Higgins M.D. Quantitative textural measurement in igneous and metamorphic petrology

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eruptions (e.g. Sparks, 1978). Vesicle size distributions (VSDs) are studied

because they may give information on degassing and magma volatile contents

(Toramaru, 1989, Gaonac’h et al., 1996b, Larsen & Gardner, 2000) and may

be used to determine eruption conditions (Blower et al., 2001).

Explosive silicic volcanic eruptions are not only important for their geolo-

gical effects, but also for their potential impact on human communities. One of

the larger Holocene eruptions was that of Mt Mazama, which produced Crater

Lake (Klug et al., 2002). The main product of this eruption was highly

vesicular pumice in which most pores are connected. The high vesicle number

densities indicate that bubble nucleation occurred rapidly at a high degree of

supersaturation; hence continuous nucleation models cannot be applied. Small

vesicles are approximately lognormal by volume reflecting this single nuclea-

tion and growth event. Larger vesicles follow a power law distribution which

may be due to coalescence (Figure 7.5). Klug et al.(2002) proposed that

nucleation was in response to a downward propagating decompression

wave, followed by bubble growth and coalescence, and finally fragmentation.

Submarine pyroclastic volcanism seems at first glance to be unlikely, but

there is abundant evidence of its occurrence in some situations. Clearly, the

question involves degassing, hence the interest in evidence provided by VSDs

log

(L = vesicle diameter) (μm)

log

L) (cm

–3

)

024

Figure 7.5 Cumulative vesicle size distributions in pumice from Mt

Mazama (Klug et al ., 2002). Size distributions of all samples depart from a

power law model (slope 3.3) at small sizes.

7.5 Typical applications 229

in pumice. The Healy caldera is an active volcano currently at a depth of

1.1–1.8 km. Wright et al.(2003) have quantified the shape and size of vesicles

in pumice from this eruption. There is a good correlation between vesicle size

and shape: increasing complexity with size is considered to reflect coalescence.

VSDs were measured by integrating slab and thin section data. Unfortunately,

the data were converted using inappropriate methods (see Section 3.3.4.6).

Despite this the VSD largely follows a power law between 0.03 and 2 mm with

d ¼ 2.5  0.4 (the effect of the conversion error on the VSD is unclear).

Departures from the distribution outside those limits are probably measure-

ment artefacts. The VSD, magma water content and temperature indicate that

pyroclastic eruptions could have occurred at depths of 500–1000 m. As the

pyroclasts cooled they ingested water and sank.

The vesicle size distribution of lava flows has been proposed as a measure of

palaeoelevation of an eruption (Sahagian & Maus, 1994). The basis of this

method is that there is a difference in pressure between the base and top of the

flow caused by the mass of the lava. This pressure can be calculated and used

to calibrate the correlation between bubble sizes and pressure. The method

can only be applied to flows that have not been inflated after the bubbles

were frozen in at the base and top. The method was first applied to recent lavas

from Mauna Loa, Hawaii, and found to have a precision of about 400 m

(Figure 7.6; Sahagian et al., 2002a). It was subsequently applied to the problem

4.0

3.0

2.0

1.0

2.0 3.0 4.0

actual elevation (km)

measured elevation (km)

Figure 7.6 Elevation determinations from differences in vesicle sizes

between the top and base of a flow against actual elevations (after Sahagian

et al., 2002a). These data are from recent lavas on the slopes of Mauna Loa,

Hawaii.

230 Textures of fluid-filled pores

of the timing of uplift of the Colorado plateau during the last 23 Ma (Sahagian

et al., 2002b). Bubble size distributions indicated that the uplift rate was low

until 5 Ma ago when it increased by a factor of four.

Bubble shapes and orientations can also be used to infer flow type, shear

rate and shear stress in magmas (Rust et al., 2003). Bubbles in volcanic silicic

glasses are almost ideal strain-rate markers as they can be measured easily in

three dimensions and their relaxation times are long. The shape of bubbles is a

balance between shear forces that deform bubbles and surface tension (inter-

facial energy) that rerounds bubbles. Bubble shapes in three obsidian flows

were quantified in terms of bubble shape, size and orientation. These data

immediately provide data on the flow type: a spatter-fed flow deformed by

pure shear whereas simple shear dominated in juvenile obsidian from a pyr-

oclastic deposit and a well-banded obsidian flow. Additional data on magma

viscosity and surface tension enabled the calculation of shear rates and shear

stresses.

Some glassy basaltic samples dredged from the ocean floor are so charged

with gas that they pop when brought to the surface. Burnard (1999) examined

one such sample that had 17% vesicles. He quantified the shape of the vesicles

against size and concluded that degassing occurred whilst the magma was

rising in a conduit at a speed of at least 1 ms

1

. This is comparable with

some explosive eruptions in Hawaii. Bubble size distributions were semi-

logarithmic, indicating that nucleation of bubbles was continuous and not a

single event.

Degassing and crystallisation are clearly linked in many volcanic systems,

but there have been few studies in which the two have been linked quantita-

tively. Gualda et al.(2004) have investigated quartz size distributions and total

vesicularity in the rhyolitic Bishop Tuff. They found that there was an inverse

correlation between the total vesicularity and the amount of the largest frac-

tion of quartz crystals. They suggested that it was the result of the sinking of

large crystals and the rise of bubbles in the magma chamber. However, it is also

possible that the link is loss of gas during coarsening of the quartz in the

magma. Very long magma storage times are certainly consistent with this idea.

Notes

1. Fluid is used here in its physical sense for a gas, liquid or supercritical fluid. It therefore

includes fluids with a wide range in chemical composition, such as those dominated by water,

hydrocarbons, carbon dioxide, silicates, carbonates, sulphides, etc.

7.5 Typical applications 231

Appendix: Computer programs for use in

quantitative textural analysis (freeware,

shareware and commercial)

An updated version of these pages will be available at http://geologie.uqac.ca/

%7Emhiggins/CSD.html

8.1 Abbreviations

8.2 Chapter 2: General analytical methods

This program can be used to segment, separate and measure data volumes

(3-D images).

These programs can be used to combine serial section images into a 3-D image.

Cþþ Uncompiled program in Cþþ

FORTRAN Uncompiled program in FORTRAN

IDL IDL language

Mac Macintosh

MacX Macintosh OS X

Win Windows

Linux Linux

All All of the above platforms

Excel Excel worksheets and macros

NIH NIHImage (ImageJ) macros

Free Freeware

Share Shareware

Com Commercial

BLOB3-D IDL, All Ketcham (2005)

ftp://ctlab.geo.utexas.edu/blob3d

232

Bitmap images ( jpeg, tiff, bmp, etc.) can be stitched together with these

programs.

Images acquired by scanning photographs, rock blocks or thin sections

must be converted to binary images before they can be analysed automatic-

ally. There are a number of commercial and shareware programs available

including:

NIHImage

http://rsb.info.nih.gov/

nih-image/

Mac, Free This is a very good freeware

program. Many versions

are available

ImageJ

http://rsb.info.nih.gov/ij/

Win, Mac, MacX,

Linux, Free

This is a java version of

NIHImage. It is being

upgraded and maintained

Adobe Photoshop

http://www.adobe.com/

Win, Mac, Com The basic version is bundled with

some digital cameras

ArcSoft Panorama maker Win, Mac, Com Bundled with some digital

cameras

PanaVue ImageAssembler

http://www.panavue.com

Win, Com Can stitch very large images

Adobe Photoshop

http://www.adobe.com/

Win, Mac, Com This is the classic image

processing program

Corel PhotoPaint

http://www.corel.com/

Win, Mac, Com This program is very similar to

Photoshop and comes included

with Corel Draw

LViewPro

http://www.lview.com/

Win, Share This program is quite compact

and does a lot for a shareware

program

Image-Pro Plus

http://www.mediacy.com/

Win, Com This program is very good but

expensive

IPLab

http://www.iplab.com/sos/

product/gen/IPLab.html

Mac, Win, Com Commercial image analysis

program

Lazy grainboundaries

http://pages.unibas. ch/

earth/micro/index.html/

grainsize/grainsize.html

NIH, Free Automatic tracing of grain

boundaries

Appendix 233

Binary images must be analysed to extract textural information. These

programs can do this.

Digitising tablets and control programs.

These special programs treats multiple images acquired at different orienta-

tions of the polarisers with computer-integrated polarising microscopy (CIP).

Image-Pro Plus

http://www.mediacy.com/

Win, Com This program is very good but

expensive

IPLab

http://www.iplab.com/sos/

product/gen/IPLab.html

Mac, Win, Com Commercial image analysis

program

Aphelion

http://www.adcis.net

Win, Linux Commercial image analysis

program

NIHImage

http://rsb.info.nih.gov/

nih-image/

Mac, Free This is a very good shareware

program. Many versions are

available

ImageJ

http://rsb.info.nih.gov/ij/

Win, Mac, MacX,

Linux, Free

This is a Java version of

NIHImage. It is being

upgraded and maintained

ImageTool

http://ddsdx.uthscsa. edu/dig/

itdesc.html

Win, Free Freeware imag e processing,

originally developed for

biological work

Visilog

http://www.norpix.com/

visilog.htm

Win, Com Commercial image analysis

program

Sigma-Scan Win, Com Made by Jandel Scientific.

http://www.spss.com/software/science/SigmaScan/

Geovision

http://

craton.geol.brocku.ca/

faculty/ff/stage/

WelcomeF.html

Win, Free Petrographic image processing of thin

sections using the rotating polariser

stage.

Image segmentation

ftp://ftp.iamg.org/VOL30/

v30-08-03.zip

Linux, Free Segmentation of petrographic images

acquired with CIP microscopy.

(Zhou et al., 2004b)

234 Appendix

Miscellaneous programs and sites.

8.3 Chapter 3: Grain and crystal sizes

8.4 Chapter 4: Grain shape

MELTS

http://ctserver.

uchicago.edu/

Mac, Unix, Java Calculation of liquid line of descent,

density and other parameters

(Ghiorso & Sack, 1995)

MinIdent-Win

http://www.

micronex.ca/

Win, Com Mineral da ta database: mineral

properties include chemical

composition, optica l, X-ray, physical,

hand-specimen. Data ranges compiled

from real analyses. About 6000 named

and unnamed miner als

International Society

for Stereology

http://www.stereology

society.org/

CSDCorrections

http://geologie.uqac.ca/

%7Emhiggins/

csdcorrections.html

Win, Free Distribution-free methods. Blocks,

ellipsoids, massive and oriented

textures. Log or linear size

intervals. Choice of output graphs.

Michael D Higgins, UQAC

CSD – Excel spreadsheet

(contact author)

Win, Free Parametric solutions – Tony Peterson,

Geological Survey of Canada

StripStar

http://pages.unibas.ch/earth/

micro/index.html

Mac, Free Distribution-free methods. Conversion

of spheres only. Only uses fixed with

bins. Not user friendly. M Strip,

University of Basel

ImageJ

http://rsb.info.

nih.gov/ij/

Win, Mac, MacX,

Linux, Free

This is a Java version of NIHImage

Box-method fractal parameters can

be determined

Fractscript

(contact author)

ImageTool macro A macro for calculating the fractal

dimension of object perimeters

in images of multiple objects

(Dillon et al., 2001)

Fraccalc

(contact author)

NIH M. Warfel in Dellino & Liotino (2002)

Appendix 235

8.5 Chapter 5: Grain orientations (rock fabric)

8.6 Chapter 6: Grain spatial distributions and relations

Gaussian

Diffusion-

Resample

(contact author)

NIH (Saiki, 1997, Saiki et al., 2003)

INTERCPT and SPO

http://www.sciences.

univ-nantes.fr/geol/

UMR6112/SPO/

index.html

Win, Free Program for applying the inertia

tensor and intercept method to

binary bitmap images. Patrick

Launeau and Pierre Robin

Ellipsoid

http://www.sciences.

univ-nantes.fr/geol/

UMR6112/SPO/

index.html

Win, Free Ellipsoid calculation of 3-D shape

preferred orientation by

combination of 2-D images.

Patrick Launeau and Pierre Robin

Various programs

http://www.sp.uconn.edu/

geo102vc/Compaction_

Programs.htm

Win, Excel,

Mathlab,

Free

Programs to estimate compaction

from scanned thin section images

and digitised plagioclase chain

networks. N. H. Gray and

A. Philpotts

Basel software package

http://www.unibas.ch/

earth/micro/software/

Mac, NIH,

FORTRAN

Package of programs and macros for

computer-integrated polarisation

microscopy (C IP)

Lazy macros

http://www.unibas.ch/

earth/micro/software/

macros/lazymacros.html

NIH, Free Package of programs and macros for

computer-integrated polarisation

microscopy (C IP)

Wavecalc

http://www.iamg.org/

CGEditor/cg1997.htm

Cþþ Software for multi-scale image

analysis: the normalised,

optimised anisotropic wavelet

coefficient method. Darrozes

(1997)

NOAWC pages

http://renass.u-strasb g.fr/

philippe/Couleur/

coul_titre.html

Big R calculations

http://geologie.uqac.ca/

%7Emhiggins/big_r.zip

Win Michael D. Higgins, UQAC

236 Appendix

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