Dave
40 years ago H2O and CO2 were standard wet chemical methods in all rock analysis labs, and they also did Fe2 as well as Fe tot. But modern methods use much smaller samples, as Simon points out. We have used a standard CHN analyser in the past (can't recall the brand), which is basically a dedicated GC with a sample treatment that ensures the C and H is oxidised. To get CO2 in carbonate as distinct from C in graphite the simplest thing is to do an appropriate acid digestion, catch the CO2 in alkali, and titrate.
Bruce
Professor Bruce Yardley
School of Earth and Environment
University of Leeds
Leeds LS2 9JT
UK
Tel. +44 (0)113 343 5227
________________________________
From: Metamorphic Studies Group [[log in to unmask]] On Behalf Of Kemp, Simon J. [[log in to unmask]]
Sent: 11 April 2011 16:25
To: [log in to unmask]
Subject: Re: Measuring volatile contet of rocks (not minerals)
Dave,
How about thermal analysis ?
Although I have never heard of anyone trying it, our Mettler-Toledo TGA/SDTA (thermogravimetric analysis/simultaneous differential thermal analysis) system is now connected to a Thermostar quad mass spectrometer and has a furnace capable of 1600degC. It should therefore be able to measure the H2O, CO2 (or any other volatile) content of whole rock samples – all from a 50 mg powder subsample !
Can I enquire as to the reason for the need ? Perhaps we could collaborate ?
Best regards,
Simon J Kemp
Facility Leader: Mineralogy, Petrology and Biostratigraphy
British Geological Survey
Kingsley Dunham Centre
Keyworth
Nottingham
UK NG12 5GG
Tel: +44(0)115 9363448
Fax: +44(0)115 9363352
e-mail: [log in to unmask]
web: Simon Kemp<http://www.bgs.ac.uk/staff/profiles/0778.html>
http://www.bgs.ac.uk<http://www.bgs.ac.uk/>
From: Metamorphic Studies Group [mailto:[log in to unmask]] On Behalf Of David Kelsey
Sent: 11 April 2011 16:09
To: [log in to unmask]
Subject: Measuring volatile contet of rocks (not minerals)
Hi all,
I am hoping to find out what analytical facilities can be used to measure the H2O and/or CO2 content of whole rock samples (i.e. not individual minerals). I am aware of the SIMS ion probe being used on occasion for the volatile content of single minerals (e.g,. harley’s cordierite work; Wade’s brand new cpx work), but it’s use for such things seem to be quite rare. In addition, these applications do not seem to extend to whole-rock analyses.
is there a more common procedure? or is the whole process so fraught with difficulties/uncertainties that such measurements are rarely done?
if anyone knows of a procedure for measuring whole-rock H2O or CO2 content I’d be very eager to know.
cheers
dave k
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Metamorphism, geochronology, tectonics
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