School of Geosciences

20 years of 3D structural modelling.Where are we at? Where next?In alphabetical order:

Laurent Ailleres, Thomas Carmichael, Eric deKemp, Lachlan Grose, Mark Jessell, Vitaly Kolin, Gautier Laurent, Mark Lindsay, Cheng Yu Chuiet al.,

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1994 My first voxet! Attempting to interpolate orientations of finite strain

ellipse in the French Alps and finite strain parameters

3

Seriously… a lot of explicit modelling was done… and still is and still will be.

at multiple scale: from plate scale on spheroid to the mine scale.

for different purposes: green field exploration, near mine exploration, hydrogeology, oil & gas, research.

3D Model of Mt Isa Inlier, Qld, Australia - After Murphy et al. (2008).

3D Model of Barwon Head aquifers, Nury et al., 2010

The Workflow

Example: Agnew Wiluna Belt

TMI AGC

Field Work

Geophysical Processing

Example: Agnew Wiluna Belt

Example: Agnew Wiluna Belt

Structural 3D Modelling: the Falun Mine

• Model built from 35+ level maps (average spacing 25m) and 50+ sections from historical underground mapping

• Aim was to understand the structural framework of the deposit

Structural 3D Modelling: the Falun Mine

3D Structural Analysis

Late Fault

Main late shear zone

(SZ3)

Early, // mineralisation, folded shear zone

(SZ1a)

Splaying off SZ1 probably during D3:

SZ3b

En-echelon tension gashes?

3D Structural Analysis

3D Structural Analysis - Reconstruction

S2

Explicit Modelling

• Non reproducible

• Labour intensive (only one model is built – no update please)

• Rarely utilised for anything more than visualisation

• Near impossible to play “what if” scenarios

• Highly uncertain and uncertainty cannot be characterised

1981

Nod

dy

1982

Arc

Info

Ver

sion

1

1989

Goc

ad E

xplic

it Mod

eller

1993

Ear

thvis

ion Im

plicit

Mod

eller

2008

1997

Geo

mod

eller

Jess

ell, 1

981

Knowledge Data Data + Knowledge Data + Knowledge + Uncertainty

(My) Short history of 3D modelling (strangely similar to Mark Jessell’s)

Perrouty et al., (2012; 2014)

Armit et al., (2012; 2014)

Implicit Modelling

• Reproducible

• Labour intensive - data need cleaning before modelling (nothing new!)

• Geological simulations are possible

• Allows uncertainty and geodiversity work

• Highly uncertain and uncertainty CAN be characterised

HOWEVER:

• Still does not use the full range of structural elements measured in the field

Better use of field data Alsop et al., 1996

(Near Moine Thrust)

Why should we care about folding… and more importantly ALL foliations

Next slide detail

Why should we care about folding… and more importantly ALL foliations

Looking South into Bermagui Heads,

stratigraphy dipping steeply West

Next slide detail

Topography

Topography

Topography

Unless drawn or over determined by lots of structural measurements (strike and dip), it is impossible to interpolate scalar field looking like below, and this is with only 2 deformation events!!!

Multiple generations (f1 + f2)

– strategy:• find f2 fold parameters• interpolate s1• find f1 fold parameters• interpolate bedding

f1 f1+f2f2

+ =

time

modelling

Implicit folding!!

S2

S1S1 S0

Implicit Modelling of Folds Motivations:

– What the implicit packages can constrain:• Value/orientation at a location• Smooth variations (gradient orientation and norm)

few constraints on fold structural parameters• In StructuralLab:

– Axial Surface: grad f axial surface– Fold Axis : grad f fold axis direction

Yes, because we actually measure more in the field than what is used

A good start

But can we use more ?

Axial surface field Foliation field

Foliation field :

– // axial surface– Relatively consistent over the whole area– Vergence helps a lot

Next antiform is this way!S1

S0

General idea:

• Interpolate foliation field• Interpolate vergence intensity (fold intensity ~ fold amplitude

and interlimb angle)• Constrain “folded surface” orientation• Is there a need for upscaling of bedding and structural data?

Intelligent upscaling

Tom Carmichael

Data: Limousin, France

Dispersed

Clustered

’ Kent Distribution

Model Comparison

Eastern Cross Section

Northern Cross Section

Modified model

Modified model

Initial Model

Initial Model

1389 Structural measurements 198 Structural “measurements”

15% of original data

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Conclusion How far have we come? Not that far until implicit modelling packages

appeared. Since then, amazing progress has been made especially for layer cake type geometries (basins… mainly).

Complicated structures still have to be drawn…

However:

Where are we at? A very interesting spot! We could be the first group of people to implement complete implementation of full structural elements into implicit schemes.

Where next? Uncertainty!!! Geodiversity, test concepts on topologically varying models

Fully constrained inversions including all input geological/structural parameters as part of geology penalty function.

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The Monash Group Laurent Ailleres - concepts development & mentoring

Gautier Laurent – implicit folding & REED; including implementations and concept development

Thomas Carmichael – PhD candidate, upscaling of structural data

Lachlan Grose – PhD candidate, uncertainty & geodiversity of poly-deformed terranes

Yu Ching Chui (Ching) – Honours student, uncertainty & geodiversity of poly-deformed terranes using simple Noddy

models

Vitaly Kolin – Honours student (to start in Aug), Uncertainty & geodiversity of poly-deformed terranes,

applications to the Davenport terrane

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Funding… ? Thanks for asking…