class5- khe nut.pdf

8/13/2019 Class5- Khe nut.pdf

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Class 05.

PH HY V KHE NT

TS. Ng Xun ThnhKhoaa cht

Trng H M - a cht

Ph hy v khe nt


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Ph hy: L thut ngm tmt vt cht bmt tnhlin tc do bph hy.

Ko cng: Hai cnh ca ph hy btch ri nhau ra tonn khe nt. Xit p (Shear): Hai cnh dch trt ln nhau dc theomt ph hy -> t gy

Ph hy ko cng (hay tch gin)

thng c smrng mt ph

hy v khng c sdch chuyn

dc hai bn cnh.

Cc khe nt c hng khc nhau

to nn hthng khe nt.

Khe nt


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H thng khe nt

Gc ca h thng khe nt

Khe nt kin to trn vTrit


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Khe nt kin to

Thng k hthng khe nt

Theo cc khe nt tch Thng cc hthng c lpy bi cc khong vt thnhto sau

ai mch


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Nhng du hiu nhn bit khe nt c stch gin hay khng

Xem hai bn cnh

Cu to dngrng lc

Mch ca cccu trc bdchchuyn.

ai mch mrng to ccmch c thnhphn a hakhc bit.

Cc mch hnhthnh c slintc trong chaibn cnh.

Mt thnh to

trc khng bdchchuyn(offset)

Cchhnh thnh ph hy

1. Ph hy cng gin

Ko cng


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Cc ph hy ko cng to

cu trc ph hy trong ,

dc i khe nt khong c

dch chuyn.

2. Ph hy do bp nn(compression) vdo b ko cng(extension)

Cchhnh thnh ph hy


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3. Ph hy do thotlc

Cchhnh thnh ph hy

Cchhnh thnh ph hy

Cc hthng phhy


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4. Cp khe nt xitp

Cchhnh thnh ph hy

1. Khe nt lng v: Nhn bit hng xit p

t gy nghch hay chm t gy thun

Cp khe nt xit p


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3. Cp khe nt cng sinh & xit p kiu R

Cp khe nt xit p

Khe nt lng v

Plumose Structure


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Qu trnh hnh thnh

Do skhng ng nht ca

Ph hy theo cchngoi sinh

Basalt dng ct

Xy ra trong phun tro basalt


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Tectonic Origin

Residual Stress

Khe nt do xut l

Khe nt dng mi


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Sheeting Joints/Exfoliation


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Phn loi theo hnh thi cc khe nt

A. Theo cu trc mt lp(1) Khe nt theo hng dc: Joint strike parallel

to dip of beds(2) Strike joints: Joint strike parallel to strike of

beds(3) Oblique joints: Joint strike oblique to strike

of beds

Dip joints

Strike joints

Oblique joints

Geometrical classification of joints

B. Beds folded(1) Longitudinal joints (ab

joints): Release joints.(2) Transverse or cross-

joints (ac joints): Extensionjoints.

(3) Diagonal joints- Intersect parallel to b-

direction (shear joint that form

during compression)

- Intersect parallel to a-

direction (Release shear

joints after folding)

(4) Radial joints: Tensionfractures in outer arc of the

buckling type fold

Longitudinal

joints

Transverse or

cross-joints

Diagonal joints

Radial joints


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Why arent joint surface smooth??

Plumose Structure

Plumose structure

Joint origin: The point on the joint at which the fracture began to propagate

Mirror region: A portion of a joint surface where the surface is very smooth

Mist region: A portion of a joint surface where the fracture surface begins to roughen

Hackle zone: The main part of a plumose structure, where the surface is relatively rough

Twist hackle: One of a set of small en echelon joints formed along the edge of a larger

joints.

Arrest line: An arcuate ridge on a joint surface, where the joint front stopped during

propagation of the joint


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Why plumose structure form??

Rocks are not homogeneous and Isotropic

Crack Tip Propagation speed

Twist Hackle


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Straight Plumose

Curvy Plumose


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Columnar Jointing

Jointing that break rock into hexagonal columns; they form

during cooling and contraction in hypabyssal intrusions of lava

flows

Tectonic Origin

Residual Stress


Jointing parallel to the exposure surface (like layers of an onion)


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class5- khe nut.pdf

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