The role of P2O5 in silicate melts

The role of P,05

in silicate melts

F. J. RYERSON Department of Terrestrial Magnetism. Carnegie Institution of Washington. Washington. DC ZOOI5. U.S.A.

P. C. HESS Department

of Geological

Sciences. Brown University.

Providence.

RI 02912.

U.S.A.

Abstract-Phase equilibria data in the systems Si02-P20,. P,O,-M.0,. and P?O,-XI,O,-SiO, are employed in conjunction with chromatographic and spectral data to investigate the role of P,03 in silicate melts. Such data indicate that the behavior of PLO5 is complex. PLO5 depolymerizes pure SiOL melts by entering the network as a four-fold coordinated cation, but polymerizes melts in which an additional metal cation other than silicon is present. The effect of this polymerization is apparent in the widening of the granite-ferrobasalt two-liquid solvus. In this complex system PLOj acts to increase phase separation by further enrichment of the high charge density cations Ti. Fe. Mg. Mn. Ca. in the ferrobasaltic liquid. P20J also produces an increase in the ferrobasalt-granite REE liquid distribution coefficients. These distribution coefficients are close to 4 in P,O,-free melts. but close to I5 in P,O,-bearing melts. The dual behavior of PLO5 is explained in a model which requires complexing of phosphate anions (analogous to silicate anions) and metal cations in the melt. This interaction destroys Si-0-M-0-Si bonds polymerizing the melt. The higher concentration of Si-0-M-0-Si bond complexes in immiscible ferrobasaltic liquids relative IO their conjugate immiscible granite liquids explains the partitioning of P105 into the ferrobasaltic liquid

INTRODUCYIION

determining

THE PHYSICAL and thermodynamic cate melts structure sition

are dependent

notable

the

ambient

exception

continuously structures stricted

melt

may

vary

occurrence

in these parameters.

The

basaltic

vary

only

variations

within

parameters

in properties

those of the crystalline

or

fractional

the change

phase to a greater silicates.

For

enrichment

instance,

mineral-melt melt

distribution

composition.

factors

melt

melt-melt

trace

structure

HESS

element

as a function

an understanding

of mineral-melt

This paper investigates compositions

of

coefficients

Hence,

controlling

comprehension

RYERSON and

values

is essential

of melts in coexisting

pairs and speculates the

PZ05 is not incorporated line phases. Therefore, residual

liquids

in which

to the crystallization regard,

P,05

in early precipitated P,05

may

is enriched

it is eventually

of phosphate play

an

of

sion

upon

the and

of

of phosphorus

has

two

of liquidus

of

and ferroboth

studies

these

in the

lunar of the

rocks

indicate

late stage liquids

important

of PZ05

etrects:

temperatures

(I)

in the

(see PL05-Si02

I). and (2) the expan-

the granitic-ferrobasaltic

two-liquid

1978). Both

factors along

solvus

WATSON, 1976;

magmas.

favor

sition

solvus

which

due

similar

determining

In this

the onset

Depression

of the liquidus

metastable

presents

of stable

the binary 611

tends to

solvi stable. while the

a larger

range

to

of compo-

the

role of PLO5 is developed that

employed

structures

by

phase equilibrium

in a man-

HESS (1977)

of binary

silica melts. At the outset the discussion

in

liquid

line of descent of anhy-

may become immiscibile.

The structural ner

1978;

the liquid

render the otherwise

crystal-

role

HESS. 1975.

immiscibility drous

to

magmas,

depleted

minerals.

of

VISSER and KOSTER VAN DE GRCIOS. 1978; FREESTONE,

in late stage

important

granitic

mesostasis

to our

mineral-melt

basaltic

in

(RYERSON and

on its implications of

P20j

basalts (ROEDDER and WEIDLES. 1970,

magmas

enlarged crystallization

immiscible the

of

of the

melt structure. During

importance

system. LEvtN rr [II.. 1964; Fig.

equilibria.

the effect of P205

magmas

of late stage mngmas is the

and RUTHERFORD. 1977). The enrichment depression

and

the

therefore.

stage

(RUTHERFORD et nl.. 1974: Hess et al., 1975: DIXON

extent

STROM and

WEILL (1978).

in

crystallization

these

have described

late

ROEDDER. 1978). Experimental

WATSON (1976. 1977). HART and DAVIS (1978). LIND(1978)

of

the

of coexisting

magmas

and terrestrial 1971;

of

the structures

re-

in mineral-melt

may very well reflect

of the melt

and.

equilibria

evolution

indication

determining

caused by changes in either composition

external

One

the

silicates

mineral-melt

geochemical

(RYERSON and HESS, 1978).

The

its compo-

and,

immiscibility,

changes

of crystalline

by both

the

with

of liquid

with

structure.

conditions

limits. As a result,

equilibria

than

upon

of a melt is determined

and

of sili-

properties

metal

in

oxide-

focuses upon

data for the Si02-P205

F. J. Rjt:aso\

611

1

and P. C. Ht-ss equilibria

1700

in simple

the activities liquidus

binary

systems can be related

of the oxygen

the chemical

to

species. At the cristobalite

potential

of SiOZ

in the melt

equals that in the cristobalite. IG:b‘: = ii?;‘:.

T”C

hence. for a given standard

state. p’(P. T).

p”(P, T) + RT In(aS:b’l). = p”(P. T) + RT Inla;;;‘:)

PO--’ 2 5.1 !

= /L’(P, T) + RT In(a$‘)‘.

1300

5iirG-700 95 ‘SiO

Therefore, with

P,,o-sIoI.

Analysis

(M,O,)

of

Ps+

systems.

with

is determined.

also supplemented

SiO,

Si02

by data

derived

a model

oxide

New

phosphorus-bearing

oxide. data

melt

and

presented

in terms of this model.

tivity

for

that

Si02-Pz05

by TEN

are

with

cristobalite

with

increasing

phosphosilicate

2Si02.PZOs, the SiO,

appear

phase diagram temperatures addition

of a metal

network-modifying

P,O, and in addition to feature of the

PLOJ

from

is found

low liquidus

reduces

temperatures

system

the

contents.

To

investigation

of

at high SiO,

of these authors liquid

no

metastable

system exists in the literature

HE.SS (1977) has shown activities

to

despite

Si02-P,Os

and (O’-)

poly-

In contrast

subsolidus

(O-)

I). The

SiOz

systems. no stable two-liquid

in the SiO?-P20s

the knowledge

(Fig. the

1713 to I25OC.

M,O,-Si02

of liquidus

depression

for the SiOZ polymorphs

liquidus

many other field

is the marked

in a binary

of the endmember

that

immiscibility

in (Fig.

the activities

melt can be related

the

I). of (0’). to the

components,

where

O”,

O-

and free oxygen

and

O’-

bond

are bridging,

complexes,

and SA.VIS, 1962a. b). Therefore,

respectively

and

be

decreases

is used here as a for various

and divalent

of Si. 0

polymerization

can

coexisting

electronegativity)

cations

and

the metal

(HESS.

in terms of cation

in a

the melt. and its effect upon the

reaction: 0”

+ 0’-

= 2l)-.

instance,

cation

the

oxygen

(4)

associated

of low electronegativity. toward

bond

the

with

i.e.. K’,

more

a metal

will

become

electronegative

Si”

MAKROI~, 1962). This causes a decrease in bond

length

and an increase in the K-O

length. The net energy change of such an inter-

action

is exothermic

This

leads

to

the

of strong

and, therefore.

interaction

the activity

of cristobalite

of SiOl.

causing

cation

becomes

interaction

of

fewer

less stable

and

MO

and

This depresses the

more

The correlation and

breaks down

for

cristobalite

with cristobalite

anamolous

is higher of

comas well

of the liquid

than expected

these

cation’s

leads to a comparatively

tration

in

(TCKIP

cations

have a fundamentally

phase

in silicate

highly

content

that of the mono-

melts,

con-

cations

and for TiOz

(lb)

these

are pro-

ZIPS. Tvvo explanations

behavior with

and

SiO,

liquidus

content

cations are: (1) the higher oxygen compared

oxygen

network-modifying

in the case of P,O,

the basis of P5+s or Ti”s

the

weaker

(Fig. 3).

(Fig. 2). In both cases the SiO, coexisting

electronegative

occurs at lower

between

ZIP

satura-

[see (3)]. As

becomes

nonbridging

tents for a given temperature

of 0’

the cristobalite

Si02

duced. Hence, the liquidus

position

the

lowers the activity

tion surface to lie at high SiOZ contents the metal

K-0-Si

(4) to the right, thus depolymerizing

melt. This strong stability

(RAMHERG. 1954: CHARLES, 1969). production

(la)

nonbridging

mineral-melt

It

temperature

cation

bond within

P,05 aMO = a$-

melts.

of the melt

in

the ac-

is the sum of the ionization

mono-

the interaction

the

asio: :: do

upon

1980: Fig. 2). This trend can be explained

bonds driving

SiO,

The most striking

of 5 mol%

morph

experi-

this range of compositions

on the liquidus

polymorphs.

(ZIP

of the cation’s

the Si-0

minerals,

in silicate

of 0’.

is helpful

cations

at a given ZIP

measure

polarized

has been studied

equilibria

content

potentials

For

also

and HU~IMEL (1962) for PZOs con-

tents of O-50 mol”j,. Within two

coexisting

to the activity

both

SiOl -P, O5 The system

0’

the SiO,

in

immiscible

pairs

and

of SiOl

(WEYL and

mentally

of the melt

the effects of various

5-O-M

and are

of P,Os

and phosphorus-free

ferrobasaltic

granitic

applied

containing

for the solution

experimental

direct

spectra of

melts

metal

the

data are

by more

complex

and an additional

melts.

a metal

and vibrational

of more

used to construct silicate

and

melts. These data are-then

to the discussion P,O,.

In this manner

The phase equilibria

means. i.e. chromatography phosphate-bearing

content

(Xsio,) may be related

of cristobalite-melt

comparing shown

interaction

the SiOZ

cristobalite

of SiOZ in the melt. and by (In) to the activity

2

Fig. I. Temperature-composition coordinates for the SiO,-polymorph saturation surface (i.e. the liquidus) in the systems Na,O-SiO,. KZO-SiOL. P,Os-Si02 and

system and M,O,-P205

(3)

i

or

(2)

O-

highly

different

melts than do the weakly

charged

of a mole of and divalent

higher the

on for

concencharged

structural

charged

role

cations.

The

role of

PLO5

in silicate melts

613

\ I o5

NSiO 2 7o

\ 0 ca \

1 Fig. 2. Liquidus

Ionization

Potential

compositions of cristobalite (mol”;) at 1500°C plotted against the sum of the ionization potentials of the cation other than Si02 in various MO-%02 systems.

this fact cannot fully resolve the anamolous behavior The first alternative above may be illustrated by a of PzOs shown in Fig. 2. As a result, we must conmodel calculation of the concentrations of 0’. Oclude that Psc (and also Ti”) has a fundamentally and O’- bond complexes in a P20,-Si02 and an different behavior in silicate melts than do the alkali-oxide SiO, system. In this case we have chosen network modifying mono- and divalent cations. K?O-SiOz (Fig. 3). To simplify the calculation, the Comparison of silicate and phosphate mineral equilibrium constant for reaction (4) in both systems structures, along with descriptions of anionic species has been assumed equal to infinity. The concenin silicate (MASSON. 1968; HESS, 1971; BAES, 1970) and trations of bond complexes were then calculated by melts (MEADOWCROFT and RICH~DSON, mass balance using the method of Toop and SAMIS phosphate 1965; WESTMAN and GARTAGANIS. 1957; WESTMAN (196Za. b). This calculation illustrates that the addiand CROWTHER. 1954) indicates that phosphate and tion of a given mol:/, PZO, to a Si02 melt produces silicate anions have very similar structures in which more nonbridging oxygens than the addition of comboth Si”’ and Ps+ tetrahedrally coordinate oxygen. parable amounts of the alkalis (Fig. 3). The general formulas for the anions in these melts are The ditference in oxygen content between P,Os indicating that and I
3

.2

.4

.6

.a

1.0

0

.2

P

.6

.a

IO

Fig. 3. Concentrations of the various types of oxygen bond complexes versus mol% Si02 in the liquid for P205-Si02 and K20-SiO: calculated after the method of Toop and SAMIS (1962a. b) assuming K = zc.

F. I.

61-t

RYERSX

o--P-o-P-o-P-o-P-o-

b

A_

&

b-

Fig. 1. Illustration of the bonding in P20s. P5- is in tetrahedral coordination; three of the phosphorus-oxygen bonds are single bonds. the fourth is a double bond.

The similarity of cationic radii for Si”’ (0.42.A) and P5+ (0.35A) indicate that these cations may be capable of copolymerization: P5* substitutes for SiJ’ in silicate anions. FIXU’Nrt al. (1974) have added up to 20 rnolyf; silica to sodium phosphate glasses and have interpreted the chromatograms as indicative of Si“+ entering phosphate anions. MASSONer al. (1974) have extracted anionic species from blast furnace slags containing 16 wtyi SiO, and 0.6wt% PzOs. Notable among the anions extracted are the chain species SiPO:-, Si,POi;. and Si, _ nPOy;+2.. The occurrence of such species shows that the substitution of P5+ for Si”’ is very common. Additional direct data on phosphorus-oxygensilicon bonding is provided by the analysis of vibrational spectra of binary silicophosphate glasses. Using the differential infrared technique (DIR), WONG (1976) has investigated a full range of compositions in the PtOs-SiO, system. The DIR spectra indicate that both P==O and P-0-Si linkages are present throughout the compositional range. In addition, the differential spectra has been compared to a quantitative model assuming (1) all Si’* are four-fold coordinated to oxygen, all of which are bridging; (2) all P5+ are four-fold coordinated to oxygen, three of which form bridges with Si”‘, the fourth is a P=O linkage; and (3) the oxygen joining a pair of Si and P atoms are randomly distributed in the glasses. On the basis of this comparison they have concluded that P-O-Si linkages reach maximum concentration near 40 mol”/;; P?O j. This corresponds closely to the phosphorus orthosilicate composition which yields the maximum concentration of O- (Fig. 3). In Summary, the data show that P-O-Si bonds are prevalent within P,05-SiO? glasses and that phosphorus and silicon may copolymerize. The decrease in activity of Si02 denoted by the pronounced freezing point depression of the silica polymorphs must be due to this substitution as well as the disruption of the network structure. of the silicate melt produced by the P=O bond. In the next section phase equilibria data and data from more direct methods are used to develop the interaction between P205 and metal cations other than SiOz. P, o,-icI,o,

Structures of both crystalline and glassy phosphates and silicates show some striking similarities. For example, LiPOJ has an infinite pyroxene-type chain

and P. C. Hess

structure (FRASER, 19771, and Caj(P0,)2 forms a nearly complete solid solution series with Ca,SiO, (L~vts et al., 1964). Polymorphs of AIPO, are isostructural with tridymite, cristobalite and quartz. and SLVPSOS (1977) has synthesized aluminum phosphate variants of feldspar. NaAI,PSiOs and KA12PSiOB. In these minerals PO:plays a structural role analogous to that of SiO:-. while in the aluminum-bearing phases, Al + P substitutes for 2Si. The coupled substitution of aluminum (3 +) and phosphorus (5 +) not only provides charge compensation, but in view of the network structure of such minerals, must also be important in allowing phosphorus to form four single P-O bonds. Chromatographic analysis of phosphates glasses indicates that they possess the same type of polydisperse distribution of anions as glassy silicates (WESTMAN and CRO~THER, 1954; WESTUN and GARTACANE,

1957;

MEADOWCROFT and RICHARDSON. 1965).

The distribution of anions is dependent upon the concentration and nature of the metal cations. For instance, MEADOWCROFT and RICHARDSON (1965) have analyzed the distribution of anions in phosphate melts containing Na, Li. Ca and Zn (Fig. 5); the ratio of M,O,/P,Os in these melts in 5,3. Two features worthy of note in these distribution patterns are: (1) the distribution of anions becomes broader and skewed toward larger anions as the electronegativity of the metal cation increases (Na < Li < Ca < Zn). and (2) alkali orthophosphates (i.e., chains where n = 1) do not exist. VAN WAZER (1950) predicted the second feature on the basis that PO:- groups represent a high local concentration of negative charge which cannot be satisfied by the coordination of alkalis. The first feature is consistent with the fact that melts with highly electronegative cations are more

-

123456

I234567HY

n= number

of Phosphorus atoms per chain

Fig. 5. Results of chromatograms of glasses of composition j M.O,-3 PzOJ where M,O, is Li20, Na,O. CaO and ZnO. WtT,A phosphorus in the melt contained in chains of length n is plotted against chain length, )I. Note: (I) the distribution of anions becomes broader and skewed toward longer chains as the electronegativity of M increases, (2) chains of length n = I do not exist for alkali-bearing melts

(after

RICHARDSON. 197-I).

61.5

The role of PLO5 in silicate melts 0

/-

separation. Such phenomenon is common in SiOl-MO systems at high SiOZ contents where a random distribution of nonbridging, O-. and free oxygen. 0’ -. cannot provide a stable coordination poly20 Zn(2.70) hedron for the metal cations. Therefore, the melt splits into two liquids. one enriched in O-, O’- and gxl M. the other enriched in 0’ and SiO,. This is es/ lr” co(z.oz) pecially true for systems containing highly electroI 40 negative cations which interact weakly with SiOr and / ~ have low concentrations of O-. The effects of PZOs on the extent of liquid immiscibility in M,O,-Si02 systems can be compared wi:h those of other cations of high electronegativity, i.e. Ti”+, Fe3+, Cr’+. The TiOr-Si02, Fez03-SiOr and CrzO,-SiOr systems have high temperature fields of liquid immiscibility that cover almost the entire comFig. 6. Enthalpies of formation of crystalline phosphates of positional range (LEVINer at., 1964, 1969). This is due Zn, Ca. Numbers in parentheses are charge densities of cations used here as a measure of electronegativity. -A H to weak interaction between these cations and SiOL. increases as charge density decreases (after RICHARDSON,producing highly polymerized and at most tempera1974). tures unstable liquids. In ternary systems containing two stable binary solvi, the boundaries of the ternary two&quid field on the tiquidus can be approximated polymerized than melts containing less electronegaby linear interpolation between the binary solvi. tive cations (HESS.in press) (Fig. 5). Hence, addition of TiOZ to M,O,-SiO, systems conIn view of the similarities between glassy and crystaining binary solvi. such as CaO-Si02 should talline silicate and phosphate structures, it is interesting to compare the energetics of P-O-M and expand the solvi. Such is the case as demonstrated by Si-O-M bond formation. The enthalpies of forma- the increase in solvus width in the CaO-TiO,-SiOr systems with increasing TiO, tion of the crystalline phosphates are strongly exo- and MgO-TiOr-Si02 content (LEVIN rf of., 1964, 1969). The critical temthermic. becoming more exothermic as the electroperatures also increase with TiO, content. Both of negativity of the metal cation decreases (Fig. 6, modified after RICHARDSON,1974). Comparison of the these effects are consistent with TiO? polymerizing enthalpies of formation of crystalline phosphates with the silicate melt relative to MgO and CaO (HESS, the analagous silicates, i.e. orthosilicate versus ortho1977). The liquidus surfaces of the P205-Si02, phosphate, etc., indicates that P-O-M bond formaTi02-Si02 and K20-Si02 systems are shown in tion is energetically more stable than Si-0-M bond formation. For instance, the enthalpies of formation Fig. 7. In contrast to the behavior of titanium the system has no two liquid field, but disare P,O,-SiO, of Ca-metasilicate and Ca-orthosilicate plays characteristics indicative of depolymerization -21 kcal.mol- ’ and -30 kcal.mol-‘, respectively, even more extreme than that produced by cations of while the enthalpies of formation of the correspondlow electronegativity. Hence, the addition of Pro, to ing phosphates are -42 kcal.moi-l and -45 kcal.mot-t (RICHARDSON,1974). The greater stability of a binary system containing a binary solvus is expected the P-O-M bond is most likely due to the greater electronegativity of P5 + with respect to Sib+.

i”Y

hkO,-P,Os-Si02

The phenomenon of silicate liquid jmmiscibiiity is a useful probe of silicate melt structure (see HESS, 19771, and may be of use in evaluating the structures of ternary ~OY-P205-Si0, melts. Liquid immiscibility occurs when the minimization of free energy within a system cannot be reconciled with a random distribution of chemical species. This occurs when an upward convexity exists in the free energy~omposition surface (i.e. the G-X surface) of the liquid such that the free energy of the system (G) may be minimized by liquid-liquid phase separation. For such liquids the negative enthalpy change, AH,i,, associated with more stable molecular configurations in the immiscible phases more than outweighs the positive TdSmi, associated with the decrease in entropy due to phase

Rufile f Liquid

T°C

0

I 2

t 4

, .6 xSiO

I .6

I400 1.0

2

of cristobalite liquidit in the Fig. 7. Comparison KrO-Si02 and P,Os-520, systems. The TiO+Or. features at SiOl contents less than 0.80 refer solely to the TiOr-Si02 system. P20,-SiO, and K20-Si02 have no stable fields of liquid immiscibility.

616

F. J. RYERSON

and P. C. HESS

similar. though compositionally more complex. immiscible granitic and ferrobasaltic magmas (RYERSOS and HESS. 1975. 1975). A cenfral two-liquid field producing immiscible granitic

Mot

%

Fig. 8. Ternar! diagram Mo-SiO,-P,O, illustrating expansion of the two-liquid fields in the CaO-Si02 ;HgO-SiO? systems when P,Os is added. The dashed indicates the composition of the low SiOL melt in CaO-SiO,-P,O, system. and the solid line that in MgO-SiO:-P,05 system.

the and line the the

the solvus.

Such is not the case, howinstance, the Cap-P205-Si02 and ~fgO_P20s-Si02 systems indicate that the binary solvi along the CaO-Si02 and MgO-Si02 joins expand with the addition of P205 (Fig. 7, after LEVIN to contract

ever.

For

et al., 1964. 1969). Similar behavior

is

PbO-P,05-SiO,

Na,O-P,05-Si02

and

also

displayed

by

systems

(LEVIN ef trl.. 1964, 1969). In these systems no stable immiscibility

exists

along

any of the binary

joins.

However. MORIYA et d. (1967) have shown metastable immiscibility

to be present

along

the

Na,O-Si02

join, while HFX (1975) has used thermodynamic ments to suggest metastable immiscibility PbO-SiO,

join. The addition of PZ05

to these binary

systems causes these metastable two-liquid become stable within

the ternary

silica-rich and metal phosphate-rich

fields

displayed

Li20-SiO,

when

system. The

P205

is

of 3mol:<

raises the intersection 1974). This tive to Pb”.

Na’

In summary,

Li20.

composition

to 105O’C (MATUSITA temperature

polymerizing

the

3 SiO,

solvus at 83O’C;

PO5 2 to this

increase in solvus

tive of phosphorus

phenomenon added to

composition

intersects the metastable two-liquid the addition

fields to such that

liquids coexist at

temperatures above the liquidus. Similar are also

argu-

along the

the SiOZ

et al.,

is indicamelt rela-

and Li’.

the data from this and the preceding

sections indicate that P,05

plays a dual role in sili-

cate melts producing effects indicative of depolymerization of simple SiOZ

melts, but polymerizing

melts in which an additional silicon

is present.

P20s

upon

most

metal cation other than

In the next section the effect of

more

complex

melt

compositions

approaching those of natural magmas is discussed. XIORE In this section the ferrobasalt’ two liquid system is summarized VAN IX GRIXS, 1978;

COMPLEX

MELTS

effect of P,Os upon the ‘granitesolvus in the quartz-leucite-fayalite (WATSON. 1976: VISSER and KOSTER FREESTONE, 1978) along with that of

and ferrobasaltic liquids is encountered within the central portion of the quartz-leucite-fayalite system (ROEDDER. 1951: WATS04, 1976: NASLL’SD. 1976). The ferrobusaltic liquid is enriched in FeO. while the granitic liquid is enriched in the feldspathic components K?O. AI,O,. and SiO,. The ferrobasaltic liquid has low Si 0 values and. hence. is characterized by a low degree of polymerization (RYERSON and HESS. 1978). The structure of this melt is dominated by oxygen bond complexes of the nonbridging type. O-. The high nonbridging oxygen content allows the formation ofstable anionic polyhedra around highly electroThe granitic liquid possesses a negative cations, i.e. Fe”. polymerized network structure in which aluminum substitutes in tetrahedral coordination for Si”. This substitution produces a local charge imbalance within the tectosilicate liquid which is satisfied by the coupled substitution of a monovalent cation, i.e. the alkalis, along with Al” (HESS and RUTHERFORD, 1974: RVERSON and HESS. 1975, 1978). In this model. the alkalis occupy sites structurally similar to those occupied by alkalis in the feldspars. WAT~CIS (1976). VISSER and KOSTER VAS DE GRGGS (1978) and FREESTOSE (1978) have performed experiments in which PLO5 has been added to the quartz-leucite fayalite system. These studies provide two important results: (I) the highly electronegative cation. P’+. is enriched in the ferrobasaltic liquids. and (2) the addition of P,O, lo these liquids expands the solvus. The first result conforms to the structural models of Hess and RUTHERFORD (1974) and RI’ERSON and HESS (1975, 1978) while the latter is similar to that produced by the addition of PZOs to simple binary solvi (see previous section). In this experimental study, the trace elements La,O,, Dy,O,, Yb203 and BaO have been added to phosphorusfree and phosphorus-bearing immiscible granitic and ferrobasaltic liquids similar to those in the lunar basalts (ROEDDER and WEIBLEN. 1970, 1971). Respresentative results of undoped phosphorus-free, ‘A’, and phosphorus-bearing. ‘B’. experiments performed at 987’C are presented in Table 1. The integrated bulk compositions of these two-liquid pairs have been calculated from modal analyses of run products and calculated liquid densities (BOTTINGA and WEILL, 1970) and are quite similar (liquid ‘A’ has a slightly higher alkali content than ‘8’) except for the presence of PLO, in liquid ‘B’. Hence, the differences in run results must be attributed solely lo PLO, content. Experimental and analytical procedures, starting materials, and all run results are presented in appendices 1. 2. and 3, respectively. The resulting liquids display fractionation patterns similar lo those in the quartz-leucite fayalite system (Table I). Si and Al are enriched in the granitic liquid along with the monovalent cations K and Na. Fe is enriched in the ferrobasalt along with the other divalent cations Mg. Mn, and Ca. The highly charged cations Ti”’ and P5+ are also enriched in the ferrobasaltic liquid. The presence of P,Os produces some alteration of the melt chemistries. This is shown in Fig. 9 where the oxide concentrations in the P,O,-bearing granitic and ferrobasaltic liquids have been normalized to those in the P,Os-free liquids. The addition of P20s causes an increase in the SiOZ content of the P,Os-bearing granitic liquid, ‘B’. The AllO, content remains virtually constant. but the concentrations of the alkalis. divalent cations. and highly charged cations decrease in granite ‘B’ relative to ‘A’. This depletion of the divalent and highly charged cations in granite ‘B’ is compensated by their relative enrichment in ferrobasaltic liquid ‘B’ (Fxe/Fx’ > I). The divalent cations Ca” and Mg’+ appear to be particularly effected. The monovalent cations K’ and Na- do not demonstrate this sympathetic enrichment in ferrobasalt ‘B’ indicating that their concentration

The role of P,O, Table

I. Compositions

in silicate melts of immiscible

liquids ‘B’

‘.A’ Lo

Hi

si

Lo

Si

Si

ii.i

S:

SiO2

16.73

55.37

38.43

Ti07

2.9’

0.96

3.10

::.lj

.;;a03

31.17 7.33

11.81 11.24

33.05 6.73

il.Oj 5.36

!lgO

0.16

0.08

0.51

O.Oj

o.io

cao

7.68

3.68

11.26

z.07

?lrIO

O.jO

O.lj

0.68

0.10

Na20

0.31

0.78

0.17

O.L?

K*O

1.23

b.38

0.57

G.17

P2Oj

-

6.76

0.22

Total

98.03

98.48

T”C

99.26

99.a9 937’

987”

Compositions

in

wtZ

in the two-melt system ‘8’ must have been lower than that in A. Hence. their concentrations cannot be compared. The K + Na + Ca’AI atomic ratios are less than unity, 0.64 and 0.53. respectively. for P,Os-bearing and P,O,-free granitic glasses. This indicates that (I) if all the aluminum is present within the tectosilicate framework of the granitic glass some cations other than Ca. K. or Na. presumably Fe” and Mg?‘, must be providing charge balance (for Sip’ _ _ Al”). or (2) some of the aluminum in the granitic liquid is present in network-modifying sites. WOOD and HESS(submitted) have concluded that all aluminum should be in tetrahedral coordination at one atmosphere provided sufficient change balancing mono- and divalent cations are present. Since this criteria is satisfied for the granitic melts, it is concluded the aluminum is in tetrahedral coordination in these melts whether or not it occupies a networkforming or network-modifying position. P20J also affects the liquid-liquid distribution coefficients, D(M0) (= wt”/ MO in ferrobasalt/wt% MO in _eranite) and the size and shape of the solvus. Normalizatlon of D(MO)‘s for the P20,-bearing melts to those of the P,O,-free melts (Fig. IO) yield values less than unity for elements which are enriched in the granitic liquids, i.e. Si, Al. K, Na. and values greater than unity for elements enriched in the ferrobasaltic liquid, i.e. Ti. Fe. Mn. Ca. Mg. In wt?,; oxide. this increased phase separation corresponds to approximately a IOOq: increase in solvus width along its projection onto the SiO, join and a 35 and 130% increase for Fe0 and CaO. respectively. Similar effects are produced when P,Os is added to the quartz-leucite-fayalite system (WATSON. 1976; VISS~K and KOSTER VAN DE GROOS, 1978; FREESTONE. 1978).

The results of partitioning experiments for the rare earth elements. La. Dy and Yb are shown in Fig. I I. Expsriments were performed at various concentration levels in order to obtain constant values for the distribution coefficients. The linear projection of these values through the origin is consistent with Henry’s Law behavior in both liquids. The experimental results are those expected on the basis of observed partitioning patterns for highly electronegative major element cations. La, Dy and Yb are all enriched approximately four-fold in the PLO,-free ferrobasaltic melt. These results arc comparable to those produced by WATSON (1976) in the quartz-leucite-fayalite system. With the addition of P,O,. the values of D(La203) and D(Yb,O,) increase to approximately 15.0 indicating a major change in the abundance of REE site concentrations within the two liquids. The partitioning of barium between P,Os-free and P,O,-bearing granite and fcrrobasaltic melts has also been determined (Appendix 3). D(Ba0) is approximately equal to 1.5, indicating only slight enrichment of BaO in the ferrobasalt. This is consistent with the charge density of Ba” which has a value intermediate to that of the REE’s and the alkalis. Morevcr. it should be noted that the value of D(Ba0) is approximately the same in the PLO,-free and P,O,-bearing immiscible liquids.

DISCUSSIOS

The role of P,05 in siliccur rwlrs The behavior When

P,Os

of P,05

is added

in silicate melts is complex.

to a pure SiOL

melt

it produces

10.0

.

5.0 a-

.

: E

FxB/Fx A-

l

GrB!eA - o

I Na

I Cu

I

I

I

I

Fe Mg Mn TI

I

I

.

1.0 -E E 0.5 0

m’

-00

.

l

I

I

---

0

I

K Al Si

Fig. 9. Comparison of P,O,-bearing and PzO,-free granitic and ferrobasaltic liquid compositions (Table I). Filled symbols are wt”; oxide in the P,O,-bearing ferrobasalt normalized to that in the PLO,-free ferrobasalt. Open symbols are computed in the same manner for the granitic liquids. c.c.* 44 J-0

0.1

1

I

I

I

I

I

I

K Si

No Al Ti

Fe Mn Ca Mg

Fig. IO. Normalization of liquid-liquid distribution coefficients for PLOs-bearing melt pairs [D(MO)‘] to those of P,O,-free melt pains [D(MO)“]. Filled symbols are for elements enriched in the ferrobasalt. open symbols for those enriched in the granite.

F. J.

RYERSOSand P. C. HECS

with the phosphorus monomers. This causes the nonbridging bond to close. polymerizing the melt as shown below: I.5 Si-OMO-Si /

t

+ PO2,J

D=lS

,!-i--:r’, /I

* I.5 Si-O-Si

+ Mi.,PO,

(5)

The net reaction corresponds to the polymerization reaction (4) of TOP AND SAMIS(l961a b) 30- = 1.5 O* + 1.5 O’-

0

Q2

0.4 0.6 0.8 WtYeOxide

I.0

1.2 1.4

Hi 510 Ltqutd 2 Fig. 11. Resultsof liquid-liquid p~~rtit~on~ngexperiments for La,O,. DytOj and Yb20, in PzOs-bearing (filled symbols) and P,O,-free melts (open symbols).

The equilibrium constant for this reaction(s) is dependent upon the relative strengths of metal-phosphate and metal-silicate interaction, and each of the metal cations has an equilibrium distribution between silicate and phosphate anions, Sip

decrease in the activity of SiO, as manifested by the freezing point depression of the Si02 polymorphs. Chromatographic and spectral studies of silica and phosphorus bearing glasses indicate that Ps+ copolymerizes with the silicate network. Hence, the decrease in silica activity is not associated with depolymerization of the silicate network, a_sis the case with most mono- and divalent cations. but rather to the substitution of tetrahedrally coordinated Psc as a fundamental component of the network. The same model applies to the coordination of Ti4’ in high SiOZ melts (WOOD and HESS, 1980). This conclusion is quite important as it indicates that physical properties such as viscosity which are correlated with the extent of polymerization in the melt, and thermodynamic properties (the activity of silica) need not be strongly correlated. For instance, the addition of P,Os to SiO, produces a large decrease in the activity of silica, but since P’+ forms part of the network, the viscosity may not be greatly affected. On the other hand, the addition of P,Os to a melt containing SiOZ and another metal cation produces effects indicative of increased activity of silica, i.e. broadening of twoliquid fields and deflection of liquidus boundaries to iovver silica concentrations (KLJSHIRO.1975; HESS, 1980). Therefore, it appears that P,O, and metal cations other than Si form complexes which no longer enter into the silicate network. The mechanism by which P,O, dissolves in silicate melts is portrayed as follows. Consider a silicate melt of intermediate SiOZ content (50mol% SiO?). In this case a majority of the metal cations other than P5+ or Si’” are bonded to oxygens which are also bonded to silicon. M-0-Si. i.e. nonbridging oxygens. When P20, is added in small amounts chromatographic data indicate that it will enter as monomers, or orthophosphate species. Enthaipy of formation data (RICHARDSON,1974) indicate that the phosphate anions have a greater affinity for metal cations than the corresponding silicate anions. As a result, the metal cation coordinated by nonbridging oxygen associated with silicon may now become associated

=

X, in silicate anions XH in phosphate anions’

(6)

a dramatic

The equilibrium constant, Kst,,. is lower for melts in which the metal cation, M, has a strong afBnity for phosphates and a weak affinity for silicates. Hence, the polymerization of metal oxide-silica melts caused by the addition of PtOS with other metal cations. The polymerization of metal oxide-silicate melts caused by the addition of phosphorus explains the extension of the ferrobasalt-granitic liquid solvus. The conversion of non-bridging oxygen to bridging oxygen further limits the number of cation sites in the granitic liquid. Hence, cations which complex readily with phosphorus are further enriched in the ferrobasaltic liquid, i.e. ‘phase separation’ increases. Cations such as Ca” and REE3+ which are readily accomodated in phosphate minerals such as apatite and whitlockite appear to be particularly affected. An equilibrium constant of the type above (6) can be applied to the distribution of cations in a melt in a much more general fashion. In order to maintain charge balance throughout the melt. each cation must occupy a site associated with an anionic complex of some sort. These sites include (I) network-forming sites (denoted by the components KAIO?. NaAIOI, CaAI,O,, BaAlO,. etc). (2) network-modifying sites, (3) sites associated with other nonvolatile anion formers [phosphates, titanates f?)], and (4) those sites associated with volatile anions (COz. SO2. F,. Cf,, etc). Each cation will have an equilibrium distribution between these various sites. This distribution will have important implications to both trace element partitioning and mineral-melt exchange equilibria. For instance, DRAKE (1976) has explained Ca-Na exchange equilibria between pIagioclase and melt as a function of the distribution of Ca between networkforming and network-modifying sites. Consideration of the anionic species to which a cation may be associated is helpful in explaining the partitioning of Na,O, K20 and BaO in the P,Os-bearing granitic-ferrobawltic liquid pairs. The addition of PIOs causes NazO and K,O to become further enriched in the granite while BaO is unaflec-

The role of PLO5 in silicate melts

ted (Figs 11 and 12). In contrast. all the other cations (exclusire of Si” and A13-) become enriched in the ferrobasaltic liquid. This result indicates that Na’. K- and Ba” have a greater affinity for the anionic complexes within the granitic liquid than for the newly formed phosphate complexes in the ferrobasaltic liquid. The behavior of K-. Na’ and Ba” is explained by their strong affinity for sites associated with tetrahedral aluminum. i.e. network-forming sites. CaO and the REE,O,‘s display the opposite effect as a result of their greater affinity for the phosphate complexes in the ferrobasaltic melt. Hence, despite the fact that enthalpy of mixing data (Fig. 6) predicts a greater stability for alkali phosphates compared to alkaline earth phosphates. the enrichment of alkalis in network-forming sites far outweighs the formation of alkali phosphates.

The crystallization of phosphate minerals from a magma can have a profound influence upon the incompatible element concentrations in the residual liquids produced by that fractionation. For instance, it is well-known that apatite and whitlockite can concentrate both rare earth and actinide elements. Apatite may also be important in determining Sr and Ba concentrations in some igneous suites (WHITE et al.. 1979). Hence. in order to better understand the trace element evolution in igneous rocks it is important to evaluate what factors influence phosphate mineral saturation during fractional crystallization. Apatite will crystallize from a magma when the chemical potential of the apatite component in the magma is equal to that of the apatite component in crystalline apatite. Hence, apatite saturation is a function of the activities of CaO and P20s in the magma as well as the fugacities of CO,. HzO. Cl2 and Fz. Granitic-ferrobasaltic liquid distribution coefficients for PZOs (RYERSONand HESS. 1975, 1978; WATSON, 1976) and the PZOs solubility model proposed earlier in this paper indicate that the activity coefficient of PLO, (and CaO) is lower in depolymerized melts than in polymerized melts. Therefore, for a constant P,Os content, the activity of P205 is higher in a polymerized melt than in a depolymerized melt. For given activities of CaO and fugacities of H20, COZ, Cl1 and FI apatite is expected to crystallize from a polymerized siliceous melt. at lower P20s contents than from a more SiO?-poor depolymerized melt. The factors above will influence the point at which apatite crystallizes in the two major igneous fractionation sequences: (I) the Fenner-trend. characterized by enrichment in alkalis and iron while silica and aluminum remain relatively constant, and (2) those trends characterized by enrichment in SiOZ. The differing chemical trends produced by these fractionation sequences are accompanied by different structural trends in the residual liquids. The state of polymerization of liquids residual to the Fenner-trend

619

remains relatively constant due to constant SiOZ. Liquids produced by fractionation trends characterized by increasing SiOZ content become more polymerized. Hence. for comparable physical conditions, e.g. in shallow volcanic bodies. the difference in melt structure should cause phosphate minerals to crystallize at an earlier stage of fractionation in the SiO, enrichment trends than in the Fenner-trend. For instance, CARMICHAELer al. (1971) have shown that magmas from Thingmuli, which follow a fractionation path of Si02 enrichment, become saturated N-ith apatite at basaltic andesite compositions when the P?O, content was approximately 0.5 wt?& Liquids in the Skaergaard intrusion which fractionated along the Fenner-trend did not become saturated with apatite until 97”/, crystallization had taken place, and the PZOs content was 1.75 wt% in the residual ferrobasalt. The differences in composition at which various liquids reach apatite saturation may have interesting effects upon the variations in incompatible element concentration that follow. For example. consider an apatite crystal in equilibrium with two immiscible liquids of granitic and ferrobasaltic composition such as the P,Os-bearing melt pairs in Appendix 3. The granitic-ferrobasaltic REE partition coefficients in this case are close to fifteen. indicating enrichment of the REE’s in the ferrobasalt. As a result the apatitegranite REE distribution coefficient will be fifteen times greater than the apatite-ferrobasalt REE distribution coefficients. These distribution coefficients for the actinide elements will bear a similar relation. though the magnitude may be different. On the basis of this model we would expect that apatite crystallization will have a much greater effect upon the trace element characteristics of suites which show SiOz enrichment compared with those following the Fenner-trend. This is true for the following reasons: (1) apatite saturation will occur earlier in the fractionation sequence of siliceous magmas and (2) apatite concentrates REE and actinide elements to a greater extent when equilibrated with anhydrous acidic magmas as compared to anhydrous basic magmas. The relationship between the activity coefficient of P,Os in the magma and the SiOL content also suggest that basic magmas can reach apatite saturation by assimilating siliceous country rock. The introduction of siliceous material will increase the number of bridging bonds in the melt driving reaction (9) to the left, thereby increasing the activity of PZO,. Depending upon the amount of material assimilated and the proximity to the apatite saturation surface prior to its addition, the hybrid magma may become saturated in apatite without any enrichment in P,Os. Inasmuch as reaction (9) may represent a generalized solubility mechanism for anionic species. i.e. S, C02. FZ, Cl?. etc. in silicate melts. the solubility of these components and their role in determining mineral-melt equilibria will also be a function of melt polymerization.

F. J. RVERSON and P. C. Hess

620

SUMMARY Phase equilibrium. chromatographic and spectral for both simple and complex systems have been employed to investigate the role of P209 in silicate melts. On the basis of these data the following conclusions are drawn:

data

(1) P20s produces a marked decrease in the activity of SiOZ in P20s-SiO, melts. This decrease is attributed to copolymerization of P” in the SiOt network. rather than its action as a network modifier. (2) P205 and M,O, interact strongly in melts producing M&P bonds which are generally stronger than the corresponding M-O-Si bonds. (3) PZOs polymerizes M,O,-P,Os-SiOI melts by complexing with M”’ and destroying Si-OM-0-Si bond complexes. (4) The polymerization caused by P,O, in M,0Y-Si02-P2~s melts expands the graniticferrobasaltic liquid solvus by further enriching the feldspathic components. Si, Al. K. Na in the granite while depleting the high charge density cations, Fe, Mg. Mn. Ca, Ti. The enrichment of K and Na in the granitic melt is indicative of the affinity for networkforming sites compared to the sites assoc_iated with phosphate anions. (5) The REE’s are also depleted in the immiscible P,OS-free granites causing their distribution coefficients to increase from approximately 4 to approximately 15. (16) PLO5 is more soluble in depolymerized melts relative to polymerized. Hence, for given fugacities of C02, HzO, F, and CIZ. and activity of CaO, apatite crystallizes from polymerized melts at lower P,Os contents than in more depolymerized melts.

Ackrlowlr~yemr,lrs-The authors wish to thank M. J. DRAKE and an anonymous reviewer for their critical reviews of this paper. The experimental aspects were supported by National Scirnce Foundation and NASA grants EAR74-13378 and NGR-40-002-123. respectively. The final preparation of the paper was done while FJR was supFoundation grant National Science ported by EAR77-13498 to A. W. HOFMANN.

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Si02

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for

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70017.

Proc.

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trace elements between immiscible silicate melts. (abstract] EOS (Trans. Am. Geophjs. Union) 56, 170. R’I.ERSOS F. J. and HESS P. C. (1975) Implications of liquidliquid distribution coefficients to mineral-liquid partitioning. Grochim. Cosmochim rlcrcl 42. 92 l-932. SINPSOS D. R. (1977) Aluminum phosphate variants of feldspar. .qm. .\fimwl. 62, 35 I-?55 TIEN T. Y. and HN~IEL F. A. (1962) The system SiO:-P20r. J. &I. Crram. Sot. 15. 422-42-t. Toop G. W. and Swans C. S. (1961a) Some new ionic concepts of silicate slags. Ctm. .\frrul[. Q. I. 129-152. Toop G. W. and SA~IIS C. S. (196Ib) Activities of ions in silicate melts. Trans. .!lrtull. Sot. .-ll.rf E 227. 492-500. VAN WAZER J. R. (1950) Structure and properties of condensed phosphates. II A theory of molecular structure of sodium phosphate gasses. J. rim. Chem. Sot. 72. 644-647. VISSER W. and KOSTER VAN DE GROOS A. F. (1978) EfTects and TiO, on the miscibility gap in of PLO, K?O-FeO-A120,-SiOZ (abstract). EOS (Trans. Am. Geophys. Union), 59. 401. VWER W. and KOSIXR VAN DE GRCKIS A. F. (1980) The effects of P,OJ and TiO, on liquid-liquid equilibria.in the system K>O-FeC&AIIO,-SiO~. Am. 1. Sci. in WC::: L. R. (1960) The major element variation of the layered se&s of the Skaergaard Intrusion. J. Petrol. I, 3643% W. .>ON E. B. (1976) Two-liquid partition coefficients: experimental data and geochemical implications. Conrrih. iLfitwrd. Prfrol. 56. I 19- 134. WATSOW E. B. (1977) Partitioning of manganese between forstcritr and silicate liquid. Geochinr. Cow~ochr. ACM 41. 1363-1374. WHITTAKER E. J. W. and MUNTUS R. (1970) Ionic radii for use in geochemistry. Grocltim. Cosmochim Acta 34, 945-956. WESTMAN A. E. R. and CROWTHN J. (1951) Constitution of soluble phosphate glasses. J. Am Cmm. Sm. 37, 420-427. WESTMAN A. E. R. and GARTAGASIS P. A. (1957) Constitution of sodium potassium, and lithium phosphate glasses. J. AWL Crrutx Sm. 40, 293-299. WEI.L W. A. and MARROE E. C. (1962) Tllr Consrirution of Ghsst A Dytanlic Inrqmfarion, Vol 1, 427 pp. Wiley. WHITE W. M.. TAPIA M. D. M. and SCHILLINC; J.-G. (1979) The petrology and geochemistry of the Azores Islands. Confrih. Mimwd. Prrrol. 69, 201-214. WOSG J. (1976) Vibrational spectra of vapor-deposited binary phosphosilicate glasses. J. Nomcrpsr. Solids 20, 83-100. WOOU M. I. and Has P. C. (1980) The role of AI,O, immiscible silicate melts. To be published.

in

APPENDIX I EXPERIMENTAL A[VD ANALYTICAL PROCEDURES Starting compositions for this study (Appendix 2) were prepared as gels to which trace elements were then added

in silicate melts

611

as either oxides or carbonates. The starting compositions were then reduced under How of hydrogen at 500’C for 20 min. a treatment experimentall> calibrated to reduce the gel to a state close to the iron-wustite buffer. The material was then wrapped in Mo-foil and sealed in evacuated SiOz glass. The production of a small amount of MOO, on the MO-foil indicates that the f02 was buffered at a state close to the MO-MOO, buffer. At these temperatures the Mo-MoOz buffer is essentially coincident with the ironwustite buffer. Runs were made by taking the charges above the liquidus (IIOO’C) and then slowly cooling (2-3 days) to final temperature. Most runs were equilibrated at final temperature for at least 48 hr. and longer runs (see Appendix 3) indicate that this time is sufficient to achieve maximum phase separation. The runs were quenched in water. Standard thin sections were prepared for all run products. which were then analyzed with an ARL-EMX microprobe in the manual mode. La. Dy. Yb and Ba were all determined at an acceleratine potential of 10 kV while all other elements were determined at 15 kV. Standard beam current was 0.1 PA. though currents were often increased in order to obtain higher count rates for the trace elements. Counting times were determined by current integration. Integration limits were 200 K counts for major elements and 400 K for minor elements. Four replications were made for each spot and IO spots were analyzed for each glass phase in every charge.

APPENDIX 2 INITIAL COMPOSITIONS Table

I.

'A' SiO? TiO; ii;"3 ?igO !GlO cao Na20 K2" p205

Compositions

'8'

61.30

45.12

1.41 7.69 17.62 1.44 0.30 6.58 0.46 3.20

3.08 9.33 31.06 0.56 0.60 9.51 0.24 0.68 0.84

in wt?;.

‘A’ is a l/l mixture of the average of ferrobasaltic and granitic immiscible liquids found as glass inclusions and within the mesostasis of lunar basalts (ROEDDER and WEIBLEN. 1970). ‘B’ is a liquid composition residual to the experimental fractional crystallization of a low TiOz mare basalt, 12038 (HESS et al., 1975).

61’

F. J. RYERSON and P. C. HIS

APPESD1.K 3 COhlPOSITIOSS OF RUS PRODUCTS Table lO?A

2.

1026

l/430

111020

Rur?Rd.

Lo Si

Hi Si

O(W)

Lo Si

Hi Si

D(H0)

Lo Si

Hi Si

D(!lO)

Lo si

Hi Si

D(UO

Sic, TiL'Z ,A?& F*h ugo urn? Cat? K-0 rid P,ji Lid3 us:cpv:;j R
51.09 3.04 6.19 28.77 1.11 o.:s 7.52 1.72 0.36

67.04 1.17 9.78 13.92 0.34 0.22 3.84 4.35 0.66

0.76 2.60 0.65 2.07 1.85 2.13 1.9j 0.10 0.55

47.i? 3.72 5.99 32.21 0.71 0.55 a.03 1.27 0.30

69.02 1.13 10.90 9.09 0.13 0.16 2.83 4.83 0.70

0.69 3.29 0.55 3.26 5.46 3.:1, 2.83 0.26 0.43

4j.j: 1.90 5.57 31.52 0.28 0.93 7.68 0.93 0.23

70.86 0.77 l?.i7 7.54 0.11 0.20 2.50 4.96 0.77

0.54 j.06 o.i4 4.24 2.54 4.65 3.07 0.19 0.36

45.7j i.:2 6.38 28.72 0.52 0.9i 5.29 1.29 0.:1

70.86 1.73 10.83 9.jl 0.16 0.29 3.21 :.90 0.67

0.5: 7.38 0.59 3.02 2.ja 3.3: 2.53 0.26 0.61

O.il

3.72 -

2.21

O.jO

i.L?

T?C31

100.68

2.61,

101.33

100.52

99.59

99.27

Hr a: T f:xl

12

26

4s

rcnrainer

x0

MO

>!!o

1020

1020

T"C

-I-101.66 48 Fe

980

Table 9/1020

-.z.-98.65

101.08

1020

3.

105

107

108

Run no.

Lo Si

Hi Si

D(XO)

Lo Si

Hi Si

D(MO)

Lo Si

Hi Si

D(NO)

Lo Si

ii1Si

D(?IO:

SiO,

48.15 4.13 6.37 26.77 0.73 0.79 8.88 1.45 0.37

67.42 1.48 lO,Q2 10.40 0.50 0.34 4.17 4.62 0.79

0.71 2.19 0.58 2.57 1.46 2.32 2.13 0.31 0.47

44.99 3.62 5.37 27.07 1.54 0.56 8.14 1.00 0.26

71.16 0.93 10.99 7.08 0.19 0.12 2.51 4.90 0.69

0.63 0.49 3.94 0.11 4.67 1.12 0.20 0.13

48.43 3.19 6.13 27.28 1.02 0.50 8.40 1.17 0.30

69.73 1.00 10.92 5.76 0.16 D.lj 2.74 4.89 0.60

0.69 3.19 0.56 3.11 6.38 1.31 3.06 0.24 0.50

47.:9 3.39 6.27 29.07 0.75 0.50 8.02 1.17 0.31

63.75 1.01 10.91 9.23 0.15 0.16 2.97 4.39 0.67

0.69 3.39 0.5; 3.1: 6.66 1.13 2.70 0.27 0 46

2.75

0.60

4.58

7.69

1.10

6.99

3.36

0.79

L.59

2.30

.61

4.57

100.39

101.24

101.24

99.67

100.07

98.89

TiOj Al20, Fe0 XX0 !lnO 00 K70 G2" P2Oj L3203 Yb203 iJ5"' Tota! Hr 3: T final Container T'C

3.89

100.05

99.7r.

216

88

27

27

x0

no

>!U

'(0

1020

1020

1020

1010

Table 4. 112

113

112c

113c

Run no.

Lo si

Hi Si

D(MO)

Lo Si

Hi Si

II

Lo Si

Hi Si

D(X0)

Lo Si

Hi Si

D(?!O)

Si02 TiO2 A12o3 Fe0 ngo %I0 cao K2O Na20 p2°j La2o3 Yb203 DY O3 5.3 b

49.07 2.96 6.27 29.25 0.73 0.46 7.70 1.44 0.31

67.44 1.30 10.19 10.57 0.24 0.20 3.89 4.52 0.67

0.71 2.28 0.62 2.77 1.04 2.10 1.98 0.12 0.46

49.41 3.01 6.36 29.02 0.51 0.49 7.64 1.46 0.14

67.93 1.28 10.48 11.53 0.26 0.20 3.59 4.56 0.66

0.72 2.35 0.61 2.52 2.04 2.45 2.13 0.12 0.52

49.09 2.99 6.57 28.90 0.82 0.46 7.68 1.16 0.37

67.93 1.21 10.10 11.74 0.30 0.21 1.60 4.26 0.62

0.72 2.L3 0.63 2.46 2.73 2.19 2.11 0.12 0.60

49.63 3.08 6.25 29.49 0.71 O.'O 7.70 1.35 0.J9

6i.00 1.11 10.14 12.13 0.33 0.20 3.54 4.10 0.61

0.7: 2.35 0.62 2.13 2.15 2.00 2.13 0.31 0.62

0.9L

.?4

3.92

0.4

.13

3.08

1.1:

.29

3.93

.07

4.Sh

Total

99.11

1::

!I: 99.26

99.66

.3i

:::I:: 100.62

99.38

100.55

99.5L

100.23

Hr ac T final

41

43

47

:7

Conuiner

MO

?lo

?,O

>kl

1020

1020

1020

T'C

lfl20

The role of P20i. in silicate melts

623

Table 5. l?i Lo Si

Xi

K20 ?I?%20

43.17 l.lL 6.2S 27.76 0.65 O.ih 8.55 1.25 0.29

Yb;O3 :::a,

4.2

R””

no.

5 iO_ TiOs ;I’;03 .e ?(gO %lO CA0

D?‘203 BaO

123 Si

Lo Si

Hi Si

51(W)

Lo

7o.ii 1.20 10.66 10.06 0.25 0.15 3.46 4.63 0.68

0.63 2.62 0.59 2.76 2.60 2.93 2.47 0.27 0.43

&a.&8 2.93 6.02 24.62 0.53 0.45 7.76 1.35 0.33

69.17 1.15 10.21. 10.35 0.21 0.13 3.25 4.73 0.69

0.70 ?.SY 0.59 :.6i ?.S? ?.SO 2.33 0.28 O.i8

49.31 2.31 6.36 29.3: 0.88 0.15 7.84 1.?2 0.35

1.00

4.18

2.11

0.59

3.58

:

A

--.I-

100.70

rota1

102.85

98.61

1:1

12:

D(W)

Si

0.38

D(!?O)

LJ 5’.

Hi 5:

D(XO)

65.95 1.18 9.59 13.2R 0.35 0.29 3.86 L.31

19.:0 3.13 6.06 20.03

0.66

0.7i, 2.38 0.6L 2.21 Z.Sl 1.96 2.03 0.39 0.54

66.3, ’ ‘3 _.10.29 11.39 0.27 0.22 3.65 L.Sb 0.6.

0.7i, 2.54 0.65 2.52 2.67 1.91 2.11 0.35 0.53

0.29

3.03

99.9L

0.72

0.52 7.82 1.5Y 0.3i

.036

.3!

100.09

100.:3

99.73

Hr at T final

48

43

48

Container

Ho

?lo

x0

no

1020

1020

1020

1020

T’C

3.60

A

A

L

101.06

%i Si

48

-

Table 6. 142

141 R””

no.

S i07 Ttfl; Al,O) Fe0 ?lpO ?lllO cao R*D Nn2cl

Lo Si

Hi

Si

48.51

70.1’3

3.37 6.64 27.92 0.29 0.49 7.56 1.64 0.63

0.91 10.65 12.60 0.10 0.24 3.62 4.36 1.00

0.55

0.25

97.hO

103.91

143

1&i

Lo SL

Hi Si

DolO)

Lo Si

Hi Si

D(MO)

Lo Si

Hi

‘0.69 3.70 0.62 2.22 2.90 2.04 2.09 0.37 0.63

51.73 3.14 6.77 29.93 0.20 0.43 7.30 1.48 0.63

69.-89 1.24 10.39 12.65 0.10 0.23 3.75 4.15 1.01

0.74 2.53 0.65 2.40 2.00 1.87 2.08 0.37 0.62

L9.32 3.12 6.33 29.99 0.31 0.49 7.85 1.51 0.61

71.24 0.76 10.87 11.64 0.12 0.19 3.14 4.50 1.00

0.69 4.11 0.58 2.58 2.58 2.58 2.50 0.33 0.61

49.00 3.26 6.3X 30. SS 0.28 0.48 i.97 1.11 0.57

71.69 1.05 10.93 10.30 0.13 0.13 2.i3 4.27 1.00

0.68 3.10 0.59 3.06 2.15 2.66 2.92 0.26 0.57

2.20

0.84

0.30

2.80

1.7:

O.L?

4.14

: 2.L6

0.53 -

4.64 -

102.95

103.51

101.26

103.66

D(MO)

Si

D(MO)

p205 LJ203 Ybz03 ;J:O 3 Total

102.06

102.:

Hr st T final

48

65

48

48

container

no

ML?

x0

x0

T’C

1020

1020

1020

1020 _-

Table 7. LSOC

101

Run no.

Lo Si

Hi Si

D(NOot

LO si

Hi

sio2 Ti02

52.19 2.65

64.85 1.32

0.81 2.01

44.41 3.10

;;a”3 $30 MI-IO cao KzO NB20 p205 La203 %%

25.78 7.00 0.28 0.48 6.58 1.83 0.35

14.92 9.57 0.28 0.30 3.92 3.71 0.65

0.73 1.73 1.00 1.60 1.67 0.49 0.54

1.15

0.78

1.47

98.2L

100.03

Dy2°3 BaO Total Hr

302 Si

D(?iO)

Lo Si

Hi

77.12 0.75

0.58 4.13

L1.57 3.11

28.40 6.47 0.18 0.68 12.74 0.76 0.17 2.99 2.14 2.32

10. 4.80lb 0.02 0.10 1.90 4.20 0.37 0.09 0.155 0.14

0.64 S.92 9.00 6.80 6.71 0.18 0.46 33.20 13.80 lb.57

102.04

99.645

303 Si

II

Lo Si

Hi Si

D(HO)

77.13 0.65

0.54 4.78

4:.10 2.65

7’.62 0.85

O.S9 3.11

27.35 6.69 0.16 0.66 11.12 0.68 0.16 2.77

10.15 4.96 0.03 0.02 2.69 4.21 0.46 0.10

0.66 5.51 5.3L 33.00 S.PY 0.16 0.35 27.70

25.3L 7.45 0.17 0.58 ll.SS 0.79 0.20 2.52

Y.S7 5.72 0.0: 0.07 2.69 3.70 0.:5 0.19

0.77 4.43 4.25 a.29 4.39 0.21 0.44 13.26

2.18

1.42

1.34

98.59

100.54

97.S3

99.52

at

T final

48

La

48

49

Container

no

no

xl

x0

96’)

969

969

T’C

1020

F. J. RYERSON and P. C. HESS CO~lPOSlfIONS OF RL’N PRODUCTS PARTIAL. ANALYSES OF P,Os-BEARING EXPERIMENTS Table 1011 Run

no.

Lo

Si

0.71

Hi

Si

0.06

8. IO13

1012 D(!!O)

Lo

Si

Hi

Si

0(4(O)

Lo

Si

til

Si

O(?!O,

IL.3 0.66

o.or,

LT.0

O.&j

0.03

15.0