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The Origin of Felsic Intrusions Within the Mantle Section of the Samail Ophiolite: Geochemical Evidence for Three Distinct Mixing and Fractionation Trends
Author(s) -
Rioux Matthew,
Benoit Mathieu,
Amri Isma,
Ceuleneer Georges,
Garber Joshua M.,
Searle Michael,
Leal Kayla
Publication year - 2021
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2020jb020760
Subject(s) - felsic , geology , geochemistry , ophiolite , mantle (geology) , fractional crystallization (geology) , oceanic crust , peridotite , dike , subduction , petrology , mafic , paleontology , tectonics
An isotopically diverse suite of felsic dikes, sills, and plugs (ε Nd (t) = −7.8 to +7.8) intrude the uppermost mantle and lower crust in the Samail ophiolite in Oman and the United Arab Emirates (UAE). These features have been interpreted to represent amphibolite and metasediment melts from an underthrust sheet of oceanic lithosphere. As such, the intrusions provide a record of melting of oceanic crust and sediment at depth, with implications for mass transfer from the down‐going plate in young, hot subduction settings. Several studies have used geochemical data to constrain the magmatic sources of the dikes; here we build on this previous work using integrated whole rock major element, trace element and Nd isotopic data from a more geographically extensive suite of dikes. New and existing data suggest the felsic intrusions preserved within mantle peridotites in the Oman portion of the ophiolite were generated by three distinct mixing and fractionation trends: (1) three‐component mixing between sediment melt, amphibolite melt and a mantle component; (2) two component mixing between amphibolite and sediment melts, with little mantle contribution; and (3) fractional crystallization of depleted, mantle derived magmas, likely related to the ophiolite V2 volcanic series. Combined geochemical and pseudosection modeling suggest that amphibolite melting occurred at P ≤ 1.4 GPa (∼40–45 km) and T ≥ 700–750°C. Felsic intrusions in the mantle section in the UAE, including garnet‐andalusite‐cordierite leucogranites, follow similar mixing trends, but crystallized ∼0.9–4.0 Ma after the Oman intrusions.