Serpentinite Formation Divergent p.b.
Tectonic settings
- Divergent plate boundaries i.e. slow spreading ridges
- Convergent plate boundaries
Serpentinite formation requires:
Mantle rocks in contact with water
- Serpentinite @ divergent p.b.
Slow spreading ridges
low magma production ∴ crust stretched
Mantle rock brought to surface along big detachment fault
∴ Serpentinisation can occur on significant scale
lotsa mantle rock in contact with percolating sea water
probably still hot
'Oceanic core complexes' associated
Oceanic core complexes
Long ridge of smooth domes ⊥ mid-ocean ridges
Corrugation (transverse ridges) atop exposed dome
Large low angle detachment faults
bring deep rock to surface
Form @ slow spreading ridges with limited upwelling magma supply
accommodate expansion
∴ no rifting occurs
Core complex builds on uplifted side of fault
due to scraping of surfaces during faulting
km-scale 'grooves'
- Serpentinite @ divergent p.b.
e.g. Atlantis Massif
At depth @ divergent p.b.
Serpentinite formation in upper tens km oceanic crust
Water percolates through fractures
High water pressure @ depth aids fluid flow
∴ Mantle peridotite = serpentinised
Serpentinised zone = thicker where...
Faulting in oceanic lithosphere
--> Facilitates greater water percolation
(hydrothermal circualtion)
∴ Thicker serpentinisation = possible where oceanic crust is faulted
i.e. over 5 km vs few km