N. BANUNAEK T. Pertambangan Undana N. Banunaek, Struktur Geology.

Presentasi berjudul: "N. BANUNAEK T. Pertambangan Undana N. Banunaek, Struktur Geology."— Transcript presentasi:

1 N. BANUNAEK T. Pertambangan Undana 2009 1 N. Banunaek, Struktur Geology

2 TIGA ARAH STRESS  Compression  Tension  Shear Material akan memberikan reaksi yang berbeda bila arah stress berbeda

3 DUA BENTUK DEFORMASI BRITTLE  Cold hard crust  Fracture  Permanently deformed (once broken) DUCTILE  Hot soft crust  Flow  Permanent (plastic) or recoverable (elastic)

4 What determines whether brittle or ductile mechanisms will prevail?  Temperature  Rate  Material properties  Stress heterogeneity  Material heterogeneity  Confining pressure  Other factors…..

5 Brittle Deformation  Shape change by breaking rather than flowing  Manifests as fractures - faults and joints  Occurs when rate of deformation exceeds rate at which material can deform plastically  Occurs when deformation exceeds elastic threshold of material

6 Ductile Deformation  Shape change through flowing (on km down to atomic scales) rather than breaking  Manifests as flow patterns, coherent shape/size change  Occurs when material can flow fast enough to keep up with deformation applied to it.

7 Features of Brittle Structures  Hard, broken edges  Cracks, grain breakage (=cataclasis)  NON recoverable  Sometimes Systematic, ie. regular spacing of joints  May begin with small cracks which line up to form one major crack  Dilation or compaction common in granular or broken materials  Volume/ layer thickness conserved

8 Features of Ductile Structures  May be fluidy-looking, marbled  Usually asystematic  Volume change or re-distribution (ie. thickening in the hinge of a fold)  May be layered or banded  Usually smooth countours  Ductile material may flow around brittle grains (= augen)  Ancient structures - non recoverable

9 BRITLE DEFORMATION  Fractures/joints  Faults/Shear zones T. Pertambangan Undana 2009N. Banunaek, Struktur Geology 9

10 FRACTURE DAN JOINT  Fractures (istilah umum = rekahan) – merupakan permukaan sepajang batuan yang pecah (rekahan).  Joints (Lebih specific) – fractures dengan sedikit atau tanpa adanya displacement parallel pada bidang permukaannya.  Fractured adalah brittle deformation dari sifat material yang brittle. T. Pertambangan Undana 2009N. Banunaek, Struktur Geology 10