Interpreting HInterpreting H22O and COO and CO22 Contents in Melt Inclusions: Contents in Melt Inclusions: Constraints from Solubility Experiments and ModelingConstraints from Solubility Experiments and Modeling

Gordon MooreGordon MooreDept of Chemistry & BiochemistryDept of Chemistry & Biochemistry

Arizona State UniversityArizona State University

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OutlineOutlineFocusFocus:: Review recent HReview recent H22O-COO-CO22 solubility experimental data, and to review solubility experimental data, and to review

and assess solubility models for and assess solubility models for natural meltsnatural melts used in the interpretation of used in the interpretation of melt inclusion measurements.melt inclusion measurements.

Review of experimental HReview of experimental H22O-COO-CO22 solubility data: solubility data:

Brief review of a “good” solubility experiment, experimental apparatus, and analytical Brief review of a “good” solubility experiment, experimental apparatus, and analytical techniques used.techniques used.

Solubility data for pure and mixed HSolubility data for pure and mixed H22O-COO-CO22 fluids. fluids.

Review and assessment of HReview and assessment of H22O-COO-CO22 solubility models for natural solubility models for natural

silicate melts:silicate melts:

Models for pure and mixed HModels for pure and mixed H22O-COO-CO22 fluids fluids

Compositionally specific models (e.g. rhyolitic, basaltic)Compositionally specific models (e.g. rhyolitic, basaltic)

General compositionally dependent modelsGeneral compositionally dependent models

Limitations of model useLimitations of model use

Application of compositionally dependent HApplication of compositionally dependent H22O-COO-CO22 solubility models solubility models

to melt inclusion data.to melt inclusion data.

Scope of reviewScope of review•To review solubility To review solubility determinations and modeling determinations and modeling relevant to natural melts and the relevant to natural melts and the interpretation of melt inclusion data.interpretation of melt inclusion data.

•Work done since “Volatiles in Work done since “Volatiles in Magmas” Rev. Mineral, v.30, 1994.Magmas” Rev. Mineral, v.30, 1994.

•Only natural melt compositions Only natural melt compositions (i.e. excludes haploid melts and (i.e. excludes haploid melts and simple synthetic systems).simple synthetic systems).

•For detailed information on HFor detailed information on H22O-O-

COCO22 in silicate melts in general, in silicate melts in general,

read the “bible”.read the “bible”.

The “good” solubility experimentThe “good” solubility experiment

1.1. Relatively large sample volume (to accommodate large Relatively large sample volume (to accommodate large molar volume of fluid and enough sample to analyze).molar volume of fluid and enough sample to analyze).

2.2. Rapid quench from run temperature to form crystal-free, Rapid quench from run temperature to form crystal-free, glassy sample (difficult for hydrous melts).glassy sample (difficult for hydrous melts).

3.3. Near-hydrostatic pressure conditions to minimize run Near-hydrostatic pressure conditions to minimize run failure and error in run pressure estimate (solid media failure and error in run pressure estimate (solid media apparatus).apparatus).

4.4. Precise characterization of volatile content of run Precise characterization of volatile content of run product and composition of fluid (mixed fluid product and composition of fluid (mixed fluid experiments).experiments).

Experimental Apparatus:Experimental Apparatus:•Rapid quench cold seal (to 200-300 MPa, max T~1100°C; Ihinger, 1991; Larsen and Rapid quench cold seal (to 200-300 MPa, max T~1100°C; Ihinger, 1991; Larsen and Gardner, 2004).Gardner, 2004).

•Rapid quench internally heated pressure vessel (to 500 MPa, ~1200°C; Holloway et al, Rapid quench internally heated pressure vessel (to 500 MPa, ~1200°C; Holloway et al, 1992; DiCarlo et al, 2006)1992; DiCarlo et al, 2006)

•Large volume piston cylinder (>300 MPa; to 1600°C; Baker, 2004; Moore et al, 2008)Large volume piston cylinder (>300 MPa; to 1600°C; Baker, 2004; Moore et al, 2008)

BasaltBasalt

RhyoliteRhyolite

Ni-NiO

H2O-CO2 fluid

Moore et al, 2008

Analytical techniques for HAnalytical techniques for H22O and COO and CO22 measurement measurement

Determining Determining glassglass H H22O-COO-CO22 contents (see Ihinger et al, 1994): contents (see Ihinger et al, 1994):Bulk techniques (Bulk techniques (primaryprimary):):

1.1. High T vacuum manometry (HHigh T vacuum manometry (H22O and COO and CO22))

2.2. Karl-Fischer titration (HKarl-Fischer titration (H22O only)O only)

3.3. Elemental Analyzer (COElemental Analyzer (CO22 only) only)

Microbeam techniques for both HMicrobeam techniques for both H22O and COO and CO2 2 ((secondarysecondary):):

1.1. Fourier-transform Infra-red spectroscopy (FTIR)Fourier-transform Infra-red spectroscopy (FTIR)

2.2. Secondary ion mass spectrometry (SIMS)Secondary ion mass spectrometry (SIMS)

3.3. Raman spectroscopyRaman spectroscopyDetermining Determining fluidfluid composition (H composition (H22O-COO-CO22 fluids only) : fluids only) :

1.1. Mass balance/gravimetryMass balance/gravimetrySimple, but error related to fluid mass and scale precision (20-100% error reported).Simple, but error related to fluid mass and scale precision (20-100% error reported).

2.2. Low T vacuum manometryLow T vacuum manometryRequires a vacuum line, precise to ± 10 micromoles of fluid (5-10% relative error).Requires a vacuum line, precise to ± 10 micromoles of fluid (5-10% relative error).

Two critical measurements: HTwo critical measurements: H22O-COO-CO22 content of melt content of melt ANDAND fluid composition fluid composition

Summary of solubility data for pure HSummary of solubility data for pure H22O and COO and CO22 in in

natural meltsnatural melts

Pure HPure H22O (Table 1):O (Table 1):

•Greater than 30 different melt compositionsGreater than 30 different melt compositions

~44-78 wt% SiO~44-78 wt% SiO22; peralkaline to peraluminous; peralkaline to peraluminous

•Broad range in P and TBroad range in P and T

0.1 to 500 MPa; 800-1250°C; good coverage for most compositions0.1 to 500 MPa; 800-1250°C; good coverage for most compositions

Pure COPure CO22 (Table 1): (Table 1):

•Only 7 compositionsOnly 7 compositions mostly mafic compositions (32-55 wt% SiOmostly mafic compositions (32-55 wt% SiO22); rhyolites studied earlier); rhyolites studied earlier

•Dominated by high P (> 1000 MPa) and T (> 1200°C)Dominated by high P (> 1000 MPa) and T (> 1200°C)Due to low solubility of CODue to low solubility of CO22 and increased solidus T; not extremely useful for and increased solidus T; not extremely useful for

understanding melt inclusion measurementsunderstanding melt inclusion measurements

General HGeneral H22O solubility behaviorO solubility behavior

•Relatively large dissolved HRelatively large dissolved H22O contents (1-8 O contents (1-8 wt%; to 20-25 mol%) at magmatic P-T wt%; to 20-25 mol%) at magmatic P-T conditions.conditions.

•Strong postive P dependence, with weaker Strong postive P dependence, with weaker negative T dependence.negative T dependence.

•Total HTotal H22O solubility has a significant O solubility has a significant

compositional dependence (e.g. Moore et al, compositional dependence (e.g. Moore et al, 1998; Behrens & Jantos, 2001).1998; Behrens & Jantos, 2001).

•Less data on mafic compositions due to higher Less data on mafic compositions due to higher T and difficulty quenching HT and difficulty quenching H22O-rich mafic O-rich mafic

melts to glass.melts to glass.

Dissolved HDissolved H22O content in silicic melts (Behrens & O content in silicic melts (Behrens &

Jantos, 2001) as a function of alkali/alumina.Jantos, 2001) as a function of alkali/alumina.

Figure 4

General pure COGeneral pure CO22 solubility behavior solubility behavior•Low dissolved concentration (100-1000’s Low dissolved concentration (100-1000’s ppm) at fluid-saturated magmatic P-T ppm) at fluid-saturated magmatic P-T conditions.conditions.

•Strong P dependence, negative T Strong P dependence, negative T dependence.dependence.

•Strong compositional dependence (e.g. Strong compositional dependence (e.g. Dixon, 1997), but much less data overall Dixon, 1997), but much less data overall relative to Hrelative to H22O solubility. O solubility.

•Dominates fluid saturation behavior of Dominates fluid saturation behavior of magmas.magmas.

•Two infra-red active species: carbonate Two infra-red active species: carbonate (mafic) and molecular CO(mafic) and molecular CO22 (silicic). (silicic).

•Mixed speciation in intermediate Mixed speciation in intermediate composition melts such as dacite and composition melts such as dacite and andesite (Behrens et al, 2004; King et al, andesite (Behrens et al, 2004; King et al, 2002).2002).

DaciteDacite AndesiteAndesite

Solubility data for mixed HSolubility data for mixed H22O + COO + CO22 fluids in natural fluids in natural

meltsmelts•Most important for melt inclusion interpretation, yet only 8 new studies Most important for melt inclusion interpretation, yet only 8 new studies (see (see Table 2)Table 2)..

•Good coverage for calc-alkaline rhyolite melts, but mafic and intermediate Good coverage for calc-alkaline rhyolite melts, but mafic and intermediate studies are sparse, as are alkaline compositions.studies are sparse, as are alkaline compositions.

Silicic:Silicic: ~20-500 MPa, 800-1100°C (e.g. Tamic et al, 2001) ~20-500 MPa, 800-1100°C (e.g. Tamic et al, 2001)Mafic and intermediate:Mafic and intermediate: ~20-700 MPa, up to 1400°C (e.g. Dixon et al, 1995; ~20-700 MPa, up to 1400°C (e.g. Dixon et al, 1995; Botcharnikov et al, 2005, 2006, 2007).Botcharnikov et al, 2005, 2006, 2007).

•Difficult experimental solubility measurements:Difficult experimental solubility measurements:Fluid composition measurement (low T manometry or weight-loss method).Fluid composition measurement (low T manometry or weight-loss method).

Dissolved CODissolved CO22 measurements can be problematic in mixed volatile bearing measurements can be problematic in mixed volatile bearing

glasses:glasses:•multiple speciation in intermediate melts (Behrens et al, 2004; King & Holloway, multiple speciation in intermediate melts (Behrens et al, 2004; King & Holloway, 2002).2002).•potential matrix effects in calibrations of secondary techniques such as SIMS and potential matrix effects in calibrations of secondary techniques such as SIMS and FTIR (Behrens et al, 2004; Moore and Roggensack, 2007). FTIR (Behrens et al, 2004; Moore and Roggensack, 2007).

General HGeneral H22O + COO + CO22 solubility behavior solubility behavior

•Simple linear solubility dependence Simple linear solubility dependence as a function of fluid composition at as a function of fluid composition at low P.low P.

Less than 150 MPa for basalts (Dixon et Less than 150 MPa for basalts (Dixon et al, 1995; Botcharnikov et al, 2005), 200 al, 1995; Botcharnikov et al, 2005), 200 MPa and lower for rhyolite (Tamic et al, MPa and lower for rhyolite (Tamic et al, 2001) and dacite (Behrens et al, 2004).2001) and dacite (Behrens et al, 2004).

•More complex, non-linear More complex, non-linear dependence for both Hdependence for both H22O and COO and CO22 at at

higher P conditions.higher P conditions.

•COCO22 speciation changes with H speciation changes with H22O O

content (molecular COcontent (molecular CO22 decreases with decreases with

increasing Hincreasing H22O)O)

Figure from Liu et al, 2005 (filled squares and circles Figure from Liu et al, 2005 (filled squares and circles from Tamic et al, 2001; triangles, Blank et al, 1993; from Tamic et al, 2001; triangles, Blank et al, 1993; open symbols, Fogel and Rutherford, 1990)open symbols, Fogel and Rutherford, 1990)

Figure from Behrens et al (2004)Figure from Behrens et al (2004)

Rhyolite

500 MPa

200 MPa

Dacite

Compositional dependence of HCompositional dependence of H22O + COO + CO22 solubility solubility

•Dissolved CODissolved CO22 is stabilized by is stabilized by

HH22O in melt (non-Henrian), O in melt (non-Henrian),

particularly at high P.particularly at high P.

•Strong dependence of COStrong dependence of CO22 and and

HH22O content on melt composition O content on melt composition E.g. dissolved COE.g. dissolved CO22 increases w/ increasing increases w/ increasing

CaO, NaCaO, Na22O, KO, K22O, etc (Dixon, 1997; O, etc (Dixon, 1997;

Roggensack & Moore, 2008)Roggensack & Moore, 2008)

•Any HAny H22O-COO-CO22 solubility model solubility model

needs to take these complexities needs to take these complexities into account.into account.

XH2O(fluid)~0.45P ~ 400 MPaT = 1200°C

Figure from Roggensack & Moore (2008)Figure from Roggensack & Moore (2008)

Modeling the solubility of HModeling the solubility of H22O-COO-CO22 in natural melts in natural meltsTypes of models:Types of models:1.1. Regular solutionRegular solution (single (single

composition; Silver and Stolper, composition; Silver and Stolper, 1985)1985)

2.2. EmpiricalEmpirical

3.3. Compositionally dependentCompositionally dependent (includes comp dependent (includes comp dependent regular solution of Papale, 1997, regular solution of Papale, 1997, 1999; Papale et al, 2006)1999; Papale et al, 2006)

Limitations and caveats:Limitations and caveats:• Extrapolation beyond range of Extrapolation beyond range of

data (P, T, or compositionally)data (P, T, or compositionally)• Interpretation of fit parameters Interpretation of fit parameters

(e.g. partial molar volume of H(e.g. partial molar volume of H22O O

and COand CO22))

Extrapolation leads to significant error when inverting melt inclusion volatile Extrapolation leads to significant error when inverting melt inclusion volatile contents to obtain saturation pressure!contents to obtain saturation pressure!

Adventures in solubility model extrapolationAdventures in solubility model extrapolation

Figure comparing rhyolite-HFigure comparing rhyolite-H22O solubility O solubility

models from Behrens & Jantos, (2001).models from Behrens & Jantos, (2001).

•Note good fit of Moore model to data up Note good fit of Moore model to data up to 200 MPa, and instability when to 200 MPa, and instability when extrapolated above 300 MPa.extrapolated above 300 MPa.

Figure showing the compositional variable (PI) from the Figure showing the compositional variable (PI) from the basalt-CObasalt-CO22 solubility model of Dixon (1997). solubility model of Dixon (1997).

•Note that calc-alkaline basalts have significantly Note that calc-alkaline basalts have significantly different CaO/Aldifferent CaO/Al22OO33 (strong effect on CO (strong effect on CO22 solubility). solubility).

•Some give zero or negative PI values.Some give zero or negative PI values.

•Basis for Newman & Lowenstern (2002) VolatileCalc Basis for Newman & Lowenstern (2002) VolatileCalc HH22O-COO-CO22 model that is widely used for melt inclusions. model that is widely used for melt inclusions.

Pressure extrapolationPressure extrapolation Compositional extrapolationCompositional extrapolation

Melt compositional variation in melt inclusions and HMelt compositional variation in melt inclusions and H22O + COO + CO22

solubility modelssolubility modelsHow significant is compositional variation in melt How significant is compositional variation in melt

inclusion suites? (inclusion suites? (See Fig 10 for ref’s)See Fig 10 for ref’s)

Only 2 compositionally dependent mixed HOnly 2 compositionally dependent mixed H22O-COO-CO22

solubility models available:solubility models available:

1.1. VolatileCalc VolatileCalc (Newman & Lowenstern, 2002)(Newman & Lowenstern, 2002)

Rhyolite:Rhyolite: regular solution model for calc-alkaline rhyolite regular solution model for calc-alkaline rhyolite (Silver et al, 1990; Blank et al, 1993). Note: No melt (Silver et al, 1990; Blank et al, 1993). Note: No melt compositional dependence for Hcompositional dependence for H22O or COO or CO22 solubility. solubility.

Basalts:Basalts: regular solution model w/ compositional dependence regular solution model w/ compositional dependence for COfor CO22 calibrated by alkali-rich basalts (Dixon et al, calibrated by alkali-rich basalts (Dixon et al,

1995; Dixon, 1997). No compositional dependence for 1995; Dixon, 1997). No compositional dependence for HH22O in model.O in model.

2.2. Papale et al (2006)Papale et al (2006)

Uses most C-O-H solubility measurements to calibrate a Uses most C-O-H solubility measurements to calibrate a compositionally dependent regular solution model across a compositionally dependent regular solution model across a broad range of P, T, and melt composition.broad range of P, T, and melt composition.

Recently made available for general use by Dr. Mark Ghiorso.Recently made available for general use by Dr. Mark Ghiorso.(http://ctserver.ofm-research.org/Papale/Papale.php)(http://ctserver.ofm-research.org/Papale/Papale.php)

Comparison of VolatileCalc and Papale to silicic solubility dataComparison of VolatileCalc and Papale to silicic solubility data

Rhyolite data from Tamic et al (2001)Rhyolite data from Tamic et al (2001)Dacite data from Behrens et al (2004)Dacite data from Behrens et al (2004)

Calculated fluid compositions and saturation Calculated fluid compositions and saturation pressures for rhyolite (77 wt% SiOpressures for rhyolite (77 wt% SiO22) and ) and

dacite (66 wt% SiOdacite (66 wt% SiO22) versus experimental ) versus experimental

valuesvalues

•Good agreement for both VolatileCalc and Good agreement for both VolatileCalc and Papale with the rhyolite data.Papale with the rhyolite data.

•Note failure of VC to estimate the dacite Note failure of VC to estimate the dacite fluid compositions and pressures (no fluid compositions and pressures (no compositional dependence), while Papale compositional dependence), while Papale matches data quite well.matches data quite well.

Comparison of VolatileCalc and Papale models to basaltic solubility dataComparison of VolatileCalc and Papale models to basaltic solubility data

1.1. VolatileCalcVolatileCalcCalcic and calc alkaline basalt data (45-53 wt% SiOCalcic and calc alkaline basalt data (45-53 wt% SiO22) from ) from

Moore et al (2006) and Moore et al (2008).Moore et al (2006) and Moore et al (2008).

Some of data beyond the stated 500 MPa Some of data beyond the stated 500 MPa limit of VC, but majority is at or below.limit of VC, but majority is at or below.

Systematic overestimation of saturation Systematic overestimation of saturation pressure and underestimation of mole pressure and underestimation of mole fraction of Hfraction of H22O in fluid.O in fluid.

Significant error (up to 50%) in pressure Significant error (up to 50%) in pressure estimate due to extrapolation of the estimate due to extrapolation of the compositional parameter used for COcompositional parameter used for CO22

solubility. The model is unable to solubility. The model is unable to account for the higher COaccount for the higher CO22 solubility in solubility in

calc-alkaline compositions.calc-alkaline compositions.

Comparison of VC and Papale to basaltic experimental dataComparison of VC and Papale to basaltic experimental data

Papale et al (2006)Papale et al (2006)2.2. Papale et al (2006)Papale et al (2006)Basalt data same as for VC, andesite (57 wt% SiOBasalt data same as for VC, andesite (57 wt% SiO22) from ) from

Botcharnikov et al (2007)Botcharnikov et al (2007)

For calculated saturation pressures and fluid For calculated saturation pressures and fluid compositions, values scatter around 1:1 compositions, values scatter around 1:1 line. Up to 30% error in pressure line. Up to 30% error in pressure estimates.estimates.

Large amount of scatter in fluid composition Large amount of scatter in fluid composition estimates (systematic error for calcic estimates (systematic error for calcic basalt). Possibly due to error in fluid basalt). Possibly due to error in fluid measurements used to calibrate model.measurements used to calibrate model.

Best model currently available that can Best model currently available that can account for broad melt compositional account for broad melt compositional variation over magmatic P-T range.variation over magmatic P-T range.

Application of VC and Papale et al (2006) to basaltic melt Application of VC and Papale et al (2006) to basaltic melt inclusionsinclusions

•Significant error in pressure using VC Significant error in pressure using VC for calc-alkaline basalts.for calc-alkaline basalts.

•Isobars and degassing paths do not Isobars and degassing paths do not account for melt composition variation account for melt composition variation (49-52 wt% SiO(49-52 wt% SiO22; 9.5-13 wt% CaO).; 9.5-13 wt% CaO).

Cerro Negro MI data from Roggensack (2001)Cerro Negro MI data from Roggensack (2001)

Isobars and degassing paths calculated using VolatileCalc for Cerro Negro inclusions.Isobars and degassing paths calculated using VolatileCalc for Cerro Negro inclusions.

Application of Papale et al (2006) to basaltic Application of Papale et al (2006) to basaltic melt inclusionsmelt inclusions

Calculated minimum saturation pressures versus Calculated minimum saturation pressures versus calculated fluid composition, measured COcalculated fluid composition, measured CO22 and H and H22O O

content of Cerro Negro melt inclusions using Papale et al content of Cerro Negro melt inclusions using Papale et al (2006).(2006).

•More precise pressure estimates for calc-alkaline melts More precise pressure estimates for calc-alkaline melts (usually lower estimated P).(usually lower estimated P).

•Accounts for solubility dependence on compositional Accounts for solubility dependence on compositional variation in melt inclusions.variation in melt inclusions.

•Recast data allows identification of pressure regions Recast data allows identification of pressure regions critical to fluid/melt evolution of the magma (150-250 critical to fluid/melt evolution of the magma (150-250 MPa).MPa).

•Theoretical degassing behavior (e.g. open vs closed) in a Theoretical degassing behavior (e.g. open vs closed) in a compositionally variable system is not easily visualized.compositionally variable system is not easily visualized.