Temu ke duabelas Metamorphism means changed form berubah

Temu ke duabelas

Metamorphism means "changed form“ (berubah bentuk)

Metamorphic u “meta” = to change u “morph” = form u Metamorphic rocks are formed from Parent rocks (pre-existing rocks) u Parent rocks can be Igneous, sedimentary, or other metamorphic rocks. u Metamorphism The process through which a rock’s structure is changed by heat and pressure

Types of Protolith Lump the common types of sedimentary and igneous rocks into six chemically based-groups 1. Ultramafic - very high Mg, Fe, Ni, Cr 2. Mafic - high Fe, Mg, and Ca 3. Shales (pelitic) - high Al, K, Si 4. Carbonates - high Ca, Mg, CO 2 5. Quartz - nearly pure Si. O 2. 6. Quartzo-feldspathic - high Si, Na, K, Al n Chemistry of the metamorphic rock is the most important clue toward deducing the parent rock

What causes metamorphism? u 1. Temperature Increase – Greater Temps at depth – Radioactive Isotopes – Intruding Magma – Friction Between Moving Bodies of Rock

2. Pressure (stress) = Force/meters 2 Increases with depth Pressure can be applied equally in all directions or differentially All Directions = “Confining Pressure” also called “lithostatic pressure” Differential = “Directed Pressure”

METAMORPHISM u u u HEAT: Temperatures needed to metamorphose rock (2000 C or 10000 C) reached near 10 km (6 miles) beneath the surface. PRESSURE: Requires pressure > 1 bar or 1000 mb, which is generally found ~ 3 km (2 miles) beneath the Earth’s surface FLUIDS: Water is the usual fluid and comes from various sources

PERUBAHAN BATUAN METAMORF u Proses metamorf menyebabkan banyak perubahan pada batuan - peningkatan kepadatan – pertumbuhan kristal yang lebih besar – reorientasi butiran mineral menjadi lapisan atau tekstur berpita u FOLIASI – transformasi mineral suhu rendah menjadi mineral suhu tinggi

Bagaimana batuan berubah? Metamorphism causes changes in: 1 Texture (definition: shape, size and orientation of mineral grains in the rocks) 2 Mineralogy (chemical composition)

METAMORPHIC ROCKS METAMORPHISM : proses dimana kondisi di dalam Bumi mengubah kandungan mineral dan struktur batuan beku, sedimen atau metamorf, tanpa melelehkannya. u Metamorfisme terjadi ketika panas dan tekanan melebihi level tertentu, mendestabilisasi mineral dalam batuan. . . tetapi tidak cukup untuk menyebabkan leleh u Cairan kaya ion yang bersirkulasi di dalam dan di sekitar batuan juga mempengaruhi metamorfisme u

CONTACT METAMORFISME JENIS REGIONAL/ DYNAMIC PREEXISTING ROCKS T, P, CHEMICAL FLUIDS HOW WHERE BATUAN METAMORFIK HOW WHERE JENIS BATUAN & CIRI KEJURUTERAAN LINEATION TEXTURE FOLIATION CHANGES MINERALOGY NONFOLIATED

Metamorphic rocks u Ketika batuan dipanggang oleh panas magma cair atau diperas oleh gerakan lempeng tektonik besar atau oleh tekanan dari suksesi tebal batuan yg menindihnya Batuan terubah atau diubah di luar kemampuannya § Misal perubahan komposisi, tekstur, dan struktur kimia § Metamorphic rocks

Metamorphism Is the process that occur in rocks due to the effects of u High temperature u High pressure u Chemically active fluids

Temperature u The source of temperature is either from magma or due to the depth factor u Metamorphism usually result into change in min. comp. and texture of rocks (Ig. and Sed. ) which are subjected to temp. > 1000 C and pressure > 1000’s Mpa. u Low-grade metamorphism: Occurs at about 1000 C to 5000 C. u High-grade metamorphism: Occurs at > 5000 C

Sedimentary rock 0 km Metamorphic rock Igneous rock Sediment Increasing depth and temperature 10 km ~200ºC 50 km ~800ºC Sedimentary rock The rocks don’t melt Metamorphism Melting Metamorfi sme terjadi pada kedalaman sekitar 10 dan 50 km

Pressure UNIFORM PRESSURE - meningkat sejalan dgn kedalaman akibat peningkatan lapisan penutup. - bertindak secara vertikal ke bawah shg mempengaruhi volume cairan & padatan. - suhu tinggi juga berhubungan dengan faktor kedalaman. - Tekanan litostatik karena overburden DIRECT or Differential PRESSURE - meningkat sejalan dgn kedalaman hingga batas tertentu, efektif di bagian atas kerak. - bertindak dalam segala arah dan hanya mempengaruhi padatan yang mengakibatkan deformasi bentuk dan perubahan komposisi mineral - suhu tinggi tidak selalu dikaitkan dgn faktor kedalaman) - Stres karena kekuatan tektonik