Using Hyperspectral Images in Mapping Alteration Minerals

Abstract

Geoscientists require fieldwork primarily when investigating underground resources. Elements and minerals of economic value can be mobilized in rocks enriched either primarily or secondarily through temperature, pressure, and tectonic activities by hydrothermal fluids. Hydrothermal solutions, becoming saturated over time, deposit ore minerals within fractures, faults, and discontinuities where they are chemically or physically suitable in geological environments. These dissolution and precipitation processes are also referred to as hydrothermal activities. Consequently, mineral transformations occur in rocks interacting with hydrothermal fluids, leading to the formation of newly created minerals known as alteration minerals (sulfate and clay minerals; such as alunite, kaolinite, sericite and Fe-bearing minerals such as hematite, limonite, etc.). Chemical components such as OH, Al, Mg, Fe, Cl, and CO3 present in the chemical compositions of minerals exhibit recognizable absorption values in certain sections of the electromagnetic spectrum. Remote sensing (RS) methods provide significant results in mapping these minerals due to their identifiable absorption values in specific segments of the electromagnetic spectrum. RS, along with associated image processing techniques, is applied to potentially prospective areas for mineral deposits. Images from multispectral (Landsat, ASTER, Worldview, etc.) or hyperspectral (Hyperion, PRISMA, HypSIS, etc.) satellites can be used for the purpose. Images are first subjected to some pre-processing such as geometric, radiometric and atmospheric. Afterwards, on the images; Image processing methods such as band ratio (BR), principal component analysis (PCA), minimum noise segmentation (MNF) and classification are applied.

Keywords

• Hyperspectral imaging
• Alteration
• Mineral mapping
• Classification

Alterasyon Minerallerinin Haritalamasında Hiperspektral Görüntülerin Kullanılması

Abstract

Yer bilimciler yeraltı kaynaklarını araştırırken öncelikle saha çalışmalarına ihtiyaç duyarlar. Araştırmacılar için yer altı kaynaklarının tespit edilmesinde yüzey verileri oldukça önem taşımaktadır. Ekonomik açıdan değerli olan element ve mineraller hidrotermal akışkanlar tarafından sıcaklık, basınç ve tektonik faaliyetlerle birincil ya da ikincil olarak zenginleştikleri kayaçlarda mobil hale getirilebilirler. Zamanla doygun hale gelen hidrotermal çözeltiler bünyesindeki cevher minerallerini kimyasal veya fiziksel olarak elverişli jeolojik ortamlarda bulundukları kırık, çatlak ve süreksizliklerde çökeltirler. Bu çözme ve çökeltme süreçleri hidrotermal faaliyet olarak da adlandırılır. Süreç sonucunda hidrotermal akışkanlarla etkileşime giren kayaçlarda mineral dönüşümleri gerçekleşir ve yeni oluşan bu minerallere alterasyon mineralleri (alunit, kaolinit, serizit vb. sülfat, kil mineralleri ve hematit, limonit vb. demirli mineraller) adı verilir. Minerallerin kimyasal bileşimlerinde bulunan OH, Al, Mg, Fe, Cl ve CO3 gibi kimyasal bileşenler elektromanyetik spektrumun belirli bölümlerinde tanınabilir absorbsiyon değerlerine sahip oldukları için bu minerallerin haritalanmasında uzaktan algılama (UA) yöntemleri dikkate değer sonuçlar verir. Maden yatakları açısından önemli bir veri kaynağı olan multispektral (Landsat, ASTER, Worldview vb.) veya hiperspektral (Hyperion, PRISMA, HypSIS vb görüntülerinden elde edilen mineral haritalarına amaca yönelik olarak görüntü işleme yöntemleri uygulanabilir. Görüntüler öncelikle geometrik, radyometrik ve atmosferik gibi bir takım ön işlemlere tabi tutulduktan sonra bant oranlama, temel bileşen analizi (PCA), minimum gürültü bölütlemesi (MNF) ve sınıflama gibi görüntü işleme yöntemleri uygulanır.

Keywords

• Hiperspektral görüntüleme
• Alterasyon
• Mineral haritalama
• Sınıflama

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