Standard lab procedures for estimating carbonate content in sediment is loss by ignition (carbonates removed after 2 hours at 1,000 degrees C) or removal by acid reaction (typical an HCL solution). Acid reaction is faster but you should know how it will alter your apparent composition. The least destructive option may be to sieve your sample (standard phi classes). After a couple of attempts you may find that the CaCO3 nodules have a near uniform size, which could be a class that was then excluded from analysis. This would also allow you to do XRF on different sediment size fractions, which may provide some interesting results. 

With the dataset you provided it looks like another option could be to just use relative weights. Sum up the percent of everything besides CaO and determine a relative percent (SiO2%/ 100 - CaO%= 55.9%). It is reasonable to have a plot showing the raw results and then focus on a subset of the data you are interested in.

Dear Joshua Caster,

Thanks for your kind suggestion. I have recalculated data in three ways:

Method 1 & 2 has given the same value (SiO2- 56.899%) while Method 3 differs slightly (SiO2- 54.529). Please look at the attached file and let me know which one I should consider. Moreover, I am also trying to remove Carbonates by adding HCl and oven dried the samples again for XRF analysis. I will then cross check the data. 

Looking forward!!

Best regards,

Ashok

HCl is by far the easiest method if this acid does not alter other mineral phases such as clay minerals. You can also try to use warm formic, acetic or citric acid I presume.  

Ashok,

 I think there are arguments for all 3 methods you have outlined. I like the Shimmield et al. equation, partially because it is an established method that can be cited, thus reducing the amount of explanation you will need to add to a methods section.

I think it is great that you are trying a few rounds with carbonate removal using the oven and acid solution. I could see these tests being a short and useful methods paper in-and-of itself. I am guessing that loss by ignition will alter the chemical composition of your sample the least (mainly you will loose C and CO). As Mario said, the acid solution could alter some of your clay minerals which I'm guessing would show up in the % Na and K oxides from your table. Good luck, it sounds like you are on the right track!

Ashok

You can  treat the bulk sample by 0.6 N HCL to remove inorganic (carbonate mineral) followed by drying the sample @   600 C so organic will remove. Then you can run your sample in XRF and this process will not alter any other minerals too.  

-To evaluate the proportional amount of non carbonate acid insoluble residues.

-10 gm weight of sample required for dissolving in 500 ml (10 N HCL) for 24 hours.

-To remove moisture, heating remain residues for another 24 hours in oven.

-To remove another contamination wash in hot water while filtering process(funnel-      filter paper).

-Remaining is Non carbonate acid insoluble residues.

-Weight the residues if required.  

Joshua Caster,

Thank you for your kind suggestion and strong encouragement.

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Mario Wipki 

Thank you for your suggestion. Yes, I am also thinking about treating the samples with 50% Acetic acid overnight. But, I have not decided yet due to the problem of altering the mineralogy. 

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Mathias H. Köster

Thank you for your suggestion. Yes, I have already done XRD analysis and going to quantify the CaCO3% . I will cross check the value with the value obtained from above mentioned technique.

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Dr. Archna Bohra

Thank you for your suggestion. What should be the quantity of 0.6N HCl to dissolve 5gm samples? I will have to decide between HCl and Acetic acid. I have gone through a paper where they treated the sample with 50% Acetic acid to remove the excess CaO (Goldberg et al., 2010). However, they treat their samples for the purpose of Paleoclimatic studies only where as I have to consider the Provenance studies along with paleoenvironment from the samples. 

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Rashmikant Niranjan Talati 

Thank you for your suggestion. It seems that HCl treatment is by far the best method to remove the carbonates from the samples. I have a very limited samples. Can I take 5gm samples instead of 10 gm? If yes then what would be the concentration of acid? Kindly let me know.

Yes you can take 5 mg sample with same concentration.This much concentration is required to dilute the CaCO3 completely(time frame is 24 hours). 500 ml is to avoid CaCO3 saturation. You can perform with 250 ml HCL now, with 5 mg sample weight.

Sample of Silt- clay in grain size will do, other wise filtering,washing and drying and remaining residual weight is quite difficult with 5 mg sample weight.

HCl is easiest method. I suggest use warm formic, acetic or citric acid I presume.