Lithium isotopes in Guatemalan and Franciscan HPLT Rocks: Insights into the role of sedimentderived

1
Lithium isotopes in Guatemalan and Franciscan
HP-LT Rocks Insights into the role of
sediment-derived fluids in the mantle wedge
Kyla Simons, George Harlow, Hannes Brueckner,
Steven Goldstein, Sorena Sorensen, N. Gary
Hemming, Charles Langmuir
2
Proto Melange
Oceanic Sediments
Altered Ocean Crust
Shear zone between plates
Metasomatism of Mantle Wedge
After Bebout (2007)
3
Subduction Fluid Trace Element Patterns
4
(No Transcript)
5
HP-LT Rocks in Guatemala
6
Physical Model Prograde
Oceanic Sediments
Altered Ocean Crust
Shear zone between plates
Dehydration of Slab
Metasomatism of Mantle Wedge
7
Physical Model Retrograde
Oceanic Sediments
Altered Ocean Crust
Shear zone between plates
Dehydration of Slab
Metasomatism of Mantle Wedge
8
Eclogites
Eclogite

• South have lawsonite ? cold and wet _at_ peak
  conditions (480C)
• Very high pressure rocks just shy of coesite
  (UHP) field
• North saw slightly higher-T (lt550C) with a
  second metamorphic event

Jadeitites

• Appear to follow down-pressure trend from
  associated Lws-eclogites and blueschist-eclogites
• South contains qtz ? higher P.
• South T 200C.
• North T 300-400C

9
Li systematics in Guatemala
IAB
MORB
Guatemala Eclogite Avg.