Kula (Batı Türkiye) Vezirler Karmaşığındaki Listvenitik Hidrotermal Alterasyonunun Uzaktan Algılanması: Landsat-7 ETM+, Crosta-PCA ve Bant-Oranı Haritalaması

Öz

Vezirler ofiyolitik melanjı (Kula’nın kuzeydoğusu, Batı Türkiye) içerisindeki listvenit tipi silis–karbonat metasomatik alterasyon, litoloji/ROI maskelemesi uygulanmış Seçimli PCA (Selective PCA) iş akışı ve tamamlayıcı bant-oranı indeksleri ile bulut içermeyen bir Landsat-7 ETM+ görüntüsü üzerinden taranmıştır. Maskeleme, bitki örtüsü, alüvyon ve hedef dışı litolojilerden kaynaklanan spektral karışımı azaltarak saha ile doğrulanmış ROI içinde anomali kontrastını artırmıştır. Ferrik demire duyarlı PC2 anomalileri, karbonatlaşmış/silisleşmiş serpantinitler (CS-Srp) ile Fe-oksit boyalı silis–karbonat şapkalar (Fscc/Cnz) boyunca kümelenmekte ve arazide gözlenen hematitleşmiş kaplamalarla uyum göstermektedir. Fe²⁺ tepkileri daha zayıftır ve yüzeyde ileri oksidasyon/overprinting koşullarında Fe²⁺ imzalarının sınırlı korunduğunu düşündürmektedir. Hidroksil ile ilişkili desenler alterasyon halelerini işaret etse de kuvvetli silisleşmiş şapkalarda OH soğurmalarının baskılanması nedeniyle zayıflayabilmektedir. Bant-oranı haritaları (Fe³⁺: B3/B2; silis: B7/B5; OH⁻: B5/(B5+B7)) ve μ ± σ ile istatistiksel sınıflama, PCA desenlerini doğrulayarak tekrarlanabilir hedef sıralaması sağlamıştır. Sonuçlar, gölgeli vadilerde topoğrafya kaynaklı sahte anomaliler ve eğim geçişlerinde piksel-içi karışım nedeniyle oluşan spektral seyrelme gibi 30 m çözünürlüğe özgü sınırlılıkları dikkate alarak, bölgesel ölçekte hızlı alterasyon taramasını mümkün kılmaktadır. Gelecek çalışmalarda ASTER TIR ve 2008 öncesi arşiv ASTER SWIR sahneleri veya modern SWIR/hiperspektral veriler ile mineral ayrımı güçlendirilebilir.

Anahtar Kelimeler

• Kula
• listvenit
• Crosta-PCA
• Landsat-7 ETM+
• demir oksit
• karbonat alterasyonu
• uzaktan algılama
• Bant oranları

Remote Sensing of Listvenite Hydrothermal Alteration in Vezirler Mélange, Kula (Western Türkiye): Landsat-7 ETM+, Crosta-PCA and Band-Ratio Mapping

Öz

Listvenite-type silica–carbonate metasomatic alteration in the Vezirler ophiolitic mélange (northeastern Kula, western Türkiye) was screened using a lithology-masked Selective PCA workflow and complementary band-ratio indices applied to a cloud-free Landsat-7 ETM+ image. Masking reduced spectral mixing from vegetation, alluvium, and non-target lithologies and increased anomaly contrast within a field-verified ROI. Ferric-iron–sensitive PC2 anomalies cluster along carbonatized/silicified serpentinites (CS-Srp) and Fe-oxide-stained silica–carbonate caps (Fscc/Cnz), consistent with hematite coatings documented in the field. Ferrous-iron responses are comparatively subdued, indicating limited preservation of surface-expressed Fe²⁺ signatures under pervasive oxidation and overprinting. Hydroxyl-related patterns delineate alteration halos but weaken over strongly silicified caps where diagnostic OH absorption is suppressed. Band-ratio maps (Fe³⁺: B3/B2; silica: B7/B5; OH⁻: B5/(B5 + B7)), statistically segmented using μ ± σ thresholds, reproduce first-order PCA patterns and support repeatable anomaly ranking. The results demonstrate a rapid regional screening approach relevant to alteration targeting and natural mineral carbonation analogues, while recognizing inherent limitations of the 30 m resolution, such as false positives in shaded valleys due to topographic effects and spectral dilution from mixed-pixel responses along slope transitions. Future work may integrate ASTER TIR and archival ASTER SWIR scenes acquired prior to 2008, or modern SWIR/hyperspectral datasets, to improve mineral discrimination.

Anahtar Kelimeler

• Kula
• listvenite
• Landsat-7 ETM+
• iron oxides
• silica-carbonate alteration
• band ratios
• Crosta-PCA
• remote sensing

Kaynakça

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