H. Muhammad Ridha Adhari, S.T., M...Klasifikasi Lipatan berdasarkan sudut antar sayap lipatan...

H. Muhammad Ridha Adhari, S.T., M.Sc

Dept. of Mining Engineering

Faculty of Engineering

Syiah Kuala University

Darussalam, Banda Aceh

2017

PengumumanSelasa depan (14-3-2017) direncanakan akan

ada quiz Geologi Struktur.

Materi dari Pertemuan pertama sampai terakhir

hari ini.

Course Outline

Secondary Structure

Plastic Deformation

Brittle Deformation

Summary

What is Secondary Structures?

Result from later deformation of the primary structures.

The structures are most easily observed if the rocks have

obvious primary structures, such as layering/bedding.

STENO’S PRINCIPLE

THE PRINCIPLE OF SUPERPOSITION

In a sequence of strata, any stratum is younger than the

sequence of strata on which it rests, and is older than the

strata that rest upon it.

PRINCIPLE OF ORIGINAL HORIZONTALITY

Strata are deposited horizontally and then deformed to

various attitudes later.

PRINCIPLE OF LATERAL CONTINUITY

Strata can be assumed to have continued laterally far

from where they presently end.

Adhari, M.R., Teknik Geologi Unsyiah

Adhari, M.R., Teknik Geologi Unsyiah

Steno’s PrincipleAdhari, M.R., Teknik Geologi Unsyiah

Law of superposition

Rock layers are deposited

from the bottom up

The deeper we dig, the

farther back in time we see

Adhari, M.R., Teknik Geologi Unsyiah

Nicolas Steno laid down the basis of modern stratigraphy and

palaeontology.

Lateral ContinuityAdhari, M.R., Teknik Geologi Unsyiah

What Happens to Steno’s Principle?

What Happens to Steno’s Principle?

What Happens to Steno’s Principle?

Deformation Caused by Differential Stress.

Deformation : the changes in the shape or position

of a rock body in response to differential stress.

Adhari, M.R., Teknik Geologi Unsyiah

Forces that cause deformation of rocksAdhari, M.R., Teknik Geologi Unsyiah

Confining Pressure and Differential Stress

Adhari, M.R., Teknik Geologi Unsyiah

Confining Pressure : Equal from all sides. Reduces

volume without deformation.

Differential Stress : Stress system where the

forces acting on a unit cube are not the same in all

directions.

Type of Stress / Pressure

Adhari, M.R., Teknik Geologi Unsyiah

Adhari, M.R., Teknik Geologi Unsyiah

Adhari, M.R., Teknik Geologi Unsyiah

Primary depositional layering is always horizontal

Steno’s Principle.

When layers are found that are not horizontal, the

geologist assumes that some force has been exerted upon

them that has destroyed their original horizontality.

Adhari, M.R., Teknik Geologi Unsyiah

Secondary Structure:

Plastic Deformation.

Brittle Deformation.

Adhari, M.R., Teknik Geologi Unsyiah

Behavior of rocks to stress & strain

Adhari, M.R., Teknik Geologi Unsyiah

(c–f) Schematic cross sections showing the behavior of rock cylinders during the

successive stages of a confined compression experiment and accompanying stress–

strain plot, emphasizing the behavior of Griffith cracks (cracks shown are much larger

than real dimensions). (c) Pre-deformation state, showing open Griffith cracks. (d)

Compression begins and volume decreases due to crack closure. (e) Crack

propagation and dilatancy (volume increase). (f) Merging of cracks along the future

throughgoing shear fracture, followed by loss of cohesion of the sample (mesoscopic

failure).

The atomic structure of materials. Solids are composed of

atoms or ions that are connected to one another by chemical

bonds that can be thought of as tiny springs.

How can a strong layer of rock permanently bend into a

fold/fault?

Elastic deformation recoverable (nonpermanent).

Plastic deformation Permanent Fold.

Brittle deformation Permanent Fault, Joint, Vein.

Ductile/Plastic Deformation

Adhari, M.R., Teknik Geologi Unsyiah

Fold. Plastic Deformation.

Adhari, M.R., Teknik Geologi Unsyiah

Fold. Plastic Deformation.Adhari, M.R., Teknik Geologi Unsyiah

Types of Fold

Anticlines.

Synclines.

Monoclines.Anticlines. Synclines.

Monoclines.Adhari, M.R., Teknik Geologi Unsyiah

Adhari, M.R., Teknik Geologi Unsyiah

Monoclines.

Adhari, M.R., Teknik Geologi Unsyiah

Klasifikasi Lipatan berdasarkan simetri dan orientasinya

Adhari, M.R., Teknik Geologi Unsyiah

Klasifikasi Lipatan berdasarkan sudut antar sayap lipatan

Adhari, M.R., Teknik Geologi Unsyiah

Adhari, M.R., Teknik Geologi Unsyiah

Adhari, M.R., Teknik Geologi Unsyiah

Ptygmatit Fold

Parasitic Fold

Dua lapisan yang terlipat dengan ketebalan yang berbeda.

Lipatan yang atas mempunyai wavelength yang lebih kecil daripada yang dibawah. Ketika lapisan yang tebal mengalami

pelipatan, lipatan kecil pada lapisan

batuan menjadi parasitic dan asimetri

karena flexural flow.

Adhari, M.R., Teknik Geologi Unsyiah

Brittle deformation : The permanent change that occurs

in a solid material due to the growth of fractures and/ or

due to sliding on fractures.

Brittle deformation only occurs when stresses exceed a

critical value, and thus only after a rock has already

undergone some elastic and/or plastic behavior.

Brittle Deformation :

Fracture

Joint (Tensile Facture)

Fault (Shear Fracture)

Vein

Brittle Deformation

Adhari, M.R., Teknik Geologi Unsyiah

Types of brittle deformation. (a) Orientation of the principal

stress directions. (b) A tensile crack (c) A shear fracture.

Adhari, M.R., Teknik Geologi Unsyiah

Normal Fault Adhari, M.R., Teknik Geologi Unsyiah

Dip-slip fault : slip parallel to dip (up or down plane).

Normal Fault, Thrust (Reverse) Fault

Strike-slip fault : slip parallel to strike (horizontal).

Transform Fault

Oblique-slip : have both strike-slip (horizontal) and

dip-slip (vertical) motion.

Type of Fault

Adhari, M.R., Teknik Geologi Unsyiah

Dip-Slip Faults Adhari, M.R., Teknik Geologi Unsyiah

Strike-Slip Faults

Adhari, M.R., Teknik Geologi Unsyiah

Oblique-Slip Faults

Adhari, M.R., Teknik Geologi Unsyiah

JointAdhari, M.R., Teknik Geologi Unsyiah

JointAdhari, M.R., Teknik Geologi Unsyiah

Gold Vein Adhari, M.R., Teknik Geologi Unsyiah

Gold VeinsAdhari, M.R., Teknik Geologi Unsyiah

VeinsAdhari, M.R., Teknik Geologi Unsyiah

VeinsAdhari, M.R., Teknik Geologi Unsyiah

Summary

Elastic deformation Recoverable (nonpermanent).

Plastic deformation Permanent Fold.

Brittle deformation Permanent Fault, Joint, Vein.

Secondary Structure : Plastic deformation and Brittle

deformation.

Type of Fold : Anticlines, Synclines, Monoclines.

Type of Fault : Dip-slip fault, Strike-slip fault, Oblique.