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Archean crust-mantle geochemical differentiationIsotope measurements on carbonatite complexes and komatiites can provide information on the geochemical character and geochemical evolution of the mantle, including the sub-continental mantle. Measurements on young samples establish the validity of the method. These are based on Sr, Nd and Pb data from the Tertiary-Mesozoic Gorgona komatiite and Sr and Pb data from the Cretaceous Oka carbonatite complex. In both cases the data describe a LIL element-depleted source similar to that observed presently in MORB. Carbonatite data have been used to study the mantle beneath the Superior Province of the Canadian Shield one billion years (1 AE) ago. The framework for this investigation was established by Bell et al., who showed that large areas of the province appear to be underlain by LIL element-depleted mantle (Sr-85/Sr-86=0.7028) at 1 AE ago. Additionally Bell et al. found four complexes to have higher initial Sr ratios (Sr-87/Sr-86=0.7038), which they correlated with less depleted (bulk earth?) mantle sources, or possibly crustal contamination. Pb isotope relationships in four of the complexes have been studied by Bell et al.
Document ID
19840012898
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Tilton, G. R.
(California Univ. Santa Barbara, CA, United States)
Date Acquired
August 11, 2013
Publication Date
January 1, 1983
Publication Information
Publication: Lunar and Planetary Inst. Workshop on a Cross Section of Archean Crust
Subject Category
Geophysics
Accession Number
84N20966
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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