Hello all--

We have measured very light d18O (as low as -15.9 per mil) in massive
calcite, altered carbonate, and associated waters collected in Hidalgo,
Mexico. We assume meteoric water to be approximately -10 per mil.  Host
rocks in the region include limestone, shale and volcanics.  The area
hosts lead-zinc deposits.  We have been unable to find reference to
similar low values, and would be grateful for citations or ideas!

Many thanks,
Alison Lathrop and Helen Mango