Serpentinite Formation Divergent p.b.

Tectonic settings

  1. Divergent plate boundaries i.e. slow spreading ridges
  1. Convergent plate boundaries

Serpentinite formation requires:

Mantle rocks in contact with water

  1. 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'

  1. 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