Pertek (Tunceli) Kuzeybatısındaki Geç Kretase Diyoritik Gabroların Petrografik, Jeokimyasal ve Jeotermobarometrik Özellikleri

Öz

Doğu Anadolu'da yer alan Güneydoğu Anadolu Orojenik Kuşağı’nın bir parçası olan Pertek (Tunceli) kuzeybatısında yüzeylenen Geç Kretase yaşlı diyoritik gabro intrüzyonları orta-iri taneli kristalin dokuda olup, başlıca plajiyoklas, amfibol ve daha az oranda piroksen minerallerinden oluşmaktadır. Diyoritik gabrolar toleyitik seri karakterinde, mafik bileşimli ve metaliminüs özelliktedir. İz element diyagramlarında büyük iyon yarıçaplı litofil elementlerde pozitif anomaly gözlenirken Nb, Ta ve Ti elementlerinde ise negatif anomaliler gözlenmektedir. Bu durum magmanın bir yitim zonu ortamında gelişmiş olabilceğini göstermektedir. NTE desenleri ise yatay bir görüntü sergilemekte olup, HNTE açısından ise sınırlı bir zenginleşme gözlenmektedir. Bu durum oluşumda spinel-faz kontrollü, yüksek dereceli kısmi ergime süreçlerinin etkili olduğunu düşündürmektedir. Plajiyoklasa ve amfibole ait jeotermobarometrik hesaplamalar kristallenme koşullarını ortaya koyarak; plajiyoklaslar için sıcaklık ~1284 °C, basınç ~11 kbar ve amfiboller için ise sıcaklık 955–1037 °C, basınç ise 1.87–2.12 kbar arasında belirlenmiştir. Bu değerler plajiyoklasların derinde ve amfibollerin daha sığ derinlikte kristallendiklerine işaret etmektedir. Tektonik ayrım diyagramları, kayaçların aktif bir yay magmatizması ortamında oluştuğunu açıkça ortaya koymaktadır. Çalışmada elde edilen tüm bulgular, Geç Kretase’de Neotetis’in güney kolunun kapanımı sürecinde aktifleşen yitim zonuna bağlı mafik magmatizmanın, Pertek kuzeybatısında gelişen diyoritik gabrolarla temsil edildiğini ortaya koymaktadır.

Anahtar Kelimeler

• Pertek (Tunceli)
• Geç Kretase
• yay tipi magmatizma
• jeotermobarometre

Petrographic, Geochemical and Geothermobarometric Characteristics of The Late Cretaceous Dioritic Gabbros in The Northwestern Pertek (Tunceli)

Öz

The northwestern Pertek region (Tunceli), located within the Eastern Anatolia segment of the Southeastern Anatolian Orogenic Belt, is characterised by Late Cretaceous dioritic gabbro intrusions. These intrusive rocks exhibit medium to coarse-grained crystalline textures and are mainly composed of plagioclase and amphibole, with minor amounts of pyroxene. The dioritic gabbros display tholeiitic affinity, mafic compositions, and metaluminous character. Trace element diagrams show pronounced positive anomalies in large-ion lithophile elements (LILE) such as Cs, Rb, Ba, Th, and U, whereas negative anomalies are evident in high field strength elements (HFSE) such as Nb, Ta, and Ti, suggesting a subduction-related magmatic setting. Chondrite-normalised rare earth element (REE) patterns are relatively flat, with limited enrichment in light rare earth elements (LREE), indicating high-degree partial melting under spinel-facies control. Geothermobarometric calculations based on plagioclase–melt and amphibole chemistry reveal crystallisation conditions, with plagioclase indicating high temperatures (~1284 °C) and pressures (~11 kbar), while amphiboles crystallised at lower temperatures (955–1037 °C) and shallower pressures (1.87–2.12 kbar). These values suggest that plagioclase formed at deeper levels and amphibole crystallised during later, shallower stages of magma evolution. Tectonomagmatic discrimination diagrams indicate that the rocks were emplaced in an active arc magmatic setting. Overall, the findings demonstrate that the dioritic gabbros of northwestern Pertek represent mafic magmatism associated with a subduction zone active during the closure of the southern branch of the Neotethys in the Late Cretaceous.

Anahtar Kelimeler

• Pertek (Tunceli)
• Late Cretaceous
• arc-related magmatism
• geothermobarometer

Kaynakça

1. [1] Chappell, B. W. & White, A. J. R., “Two contrasting granite types”, Pacific Geology, 8, 173–174, (1974).
2. [2] Eby, G. N., “Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications”, Geology, 20(7), 641–644, (1992).
3. [3] Karaoğlan, F., Parlak, O., Hejl, E., Neubauer, F. & Klötzli, U., “The temporal evolution of the active margin along the Southeast Anatolian Orogenic Belt (SE Turkey): Evidence from U–Pb, Ar–Ar and fission track chronology”, Gondwana Research, 33, 190–208, (2016).
4. [4] Sar, A., Ertürk, M. A. & Rizeli, M. E., “Genesis of Late Cretaceous intra-oceanic arc intrusions in the Pertek area of Tunceli Province, eastern Turkey, and implications for the geodynamic evolution of the southern Neo-Tethys: Results of zircon U–Pb geochronology and geochemical and Sr–Nd isotopic analyses”, Lithos, 350–351, 105263, (2019).
5. [5] Ertürk, M. A., “Geochronology and petrology of Late Cretaceous subduction-related volcanics from Elazığ, SE Türkiye: Insights into deciphering petrogenesis and magma generation processes”, Geochemistry, 85, 126234, (2025).
6. [6] Ertürk, M. A., Beyarslan, M., Chung, S.-L. & Lin, T.-H., “Eocene magmatism (Maden Complex) in the Southeast Anatolian Orogenic Belt: Magma genesis and tectonic implications”, Geoscience Frontiers, 9(6), 1829–1847, (2018).
7. [7] Rızaoğlu, T., Parlak, O., Höck, V., Koller, F., Hames, W. E. & Billor, Z., “Andean-type active margin formation in the eastern Taurides: Geochemical and geochronological evidence from the Baskil granitoid (Elazığ, SE Turkey)”, Tectonophysics, 473, 188–207, (2009).
8. [8] Sar, A., Rizeli, M. E. & Ertürk, M. A., “Geçityaka Köyü (Tunceli) Çevresindeki Elazığ Magmatik Kompleksi’ne Ait Kayaçların Petrografik ve Jeokimyasal Özellikleri”, El-Cezerî Fen ve Mühendislik Dergisi, 9(2), 680–694, (2022).

9. [9] Beyarslan, M. & Bingöl, A. F., “Zircon U-Pb age and geochemical constraints on the origin and tectonic implications of Late Cretaceous intra-oceanic arc magmatics in the Southeast Anatolian Orogenic Belt (SE-Turkey)”, Journal of African Earth Sciences, 147, 477–497, (2018).
10. [10] Ertürk, M. A., Sar, A. & Rizeli, M. E., “Petrology, zircon U–Pb geochronology and tectonic implications of the A1-type intrusions: Keban region, eastern Turkey”, Geochemistry, 82(3), 125882, (2022).
11. [11] Altunbey, M. & Sağıroğlu, A., “Skarn-type Ilmenite mineralization of the Tuzbaşi–Tunceli region, Eastern Turkey”, Journal of Asian Earth Science, 21, 481–488, (2003).
12. [12] Kara, H., Yalçın, C., Ertürk, M. A. & Kalender, L., “Mineral chemistry and iron isotope characteristics of magnetites in Pertek Fe-skarn deposit (Türkiye)”, Minerals, 15, 369, (2025).
13. [13] Liu, Y. S., Hu, Z. C., Gao, S., Günther, D., Xu, J., Gao, C. G. & Chen, H. H., “In situ analysis of major and trace elements of anhydrous minerals by LA–ICP-MS without applying an internal standard”, Chemical Geology, 257(1–2), 34–43, (2008).
14. [14] Middlemost, E. A. K., “Naming materials in the magma/igneous rock system”, Earth-Science Reviews, 37(3–4), 215–224, (1994).
15. [15] Peccerillo, A. & Taylor, S. R., “Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, northern Turkey”, Contributions to Mineralogy and Petrology, 58(1), 63–81, (1976).
16. [16] Gill, J. B., Orogenic andesites and plate tectonics, Springer-Verlag, (1981).
17. [17] Pearce, J. A. & Peate, D. W., “Tectonic implications of the composition of volcanic arc magmas”, Annual Review of Earth and Planetary Sciences, 23, 251–285, (1995).
18. [18] Hawkesworth, C. J., Turner, S. P., McDermott, F., Peate, D. W. & Van Calsteren, P., “Thorium and uranium isotope variations in arc magmas: Implications for element transfer from the subducted crust”, Science, 260(5106), 1157–1161, (1993).
19. [19] Wood, D. A., “The application of a Th–Hf–Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary Volcanic Province”, Earth and Planetary Science Letters, 50(1), 11–30, (1980).
20. [20] Pearce, J. A., “A user’s guide to basalt discrimination diagrams”, in: Wyman, D. A. (Ed.), Trace element geochemistry of volcanic rocks: Applications for massive sulphide exploration, 12, 79–113, Geological Association of Canada, Short Course Notes, (1996).
21. [21] Sun, S. S. & McDonough, W. F., “Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes”, in: Saunders, A. D. & Norry, M. J. (Eds.), Magmatism in the ocean basins, 42, 313–345, Geological Society (Special Publications), (1989).
22. [22] McKenzie, D. & O’Nions, R. K., “Partial melt distributions from inversion of rare earth element concentrations”, Journal of Petrology, 32(5), 1021–1091, (1991).
23. [23] Rollinson, H., Using geochemical data: Evaluation, presentation, interpretation, Longman Scientific & Technical, (1993).
24. [24] Shand, S. J., Eruptive rocks: Their genesis, composition, classification, and their relation to ore deposits with a chapter on meteorites, John Wiley and Sons, (1943).
25. [25] Maniar, P. D. & Piccoli, P. M., “Tectonic discrimination of granitoids”, Geological Society of America Bulletin, 101(5), 635–643, (1989).
26. [26] Deer, W. A., Howie, R. A. & Zussman, J., An introduction to the rock-forming minerals (2nd ed.), Longman, (1992).
27. [27] Winter, J. D., Principles of igneous and metamorphic petrology (2nd ed.), Pearson Education, (2010).
28. [28] Leake, B. E. et al., “Nomenclature of amphiboles: Report of the subcommittee on amphiboles of the International Mineralogical Association”, European Journal of Mineralogy, 9(4), 623–651, (1997).
29. [29] Putirka, K. D., “Igneous thermometers and barometers based on plagioclase + liquid equilibria: Tests of some existing models and new calibrations”, American Mineralogist, 90, 336–346, (2005).
30. [30] Putirka, K. D., “Thermometers and barometers for volcanic systems”, in: Putirka, K. D. & Tepley, F. J. (Eds.), Reviews in Mineralogy and Geochemistry, 69(1), 61–120, (2008).
31. [31] Ridolfi, F. & Renzulli, A., “Calcic amphiboles in calc-alkaline and alkaline magmas: Thermobarometric and chemometric empirical equations valid up to 1,130 °C and 2.2 GPa”, Contributions to Mineralogy and Petrology, 163(5), 877–895, (2012).
32. [32] Putirka, K., “Amphibole thermometers and barometers for igneous systems and some implications for eruption mechanisms of felsic magmas at arc volcanoes”, American Mineralogist, 101(4), 841–858, (2016).
33. [33] Spear, F. S., Metamorphic phase equilibria and pressure–temperature–time paths, Mineralogical Society of America, (1993).
34. [34] Şimşek, O., “Nevşehir (Kavak) yöresi vişne renkli ignimbiritin duvar kaplamasında kullanılabilirliğinin araştırılması”, Politeknik Dergisi, 25(1), 281–289, (2022).
35. [35] Gültekin, A., Hosseinnezhad, H. & Ramyar, K., “Agrega türünün geopolimer betonun yüksek sıcaklık direncine etkisi”, Politeknik Dergisi, 26(2), 913–921, (2023).
36. [36] Arı, A. C., “Investigation of the effect of using epoxy coatings on salt crystallization in ignimbrite (Nevsehir-Turkiye) stones”, Politeknik Dergisi, 28(1), [in press], (2025).
37. [37] Pearce, J. A., Harris, N. B. W. & Tindle, A. G., “Trace element discrimination diagrams for the tectonic interpretation of granitic rocks”, Journal of Petrology, 25(4), 956–983, (1984).
38. [38] Pearce, J. A., “Trace element characteristics of lavas from destructive plate boundaries”, in: Thorpe, R. S. (Ed.), Andesites: Orogenic andesites and related rocks, 525–548, Wiley, (1982).
39. [39] Harris, N. B. W., Pearce, J. A. & Tindle, A. G., “Geochemical characteristics of collision zone magmatism”, Geological Society, London, Special Publications, 19, 67–81, (1986).