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| Titel |
Magma storage and plumbing of adakite-type post-ophiolite intrusions in the Sabzevar ophiolitic zone, northeast Iran |
| VerfasserIn |
K. Jamshidi, H. Ghasemi, V. R. Troll, M. Sadeghian, B. Dahren |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 6, no. 1 ; Nr. 6, no. 1 (2015-01-14), S.49-72 |
| Datensatznummer |
250115386
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| Publikation (Nr.) |
 copernicus.org/se-6-49-2015.pdf |
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| Zusammenfassung |
| Subduction-related adakite-type intrusive rocks emplaced into the late
Cretaceous–Paleocene Sabzevar ophiolite zone, northeast Iran, range from Mg-andesite
to rhyodacite in composition. Here we investigate the magma supply system to
these subvolcanic intrusive rocks by applying thermobarometric mineral and
mineral–melt equilibrium models, including amphibole thermobarometry,
plagioclase–melt thermobarometry and clinopyroxene–melt barometry. Based on
the results of these thermobarometric models, plagioclase crystallized
dominantly at pressures of ~350 (130 to 468) MPa, while amphiboles
record both low pressures (~300 MPa) and very high pressures
(>700 MPa) of crystallization. The latter is supported by the calculated
pressures for clinopyroxene crystallization (550 to 730 MPa). The
association of amphibole with clinopyroxene and no plagioclase in the most
primitive samples (Mg-andesites) is consistent with amphibole fractionation
from very hydrous magmas at deep crustal levels of the plumbing system, which
may have been a key process in intensifying adakite-type affinities in this rock
suite. Barometry, combined with frequent disequilibrium features such as
oscillatory-zoned and sieve-textured plagioclase crystals with An-rich
overgrowths in more evolved samples, implies that final magma differentiation
occurred in an open upper crustal magma system that developed progressively
stronger compositional modifications during high-level magma storage. |
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