Dear Jens,

yes, nice to feel like "anybody out there in the world"!

Craw et al (in CLAY MINERALS 30, 165-172, 1995) describe
aragonite grown some 5k years ago at 7 or 8 deg C in a debris
flow. The water was minus 9.5 permil del 18-O, the aragonite has
24.0 permil (3 samples, plus/minus 0.1). Calcite has 22.9 permil.
I don't have Mg data, but there is pyroaurite present (a hydrous
Mg carbonate), as well as chrysotile, which has 5.5 permil. 

Hope that helps. We did note a discrepancy with Tarutani's data,
which are supposed to be inorganic.

Peter