Please enable JavaScript.
Coggle requires JavaScript to display documents.
Cala Portal/ D'Agulles Kinematic Data (Sigma clast (Tail =…
Cala Portal/ D'Agulles
Kinematic Data
SZ network Morphology
Cala Portal / D'Agulles
Major shear zone where bay pronounced
(preferentially eroded to form inlet)
Pegmatite
abuts mouth of bay
Sigmoid shape
on hill / headland adjacent indicates top-to-the-right shear sense
Comprises 3 shear zones
Shear sense indicators
Sigma clasts - hill/headland asymmetry
Shear band - deflection sense of mylonitic foliation
Delta clast - tourmaline aggregate
Stair stepping direction on asymmetric clasts
Sigma
clast
Tail = asymmetric wrt mylonitic foliation
Stair-
stepping
geometry
Tails located either side of reference line - do not cross it
Asymmetry - result of rotational deformation
Sigmoid shape on hill / headland adjacent
Indicates
TOP TO THE RIGHT
shear sense
Shear zone networks
Where shear zones exceed critical scale they connect with others
Form km-scale braided SZ networks
Accommodated plate motion @ depth - Probably typical for middle crust
Shear zones work together / interact kinematically
to accomodate deformation @ Cap de Creus
Cap de Creus Shear Sense
Top to the right
Stereonets
Great circle = mylonitic foliation
measured in individual SZs
Poles = stretching lineation
(corresponding to foliation)
3 stereonets: W, Central, E sections SZ
Three shear zones make up this braid/network
Kinematic
SZ Data
Dominant shear zone dip
~45-80° (NE)
Stretching Lineations
Orientation ~ consistent
Shear sense dominantly top-to-SE
Dip direction - highly variably
Shear sense variable :
East sz: Dominantly top-to-SE
NW dipping sz: Top-to-NW (weak signal)
NW dipping shear zones tend to exhibit top-to-NW shear sense
Top-to-SE =
Most robust
i.e. nothing rotates beyond this
All segments evolving toward mature/stable top-to-SE shear sense
Top to NW segments
= Rotating
to try & assume stable top-to-SE orientation
Cross Section of Cala D'Agulles SZ
Looking into mvmt/stretching direction
LHS: Steep vertical dextral shear zone joins
RHS: Narrower sinistral SZ
dextral - top to right etc
Complex deformation in unit between
Delta
Clast
Top-to-SE shear sense indicator
Stair stepping
Direction tail rotated
Tourmaline aggregate
At margin between
high grade metapelite
highly deformed pegmatite
Clast rolling along sheared margin
Recrystallises & tail dragged around as rotates
Tourmaline
= common in pegmatite
Collect elements unused in pegmatite
~effectively waste buckets
Strain Partitioning
Folding in less deformed domains
between braided shear zones
Fold axes & axial planes = steeply dipping
Orientations variable - suggests folds largely formed independently