Late Paleocene adakitic granitoid from NW Iran and comparison with adakites in the NE Turkey: Adakitic melt generation in normal continental crust

Hossein Azizi*, Robert J. Stern, Gültekin Topuz, Yoshihiro Asahara, Hadi Shafaii Moghadam

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32 Atıf (Scopus)

Özet

Late Paleocene adakitic granitoids are rare in Iran except in the northwest. We focused on the adakitic Saqqez-Takab pluton, which occupies an area of ~600 km2. New U-Pb zircon dating yield crystallization ages of 58–56 Ma (Thanetian). These granitoids comprises granite, quartz monzonite and monzogranite with granular to mylonitic textures. They have high SiO2 abundances (59.1–78.6 wt%), high ratios of Sr/Y (50–490) and La/Yb ratios (19–237), along with high Ba (779–2466 ppm) and light rare earth element contents (e.g., La = 11–70 ppm). Saqqez-Takab granitoids have compositions that are similar to high-silica adakites, including low Mg- number (Mg# < 0.5), TiO2 (<0.93 wt%), Cr (<38 ppm) and Ni (<55 ppm). K2O/Na2O ratios of these granitoids are high (>0.7), resembling K-rich adakitic granitoids. Initial ratios of 87Sr/86Sr and εNd(t) vary from 0.7044 to 0.7053 and −2.8 to +2.0 respectively. These isotopic signatures differ from those of typical subducting slab-derived adakites (O-type adakite) with high positive εNd(t) and from collision-related adakites (C-type adakite) with negative εNd(t). The geochemical and isotopic characteristics of Saqqez-Takab granitoids are most consistent with magma being produced by amphibole-dominated fractionation of hydrous melts of subcontinental lithospheric mantle accompanied by minor assimilation of lower mafic calc alkaline continental crust. Distribution of similar-ages adakites in the NW Iran and E Pontides of Turkey suggests that these melts formed similarly. Upwelling of hot asthenosphere due to Neotethys slab rollback led to partial melting of lower continental crust calc alkaline mafic rocks and/or amphibole fractionation from mafic magma produced K-rich adakitic rocks in eastern Turkey and NW Iran during the late Paleocene.

Orijinal dilİngilizce
Makale numarası105151
DergiLithos
Hacim346-347
DOI'lar
Yayın durumuYayınlandı - 15 Ara 2019

Bibliyografik not

Publisher Copyright:
© 2019 Elsevier B.V.

Finansman

Fieldwork and sampling were supported by the Geological Survey of Iran, Sanandaj-Branch. We thank F. Rezaei, S. Gholipour and Z. Abbasi for assistance with fieldwork. H. Azizi thanks Kurdistan University and Nagoya University for supporting his sabbatical studies in 2017-2018. Analytical studies were supported by Japan Society for Promotion of the Science (JSPS) KAKENHI grant number 17H01671 . This version is much improved based on critical comments by two anonymous reviewers and Şenel Özdamar and also editors Neslon Eby and Michael Roden. This is UTD Geosciences contribution number 1331. Fieldwork and sampling were supported by the Geological Survey of Iran, Sanandaj-Branch. We thank F. Rezaei, S. Gholipour and Z. Abbasi for assistance with fieldwork. H. Azizi thanks Kurdistan University and Nagoya University for supporting his sabbatical studies in 2017-2018. Analytical studies were supported by Japan Society for Promotion of the Science (JSPS) KAKENHI grant number 17H01671. This version is much improved based on critical comments by two anonymous reviewers and ?enel ?zdamar and also editors Neslon Eby and Michael Roden. This is UTD Geosciences contribution number 1331.

FinansörlerFinansör numarası
Geological Survey of Iran, Sanandaj-Branch
Japan Society for the Promotion of Science17H01671, 1331
University of Kurdistan

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