> Hello Alison and others,
>
> Those very negative values are really impressive.  As all of you know,
however, we need to mention a standard used (VPDB vs. VSMOW) to
> make the cited values more meaningful and comparable.  Although
> VPDB has been recommended for citing carbonate d18O values,
> using VSMOW is also allowed, I think.
>
> On the basis of Friedman and O'Neil (1977), the conversion is:
> d18O (VSMOW) = 1.03086 d18O (VPDB) + 30.86.
> So -20.5 per mil (VSMOW) as cited in Yong-Fei's message would be
> converted to ~ -50 per mil (VPDB).  That is even more impressive value.
Is that right?

> Cheers,
> Zicheng Yu
> ______________________________
> Zicheng YU, Ph.D.
> Canadian Forest Service - NRCan
> 5320 - 122 Street
> Edmonton, Alberta T6H 3S5
> Canada
>
> Phone: (780) 435-7304
> Fax:      (780) 435-7359
> Email: [log in to unmask]
> ______________________________
>
> ----------
> From:         Yong-Fei Zheng[SMTP:[log in to unmask]]
> Reply To:     [log in to unmask]
> Sent:         Tuesday, 20 July, 1999 9:35 AM
> To:   [log in to unmask]
> Subject:      Re: light d18O in carbonate query
>
> Dear Aloson,
>
> Extreme 18O-depleted calcite was reported by Faure et al. (1988) in
> Nature, 332 (6162): 352-354, whode d18O value as low as -20.5 permil
> relative to SMOW. The low d18O value of -13 permil was reported by
> Blattner and Williams (1991, EPSL 103:270-284) for altered volcanic
> rocks from New Zealand. The low d18O values of -10 to -8 permil were
> reported by Zheng et al. (1996, Eur. J. Mineral. 8:317-323) and Yui et
> al. (1995, GCA 59: 2859-2864) fro eclogite from China. Obviously,
> meteoric water has contributed such low d18O values to the calcite and
> the rocks.
>
> Yong-Fei
>
>
>
> Alison Lathrop wrote:
> >
> > 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
>
> --
>
> **************************************************************************
> **********
> Dr. Yong-Fei Zheng
> Professor and Chairman
> Department of Earth and Space Sciences
> University of Science and Technology of China
> Hefei 230026, PR China
> Tel.: (+86) 551 3603384        Fax: (+86) 551 3603554
> Email: [log in to unmask]
> **************************************************************************
> **********
>
>