Plajiyoklazların Dokusal Stratigrafisi ile Magma Odası Süreçlerinin Yorumlanması (Konya-Orta Anadolu)

Öz

Çekirdekten kenara bir mineralin kimyasal bileşimindeki ve mikro dokusundaki varyasyonlar, magma odası süreçlerinin oluşumunun sıralanmasına ve hangi dokunun hangi süreçle oluşmuş olabileceğinin yorumlanmasına olanak tanır. Bu çalışmada, Karapınar Karacadağ Volkanik Kompleksi'nden bazı anklav içeren andezit (kalk-alkalen) ve bazaltlardan (kalk-alkalen) alınan, magma odası süreçlerinin önemli bir kaydedicisi olan plajiyoklazların dokusal ve kimyasal zonlanması incelenmiştir ve dokusal stratigrafileri magma odası süreçlerini aydınlatmak için oluşturulmuştur. Anklav içeren andezitler ve bunların anklavları içindeki plajiyoklazlar aynı bileşime sahiptirler ve bileşimleri andezin-bitovnit (An34-An75)tir. Ana kayadaki plajiyoklazların çoğunlukla yuvarlaklaşmış ve Fe, Mg, An, Sr ve Ba ile ters ve salınımlı zonlu olması dikkat çekicidir. Ancak anklavlarda yer alan plajiyoklazlar genellikle ince elek dokusu ve kirli yüzeyli elek dokusu sergilerler. Kalk-alkalen bazaltlardaki plajiyoklaz mikro-fenokristalleri, çekirdekten kenara bileşimde andezin-labrador (An32-An66) olup, bu durum onların fenokristallerden ziyade ksenokristal olabileceklerini düşündürmektedir. Dikkat çekici bir şekilde, bazaltlardaki plajiyoklazlar, Fe, Mg, An, Sr ve Ba ile ters ve salınımlı zonlanma gösterirler ve ayrıca cam ve mikrolitik kapanımlarla iri taneli elek dokusu ve süngerimsi hücresel dokular sergilerler. Plajiyoklazların dokusal ve kimyasal özellikleri göz önüne alındığında, bazaltik kayaçlarda ters ve salınımlı zonlanma oluşumunda, magma karışımı işlemlerinin (magma karışımı/kendi kendine karışma) yanı sıra dekompresyon süreçleri de bazaltların oluşumunu etkilemektedir. Bununla birlikte, andezitik kayaçların oluşumunda, magmanın yeniden beslenmesi süreçleri, dekompresyon veya sıcaklık-basınç değişiminden ziyade anahtar bir role sahiptir.

Anahtar Kelimeler

• dekompresyon
• plajiyoklaz
• elek dokusu
• magma karışmı
• salınımlı zonlanma

Interpretation of the Magma Chamber Processes with the help of Textural Stratigraphy of the Plagioclases (Konya-Central Anatolia)

Abstract

The variations in the chemical composition and micro-texture of a mineral from the core to the rim allow the sequencing of the formation of the magma chamber processes and the interpretation of which texture might have been formed by which process. In this study, the textural and chemical zoning of the plagioclases, which are a significant recorder of magma chamber processes, from some enclave-containing andesite (calc-alkaline) and basalts (calc-alkaline) from the Karapınar Karacadağ Volcanic Complex, were examined and their textural stratigraphies were created to enlight the magma chamber processes. Plagioclases in enclave bearing andesites and their enclaves have the same composition and are andesine-bitovnite (An34-An75) in composition. It is noteworthy that the plagioclases in the host-rock are mostly rounded, and reverse and oscillatory zoned with Fe, Mg, An, Sr, and Ba. However in the enclaves they display generally fine sieve texture and dusty sieve texture. Plagioclase micro-phenocrysts in calc-alkaline basalts are andesine-labrador (An32-An66) in composition from core-to-rim, suggesting that they may be xenocrysts rather than phenocrysts. Remarkably, plagioclases in basalts show reverse and oscillatory zoning with Fe, Mg, An, Sr, and Ba, and as well as exhibit coarse-grained sieve texture with glass and microlithic inclusions, and spongy cellular textures. Considering the textural and chemical properties of the plagioclases, in the formation of reverse and oscillatory zoning in the basaltic rocks, the decompression processes in addition to the magma mixing processes (magma mixing/self-mixing) also affect the genesis of the basalts. However, in the formation of andesitic rocks, the magma replenishment processes have a key role rather than decompression or temperature-pressure change.

Keywords

• decompression
• magma mixing
• oscillatory zoning
• plagioclase
• sieve texture

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