Constraints on the magmatic evolution of the oceanic crust from plagiogranite intrusions in the Oman ophiolite

Haase, Karsten M., Freund, Sarah, Beier, Christoph, Koepke, Jürgen, Erdmann, Martin and Hauff, Folkmar (2016) Constraints on the magmatic evolution of the oceanic crust from plagiogranite intrusions in the Oman ophiolite Contributions to Mineralogy and Petrology, 171 ( Art.No. 46). DOI 10.1007/s00410-016-1261-9.

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Abstract

We present major and trace element as well as
Sr, Nd, and Hf isotope data on a suite of 87 plutonic rock
samples from 27 felsic crustal intrusions in seven blocks of
the Oman ophiolite. The rock compositions of the sample
suite including associated more mafic rocks range from 48
to 79 wt% SiO2, i.e. from gabbros to tonalites. The samples
are grouped into a Ti-rich and relatively light rare earth element
(LREE)-enriched P1 group [(Ce/Yb)N > 0.7] resembling
the early V1 lavas, and a Ti-poor and LREE-depleted
P2 group [(Ce/Yb)N < 0.7] resembling the late-stage V2
lavas. Based on the geochemical differences and in agreement
with previous structural and petrographic models, we
define phase 1 (P1) and phase 2 (P2) plutonic rocks. Felsic
magmas in both groups formed by extensive fractional
crystallization of olivine, clinopyroxene, plagioclase, apatite,
and Ti-magnetite from mafic melts. The incompatible
element compositions of P1 rocks overlap with those from
mid-ocean ridges but have higher Ba/Nb and Th/Nb trending
towards the P2 rock compositions and indicating an
influence of a subducting slab. The P2 rocks formed from a more
depleted mantle source but show a more pronounced
slab signature. These rocks also occur in the southern
blocks (with the exception of the Tayin block) of the Oman
ophiolite implying that the entire ophiolite formed above
a subducting slab. Initial Nd and Hf isotope compositions
suggest an Indian-MORB-type mantle source for the Oman
ophiolite magmas. Isotope compositions and high Th/Nb in
some P2 rocks indicate mixing of a melt from subducted
sediment into this mantle.

Document Type: Article
Keywords: Mid-ocean ridge, Fractional crystallization, Subduction, Oman, Ophiolite, Plagiogranite, Ocean Crust, Magmatic Geochemistry
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Refereed: Yes
DOI etc.: 10.1007/s00410-016-1261-9
ISSN: 0010-7999
Date Deposited: 02 May 2016 12:01
Last Modified: 10 Jan 2018 14:27
URI: http://eprints.uni-kiel.de/id/eprint/32278

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