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

Year 2025, Volume: 28 Issue: 5, 1469 - 1484

Mehmet Ali Ertürk

https://doi.org/10.2339/politeknik.1717879

Abstract

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.

Keywords

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

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

Abstract

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.

Keywords

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

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