An experimental study of the effects of melt composition on plagioclase-melt equilibria at 5 and 10 kbar: implications for the origin of magmatic high-An plagioclase

Panjasawatwong, Yuenyong; Danyushevsky, Leonid V.; Crawford, Anthony J.; Harris, K.L.

doi:10.1007/s004100050024

Cited by 268 publications

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“…Housh and Luhr (1991) presented a useful thermodynamic model of the plagioclase-melt equilibria. However, this model failed to reproduce the plagioclase-melt equilibria at H 2 O-undersaturated conditions and at H 2 O-saturated and low pressure conditions (Panjasawatwong et al, 1995;Danyushevsky et al, 1997), presumably because the temperature is higher than Housh and Luhr's calibration temperature range (800°C ≤ T ≤ 950°C). Putirka (2005) proposed some useful formulations to predict the temperature, pressure, H 2 O content of the melt and plagioclase composition based on the plagioclase-melt equilibria of the various compositional ranges from literature.…”

Section: Empirical Calibration Of Plagioclase-hydrous Basaltic Melt Ementioning

confidence: 97%

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H2O-rich island arc low-K tholeiite magma inferred from Ca-rich plagioclase-melt inclusion equilibria

Hamada

Fujii

2007

Geochem. J.

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In order to quantify H 2 O content and chemical composition of island arc low-K tholeiite magma that crystallized Carich plagioclase, melt inclusions of a typical island arc tholeiite from Izu-Oshima volcano (34°N 44′, 139°E 24′) were analyzed. Composition of studied plagioclase ranges widely from An 83 to An 95 . Composition of studied melt inclusions also shows wide variation, which suggests that the melt inclusions represent various stages of crystallization differentiation at Izu-Oshima volcano. Ca/Na ratios of plagioclase-hosted melt inclusions are comparable with compositions of aphyric lava, which preclude an exotic origin for the Ca-rich plagioclase. Analyzed H 2 O content of the melt inclusions ranges from 0.2 to 2.4 wt.% (0.2 to 1.4 wt.% for plagioclase-hosted melt inclusions and 0.8 to 2.4 wt.% for olivine-hosted melt inclusions).Ca/Na partition coefficient between plagioclase and hydrous basaltic melt, K D(Ca-Na) plag-melt , is empirically calibrated based on experimental data as Based on the equilibria between host plagioclase and melt inclusion and taking effect of overgrowth into consideration, 3 to 6 wt.% H 2 O in melt is required. The lower H 2 O content of the analyzed melt inclusions is probably due to the leakage of volatiles through the host crystal during decompression, eruption and quench. Variation in estimated H 2 O content in the melt at the time of crystallization of plagioclase (3 to 6 wt.%) can be due to polybaric crystallization from H 2 O-saturated melt.Keywords: melt inclusion, Ca-rich plagioclase, island arc low-K tholeiite magma, H 2 O content in melt, hydrous melting experiment tic melt inclusions from the subaqueous Izu arc front ranges from 1 to 5 wt.% (Straub and Layne, 2003). Takagi et al. (2005) claimed that optimal H 2 O content for crystallization of Ca-rich plagioclase from island arc tholeiite magma is ~5 wt.%. However, quantitative discussions on H 2 O content of island arc basalt at the volcanic front have not reached consensus to date. Sakuyama (1979) proposed lateral variation of H 2 O content in northeast Japan arc based on the crystallization sequence and temperature, which lead to the conclusion that the H 2 O content of island arc basalt at the volcanic front was small. Aoki et al. (1981) also proposed similar lateral variations of H 2 O content based on fluorine geochemistry assuming constant proportions of K 2 O:H 2 O:F during fractional crystallization. The 1986 eruption of Izu-Oshima volcano (34°N 44′, 139°E 24′), which is a typical frontal arc volcano and issues island arc low-K tholeiite magma, stimulated the discussion on H 2 O content in island arc basalt. Aramaki and Fujii (1988) calculated the H 2 O content of basaltic melt to explain the INTRODUCTIONQuantifying the H 2 O content of island arc basalt at the volcanic front, especially island arc low-K tholeiite magma, is fundamental in understanding the generation and differentiation of magma at island arc settings. Carich plagioclase (mostly An ≥90 ), commonly found in island arc basalt at the volcan...

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Section: Empirical Calibration Of Plagioclase-hydrous Basaltic Melt Ementioning

confidence: 97%

“…In order to assess the error in estimated temperature, Eq. (3) was applied to the melt compositions saturated with olivine + clinopyroxene + plagioclase from the literature (Baker and Eggler, 1987;Panjasawatwong et al, 1995) (Fig. 8(a)).…”

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confidence: 99%

H2O-rich island arc low-K tholeiite magma inferred from Ca-rich plagioclase-melt inclusion equilibria

Hamada

Fujii

2007

Geochem. J.

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“…Experimental results suggest that melts with CaO/Na 2 O >IO are required to crystallize plagioclase of >An 90 under anhydrous conditions at pressures of <5 kbar (Fisk, 1984;Panjasawatwong, 1991), although more recent data show that high melt A1 2 O 3 will stabilize high-An plagioclase at lower CaO/Na 2 O (Haskall et al, 1993;Panjasawatwong et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Composition and Crystallization Temperatures of Primary Melts from Hole 896A Basalts: Evidence from Melt Inclusion Studies

McNeill¹,

Danyushevsky²

1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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Glass and mineral geochemical data are presented for basalts from Ocean Drilling Program (ODP) Hole 896A. Phenocryst assemblages are dominated by calcic plagioclase (An 76 _ 945 ) with olivine (Fo 80 _ 91 6 ), Cr-Al spinel, and clinopyroxene. The origin of the calcic plagioclase phenocrysts was investigated by heating-stage experiments on silicate melt inclusions in plagioclase and olivine mineral separates. Trapping temperatures of 1195°-1215°C are inferred for plagioclase (An 83 _ 945 ). Inclusion compositions, interpreted to be in equilibrium with host plagioclase, are similar to the range of pillow-rim glasses from this hole. Primary melts, in equilibrium with Fo 9 | 6 , are estimated to have -15 wt% MgO and crystallization temperatures of 1340°C.

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“…Less commonly, anorthitic plagioclase has been reported in anhydrous mid-ocean ridge basalts (MORBs) (Donaldson and Brown, 1977;Wilkinson, 1982;Autio and Rhodes, 1984;Fisk, 1984;Stakes et al, 1984;Koyagnchi, 1986;Price et al, 1986;Sinton et al, 1993). Experimental studies indicate, however, that anorthite generated under these conditions requires refractory melts with high CaO/Na 2 O (12-15), or melts with exceptionally high Al 2 O 3 (>18 wt.%) (Panjasawatwong et al, 1995). These characteristics are inconsistent with the normal CaO/Na 2 O ratios (6.16-12.6) and Al 2 O 3 contents (13.8-19.8 wt.%, average 16.2 wt.%) of the Zhengga mafic rocks, which therefore favor a subduction-related environment where water liberated from the subducting slab may trigger the widespread melting of refractory lithospheric peridotites (Tatsumi and Eggins, 1995).…”

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Late Cretaceous crustal growth in the Gangdese area, southern Tibet: Petrological and Sr–Nd–Hf–O isotopic evidence from Zhengga diorite–gabbro

et al. 2013

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An experimental study of the effects of melt composition on plagioclase-melt equilibria at 5 and 10 kbar: implications for the origin of magmatic high-An plagioclase

Cited by 268 publications

References 54 publications

H2O-rich island arc low-K tholeiite magma inferred from Ca-rich plagioclase-melt inclusion equilibria

H2O-rich island arc low-K tholeiite magma inferred from Ca-rich plagioclase-melt inclusion equilibria

Composition and Crystallization Temperatures of Primary Melts from Hole 896A Basalts: Evidence from Melt Inclusion Studies

Late Cretaceous crustal growth in the Gangdese area, southern Tibet: Petrological and Sr–Nd–Hf–O isotopic evidence from Zhengga diorite–gabbro

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