New evidence on the timing of Southern Neotethys closure from geochronology and geochemistry of Harmanlı region ophiolite (SE Anatolia) and Late Cretaceous granitic rocks : Petrology and geochronology of the felsic intrusive and ophiolitic host rocks

The felsic-intermediate intrusions of the Harmanlı region are situated in proximity to the Tauride thrust front in south-eastern Turkey. The region containing intrusive and ophiolitic rocks indeed plays a crucial role in understanding the magmatic framework of Late Cretaceous felsic-intermediate igneous rocks in the Adıyaman region of south-eastern Anatolia. The geological evolution of south-eastern Anatolia during the Late Cretaceous is unraveled through integrated field observations, whole-rock geochemical, petrographic analyses, U-Pb zircon geochronology, and mineral chemistry of granitic rocks that intrude the Harmanlı region ophiolite (HRO). The intrusions in the HRO, which is part of the SAOB, include felsic-intermediate plutonic/subvolcanic rocks and consist of tonalite, granodiorite, and occasionally granite, with the subvolcanic phase represented by granophyre, aplite, and granite porphyry. Additionally, the mafic plutonic rocks of HRO are predominantly composed of diorite and gabbro, while the subvolcanic phase is characterized by microdiorite and diabase. The new, high-precision LA-ICP-MS U-Pb zircon data provides crystallization ages for the mafic rocks of the Harmanlı ophiolite (gabbro) ranging from 81.7 to 83.8 Ma, while the felsic intrusives (granodiorite) have yielded crystallization ages ranging from 79.5 to 80.8 Ma. The intrusive rocks in the Harmanlı region range from granite to diorite and exhibit metaluminous to slightly peraluminous, calc-alkaline, I-type volcanic arc granite characteristics. On the Chondrite-normalized REE diagram, the intrusive rocks show moderate to high enrichment with indistinct negative Eu anomalies. The intrusive rocks display remarkable depletion in high field strength (HFS) elements (Ta, Nb, Zr, Sm, Y, Hf) and enrichment in large ion lithophile elements (LILEs) (K2O, Rb, Ba, Th) on the ORG-normalized multi-element patterns. The mafic rocks of HRO exhibit distinct characteristics, including (I) depletion in Nb and Pr, (II) enrichment in LILEs (Ce, Rb, K, and Th), and (III) a nearly horizontal pattern of HFSEs (high field strength elements) compared to N-MORB. The utilization of electron microprobe analyses (EMPA) in conjunction with whole-rock major, (trace element, and rare earth element) analyses of the intrusive rocks indicates that these magmatic rocks exhibit a calc-alkaline composition and range from metaluminous to peraluminous. The magmatic arc environment is characterized by the presence of ocean ridge granite-normalized multi-element patterns, tectonomagmatic discrimination, and the biotite geochemistry of the intruded rocks.