Cenozoic Lamprophyres From NE Turkiye: New Constraints on Post-Collisional Metasomatism and Alkaline Magma Origin in the Juvenile Subcontinental Lithospheric Mantle
GEOLOGICAL JOURNAL, 2025 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Basım Tarihi: 2025
- Doi Numarası: 10.1002/gj.70114
- Dergi Adı: GEOLOGICAL JOURNAL
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Geobase, INSPEC
- Anahtar Kelimeler: alkaline magmatism, delamination, lamprophyre, mantle metasomatism, petrogenesis, Türkiye
- Karadeniz Teknik Üniversitesi Adresli: Evet
Özet
The Middle Eocene (similar to 43 Ma) and Late Miocene (similar to 6 Ma) lamprophyres cropping out as sills from NE Turkiye can be classified as alkaline lamprophyres. These lamprophyres exhibit moderate contents of K2O (2.22-2.59 and 2.58-2.98 wt%), K2O/Na2O ratios (0.78-1.14 and 0.62-0.94) and Mg# (40.55-46.32 and 56.93-61.52), respectively, and low concentrations of mantle compatible elements. The lamprophyres also have a moderate to relatively high abundance of rare earth elements (Sigma REEs = 140-159 and 547-604 ppm, respectively) with significantly fractionated REE patterns (La-N/Yb-N = 6.82-9.10 and 65.17-71.31, respectively), and are enriched in large-ion lithophile and light REEs but depleted in high-field-strength and heavy REEs. The lamprophyres have homogeneous and moderately low (Sr-87/Sr-86)(i) of 0.705048-0.705474 and 0.705252-0.705401, and nearly uniform epsilon Nd-(i) values varying from -0.47 to 0.20 and 0.54 to 0.79 and epsilon Hf-(i) values varying from 4.51-6.71 and 5.83-6.18, respectively. They also have a narrow and moderately high Delta 7/4Pb range of 6.19-15.41 and 10.62-10.88 and Delta 8/4Pb range of 49.56-56.14 and 46.86-47.99, respectively. Petrological modelling suggests that the parental magmas of both the Eocene and Miocene lamprophyres were generated by the low-degree partial melting of phlogopite-bearing spinel-garnet and amphibole-bearing garnet lherzolite sources, respectively. By integrating whole-rock trace elements and isotope compositions with regional geological observations, we propose that the post-collisional Middle Eocene and Late Miocene lamprophyres in the Eastern Pontides Orogenic Belt originated from the juvenile subcontinental lithospheric mantle sources metasomatized initially by Neotethyan subduction-related fluids during the Eocene, and subsequently overprinted by delaminated lithosphere-derived carbonate components in the Miocene. The lamprophyres likely record a temporal magmatic response to lithospheric delamination and regional thermal upwelling associated with Eocene extensional tectonics, followed by lithospheric thinning during the Miocene in a post-collisional tectonic setting.