Post on 08-Jul-2018
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PENGANTAR
(TSL)
I Gde Budi Indrawan, Ph.D.
ma : g n rawan.ugm gma .com
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V. BATUAN - Pengertian
Batuan
.
2Jurusan Teknik Geologi | Universitas Gadjah Mada
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V. BATUAN - Batuan Metamorf
Metamorfisme
yang berbeda.
• Jenis- enis:
1. Metamorfisme termal (sentuh)
2. Metamorfisme dinamik (tekan)
3. Metamorfisme regional
3Jurusan Teknik Geologi | Universitas Gadjah Mada
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V. BATUAN - Batuan Metamorf
1. Metamorfisme termal (sentuh)
.
• Terjadi pada jalur magma yang menerobos batuan lain.
.
4Jurusan Teknik Geologi | Universitas Gadjah Mada
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V. BATUAN - Batuan Metamorf
2. Metamorfisme dinamik
.
• Terjadi pada daerah yang mengalami tektonik yang
men hasilkan retakan dan atahan sesar .
• Bersifat lokal.
5Jurusan Teknik Geologi | Universitas Gadjah Mada
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3. Metamorfisme regional
.
• Terjadi pada daerah dekat tumbukan lempeng.
.
6Jurusan Teknik Geologi | Universitas Gadjah Mada
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Tanda-tanda metamorfisme
• en e orme ayers
Shale
7Jurusan Teknik Geologi | Universitas Gadjah Mada Gneiss
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• Flattened rock fragments
Conglomerate
8Jurusan Teknik Geologi | Universitas Gadjah Mada
Metaconglomerate
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• Minerals tightly interlocked due to recrystallization under
Quartz Sandstone
Quartzite
9Jurusan Teknik Geologi | Universitas Gadjah Mada
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• New mineral assemblages
Shale: Clay minerals
Metamor hism
(Mid-grade)
Schist: Mica, Feldspar and
o er s ca e m nera s
10Jurusan Teknik Geologi | Universitas Gadjah Mada
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Proses metamorfisme
• aren roc
– Even though original
elements are provided by
parent rock, except water
Shale
11Jurusan Teknik Geologi | Universitas Gadjah MadaSchist
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• Increased Temperature (geothermal gradients)
–
minerals stable at higher temperatures Temp.
(ºC)
B
A B C
12Jurusan Teknik Geologi | Universitas Gadjah Mada
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• Increased Pressure (and stress)
–
– Compression at convergent plate boundary or – Sheared as plates slide past each other
13Jurusan Teknik Geologi | Universitas Gadjah Mada
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•
– Water (and other fluids) within rocks and minerals
– Moving during metamorphism
– Accelerates solid-state chemical reactions and – May change rock composition
• Time Millions of ears!
14Jurusan Teknik Geologi | Universitas Gadjah Mada
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V. BATUAN - Batuan Metamorf
Batuan metamorf
batuan ubahan
• Berfoliasi
» Semacam erla isan ada
batuan sedimen namun
tersusun atas mineral-mineral.Schist (foliated) (http://www.snyder.shp.org/)
•
15Jurusan Teknik Geologi | Universitas Gadjah Mada
Quartzite (non foliated)
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16Jurusan Teknik Geologi | Universitas Gadjah Mada
Contoh pembentukan foliasi pada batuan metamorf (Lutgens et al., 2012)
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• Macam-macam foliasi:
−
» Foliasi mineral-mineral berbutir sangat halus (lempung)
sehin a men eru ai lem en -lem en an teratur dan
mudah dibelah searah dengan lempeng tersebut.
−Skistosik» Foliasi yang ditunjukkan oleh susunan mineral-mineral
pipih, misalnya mika.
−
» Foliasi yang ditunjukkan oleh deretan mineral berbutir
kasar umumn a beru a mineral felds ar dan kwarsa.
17Jurusan Teknik Geologi | Universitas Gadjah Mada
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18Jurusan Teknik Geologi | Universitas Gadjah Mada
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Contoh Proses Metamorfisme
1. Parent rock: Shale
– Minerals stable under low T& P
(atmospheric): clay (and quartz)
– Compaction due to accumulation of sediment
– Water bound in crystalline structure of clay
2. Low- rade metamor hism: Slate
– Minerals stable under low-grade metamorphic
conditions: fine grained mica (and chlorite and
quartz)
– Slaty Cleavage due to realignment of platyminerals
– Water is expelled from crystalline structure of
Jurusan Teknik Geologi | Universitas Gadjah Mada
c ay
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3. Medium-grade metamorphism: Phillite
– Medium-grade metamorphic T& P causes
minerals to grow
– Minerals stable under medium-grade
metamorphic conditions: coarser grained
– Slaty cleavage becomes rippled and rock has
a sheen
4. Medium to high-grade metamorphism :
Schist
–needle like minerals
– Minerals stable under medium to high-grademetamorphic conditions: coarser grained
Jurusan Teknik Geologi | Universitas Gadjah Mada
mica and quartz
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5. High-grade metamorphism: Gneiss
– High-grade metamorphic T& P causes
minerals to separate into bands
– Minerals stable under high-grademetamorphic conditions: feldspar
–minerals
. -
partial melting: Migmatite
– Silica rich minerals melt first (quartz and
felds ar to form silicic ma ma
– Injected into fractures resulting in silicic veins
if intrusive igneous rock
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Metamorphism of other parent rocks into non-foliated
metamorphic rocks
Quartz Sandstone
Quartzite
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Asal batuan metamorf
BATUAN ASAL BATUAN METAMORF
Batuan beku, endapan, piroklastik, dan
batuan metamorf berbutir kasar,
Gneis (gneiss)
misalnya granit, konglomerat, breksi.
Batuan beku, endapan, piroklastik, dan
batuan metamorf berbutir sedang-halus,
Sekis (schist)
m sa nya asa , a u pas r, u .
Batuan beku, endapan, piroklastik, dan
batuan metamorf berbutir halus-sangat
Batu sabak (slate)
, , ,
lempung.
Batugamping, dolomit Marmer (marble)
Batu asir kwarsa Kwarsit uartzite
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Klasifikasi batuan metamorf
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Klasifikasi batuan metamorf
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Lutgens et al. (2012)