Petrography, mineral chemistry and whole-rock geochemical properties of orthopyroxenites in the mantle section of the Kırdağ ophiolite (Erzurum, NE Turkey)

Yıl 2025, Cilt: 15 Sayı: 1, 140 - 160, 15.03.2025

Özgür Bilici

Öz

In this study, the formation conditions and petrogenetic characteristics of orthopyroxenites in the mantle section of the Kırdağ ophiolite (Erzurum, NE Turkey), which outcrops within the Erzurum-Kars Ophiolite Zone in the Eastern Pontides, have been evaluated for the first time using mineral chemistry and whole-rock geochemical data. The main mineralogical composition of the samples taken from the orthopyroxenites consists predominantly of orthopyroxenes, with lesser amounts of clinopyroxenes and subhedral to euhedral chromian spinels. The mineral compositions, characterized by partially high Cr# and low TiO2 contents in chromian spinels, and high Mg# and low Al2O3 contents in pyroxenes, indicate that the formation conditions involve the re-melting of a depleted mantle source. Additionally, high whole-rock Mg# values, concave-shaped rare earth element (REE) patterns, and enrichment in large-ion lithophile elements (LILE) explain metasomatic events during melt-peridotite interaction processes in the subduction zone. As a result, it is understood that the petrographic and petrological characteristics of the studied orthopyroxenites indicate that they formed through the transformation of olivines into orthopyroxenes via the reaction of the parent peridotite with high-silica melts in a subduction zone.

Anahtar Kelimeler

Kırdağ ophiolite, Mineral chemistry, Orthopyroxenite, Petrology, Erzurum, Turkey

Proje Numarası

FBA-2018-6828

Kırdağ ofiyoliti (Erzurum, KD Türkiye) manto bölümü içerisindeki ortopiroksenitlerin petrografisi, mineral kimyası ve tüm kaya jeokimyasal özellikleri

Öz

Bu çalışmada, Doğu Pontidlerin doğusunda, Erzurum-Kars Ofiyolit Zonu içerisinde yüzeyleyen Kırdağ ofiyolitinin (Erzurum, KD Türkiye) manto bölümündeki ortopiroksenitlerin oluşum koşulları ve petrojenetik özellikleri, mineral kimyası ve tüm kaya jeokimyasal verileri kullanılarak ilk kez değerlendirilmiştir. Ortopiroksenitlerden alınan örneklerde ana mineralojik bileşimi çoğunlukla ortopiroksenler, daha az oranda klinopiroksenlerle öz ve yarı özşekilli krom spineller oluşturmaktadır. Mineral bileşimlerinde krom spinellerin kısmen yüksek Cr#, düşük TiO2 içerikleri ve piroksenlerin yüksek Mg# ve düşük Al2O3 içerikleri oluşum koşullarının tüketilmiş manto kaynağının yeniden ergimesini işaret etmektedir. Ayrıca, yüksek tüm kaya Mg# değerleri ile konkav şekilli nadir toprak element (NTE) desenleri ve büyük iyon yarıçaplı litofil elementler (BİLE) bakımından zenginleşmiş özellikleri, yitim zonundaki ergiyik-peridotit etkileşim süreçlerindeki metasomatik olayları açıklamaktadır. Sonuç itibariyle, incelenen ortopiroksenitlerin petrografik ve petrolojik özellikleri bir yitim ortamında ana peridotitin yüksek silisli ergiyiklerle reaksiyonu sonucu olivinlerin ortopiroksenlere dönüşümü yoluyla oluştuğu anlaşılmaktadır.

Anahtar Kelimeler

Kırdağ ofiyoliti, Mineral Kimyası, Ortopiroksenit, Petroloji, Erzurum, Türkiye

Destekleyen Kurum

Atatürk Üniversitesi

Proje Numarası

FBA-2018-6828

Kaynakça

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