Carbonate assimilation at Merapi volcano, Java Indonesia: insights from crystal isotope stratigraphy
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Carbonate assimilation at Merapi volcano, Java Indonesia : insights from crystal isotope stratigraphy. / Chadwick, J.P; Troll, V.R; Ginibre, C.; Morgan, D.; Gertisser, R.; Waight, Tod Earle; Davidson, J.P.
In: Journal of Petrology, Vol. 48, 2007, p. 1793-1812.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Carbonate assimilation at Merapi volcano, Java Indonesia
T2 - insights from crystal isotope stratigraphy
AU - Chadwick, J.P
AU - Troll, V.R
AU - Ginibre,, C.
AU - Morgan, D.
AU - Gertisser, R.
AU - Waight, Tod Earle
AU - Davidson, J.P.
PY - 2007
Y1 - 2007
N2 - Recent basaltic andesite lavas from Merapi volcano contain abundant, complexly zoned, plagioclase phenocrysts, analysed here for their petrographic textures, major element composition and Sr isotope composition. Anorthite (An) content in individual crystals can vary by as much as 55 mol% (An40^95) across internal resorption surfaces with a negative correlation between high An mol% (470), MgO wt% and FeO wt%. In situ Sr isotope analyses of zoned plagioclase phenocrysts show that the 87Sr/86Sr ratios of individual zones range from 0.70568 to 0.70627.The upper end of this range is notably more radiogenic than the host basaltic andesite whole-rocks (0.70574). Crystal zones with the highest An content have the highest 87Sr/86Sr values, requiring a source or melt with elevated radiogenic Sr, rich in Ca and with lower Mg and Fe. Recent Merapi eruptive rocks contain abundant xenoliths, including metamorphosed volcanoclastic sediment and carbonate country rock (calc-silicate skarns) analysed here for petrographic textures, mineralogy, major element composition and Sr isotope composition. The xenoliths contain extremely calcic plagioclase (up to An100) and have whole-rock 87Sr/86Sr ratios of 0.70584 to 0.70786.The presence of these xenoliths and their mineralogy and geochemistry, coupled with the 87Sr/86Sr ratios observed in different zones of individual phenocrysts, indicate that magma-crust interaction at Merapi is potentially more significant than previously thought, as numerous crystal cores in the phenocrysts appear to be inherited from a metamorphosed sedimentary crustal source. This has potentially significant consequences for geochemical mass-balance calculations, volatile saturation and flux and eruptive behaviour at Merapi and similar island arc volcanic systems elsewhere.
AB - Recent basaltic andesite lavas from Merapi volcano contain abundant, complexly zoned, plagioclase phenocrysts, analysed here for their petrographic textures, major element composition and Sr isotope composition. Anorthite (An) content in individual crystals can vary by as much as 55 mol% (An40^95) across internal resorption surfaces with a negative correlation between high An mol% (470), MgO wt% and FeO wt%. In situ Sr isotope analyses of zoned plagioclase phenocrysts show that the 87Sr/86Sr ratios of individual zones range from 0.70568 to 0.70627.The upper end of this range is notably more radiogenic than the host basaltic andesite whole-rocks (0.70574). Crystal zones with the highest An content have the highest 87Sr/86Sr values, requiring a source or melt with elevated radiogenic Sr, rich in Ca and with lower Mg and Fe. Recent Merapi eruptive rocks contain abundant xenoliths, including metamorphosed volcanoclastic sediment and carbonate country rock (calc-silicate skarns) analysed here for petrographic textures, mineralogy, major element composition and Sr isotope composition. The xenoliths contain extremely calcic plagioclase (up to An100) and have whole-rock 87Sr/86Sr ratios of 0.70584 to 0.70786.The presence of these xenoliths and their mineralogy and geochemistry, coupled with the 87Sr/86Sr ratios observed in different zones of individual phenocrysts, indicate that magma-crust interaction at Merapi is potentially more significant than previously thought, as numerous crystal cores in the phenocrysts appear to be inherited from a metamorphosed sedimentary crustal source. This has potentially significant consequences for geochemical mass-balance calculations, volatile saturation and flux and eruptive behaviour at Merapi and similar island arc volcanic systems elsewhere.
KW - Faculty of Science
KW - Indonesien
KW - isotoper
KW - assimilation
KW - calc-silicate
KW - xenolith
KW - Indonesia
KW - Merapi
KW - isotopes
U2 - 10.1093/petrology/egm038
DO - 10.1093/petrology/egm038
M3 - Journal article
VL - 48
SP - 1793
EP - 1812
JO - Journal of Petrology
JF - Journal of Petrology
SN - 0022-3530
ER -
ID: 1730624