Crystal-chemical controls on the partitioning of Sr and Ba between plagioclase feldspar, silicate melts, and hydrothermal solutions

Blundy, Jonathan D.; Wood, Bernard J.

doi:10.1016/0016-7037(91)90411-w

Cited by 454 publications

(231 citation statements)

References 63 publications

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“…These high Kd values are surpassed by plagioclase, which contains 613 ppm of Sr, and considering the 23 ppm in the glass, it indicates a mineral-melt partitioning ratio of 30 . The values are in the range inferred and reported in previous studies (Blundy and Wood, 1991;Davies et al, 1994).…”

Section: Rb-sr Isotope Datasupporting

confidence: 87%

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics

Heumann

Davies

Elliott

2002

Geochimica et Cosmochimica Acta

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Abstract-In this study, we present 87 Rb/ 86 Sr and 230 Th/ 238 U isotope analyses of glasses and phenocrysts from postcaldera rhyolites erupted between 150 to 100 ka from the Long Valley magmatic system. Both isotope systems indicate complex magma evolution with preeruptive mineral crystallization and magma fractionation, followed by extended storage in a silicic magma reservoir. Glass analyses yield a Rb-Sr isochron of 257 Ϯ 39 ka, which can be explained by a feldspar-fractionation event ϳ150 ky before eruption. Individual feldspar-glass pairs confirm this age result. A mineral 230 Th-238 U isochron in a low-silica rhyolite from the Deer Mountain Dome defines an age of 236 Ϯ 1 ka, but the glass and whole rock do not lie on the isochron. U-Th fractionation of the rocks is controlled by the accessory minerals zircon and probably allanite, which crystallized at 250 Ϯ 3 ka and 187 Ϯ 9 ka, respectively. All major mineral phases contain accessory mineral phases; therefore, the mineral isochron represents a mixture of zircon and allanite populations. A precision of Ϯ1 ka for the mixing array implies that the minor phases must have crystallized within this timescale. Longer periods of crystal growth would cause the mixing array to be less well defined. U-series data from other lowand high-silica rhyolites indicate younger accessory mineral crystallization events at ϳ200 and 140 ka, probably related to the thermal evolution of the magma reservoir. These crystallization events are, however, only documented by the accessory minerals and had no further influence on bulk magma compositions. We interpret the indistinguishable age results from both isotope systems (ϳ250 ka) to record the fractionation of small magma batches by filter pressing from a much larger underlying magma volume, followed by physical isolation and extended storage at the top of the magma reservoir for up to 150 ky.

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Section: Rb-sr Isotope Datasupporting

confidence: 87%

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics

Heumann

Davies

Elliott

2002

Geochimica et Cosmochimica Acta

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“…Fig. 10b uses the equation of Blundy and Wood (1991) for D Sr varying with X An to calculate equilibrium melt Sr. Equilibrium melt compositions slope steeply down from high initial Sr (~1000 ppm) as X An decreases, within both the mugearite/ benmoreite group and trachyte groups. Closed system crystallisation of plagioclase is the most obvious explanation of the trend within a group -plagioclase crystallises, progressively exhausting the melt of Sr. Plagioclase fractionation is limited, at least within the trachytes, as whole rock Sr is greater than any calculated melt composition.…”

Section: Discussionmentioning

confidence: 99%

The petrogenesis of sodic island arc magmas at Savo volcano, Solomon Islands

Smith

Petterson

Saunders

et al. 2009

Contrib Mineral Petrol

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Savo, Solomon Islands, is a historically active volcano dominated by sodic, alkaline lavas and pyroclastic rocks with up to 7.5 wt % Na 2 O, and high Sr, arc-like trace element chemistry. The suite is dominated by mugearites (plagioclase-clinopyroxene-magnetite ± amphibole ± olivine) and trachytes (plagioclaseamphibole-magnetite ± biotite). The presence of hydrous minerals (amphibole, biotite) indicates relatively wet magmas. In such melts, plagioclase is relatively unstable relative to iron oxides and ferromagnesian silicates; it is the latter minerals (particularly hornblende) that dominate cumulate nodules at Savo and drive the chemical differentiation of the suite, with a limited role for plagioclase. This is potentially occurring in a crustal "hot zone", with major chemical differentiation occurring at depth. Batches of magma ascend periodically, where they are subject to decompression, water saturation and further cooling, resulting in closed-system crystallisation of plagioclase, and ultimately the production of sodic, crystal and feldspar-rich, high-Sr rocks.The sodic and hydrous nature of the parental magmas is interpreted to be the result of partial melting of metasomatised mantle, but radiogenic isotope data (Pb, Sr, Nd) cannot uniquely identify the source of the metasomatic agent.

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“…Rubidium, Ba, and Sr all partition into micas and feldspars, rather than accessory minerals (e.g. Blundy and Wood, 1991) and are used here to model these processes. Rare earth elements partition into micas and feldspars also, but are often controlled by accessory minerals so care must be taken in using them for modelling (e.g.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

Simons

Shail

Andersen

2016

Lithos

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The Early Permian Cornubian Batholith was generated during an extensional regime following Variscan convergence within the Rhenohercynian Zone of SW England. Its component granites can be classified, using mineralogical, textural and geochemical criteria, into five main types, all of which are peraluminous (A/CNK >1.1): G1 (two-mica), G2 (muscovite), G3 (biotite), G4 (tourmaline) and G5 (topaz). G1 granites formed through up to 20% muscovite and minor biotite dehydration melting of a metagreywacke source at moderate temperatures and pressures (731-806°C, >5 kbar). Younger G3 granites formed through higher temperature, lower pressure (768-847°C, <4 kbar) biotite-dominated melting of a similar source. Partial melting was strongly influenced by the progressive lower-mid crustal emplacement of mafic igneous rocks during post-Variscan extension and a minor (<5-10%) mantle-derived component in the granites is possible. Two distinct fractionation series, G1-G2 and G3-G4, are defined using whole rock geochemical and mineral chemical data.Variations in the major elements, Ba, Sr and Rb indicate that G1 and G3 granites underwent 15-30% fractionation of an assemblage dominated by plagioclase, alkali feldspar and biotite to form, more evolved G2 and G4 granites respectively. Decreasing whole rock abundances of Zr, Th and REE support fractionation of zircon, monazite, apatite and allanite. Subsolidus alteration in G2 and G4 granites is indicated by non-primary muscovite and tourmaline and modification of major and trace element trends for G3-G4 granites, particularly for P 2 O 5 and Rb. Topaz (G5) granites show low Zr, REE and extreme enrichment in Rb (up to 1530 ppm) and Nb (79 ppm) that cannot be related in a straightforward manner to continued differentiation of the G1-G2 or G3-G4 series. Instead, they are considered to represent partial melting, mediated by granulite facies fluids, of a biotite-rich restite following extraction of

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Crystal-chemical controls on the partitioning of Sr and Ba between plagioclase feldspar, silicate melts, and hydrothermal solutions

Cited by 454 publications

References 63 publications

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics

The petrogenesis of sodic island arc magmas at Savo volcano, Solomon Islands

The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

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