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New petrological constraints on the last eruptive phase of the Sabatini Volcanic District (central Italy): Clues from mineralogy, geochemistry, and Sr–Nd isotopes
Author(s)
Language
English
Obiettivo Specifico
2IT. Laboratori sperimentali e analitici
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/205 (2014)
ISSN
0024-4937
Electronic ISSN
1872-6143
Publisher
Elsevier Science Limited
Pages (printed)
28-38
Issued date
2014
Keywords
Abstract
We report results from mineralogical, geochemical and isotopic analyses of the three youngest pyroclastic products
(ca. 86 ky) belonging to the Sabatini Volcanic District (Roman Province, central Italy). By means of thermometers,
hygrometers and oxygen barometers, we have estimated that the crystallization temperature of magma
progressively decreases over time (910–740 °C),whereas the amount ofwater dissolved in the melt and fO2 progressively
increases as compositions of magmas become more differentiated (4.5–6.4 wt.% H2O and 0.4–2.6
ΔQFM buffer, respectively). Thermodynamic simulations of phase equilibria indicate that geochemical trends
in mafic magmas (MgO N 4 wt.%) can be reproduced by abundant fractionation of olivine and clinopyroxene
(~50 wt.% crystallization), while the trends of more evolved magmas (MgO ≤ 4 wt.%) originated by fractional
crystallization of plagioclase and sanidine (~45 wt.% crystallization). The behavior of trace elements highlights
that magmatic differentiation is controlled by polybaric differentiation that includes: (1) prolonged fractionation
of mafic, anhydrous minerals from a primitive, H2O-poor magma at depth and (2) extraction of a more evolved,
H2O-rich magma that crystallizes abundant felsic and subordinated hydrous minerals at shallow crustal levels.
Assimilation and fractional crystallization modeling also reveal that magmas interacted with the carbonate
rocks of the subvolcanic basement. The effect of carbonate assimilation accounts for both trace element and
Sr–Nd isotopic variations inmagmas, suggesting amaximumdegree of carbonate assimilation of less than 5 wt.%.
(ca. 86 ky) belonging to the Sabatini Volcanic District (Roman Province, central Italy). By means of thermometers,
hygrometers and oxygen barometers, we have estimated that the crystallization temperature of magma
progressively decreases over time (910–740 °C),whereas the amount ofwater dissolved in the melt and fO2 progressively
increases as compositions of magmas become more differentiated (4.5–6.4 wt.% H2O and 0.4–2.6
ΔQFM buffer, respectively). Thermodynamic simulations of phase equilibria indicate that geochemical trends
in mafic magmas (MgO N 4 wt.%) can be reproduced by abundant fractionation of olivine and clinopyroxene
(~50 wt.% crystallization), while the trends of more evolved magmas (MgO ≤ 4 wt.%) originated by fractional
crystallization of plagioclase and sanidine (~45 wt.% crystallization). The behavior of trace elements highlights
that magmatic differentiation is controlled by polybaric differentiation that includes: (1) prolonged fractionation
of mafic, anhydrous minerals from a primitive, H2O-poor magma at depth and (2) extraction of a more evolved,
H2O-rich magma that crystallizes abundant felsic and subordinated hydrous minerals at shallow crustal levels.
Assimilation and fractional crystallization modeling also reveal that magmas interacted with the carbonate
rocks of the subvolcanic basement. The effect of carbonate assimilation accounts for both trace element and
Sr–Nd isotopic variations inmagmas, suggesting amaximumdegree of carbonate assimilation of less than 5 wt.%.
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article
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