Microstructures, textures and material properties of marble rocks - - PowerPoint PPT Presentation

Paolo Conti

Samos Training School, 26-30 August 2013

conti@unisi.it

Microstructures, textures and material properties

• f marble rocks

, Italy

• Marble behaviour
• Crystal structure of minerals and rocks
• Rock fabrics
• Marble deterioration
• Mechanical properties
• Natural examples

2

Contents

Marbles: different behaviour

3

(from Shushakova et al., 2010) (Ephesus, Turkey)

Marbles: different behaviour

4

panels

Marbles: different behaviour

5

Marbles

6

Same composition (≃100 % CaCO3) Different behaviour due to:

• anisotropic physical properties of calcite crystals
• texture of rocks
• microstructure of rocks

Anisotropic physical properties:

Crystal structure of rocks

7

Anisotropic physical properties: strength

8

crystal “weak” bond “strong” bond

Anisotropic physical properties: strength

9

crystal “weak” bond “strong” bond

Anisotropic physical properties:

thermal expansion

10

Increasing temperature: stretch of bond length

“weak” bond “strong” bond

Anisotropic physical properties:

thermal expansion

11

(Winkler, 1994)

Anisotropic physical properties:

natural texture

12

crystallographic direction

(b) (c)

strong crystallographic preferred

• rientation

weak crystallographic preferred

• rientation

Anisotropic physical properties: shapes

13

(Ruedrich et al., 2011)

A l

• n

g g r a i n b u

• n

d a r i e s , w e a t e r i n g : m i c r

• k

a r s t , b r e a k

• u

t s , c

• l
• r

a t i

• n

, f

• r

m a t i

• n
• f

c r u s t s , b i

• l
• g

i c a l c

• l
• n

i z a t i

• n

, g r a n u l a r d e s i n t e g r a t i

• n

, p e e l i n g , m

• i

s t u r e e x p a n s i

• n

, e t c . S u p e r f i c i a l d i s i n t r e g r a t i

• n
• l
• s

s

• f

c

• h

e s i

• n

( d i l a t a n c y )

• t
• t

a l d e c a y

• f

t h e m a t e r i a l

Anisotropic physical properties: shapes

14

straight grain boundaries lobate grain boundaries “slide” “locked”

Anisotropic physical properties: shapes

15

shape preferred

• rientation of crystals

no shape preferred

• rientation of crystals

(anisotropic volume increase)

Developement of microstructures (movies)

16

dynamic (syn-tectonic) recrystallization static recrystallization (annealing) Octachloropropane (organic material)

Means et al. (1994) J. Struct. Geol.,16, 403-418 before: no shape preferred

• rientation, straight

grain boundaries before: shape preferred

• rientation, lobate

grain boundaries

http://www.atmos.albany.edu/geology/ webpages/wdmovies/wdmoviep.html

Anisotropic physical properties

17

(b) (c) (d) (e)

• no shape preferred
• rientation of

grains

• no crystallographic

preferred

• rientation
• no shape preferred
• rientation of

grains

• crystallographic

preferred

• rientation
• shape preferred
• rientation of

grains

• no crystallographic

preferred

• rientation
• shape preferred
• rientation of

grains

• crystallographic

preferred

• rientation

crystallographic preferred orientation of crystals = texture of rock shape preferred orientation of crystals = microstructure of rock

(texture + microstructure = fabric)

In marbles...

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limited informations from outcrop studies only

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Microstructures in marbles

“ultra” thin section (<8 µm)

Microstructures in marbles

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(Carmignani, Conti, et al., 2007)

Carrara marble (Italy)

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Microstructures in marbles: measure

(Molli, Conti et al., 2007)

T extures in marbles: measure

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(same color, same crystallographic orientation)

(Molli, Conti et al., 2007)

CIP analysis (Heilbronner Panozzo R. & Pauli C. (1993) - Integrated spatial and orientation analysis of quartz c-axis by computer-aided microscopy. Journal of Structural Geology, 13, 369–382.)

In marble rocks ...

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• Physical properties of rock linked with texture and

microstructure;

• Laboratory studies yield informations about rock

texture and microstructure and therefore inferences about physical properties;

• Development of texture and microstructure related

to geological history of rock;

• Field geology and laboratory studies allow to estimate

the microstucture and texture expected in an area.

Microstructure, texture and geological evolution

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a

SW SW NE NE

N

• M. Sumbra

a b c d

e

c b a d e

Carrara marble, Alpi Apuane, Italian Northern Apennines

• Alpi Apuane tectonic

window

• Jurassic limestones:

marbles

• greenschists facies

metamorphism during Tertiary

Microstructure, texture and geological evolution

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1) subduction, main thrusting, folding 2) metamorphism 3) later thrusting 4) extension, exhumation, normal faulting

Conclusions

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• marbles usually are NOT homogeneous rocks;
• marbles are thermally sensitive rocks because calcite

anisotropic behaviour, damages at low temperature;

• studies on microstructures and textures in marbles

are performed at thin section scale (or even at smaller scale)

• regional and field geology investigations important to

link microstructures with tectonic features in the field;

• investigating microstructure and texture in rocks is an

appropriate tool for:

• better set recovery and preservations of marble

artifacts;

• inferences about marble behaviour;
• evaluation of marble quality.

... evaluation of marble quality ...

• Amoco Corporation Building, Chicago, USA
• Bowing of external marble panels: replacement

27

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www.geotecnologie .unisi.it/conti

Slides, handouts, papers:

conti@unisi.it