Effect of oxygen fugacity and water on phase equilibria of a hydrous tholeiitic basalt

Feig, Sandrin T.; Koepke, Jürgen; Snow, J. E.

doi:10.1007/s00410-010-0493-3

Cited by 142 publications

(49 citation statements)

References 59 publications

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“…Tormey et al 1987), the offset is still present when the thermobarometer is applied to clinopyroxene-melt pairs from experiments carried out at 1-7 kbar ( Fig. 12b; Grove et al 1992;Feig et al 2006;Villiger et al 2007;Feig et al 2010). Nevertheless, if a pressure-dependent correction factor is applied to equilibrium low-Mg# clinopyroxene-matrix glass pairs a posteriori (see regression in Fig.…”

Section: Magma Storage Depths and Barometric Inconsistenciesmentioning

confidence: 99%

“…b Plot comparing calculated and observed pressures for equilibrium clinopyroxene-melt pairs from experiments carried out in the pressure range 1-8 kbar. Experimental data were collated from Grove et al (1992), Feig et al (2006Feig et al ( , 2010 and Villiger et al (2007) and are not used in the calibration of the Putirka et al (1996) model. Corrected clinopyroxene pressures shown in (a) were calculated using the regression line shown as a dotted line.…”

Section: Magma Storage Depths and Barometric Inconsistenciesmentioning

confidence: 99%

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The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

Neave

Maclennan

Thordarson

et al. 2015

Contrib Mineral Petrol

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evolved assemblage is close to being in equilibrium with the matrix glass, trace element disequilibrium between primitive and evolved assemblages indicates that they were derived from different distributions of mantle melt compositions. Juxtaposition of disequilibrium assemblages probably occurred during disaggregation of incompatible trace element-depleted mushes (mean La/Yb melt = 2.1) into aphyric and incompatible trace element-enriched liquids (La/Yb melt = 3.6) shortly before the growth of the evolved macrocryst assemblage. Post-entrapment modification of plagioclase-hosted melt inclusions has been minimal and high-Mg# inclusions record differentiation and mixing of compositionally variable mantle melts that are amongst the most primitive liquids known from the EVZ. Coupled highfield strength element (HFSE) depletion and incompatible trace element enrichment in a subset of primitive plagioclase-hosted melt inclusions can be accounted for by inclusion formation following plagioclase dissolution driven by interaction with plagioclase-undersaturated melts. Thermobarometric calculations indicate that final crystal-melt equilibration within the evolved assemblage occurred at ~1140 °C and 0.0-1.5 kbar. Considering the large volume of the erupted tephra and textural evidence for rapid crystallisation of the evolved assemblage, 0.0-1.5 kbar is considered unlikely to represent a pressure of long-term magma accumulation and storage. Multiple thermometers indicate that the primitive assemblage crystallised at high temperatures of 1240-1300 °C. Different barometers, however, return markedly different crystallisation depth estimates. Raw clinopyroxene-melt pressures of 5.5-7.5 kbar conflict with apparent melt inclusion entrapment pressures of 1.4 kbar. After applying a correction derived from published experimental data, clinopyroxene-melt equilibria return mid-crustal pressures of 4 ± 1.5 kbar, which are consistent with pressures estimated from the major element Abstract Major, trace and volatile elements were measured in a suite of primitive macrocrysts and melt inclusions from the thickest layer of the 10 ka Grímsvötn tephra series (i.e. Saksunarvatn ash) at Lake Hvítárvatn in central Iceland. In the absence of primitive tholeiitic eruptions (MgO > 7 wt%) within the Eastern Volcanic Zone (EVZ) of Iceland, these crystal and inclusion compositions provide an important insight into magmatic processes in this volcanically productive region. Matrix glass compositions show strong similarities with glass compositions from the AD 1783-1784 Laki eruption, confirming the affinity of the tephra series with the Grímsvötn volcanic system. content of primitive melt inclusions. Long-term storage of primitive magmas in the mid-crust implies that low CO 2 concentrations measured in primitive plagioclase-hosted inclusions (262-800 ppm) result from post-entrapment CO 2 loss during transport through the shallow crust. In order to reconstruct basaltic plumbing system geometries from petrological data with greater confidence, mineral-mel...

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Section: Magma Storage Depths and Barometric Inconsistenciesmentioning

confidence: 99%

Section: Magma Storage Depths and Barometric Inconsistenciesmentioning

confidence: 99%

The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

Neave

Maclennan

Thordarson

et al. 2015

Contrib Mineral Petrol

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“…For example, the most magnesian olivine crystallized from arc-related magma (e.g., Kamenetsky et al, 2006) have Fo of 92 to 94 mol%, equivalent to the magnesian olivine crystallized from a mantle plume-derived magma with~24% MgO (Thompson and Gibson, 2000), or to the olivine in old refractory continental lithosphere mantle beneath NCC (Zheng et al, 2006). A likely explanation is that under hydrous conditions the increased oxygen fugacity leads to a decrease in the Fe 2+ /Fe 3+ ratio of the melt, which in turn increases the Fo of olivine and Mg# of clinopyroxene (Feig et al, 2006(Feig et al, , 2010. The most magnesian olivine crystallized under hydrous conditions will also have lower CaO (b 0.1% wt.%) than those in relatively dry conditions, e.g., MORBs rarely contain Fo > 90 olivine and generally have CaO > 0.2 wt.% (Fig.…”

Section: Fractional Crystallization Of a Hydrous Parental Magmamentioning

confidence: 99%

Crustal recycling processes in generating the early Cretaceous Fangcheng basalts, North China Craton: New constraints from mineral chemistry, oxygen isotopes of olivine and whole-rock geochemistry

Guo

Wang

et al. 2013

Lithos

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“…assimilation-free) fractional crystallisation of primitive magmas can generate subpermil increases in the d 18 O of melt due to increases in SiO 2 content and the removal of isotopically light mafic mineral phases (Eiler et al 2000;Harris et al 2000;Bindeman et al 2004;Cooper et al 2004;Valley et al 2005;Bolhar et al 2008). Previous modelling of the change in isotopic composition of melt during magmatic differentiation has demonstrated an important mineral control on the precise trajectory taken (Macpherson and Mattey 1998;Bindeman et al 2004;Cooper et al 2004 In arc magmas, the appearance and modal proportion of plagioclase in the crystallising assemblage vary greatly as a function of the water content of the magma (Sisson and Grove 1993;Grove et al 2003;Pichavant and Macdonald 2007;Feig et al 2010). Therefore, variations in the oxygen isotope composition of evolving arc magmas may be anticipated due to variations in water content.…”

Section: Fractional Crystallisationmentioning

confidence: 99%

Cumulate xenoliths from St. Vincent, Lesser Antilles Island Arc: a window into upper crustal differentiation of mantle-derived basalts

Tollan

Bindeman

Blundy

2011

Contrib Mineral Petrol

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In order to shed light on upper crustal differentiation of mantle-derived basaltic magmas in a subduction zone setting, we have determined the mineral chemistry and oxygen and hydrogen isotope composition of individual cumulus minerals in plutonic blocks from St. Vincent, Lesser Antilles. Plutonic rock types display great variation in mineralogy, from olivine-gabbros to troctolites and hornblendites, with a corresponding variety of cumulate textures. O Olivine is up to 0.2% higher than modelled values for closed system fractional crystallisation of a primary melt. We attribute this to isotopic disequilibria between cumulus minerals crystallising at different temperatures, with equilibration retarded by slow oxygen diffusion in olivine during prolonged crustal storage. We used melt inclusion and plagioclase compositions to determine parental magmatic water contents (water saturated, 4.6 ± 0.5 wt% H 2 O) and crystallisation pressures (173 ± 50 MPa). Applying these values to previously reported basaltic and basaltic andesite lava compositions, we can reproduce the cumulus plagioclase and olivine compositions and their associated trend. We conclude that differentiation of primitive hydrous basalts on St. Vincent involves crystallisation of olivine and Cr-rich spinel at depth within the crust, lowering MgO and Cr 2 O 3 and raising Al 2 O 3 and CaO of residual melt due to suppression of plagioclase. Low density, hydrous basaltic and basaltic andesite melts then ascend rapidly through the crust, stalling at shallow depth upon water saturation where crystallisation of the chemically distinct cumulus phases observed in this study can occur. Deposited crystals armour the shallow magma chamber where oxygen isotope equilibration between minerals is slowly approached, before remobilisation and entrainment by later injections of magma.

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Effect of oxygen fugacity and water on phase equilibria of a hydrous tholeiitic basalt

Cited by 142 publications

References 59 publications

The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

The evolution and storage of primitive melts in the Eastern Volcanic Zone of Iceland: the 10 ka Grímsvötn tephra series (i.e. the Saksunarvatn ash)

Crustal recycling processes in generating the early Cretaceous Fangcheng basalts, North China Craton: New constraints from mineral chemistry, oxygen isotopes of olivine and whole-rock geochemistry

Cumulate xenoliths from St. Vincent, Lesser Antilles Island Arc: a window into upper crustal differentiation of mantle-derived basalts

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