Topic 2

1
Topic 2 

• Magmatic/thermal history of RM-CP region
• A. COMB summary
• B. Hydro/ xenowhiffs, continental smokers
• C. stress fields through time (dikes sill
  orientations)

2
CMB Research Theme

• Determination of relative contributions to
  magmatism related to
• Cenozoic processes (flat slab subduction, slab
  delamination, asthenospheric upwelling)
• Lithospheric control on distribution in space,
  preconditioning and response to the Cenozoic
  processes

3
Magmatism Hypotheses

• Space and time distribution of magmatism is
  directly controlled by subduction slab geometry
  and history
• Spatial distribution is controlled by
  pre-existing lithospheric structures

4
Driving Mechanism

• Times of slab angle increase may trigger partial
  melting and magmatism.
• Flat slab intervals may provide opportunity for
  hydration and future fertility that can be
  exploited for pulsed magmatism. Also an interval
  of refrigeration suppressing magmatism

5
Tests - Geochronology

• Systematic migration of magmatism in space and
  time may indicate propagation of slab tear.
• Non systematic distribution in time may indicate
  a broad source for partial melt that is focused
  along pre-existing crustal structure.

6
Tests - Geochemistry

• Source of Cenozoic magmas and time integrated
  evolution of mantle lithosphere
• Mantle xenoliths from Cenozoic magmas. 1 so far.
• Spatial distribution of mantle He to recent
  volcanism and seismic activity.

7
Work plan

• Fully compile existing data. NAVDAT, USGS, CREST
  GIS/data exchange
• Geochronology of intrusive rocks, Laramide and
  younger (cf incision group)
• Geochronology and geochemistry of limited Larmide
  volcanic rocks.
• Clasts in Early Tertiary seds.
• Assemble and augment He isotope database on
  springs and groundwater.
• To assess mantle contribution of both He and CO2.

8
Integration

• GIS data exchange portal
• Geochron, geochem, maps, DEM
• Link magmatic history to tomography
• Geodynamic predictions to
• Partial melt extraction volumes
• Gravity implications of intrusive (hidden?) magma
  bodies - heat flow response
• Buoyancy evolution to surface elevation
  expression.