, and an amount of water calculated to give the desired composition was loaded next using a microliter syringe. Owing to dilliculties in loading such small amounts of material precisely. the final composition ranged from 39.90-40.10 wt? NaCI. This range in compositions corresponds to a 2.4”C range in halite dissolution temperature (from 32 I .6”-324,O”C) along the vapor-saturation curve according to the equations in BODNAR et al. ( 1989). The loaded capsules were run in cold-seal pressure vessels at temperatures ranging from 350”-800°C and pressures of l-6 kbars. Run durations lasted from 5 days to 2 weeks, with longer run durations generally corresponding to lower formation temperatures. After the run. the samples were prepared for microthermometric analysis using standard procedures described by BODNAR and STERNER ( 1987).

When producing inclusions with high salinities or containing components which are slow to dissolve. it is often necessary to use an in situ fracturing technique to assure that the solution has reached equilibrium before the inclusions are trapped (STERNER, 1992). During the early stages of this study. several samples were run at P- 7‘conditions along the dashed isochore B in Fig. 2 to produce inclusions with similar temperatures for liquid-vapor homogenization and halite dissolution. The halite dissolution temperatures of inclusions within individual samples agreed with values predicted by equations in BODNAR et al. ( 1989) for a salinity of 40 wt% NaCI. indicating that all of the NaCl had dissolved before the inclusions were trapped. Thus, it was not necessary to employ the in situ fracturing technique in this study. It should be noted. however. that in a small percentage of the runs the halite dissolution temperatures were sufficiently different. and always much higher (on the order of several tens to hundreds of degrees) than the expected values of ~323°C. This behavior suggests that either immiscibility occurred during the run (although vapor-rich inclusions were not observed) or that leakage occurred during welding of the capsule (resulting in water loss from the capsule). When such samples were encountered, they were dis- carded and a new sample was prepared at the same P-7’condition. In every case, the duplicate sample gave values much different than the original (incorrect) values and in agreement with other data along the isobar or isotherm.

Each sample containing synthetic fluid inclusions was examined on a gas-flow heating/cooling stage that was routinely calibrated at O.O”C and 374. I “C using the ice-melting and homogenization temperatures. respectively, of a pure water synthetic fluid inclusion having the critical density. The reproducibility of the measurements over this temperature range was generally *O. I “C. and the accuracy has conservatively been estimated as +2.0°C in the temperature range over which halite dissolved (=300-325°C). The temperatures of liquid-vapor homogenization [ Th (L-V)] and halite dissolution [ Tm (halite)] were measured for I S-20 inclusions selected from several different healed fractures in each sample. Only those samples which gave reproducible and consistent temperatures from several fractures were used in this study. Additionally, many duplicate samples were run at the same P-Tconditions (see Tables I and 2). with consistent results between samples run at the same conditions.

Experimental conditions and microthermometric data for inclusions used for the liquidus determination are summarized in Table

1. Microthermometric data were obtained from a total of 560 inclusions from thirty-five samples. The total range in measured halite dissolution temperatures in a given sample varied from 0.6-10.1 “C, with twenty-three out of the thirty-five samples exhibiting a range of 5°C or less. This observed range in temperatures ofdaughter mineral dissolution for fluid inclusions trapped in the single-phase field is similar to that reported in other synthetic fluid inclusion studies (cf. STERNER et al.. 1988). and is typical of the synthetic fluid inclusion technique. Table 2 contains experimental and microthermometric data for samples which exhibited homogenization by vapor-bubble disappearance and which were used to define the iso-Th lines within Field A. as described below.

Location of Liquidus

The assumptions and logical steps employed in locating the P-T position of the 40 wt% NaCl liquidus are as follows. First, liquid- vapor homogenization temperatures [Th (L-V)] from the different samples were plotted along formation pressure isobars as a function of formation temperature, and the data were smoothed graphically. These data were then used to construct iso-Th lines within the one- phase liquid held. and the slopes of the isochores in P-T space were determined. The results were fit using a simple linear model describing the relationship between Th (L-C’) and the slope of the iso-Th line in the one-phase field to provide the following equation:

dP/dT(bars/“C) = 25.9 - O.O364*[Th(L-I’)], (I)

where dT/dP is the slope of the iso-Th line in bars/“C and Th (L- 1’) is the average measured liquid-vapor homogenization temperature (in “C) of the inclusions in a given sample.

Equation I. combined with the measured temperatures of liquid- vapor homogenization and halite dissolution, was used to determine the pressure along the liquidus at the temperature of halite dissolution for each of the 25 samples listed in Table I. For example, seventeen inclusions in a sample run at 500°C and 6 kbar and containing 39.96 wt%, NaCl showed an average liquid-vapor homogenization temperature of 191.5”C (Table I ). According to Eqn. I, the slope of the iso-Th line for this sample is 18.93 bars/“C. Extrapolation of a line with this slope from the formation conditions (500°C. 6 kbar) to the average measured halite dissolution temperature ( 3 I3.2”C) gives a liquidus pressure of =2.47 kbar (Fig. 3 ). The intersection of the iso- Th line with the measured minimum and maximum halite dissolution temperatures for this sample gives liquidus pressures of =2.43 and 2.52 kbar. respectively (Fig. 3, inset). This same procedure was used to determine the average liquidus pressure as well as the range in liquidus pressures for each of the thirty-five samples, and these results are listed in Table I.

RESULTS AND INTERPRETATION OF DATA

Halite Liquidus

Pressures along the liquidus determined as described above

are plotted as a function of the measured halite dissolution temperature [ Tm (halite)] on Fig. 4. The data illustrate clearly that the average Tm (halite) decreases with increasing pressure. Note. however, that the slope of the Tm (halite) vs. P trend flattens with increasing pressure, with a notable change in slope at about 2 kbar. In fact, this trend is exactly what

one would expect for pressures determined using the synthetic fluid inclusion technique, for reasons described below.

The assumption employed in the determination of pressures along the liquidus is that the inclusions behave as constant volume, i.e., isochoric systems. During heating from room temperature to the temperature of liquid-vapor homogenization, the inclusion volume will increase insignifi- cantly owing to thermal expansion of the quartz host. The volume change resulting from internal pressure in the fluid inclusions at this point can be ignored, as the pressure inside

Experimental determination of the halite liquidus and isochores for a 40 wt% NaCl solution

ed is the calculated liquidus pressure (P lqds)

350 350 350

350

400

400

400

450

4.50

350

400

450

500

350

400

400

400

500

500

550

600

400

400

500

500

500

600

400

400

500

600

600

600

700

700

1.0 39.98

1.0 40.02

2.0 40.08

2.0 39.95

2.0 40.04

2.0 39.95

2.0 40.10

2.0 40.04

2.0 40.09

3.0 40.06

3.0 39.95

3.0 39.98

3.0 39.98

4.0 40.02

4.0 40.01

4.0 39.97

4.0 40.01

4.0 40.05

4.0 40.00

4.0 39.98

4.0 39.98

5.0 40.03

5.0 40.00

5.0 39.90

5.0 40.00

5.0 40.02

5.0 40.03

6.0 40.08

6.0 39.90

6.0 39.96

6.0 40.00

6.0 40.01

6.0 40.00

6.0 40.04

6.0 40.00

3 4

18

9

16

15

8

19

13

17

15

13

16

17

39

24

12

31

18

13

18

14

14

23

13

16

18

16

9

17

17

15

13

17

le

292.7 1 284.3 - 296.3

294.0 291.3 - 297.7

238.0 222.9 - 252.7

244.2 240.6 - 246.5

219.4 259.5 - 287.9

274.2 272.9 - 277.8

271.5 260.9 - 280.2

315.2 305.1 - 327.5

315.7 297.8 - 328.7

211.1 208.0 - 217.2

244.6 241.3 - 249.4

269.2 268.0 - 271.9

306.6 306.0 - 308.3

167.7 165.5 - 171.5

205.2 201.7 - 214.0

210.9 202.2 - 218.2

199.0 197.8 - 200.8

265.6 261.5 - 269.6

262.2 260.1 - 268.7

291.1 288.8 - 298.8

323.1 321.8 - 323.1

156.5 153.8 - 158.7

157.0 153.9 - 163.8

236.5 234.6 - 237.1

216.7 214.0 - 219.8

222.3 218.3 - 225.5

281.6 278.8 - 283.5

153.4 136.8 - 164.2

144.7 141.9 - 149.8

191.5 186.3 - 197.6

246.0 245.1 - 247.8

245.3 239.1 - 248.8

240.6 237.1 - 251.7

293.4 284.3 - 299.2

290.9 287.7 - 297.2

319.0 316.5 - 320.3 0.53 IO.49 - 0.551

320.7 320.4 - 321.7 0.56 lo.55 - 0.571

315.5 313.5 - 317.3 1.41 [1.37 - 1.441

315.3 312.0 - 319.4 1.41 [1.35 - 1.481

318.0 315.5 - 319.6 0.71 (0.67 - 0.741

317.9 316.5 - 320.9 0.69 [0.67 _ 0.741

313.6 311.6- 319.3 0.62 [0.58 - 0.711

323.6 319.0 - 326.3 0.18 [O.ll - 0.221

322.1 318.1 - 325.3 0.17 [O.lO - 0.211

310.1 305.0 - 311.8 2.27 L2.18 - 2.301

313.8 313.2 _ 317.5 1.54 [1.53 - 1.60]

316.2 315.5 - 317.9 0.85 LO.84 - 0.871

321.8 321 .O - 322.4 0.38 LO.36 _ 0.381

311.9 308.4 - 315.6 3.25 [3.18 - 3.321

312.9 309.5 - 317.7 2.40 [2.33 - 2.481

305.9 305.0 310.5 2.29 [2.27 2.371

313.6 313.0 314.2 2.39 12.38 - 2.401

312.1 310.0 - 314.4 0.95 IO.92 - 0.991

316.7 316.2 - 318.2 1.00 [l.Kl- 1.031

320.3 319.3 - 321.6 0.49 LO.47 - 0.511

323.1 323.6 - 324.2 0.10 [0.09 - 0.101

3 12.7 310.7 - 315.3 3.24 (3.20 - 3.291

315.8 312.5 - 317.8 3.30 [3.23 - 3.341

314.4 313.8 - 315.0 1.79 L1.78 - 1.801

316.5 315.6 - 317.0 1.70 L1.68 - 1.711

317.6 316.4 - 321.4 1.75 cl.73 - 1.821

321.4 317.6 - 323.3 0.64 CO.58 - 0.671

315.9 312.6 - 319.2 4.29 [4.23 - 4.361

312.5 311.5 - 314.8 4.20 c4.17 - 4.241

313.2 311.3 - 315.8 2.47 [2.43 - 2.521

316.9 315.9 - 321.6 1.21 [1.19 - 1.291

313.9 311.1 - 316.1 1.15 [l.lO 1.181

314.6 307.2 - 317.3 1.11 CO.98 - 1.161

321.7 320.4 - 323.2 0.25 IO.23 - 0.271

319.8 316.9 - 321.6 0.18 (0.14 - 0.211

7 V Yf = formation temperature (“C); Pf = formation pressure (kbar); Salinity = inclusion salinity in veight percent NaCl; n= number of inclusions measured; Th (ave) = the average liquid-vapor lomogenization temperature (“C); Th (range) = the range in measured liquid-vapor lomogenization temperatures (“C); Tm (ave) = the average halite dissolution temperature (“C); Ym (range) = the range in measured halite dissolution temperatures (“C); P lqds [range] = the . . . . . . . . . . . . . . . .

h h 7 calculated average llqtndus pressure (kbar), wth the range In calculated pressures in brackets.

Table 2. Experimental and microthetmometric data for fluid inclusions which homogenize by vapor bubble disappearance.

450. 1.0 40.00 11 359.0 323.0

500. 2.0 39.99 15 356.3 325.0

700. 2.0 40.02 18 501.7 327.7

800. 2.0 39.97 16 638.3 328.9

700. 3.0 40.02 16 433.4 323.6

600. 4.0 40.03 33 341.4 319.9

650. 4.0 39.98 18 356.0 324.0 700. 4.0 40.08 22 373.6 323.1

700. 5.0 40.04 17 327.7 323.9 700. 5.0 40.01 18 336.1 327.8 700. 5.0 40.03 17 329.2 326.9

Tf = formation temperature (“C); Pf = formation pressure (kbar); Salinity = inclusion salinity in weight percent N&I; n = number of inclusions measured: Th (we) = the average liquid-vapor homogenization temperature (“C); Tm (we) = the average halite dissolution temperature (‘C).

1057

the inclusion is equal to the pressure along the three-phase (liquid + vapor + halite) curve, and will, therefore, always be less than about 80 bars. This is the pressure on the three- phase curve at 323”C, which is the temperature at which the solubility of NaCl under vapor-saturated conditions is 40 wt%. At lower temperatures along the three-phase curve the pressure will be less than 80 bars.

During heating from Th (L-V) to the temperature of halite dissolution the pressure in the fluid inclusions increases rap- idly owing to the much lower average compressibility of the inclusions following vapor disappearance. Although it is not possible to determine the exact pressure-temperature path followed by the inclusion during heating from Th (L-V) to Ttn (halite), the average slope of the path within the halite + liquid field determined in this study varies from about 20- 25 bars/“C. The large increase in internal pressure that results

1058 R. J. Bodnar

6

Temperature (“C)

J- ’ ’ 1 ’ ’ ’ ’ I ’ ’ ’ ’ I ’ ’ ’ ’ I ’ ’ ’ ’

350 400 450 500

Temperature (OC)

550

FIG. 3. P-T diagram illustrating the technique used to locate the pressure along the halite liquidus corresponding to a particular formation temperature and pressure ( T,f, PJ) and measured halite dissolution temperature [ Tm halite]. The intersection of the isochore for the inclusion (heavy solid line) with the average halite dissolution temperature (light vertical solid line) defines the average liquidus pressure [P lqds (ave)] for the sample. The slope of the isochore was determined using Eqn. I The minimum and maximum measured halite dissolution temperatures are indicated by the vertical dashed lines. The P-T region (indicated by the box) of intersection of the inclusion isochore with the minimum, average, and maximum halite dissolution temperatures is shown in the inset. The intersection of the isochore with the minimum [ Tm halite (min)] and maximum [ Tm halite (max)] measured halite dissolution temperatures define the range of pressures along the liquidus.

as the inclusion is heated through the liquid + halite field to determine the temperature of halite dissolution causes the inclusion volume to increase, at first elastically, and later inelastically, resulting in a larger inclusion volume at the temperature of halite dissolution compared to the volume at room temperature, or at the temperature of liquid-vapor homogenization. The result of this increase in inclusion volume is that the pressure in the inclusion is less than the pressure predicted from the intersection of the isochore in the one- phase field with the measured Tm (halite). Thus, each datum point plotted on Fig. 4, calculated assuming a constant volume, must be shifted to the left along the pressure axis (to lower pressures) to bring it into agreement with the actual pressure in the inclusion at the moment the halite dissolved. Furthermore, the higher pressure data points must be shifted by a larger amount than the lower pressure data, because the volume increase, and thus the divergence from isochoricity

is greater for higher pressure inclusions than for lower pressure inclusions.

Evidence for the increase in inclusion volume with increasing internal pressure is provided by results of heating experiments on the inclusions. Those inclusions with Th (L- V) relatively close to Tm (halite), i.e., within several tens of degrees, exhibited Th (L-V) values after measurement of Tm (halite) that were identical to those measured before Tm (halite) was determined. However, as the difference between Th (L-V) and Tm (halite) increased, i.e., as Th (L-V) de- creased, a larger proportion of the inclusions gave Th (L-V) values that were higher after the inclusions were heated to Tm (halite) than they were before heating to this temperature. Moreover, for the lowest Th (L-V) values, all but the very smallest inclusions decrepitated before Tm (halite) was reached, reflecting the very high internal pressures being generated during heating to Tm (halite). Previous work by BOD-


325

g 320

; 315

Z E 310 l-

3oot i

0 1 2 3 4 5

Pressure (kbar)

FIG. 4. Pressure along the 40 wt% NaCl liquidus as a function of halite dissolution temperature [ Tm halite] for synthetic fluid inclusions from thirty-five samples. Each datum point represents the average halite dissolution temperature [Tm (ave)] and average liquidus pressure [P lqds] listed in Table 1. The vertical lines through the data points represent the complete range in measured halite dissolution temperatures for each sample. The single horizontal line in the box represents the maximum error in pressure resulting from the range in halite dissolution temperatures. In all but one case the error in pressure resulting from the variation in Tm (halite) is smaller than the diameter of the data point.

NAR et al. ( 1989) has shown that average-sized (5-25 cc) fluid inclusions in quartz will stretch or decrepitate when the pressure reaches values of 500 to approximately 2500 bars, with smaller inclusions requiring higher pressures than larger inclusions. Very small inclusions, 12 cc, may withstand internal pressures up to 4-5 kbars before decrepitating. These pressures were determined assuming that the volume of the inclusion was constant during heating to decrepitation. As the volume was certainly not constant but, rather, was increasing during heating to the decrepitation temperature, the pressures reported by BODNAR et al. ( 1989) necessarily represent maximum values. Most of the inclusions measured in this study had diameters 25 p.

The effect of nonisochoricity on the calculated slope of the liquidus is illustrated by considering the calculated slope of the liquidus after eliminating various portions of the data set. We assume that the liquidus for 40 wt% NaCl is a straight line in P-T space, as suggested by results of previous studies ( GUNTER et al., 1983; KOSTER VAN GROOS, 199 1 ), and determine the slope of the liquidus by fitting a line through the data using simple linear least-squares regression techniques. The slope of the liquidus calculated using all of the data shown on Fig. 4 is approximately -2.l”C/kbar; using only those data for calculated pressures 13 kbars gives a slope of -3.8”C/ kbar; using only those data for pressures I 1 kbar gives a slope of -9.9”C/kbar.

We have stated two assumptions above, namely that the actual pressure in each inclusion is less than the calculated pressure, and that the difference between the actual and calculated pressures increases as the calculated pressures increases. If these assumptions are correct, then the most accurate liquidus pressure data are those for the lowest calculated pressures, and it might seem reasonable to use only the

lowest pressure data, i.e., data for pressures ~1 kbar, in the regression analysis to determine the slope of the liquidus. However, this approach results in such a small pressure range over which the data are fit, and so few data for the regression analysis, that the calculated slope does not reflect the overall trend that is obvious from visual inspection of the data shown on Fig. 4. Therefore, we have elected to use those samples with calculated liquidus pressures 12 kbars to calculate the slope of the 40 wt% liquidus because this eliminates the higher pressure data and because visual inspection of the data on Fig. 4 suggests that the break in slope of the Tm (halite) vs. pressure trend occurs at about 2 kbars. Using only data for calculated pressures ~2 kbars gives a slope for the 40 wt% NaCl liquidus of -5.5”C/kbar (Fig. 5). This calculated value, as well as the range in calculated values (-2.1 to -9.9”C/ kbar) obtained using the various upper pressure limits described above are plotted on Fig. 6 and compared with the previously published results of GUNTER et al. (1983) and ~(OSTER VAN GROOS ( 199 1) A single data point determined by MILNE ( 1978) for a composition of 2 27 wt% NaCl is also shown for comparison.

As shown on Fig. 6, the results of GUNTER et al. ( 1983), MILNE ( 1978), this study, and data from the cooling runs of KOSTER VAN GROOS ( 199 1) all fall along a similar trend. In fact, the only datum point that diverges significantly from the trend defined by the combined data is that for a composition of 55.3 wt% from a heating run from the study of KOSTER VAN GROOS ( 199 1). Therefore, we have used data from GUNTER et al. (1983), MILNE ( 1978), this study, and data from the cooling runs of KOSTER VAN GROOS ( 199 1) to generate a polynomial equation describing the relationship between the slope of the liquidus and salinity according to

3301.. ‘. 1 ” ” 1, ” I. ” ‘,

325

E 320

Q) C

E

315

E 310 l-

305 Tm (halite) = 323.4 - 5.5 l P (kbar)

3001 u.0 0.5 1 .o 1.5 2.0

Pressure (kbar)

FIG. 5. Pressure along the 40 wt% NaCl liquidus as a function of halite dissolution temperature [ Tm halite] for synthetic fluid inclusions of this study in which the calculated pressure was ~2 kbar. The line represents a simple least-squares linear regression of the data shown on the diagram. Each datum point represents the average halite dissolution temperature [ Tm (ave)] and calculated liquidus pressure [P Iqds] listed in Table I. Vertical lines through the data points represent the total range in measured Tm (halite) for each sample, and the horizontal lines represent the range in pressure resulting from the range in Tm (halite) as shown on Fig. 3. The open circle represents the conditions where Th (L-V) = Tm (halite) (323”C, 80 bars).

1060 R. J. Bodnar

25

0 Gunter et al. (1983)

1 Koster Van Groos (1991) [heating data]

-20 20 40 60 80 100

Salinity (wt. %) FIG. 6. Comparison of the experimentally determined slope of the 40 wt 9io NaCl liquidus from this study with

previously published experimental values. The filled circle labeled “This Study” is the slope predicted (-5.5”C/kbar) using only data for calculated pressures 52 kbars, as described in the text. The calculated dT/dP values in this study range from -9.9”C/kbar, using only data with calculated liquidus pressures I I kbar, to -2. I “C/ kbar if all of the data are included in the regression analysis. This range is represented by the vertical line through the datum point. The regression line incorporates data from GUNTER et al. ( 1983). MILNE ( 1978), this study, and the cooling run data of KOSTER VAN GROOS ( I99 I ). The data points from KOSTER VAN GROOS ( 199 I ) were generated by fitting a simple regression equation to heating and cooling data listed in his Table I.

dT/dP( “C/kbar) = -38.38 + 0.90s - 0.0029S2, (2)

where dT/dP is the slope of the liquidus in “C/kbar and S is the salinity in weight percent NaCl. According to Eqn. 2. the slope of the halite liquidus changes from positive to neg- ative at about 5 1.3 wt% NaCI. Note that we have assumed that the slope of the liquidus for a given salinity is independent

of pressure. However, KOSTER VAN GROOS ( 199 1 and pers. commun., 1993) suggests that the slopes of the liquidi are a function of pressure, particularly for more water-rich compositions. In this study uncertainties in pressure estimation at the moment of halite dissolution described above preclude

a rigorous evaluation of the effect of pressure on the slope of the 40 wt% NaCl liquidus and we have assumed that the slopes do not change with pressure.

The data of GUNTER et al. ( 1983) and KOSTER VAN GROOS

( 1991) were obtained using a different experimental technique ( DTA) than that used in the present study, and neither of these authors suggested that their data could or should be extrapolated beyond the limits of their experimental com-

positions. Further, there is no reason a priori to indicate what form any extrapolations to lower salinity would follow. We have chosen to use a second-order polynomial fit, as rec- ommended by Chou (pers. commun., 1993).

Equation 2 has been used to calculate the P-T position of the liquidi at regular ten weight percent intervals from lOO- 30 wt% NaCI, and the results are plotted on Fig. 7.

Volumetric Properties

It should be noted that although the cooling data of KOSTER Synthetic fluid inclusions provide a simple technique for VAN GROOS ( 199 1) agree reasonably well with the other data determining the PVT properties for fluids of geologic interest shown on Fig. 6, KOSTER VAN GROOS ( I99 1) dismisses the ( BODNAR and STERNER, 1985). The results obtained in this cooling data in his study as being incorrect because of nu- study have been combined with information on the vapor cleation problems during cooling. So, even though we have pressures of H20-NaCl solutions ( BODNAR, 1992a) to de- used his cooling data, KOSTER VAN GROWS ( I99 1) calculated termine the location of lines of constant liquid-vapor ho- slopes ofthe liquidi using only his heating data. For the highest mogenization temperature (iso-Th) for a 40 wt% NaCl so- salinities of his study, there is relatively little difference be- lution up to 6 kbars and 800°C (Fig. 8 ). Experimental and tween the heating and cooling results, and both agree closely microthermometric data for those inclusions from this study with the earlier data of GUNTER et al. ( 1983). No significance which homogenized by vapor-bubble disappearance are listed should be attached to the degree with which the data from in Table 2. It should be noted that the iso-Th lines shown in this study agree or disagree with other data shown on Fig. 6. Fig. 8 are not isochores because they have not been corrected


2.0 I---- r 0 m . .

0.0 ’ 0 200 400 600 800 1000

Temperature (“C)

FIG. 7. Pressure-temperature plot of liquidi for the H20-NaCI system calculated from Eqn. 2. The vapor pressure along the three phase (L + V + H) curve was calculated using equations in BODNAR (1992a).

for the small volume changes of the quartz host resulting from thermal expansion and compressibility (see BODNAR and STERNER, 1985; STERNER, 1992). These corrections were not made for a specific reason. The goal of this study is to present information which may be used to interpret and un- derstand microthermometric data obtained from halite- bearing fluid inclusions, and iso-Th diagrams are more ap- plicable than isochoric diagrams for this purpose. Notably, the difference in P-T location of a given iso-Th line and the

isochore that corresponds to that same Th will differ by an insignificant amount at the scale used to construct Fig. 8. Thus, for practical purposes, the iso-Th lines shown on Fig. 8 may be considered as close approximations of the P-T pro- jections of the isochores for a 40 wt% NaCl solution. The actual difference between the two is zero at Th, and increases to a few percent at the highest temperatures (800°C) and pressures (6 kbar) along the iso-Th lines.

The dashed iso-Th line labeled Th (L-F) = Tm (halite) = 323°C shown in Fig. 8 represents the loci of P-T trapping conditions over which fluid inclusions will homogenize by the simultaneous disappearance of the vapor bubble and the halite daughter mineral at 323°C. Inclusions trapped to the left of this iso-Th line will homogenize by halite dissolution after the vapor bubble has disappeared, and inclusions trapped to the right of the iso-Th line will exhibit liquid-vapor homogenization after halite dissolution.

IMPLICATIONS FOR FLUID INCLUSION STUDIES

The impetus for initiating this study was our inability to interpret results of microthermometric analyses of halite- bearing fluid inclusions, and the concomitant large variations in estimated P-Tformation conditions that have resulted from assumptions that workers have made concerning PVTX properties of high-salinity aqueous solutions. The results presented here, and similar data for 30 and 50 wt% NaCl solutions from studies currently in progress in our laboratory, will permit accurate determination of the P-T formation conditions using halite-bearing inclusions. Of particular im- portance are data for the slopes of the liquidi and the average slopes of the iso-Th lines within the liquid + halite field.

200 400 600

Temperature (“C)

800

FIG. 8. Lines of constant liquid-vapor homogenization temperature (iso-Th) for fluid inclusions with a salinity of 40 wt% H20-NaCI. The 40 wt% NaCl vapor-pressure curve [ ~3 40) + V)] was calculated using equations in BODNAR ( 1992a), the 40 wt% NaCl liquidus [ L(40) + H] is from this study.

I062 R. J. Bodnar

ROEDDER and BODNAR ( 1980) attempted to evaluate the

different techniques for calculating pressures at homogenization for halite-bearing inclusions which homogenize by halite disappearance, i.e., along the liquidus. The LEMMLEIN and KLEVSTOV ( 196 1) technique, first used by KLEVSTOV and LEMMLEIN ( 1959 ), suggested using data for the slope of

the isochore within the one-phase liquid field to approximate the slope of the isochore within the halite + liquid field. The LYAKHOV ( 1973) technique suggested that the slope of the isochore within the halite + liquid field was much steeper than the isochore in the one phase field, although details of how this conclusion was arrived at were not provided. Thus, depending upon which technique was used to calculate pres-

sure at homogenization of an inclusion with Th (L-V) of 310°C and Tm (NaCl) of 4OO”C, pressures ranging from I 100 bars ( LEMMLEIN and KLEVS~OV, 196 1) to 5000 bars

( LYAKHOV, 1973) are obtained. The geologic significance of these calculations is that, if one accepts the LEMMLEIN and KLEVS-~OV ( 1961) value, porphyry copper deposits are in- terpreted to form in a relatively shallow subvolcanic environment, consistent with current models of porphyry copper genesis. However, the LYAKHOV (1973) interpretation re-

quires much deeper formation conditions, in a batholithic or deep crustal environment.

Based on mass balance constraints and available PVTand

solubility data for vapor-saturated HSO-NaCl solutions, ROEDDER and BODNAR ( 1980) predicted a pressure at homogenization of ~650 bars for the inclusion described above. ROEDDER and BODNAR ( 1980) further suggested that the slopes of the isochores (or iso-Th lines) within the halite + liquid field were considerably less than the slopes of the isochores in the one-phase (liquid) field, contrary to predic- tions of LYAKHOV ( 1973). The average slope of the iso-Th lines in the halite + liquid field (the dot-dashed portions of the 150”, 200”, 250”. and 300°C iso-Th lines on Fig. 8) vary from 24.8 bars/Y at 150°C to 20.3 bars/“C at 300°C. The slopes of the iso-Th lines in the one-phase field range from

2 1.5 bars/ “C for the 150°C iso-Th line to 14.1 bars/ “C for

the 323°C iso-Th line. The origin of halite-bearing fluid inclusions which ho-

mogenize by halite disappearance has puzzled many inclu- sionists. Many have suggested that the presence of such inclusions indicates that the inclusions trapped a halite-saturated solution at elevated temperatures, and pressures above the vapor-saturation pressure. It is true that trapping conditions such as these will result in fluid inclusions which homogenize by halite disappearance, but this is probably not the most common origin of this inclusion type. As noted above, any inclusion trapped within the P-T region bounded by the liquidus and the isochore defining simultaneous disappearance of halite and vapor (Field C, Fig. 2) will homogenize by halite disappearance. In most fluid inclusion studies of porphyry copper deposits, workers report halite-bearing fluid inclusions which display all three modes of homogenization described earlier, with a relatively consistent salinity that is independent of mode of homogenization (cf. BODNAR and BEANE, 1980). The most likely scenario for the origin of these inclusions is the generation of a high-salinity (but halite undersaturated) fluid at magmatic temperatures, either through aqueous immiscibility or by direct exsolution of a

high-salinity fluid from a shallow magma during the final stages of crystallization. Inclusions trapping the high-salinity

fluid at these conditions (Field A, Fig. 2) will contain a halite daughter mineral at room temperature and will homogenize by vapor-bubble disappearance. As this magmatic-hydrothermal fluid cools, P-T conditions may reach the Th (L-V) = Tm (halite) isochore (B on Fig. 2), and any inclusions trapped at this point will homogenize by the simultaneous disappearance of halite and vapor. Continued cooling will move the fluid into the P-T region of trapping in which inclusions homogenizing by halite dissolution are produced (Field C, Fig. 2).

An alternative model for generating halite-bearing inclusions exhibiting all three modes of homogenization is by

pressure fluctuations at a relatively constant temperature. If the P-T conditions are in Field C (Fig. 2), resulting in the formation of inclusions which homogenize by halite-disso-

lution, and subsequently the pressure drops to a value below the Th (L-V) = Tm (halite) isochore (B on Fig. 2)) inclusions which homogenize by vapor-bubble disappearance will be trapped. This is the model which has been proposed to ac- count for the different types and modes of homogenization

of inclusions in the Questa, New Mexico, porphyry molybdenum deposit (CLINE and BODNAR, 1993).

Note that in the temperature decrease model described above the earliest inclusions will homogenize by vapor-bubble disappearance and the later inclusions will homogenize by

halite dissolution, whereas in the pressure decrease model the reverse paragenesis results. Therefore, careful petrographic studies to determine the paragenesis of the inclusions in a given sample will be necessary to distinguish between the two models. Moreover, the pressure decrease model will result not only in halite-bearing inclusions exhibiting all three modes of homogenization, but also in a wide range of vapor-bubble disappearance temperatures for inclusions trapped at essen- tially constant temperature. In this example, those inclusions with the lowest Th (L-V) values will be the earliest trapped, and the highest liquid-vapor homogenization temperatures will be displayed by the latest inclusions. Similar reverse-Th trends have been reported and are expected in magmatic- hydrothermal systems which have undergone large pressure fluctuations during their evolution ( BODNAR, 1992b).

.dc.X.no~l,/~~~~/nc,n/.t-R. Sheets and B. Kutz are thanked for carefully and diligently collecting the microthermometric data for this study, and for assisting with the hydrothermal experiments to produce the synthetic fluid inclusions. Reviews of earlier versions of this manu- script by Alan Anderson. I-Ming Chou, Gus Koster Van Groos, John Mavrogenes, and Mike Sterner have improved the presentation and helped to clarify many points in the text. This research was sponsored by the Division of Engineering and Geosciences, Office of Basic Energy Sciences, U.S. Department of Energy under Grant DE-FGOS- 89ER14065 to RJB.

Editorid hndlin~: M. A. McKibben

REFERENCES

BISCHOFF J. L. ( 199 I ) Densities of liquids and vapors in boiling NaCI-H,O solutions: A P1’TX summary from 300” to 500°C. Amer. J. Sci. 291, 309-338.

BODNAR R. J. ( 1985) Pressure-volume-temperature-composition (PVTX) properties of the system HZO-NaCI at elevated temper-


atures and pressures. Unpub. Ph. D. Dissertation, Pennsylvania State Univ.

BODNAR R. J. ( 1992a) The system NaCI-HzO. Fourth Biennial PA- CROFI Prog. Abstr. pp. 108-I I 1.

BODNAR R. J. ( 1992b) Can we recognize magmatic fluid inclusions in fossil systems based on room temperature phase relations and microthermometric behavior? Geol. Survey Japan Rep. 279, 26- 30.

BODNAR R. J. and BEANE R. E. ( 1980) Temporal and spatial variations in hydrothermal fluid characteristics during vein filling in preore cover overlying deeply buried porphyry copper-type min- eralization at Red Mountain, Arizona. Econ. Geol. 75, 876-893.

BODNAR R. J. and STERNER S. M. ( 1985) Synthetic fluid inclusions in natural quartz. II. Application to PVT studies. Geochim. Cos- mochim. Acta 49, 1855-1859.

BODNAR R. J. and STERNER S. M. ( 1987) Synthetic fluid inclusions. In Hydrothermal Experimental Techniques (ed. G. C. ULMER and H. L. BARNES), pp. 423-457. Wiley.

BODNAR R. J., BURNHAM C. W., and STERNER S. M. ( 1985) Syn- thetic fluid inclusions in natural quartz. III. Determination of phase equilibrium properties in the system H20-NaCI to 1000°C and 1500 bars. Geochim. Cosmochim. Acta 49, 1861-1873.

BODNAR R. J., BINNS P. R., and HALL D. L. ( 1989a) Synthetic fluid inclusions. VI. Quantitative evaluation of the decrepitation behavior of fluid inclusions in quartz at one atmosphere confining pressure. J. Met. Geol. 7, 229-242.

BODNAR R. J., STERNER S. M., and HALL D. L. ( 1989b) SALTY: A FORTRAN program to calculate compositions of fluid inclusions in the system NaCl-KCI-H20. Computers Geosci. 15, 19-41.

CLINE J. S. and BODNAR R. J. (1993) Generation of saline brines from a crystallizing silicic melt: Evidence from the Questa, New Mexico, porphyry molybdenum deposit. Econ. Geol (in press).

GUNTER W. D., CHOU I-M., and GIRSPERGER S. (1983) Phase relations in the system NaCI-KCI-H20. Part II. Differential thermal analysis ofthe halite liquidus in the NaCI-HZ0 binary above 450°C. Geochim. Cosmochim. Acra 47, 863-873.

KLEVSTOV P. V. and LEMMLEIN G. G. ( 1959) Determination of the minimum pressure of quartz crystal formation as exemplified by crystals from the Pamir. Zap. Vses. Mineral. Obshch. 85( 6), 66 I-

666 (in Russian). Translated in Fluid Inclusion Res.. Proc. of COFFI, Vol. IO (ed. E. ROEDDER), pp. 320-326, (1977).

KOSTER VAN GROOS A. F. ( I99 I ) Differential thermal analysis of the liquidus relations in the system NaCl-Hz0 to 6 kbar. Geochim. Cosmochim. Acla 55,28 I 1-28 17.

LEMMLEIN G. G. and KLEVSTOV P. V. ( 196 I ) Relations among the principal thermodynamic parameters in a part of the system HzO- NaCI. Geokhimiva. 196 I f 2 ). 133-I 42. Translated in Geochem- istr.y, 1961(2), Ib8-158. ~

LYAKHOV Y. V. ( 1973) Errors in determining pressure of mineral- ization from gas-liquid inclusions with halite, their causes and ways of eliminating them. Zap. Vses. Mineral. Obshch. 104(2), 385- 393 (in Russian). Abstract translated in Fluid Inclusion Res., Proc. ofCOFF1, Vol. 6 (ed. E. ROEDDER), p. 95, (1973).

MILNE J. K. ( 1978) An experimental study of the system NaCI-Hz0 at 25°C and pressures up to 2.5 kb. In Progress in Experimental Petrology, Fourth Progress Report of Research Supported by N.E.R.C., 1975-1978; The Natural Environment Research Council, Publications Series D, no. II, 1978, Edinburgh, U.K., p. 127- 13 I.

NASH T. J. (1976) Fluid inclusion petrology-data from porphyry copper deposits and applications to exploration. USGS Prof Paper 907-D.

ROEDDER E. and BODNAR R. J. ( 1980) Geologic pressure determi- nations from fluid inclusion studies. Ann. Rev. Earth Planet. Sci. 8,263-301.

STERNER S. M. ( 1992) Synthetic fluid inclusions. XI. Notes on the application of synthetic fluid inclusions to high P-T experimental aqueous geochemistry. Amer. Mineral. 77, 156-l 67.

STERNER S. M. and BODNAR R. J. ( 1984) Synthetic fluid inclusions in natural quartz. I. Compositional types synthesized and applications to experimental geochemistry. Geochim. Cosmochim. Acta 48,2659-2668.

STERNER S. M., HALL D. L., and BODNAR R. J. ( 1988) Synthetic fluid inclusions. V. Solubility relations in the NaCI-KCI-Hz0 system under vapor-saturated conditions. Geochim. Cosmochim. Ada 52,989-1005.

URUSOVA M. A. ( 1975) Volume properties of aqueous solutions of sodium chloride at elevated temperatures and pressures. Russian J. Inorg. Chem. 20, 17 I7- I72 I (English Translation).

synthetic fluid inclusions: xii. the system h20 … bodnar, gca 58.pdfexperimental determination of...

Documents