Kevin:
check my paper published in JSR in 1993, v. 63, p. 282-294. You will
find there very negative values for vein calcite in septarian
concretions.
Cheers
Ihsan



Dr. Ihsan Al-Aasm
Associate Professor
Department of Earth Sciences
University of Windsor, Windsor, Ontario
Canada N9B 3P4
1-519-253-4232 Ext. 2494, FAX: 1-519-973-7081
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