Shear zones, Catalina and Tanque Verde Outline Review structures you saw on Saturday Clarify some questions Come up with a geologic model for the Catalinas.

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Presentation transcript:

Shear zones, Catalina and Tanque Verde

Outline Review structures you saw on Saturday Clarify some questions Come up with a geologic model for the Catalinas Takehome points - shear zones

Undeformed granite Mylonite

Low strain High strain

Still nature with dudes

Normal faults throughout - cut foliation and other ductile structures

Normal fault

Foliation- not sedimentary layering Measurable like bedding-good first indication of direction of ductile deformation

Mylonites Porphyroclasts Gneissic banding Rotated crystals

Fractured fold - top to the south

S C

Lineation- not as clearly defined as foliation; why? What kinda tectonites are these then? Dudes

Top to the south sense of shear

Ductile first Brittle later

Beware of dog approaching

X-cutting dike (or discordant igneous intrusion if you wish) - seals all the ductile deformation- an absolute age on this basaltic material would constrain the end of ductile deformation

Ductile deformation top to the south is given by foliation (direction), sense of shear indicators (folding, S-Cs) and lineation Brittle is overprinted- low angle normal faults cutting the old foliation

Sequence of events:

The strength versus depth issue

Reminder-simple shear deformation

Assignment due a week from Thursday