Alterasi Batuan

Alterasi Batuan
Oleh
Dr. SUFRIADIN
Bahan Kuliah Magister Teknik Geologi
Universitas Hasanuddin
2015
Materi Kuliah
• Pendahuluan “Alterasi Batuan”
• Sampling dan Metode Analisis Data
• Pengolahan dan Interpretasi data
Pendahuluan
Empat proses yang menyebabkan
mineral/batuan berubah:
1. Magmatik proses
2. Metamorfik proses
Endogen
3. Hidrotermal proses
4. Weathering proses------------- Supergen
Manfaat Studi Alterasi
• Eksplorasi mineral
• Eksplorasi Geotermal
• Geoteknik
– Kestabilan lereng
– Pondasi
• Geokimia Lingkungan
– Release and uptake toxic elements.
– Tailing Disposal
Alterasi Hidrotermal
• Defenisi:
The change in mineralogy, texture, physics
composition of rock that rock interact with
hydrothermal fluids (Guilbert and Park,
1986).
Aspek-aspek yang mempengaruhi alterasi
• Karakter batuan samping (komposisi
mineralogi, kimia, tekstur)
• Nisbah air-batuan (water: rock ratio)
• Komposisi kimia fluida
• Temperatur dan tekanan
Mekanisme Alterasi
• Infiltration: fluid mass moving because of
fluid flow through rocks (misal. rekahan,
• Diffusion: movement of chemical species
through rock pores
• Both infiltration and diffusion
Reaksi-reaksi Alterasi
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Hidrolisis
Hidrasi – Dehidrasi
Metasomatisme
Dekarbonasi
Silikasi
Silisifikasi
Oksidasi-reduksi
Type-type Alterasi
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Potassic (biotite, K-feldspar, magnetite)
Phyllic,Sericitic (Sericite)
Intermediate Argillic (Sericite, Chlorite, Kaolinite)
Advanced Argillic (Pyrophyllite, Pyrophyllite,
andalusite, Quartz)
Greisen (topaz, muscovite)
Calcic Skarn (Garnet, Clinopyroxene, Wollastonite)
Magnesium Skarn (Forsterite-diopsite, Serpentinitetalc)
Retrograde Skarn (Calcite, Chlorite)
Prophylitic (Chlorite, epidote, albite, calcite)
Referensi
BUKU:
• Guilbert, J.M and Park, 1986, The Geology of
Ore Deposits, W.H Freeman & Company.
• Pirajno, F, 2009, Hydrothermal Process and
Mineral Systems, Springer.
• Thompson..1996, Atlas of Alteration, MAC.
JURNAL:
1. Mineralium Deposita (Springer)
2. Ore Geology Reviews (Elsevier)
3. Economic Geology (SEG)
Terima Kasih