Guy F. Atkinson Distinguished Lecture Series: Chlorine Isotope Homogeneity of the Mantle, Crust and Carbonaceous Chondrites
| What | Event |
|---|---|
| When |
2009-04-23 from 15:30 to 17:00 |
| Where | 295 FASB Auditorium |
Guest Speaker:
Zach Sharp
University of New Mexico
Earth & Planetary Sciences
Abstract: Chlorine in the Earth is highly depleted relative to carbonaceous
chondrites and solar abundances. Knowledge of the Cl concentrations
and distribution on Earth is essential for understanding the
origin of these depletions. Large differences in the stable chlorine
isotope ratios of meteoritic, mantle and crustal materials have
been used as evidence for distinct reservoirs in the solar nebula2
and to calculate the relative proportions of Cl in the mantle and
crust3. Here we report that large isotopic differences do not exist,
and that carbonaceous chondrites, mantle and crust all have the
same 37Cl/35Cl ratios. We have further analysed crustal sediments
from the early Archaean era to the Recent epoch and find no
systematic isotopic variations with age, demonstrating that the
mantle and crust have always had the same d37Cl value. The similarity
ofmantle, crust and carbonaceous chondrites establishes that
there were no nebular reservoirs with distinct isotopic compositions,
no isotopic fractionation during differentiation of the
Earth and no late (post-core formation) Cl-bearing volatile additions
to the crustal veneer with a unique isotopic composition.
Zach Sharp
University of New Mexico
Earth & Planetary Sciences
Abstract: Chlorine in the Earth is highly depleted relative to carbonaceous
chondrites and solar abundances. Knowledge of the Cl concentrations
and distribution on Earth is essential for understanding the
origin of these depletions. Large differences in the stable chlorine
isotope ratios of meteoritic, mantle and crustal materials have
been used as evidence for distinct reservoirs in the solar nebula2
and to calculate the relative proportions of Cl in the mantle and
crust3. Here we report that large isotopic differences do not exist,
and that carbonaceous chondrites, mantle and crust all have the
same 37Cl/35Cl ratios. We have further analysed crustal sediments
from the early Archaean era to the Recent epoch and find no
systematic isotopic variations with age, demonstrating that the
mantle and crust have always had the same d37Cl value. The similarity
ofmantle, crust and carbonaceous chondrites establishes that
there were no nebular reservoirs with distinct isotopic compositions,
no isotopic fractionation during differentiation of the
Earth and no late (post-core formation) Cl-bearing volatile additions
to the crustal veneer with a unique isotopic composition.
