All,
LECO used to sell the RC-412 multi-carbon determinator (~40,000 USD). It combusted rock samples and measured CO2 and H2O in the gas by IR(?). Depending on the temperature ramp, it was claimed to be able to distinguish organic/inorganic carbon and adsorbed/structural water. (All in one cycle.)
I don't know if they still offer this, and I don't know how well it actually performed.
Ed
-----Original Message-----
From: Metamorphic Studies Group [mailto:[log in to unmask]] On Behalf Of Wagner Thomas
Sent: Monday, April 11, 2011 9:30 AM
To: [log in to unmask]
Subject: Re: Measuring volatile contet of rocks (not minerals)
Dear Dave,
I agree that determination of loss on ignition (LOI) is a first and important step in determining the volatile content. But LOI is not the full story, because LOI reflects contributions from CO2 and H2O release, and gain of oxygen by oxidation of ferrous to ferric iron. To have the full volatile budget, you need to determine at least 3 of the 4 following peices of information:
1) LOI analysis
2) H2O content (classical Penfield tube method)
3) CO2 content (element analyzer or acid treatment and volumetric/gasometric determination of the CO2 released)
4) Fe2+/Fe3+ ratio (from acid digestion and photometric measurement)
From 3 of these you can readily calculate the missing number 4. Complications might arise when samples contain substantial amounts of reduced sulfur and organic carbon. Then one needs to determine these entities separately. Many of the above mentioned techniques might be readily available in sedimentology or petroleum engineering groups rather than in the hardrock geochem labs.
Cheers,
Thomas
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Dr. Thomas Wagner
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From: Metamorphic Studies Group [[log in to unmask]] on behalf of Jochen Mezger [[log in to unmask]]
Sent: Monday, April 11, 2011 5:16 PM
To: [log in to unmask]
Subject: Re: Measuring volatile contet of rocks (not minerals)
Dave,
can you be more specific. Do you want to preserve the sample? Otherwise, crush it up, get a regular XRF analysis done, and you have your LOI (loss on ignition). However, it does not differentiate between the volatiles. I presume that this is not what you thought of?
Best wishes,
Jochen
At 17:08 11.04.2011, you wrote:
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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