Late Jurassic Paleotethyan oceanic slab break-off revealed by Sr-Nd-Hf isotopes of Na-rich adakitic granites from northwestern Turkey
Yükleniyor...
Tarih
2022
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Elsevier Inc.
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
The Mesozoic geodynamic evolution of the Paleotethys Ocean is critical but a poorly known piece of the
geological history of the Sakarya Zone, north Turkey. Here, we describe new integrated research of zircon
U-Pb geochronology, bulk-rock major-trace element and Sr–Nd isotopes as well as Hf isotope of zircons
from the granitic rocks of the Demirköy and Kızıldamlar plutons located in Bilecik area along the western
Sakarya Zone, northwestern Turkey. Zircon U–Pb ages obtained by LA-ICP-MS reveal that the granitic
magma intruded into the basement rocks during the Late Jurassic (ca. 162–157 Ma). The granites are
tholeiitic and show slightly metaluminous to peraluminous geochemical affinities. The granite samples
are adakitic, having relatively high Na2O (6.35–7.58 wt%) and Sr (172–580 ppm), and low K2O
(0.39–1.13 wt%) and Y (3.2–5.3 ppm), and thus have high Sr/Y (70–250). The samples exhibit enrichment
of light rare earth elements (REE) and large ion lithophile elements (LILE) and depletion in heavy REE and
the high field strength elements (HFSE; e.g., Nb, Ti, Ta). The samples possess low 87Sr/86Sr(t) values of
0.70313 to 0.70372, and eNd(t) of 0.66 to +9.24. Zircon grains exhibit positive eHf (t) values of 5.0 to
12.8 and depleted mantle model ages of Hf (TDM1 = 0.24 to 0.68 Ga). These geochemical features and
Sr–Nd–Hf radiogenic isotope systematics reveal that the adakitic rocks were likely formed by low degree
melting (<10%) of the eclogitic part of an oceanic slab and subsequent melt fractionation and crustal con-
tamination. An ongoing subduction scenario cannot explain the formation of the investigated adakitic
rocks. We suggest that the adakitic plutons were generated through slab break-off after the final closure
of the Paleotethys Ocean throughout the Late Jurassic (ca. 162–157 Ma). Considering the previous data,
the continental back-arc basin system, leading to the opening of Neotethys Ocean at the southern margin
of the continent, has been put forward to decipher the Late Jurassic tectonic evolution of the Paleotethys
Ocean and the western Sakarya Zone.
Açıklama
Anahtar Kelimeler
Melting of oceanic slab, Na-rich adakites, NW Turkey, Slab break-off, The western Sakarya Zone
Kaynak
Gondwana Research
WoS Q Değeri
Q1
Scopus Q Değeri
Cilt
103
Sayı
Künye
Karslı, O., Şengün, F., Santos, J. F., Uysal, İ., Dokuz, A., Aydin, F., & Kandemir, R. (2022). Late jurassic paleotethyan oceanic slab break-off revealed by sr-nd-hf isotopes of na-rich adakitic granites from northwestern turkey. Gondwana Research, 103, 205-220. doi:10.1016/j.gr.2021.11.014
