Whole rock geochemistry zircon U Pb geochronology and Lu Hf isotope systematics of the Çangaldağ Pluton Central Pontides Turkey

2016-04-11
Çimen, Okay
Göncüoğlu, Mehmet Cemal
Sayıt, Kaan
Simonetti, Antonio
The Central Pontides include several granitoid complexes, which are predominantly PermoCarboniferous and Middle Jurassic in age. Currently, there is no geochemical and radiometric age data from one of the largest igneous bodies, namely the Çangaldağ Pluton to the northeast of the Çangaldağ Complex. The pluton intrudes the Çangaldağ Volcanic Complex and mainly comprises non-metamorphic diorite, dacite porphyry, and lesser amount of granitic rocks. The dioritic rocks are surrounded by dacite porphyries, which indicate a zoned nature (mafic core with felsic rim) of the complex. Petrographically, the diorites consist mainly of plagioclase, amphibole and biotite. In contrast, the dacite porphyries display porphyritic texture with quartz, K-feldspar and plagioclase phenocrysts within a fine-grained groundmass. The dioritic rocks are cut by granitic rocks, which are composed predominantly of quartz, K-feldspar, plagioclase, biotite and muscovite. Geochemically, various rock types from this pluton exhibit subalkaline, calc-alkaline features and are akin to volcanic arc magmatics displaying LILE/HFSE enrichment coupled with Nb depletion. The remaining data suggest derivation primarily by partial melting of an amphibolitic source. Moreover, the diorites and dacite porphyries exhibit geochemical characteristics of I-type granites, whereas the granitic rocks show typical features of S-type granites. In-situ U-Pb dating of zircons from dacite porphyry and granite samples indicate ages of 161.4 ± 5.3 Ma and 168.3 ± 2.1 Ma, respectively. In addition, corresponding in-situ 176Hf/ 177Hf initial ratios are 0.28287 ± 0.00004 and 0.28279 ± 0.00004 for the dacite porphyry and granite samples, respectively. These results support their generation in an arc system with the involvement of a subduction-modified mantle source. TDM model ages vary between 624 and 639 Ma and suggest that the magmatism associated with the Çangaldağ Pluton may have involved partial melting of Neoproterozoic crustal rocks, which are common in Gondwana-derived terranes. The geochemical, Hf isotope and geochronological data reported here confirm the presence of an arc system during the Middle Jurassic in the Central Pontides, and propose that the Çangaldağ Pluton formed within an island arc during northward subduction of the Intra-Pontide Ocean.
Citation Formats
O. Çimen, M. C. Göncüoğlu, K. Sayıt, and A. Simonetti, “Whole rock geochemistry zircon U Pb geochronology and Lu Hf isotope systematics of the Çangaldağ Pluton Central Pontides Turkey,” 2016, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/74514.