TY - JOUR
T1 - Role of mantle and lower continental crust in the genesis of Eocene post-collisional granitoids
T2 - Insights from the Topuk pluton (NW Turkey)
AU - Güraslan, Işıl Nur
AU - Altunkaynak, Şafak
N1 - Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/8/1
Y1 - 2019/8/1
N2 - We present here new mineral chemistry and major trace element and Sr-Nd-Pb-O isotope data as well as detailed field and petrographic studies of the Topuk Pluton (TP; ca. 48 Ma) and its hypabyssal counterparts. We aim to constrain the granitic magma genesis and emplacement and magmatic processes within the framework of post-collisional evolution of NW Anatolia. The TP is a shallow level intrusion (1.5–2.1 kbar, 680–760 °C, and 4.5–6.3 km depth) which is characterized by a dominant granodiorite composition and presents holocrystalline porphyritic texture. The pluton includes mafic microgranular enclaves (MMEs) of diorite/quartz diorite composition. During its emplacement, the pluton developed radial and ring fractures around itself, and aplite, porphyry dykes, and stocks were emplaced coeval with the pluton along these ring and radial fractures. The TP shows metaluminous and calc-alkaline I-type characteristics. Normal-mid ocean ridge basalt-normalized trace element patterns show that the samples are enriched in large-ion lithophile elements and light rare earth elements but depleted in Nb, Ti, and Ta elements. Granodiorite, MMEs, and hypabyssal rocks present similar initial 87Sr/86Sr and 143Nd/144Nd isotopic values, which lie in the ranges 0.705860–0.706247 and 0.512455–0.512584, respectively. The 206Pb/204Pb, 207Pb/204Pb, 208Pb/206Pb, and 207Pb/206Pb ratios are 18.831–19.046, 15.673–15.748, 2.0621–2.0725, and 0.82816–0.83321 values, respectively, while the δ18O isotope values range from 9.6 to 10.7. These similar Sr-Nd-Pb-O isotopic features of MMEs and host granodiorites indicate a common igneous precursor as the magma source. We infer that the magma-forming TP originated from enriched mantle type II (EMII) with contribution from the lower crust. The results of numerical modelling indicate that this lower crustal input ranges from 5 to 20%. The Eocene melt generation was most probably caused by the upwelling asthenosphere due to the break-off of Neo-Tethys slab in NW Anatolia.
AB - We present here new mineral chemistry and major trace element and Sr-Nd-Pb-O isotope data as well as detailed field and petrographic studies of the Topuk Pluton (TP; ca. 48 Ma) and its hypabyssal counterparts. We aim to constrain the granitic magma genesis and emplacement and magmatic processes within the framework of post-collisional evolution of NW Anatolia. The TP is a shallow level intrusion (1.5–2.1 kbar, 680–760 °C, and 4.5–6.3 km depth) which is characterized by a dominant granodiorite composition and presents holocrystalline porphyritic texture. The pluton includes mafic microgranular enclaves (MMEs) of diorite/quartz diorite composition. During its emplacement, the pluton developed radial and ring fractures around itself, and aplite, porphyry dykes, and stocks were emplaced coeval with the pluton along these ring and radial fractures. The TP shows metaluminous and calc-alkaline I-type characteristics. Normal-mid ocean ridge basalt-normalized trace element patterns show that the samples are enriched in large-ion lithophile elements and light rare earth elements but depleted in Nb, Ti, and Ta elements. Granodiorite, MMEs, and hypabyssal rocks present similar initial 87Sr/86Sr and 143Nd/144Nd isotopic values, which lie in the ranges 0.705860–0.706247 and 0.512455–0.512584, respectively. The 206Pb/204Pb, 207Pb/204Pb, 208Pb/206Pb, and 207Pb/206Pb ratios are 18.831–19.046, 15.673–15.748, 2.0621–2.0725, and 0.82816–0.83321 values, respectively, while the δ18O isotope values range from 9.6 to 10.7. These similar Sr-Nd-Pb-O isotopic features of MMEs and host granodiorites indicate a common igneous precursor as the magma source. We infer that the magma-forming TP originated from enriched mantle type II (EMII) with contribution from the lower crust. The results of numerical modelling indicate that this lower crustal input ranges from 5 to 20%. The Eocene melt generation was most probably caused by the upwelling asthenosphere due to the break-off of Neo-Tethys slab in NW Anatolia.
KW - Eocene
KW - Granite genesis
KW - NW anatolia
KW - Sr-Nd-Pb-O isotope
KW - Topuk pluton
UR - http://www.scopus.com/inward/record.url?scp=85065661604&partnerID=8YFLogxK
U2 - 10.1016/j.jseaes.2019.05.012
DO - 10.1016/j.jseaes.2019.05.012
M3 - Article
AN - SCOPUS:85065661604
SN - 1367-9120
VL - 179
SP - 365
EP - 384
JO - Journal of Asian Earth Sciences
JF - Journal of Asian Earth Sciences
ER -