Floating 'K' in assemblage

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WillM
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Joined: 03 Nov 2015, 09:27

Floating 'K' in assemblage

Post by WillM »

Hello All,

I was recently trying to model a high-pressure metapelite and within all the assemblages I get a floating 'K' (e.g., GRT (2)WM BI14 K H2O q ru). I am using the td-ds62-mp50-03 data set and am unable to find 'K' as an abbreviation for anything. Does anyone know what this means? Thanks!

Will
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Blakelee
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Joined: 07 Nov 2018, 19:29
Location: Beijing, China
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Re: Floating 'K' in assemblage

Post by Blakelee »

Hi Will,

Could you please upload the bulk composition file so that we may reproduce the error and find out what's wrong? I guess you assign too much K content in the input file to leave the excess K.

Kind regards!
Blakelee, PHD student
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WillM
Posts: 7
Joined: 03 Nov 2015, 09:27

Re: Floating 'K' in assemblage

Post by WillM »

Hi Blakelee,

Thanks for the response. Below are my calculations (bulk+THERIN input; it wasn't letting me attach the .xls file I had it on). I have added Qz and H2O to the calculation, as Qz was texturally stable throughout the history of the sample, as was white mica. I also tried to do the calculations on another HP metapelite and got the same floating K. Unfortunately, calculations take ~12 hrs.

SiO2 TiO2 Al2O3 FeO* MnO MgO CaO Na2O K2O Total
56.41 0.9 21.61 7.86 0.141 2.32 1.3 2.07 3.98 96.591

THERIN Input +Qz+H2O
Si Ti Al Fe Mn Mg Ca Na K O H O Si O
55.019 0.660 24.839 5.769 0.116 3.373 1.358 3.914 4.952 163.665 60 30 30 60

Any suggestions you have would be greatly appreciated.

Best regards,
William
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Blakelee
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Re: Floating 'K' in assemblage

Post by Blakelee »

Hi Will,
Sorry for my late response! I use your bulk info:
0 MN(0.116)NA(3.914)CA(1.358)K(4.952)FE(5.769)MG(3.373)AL(24.839)SI(55.019)TI(0.660)H(60)SI(30)O(?) * as input file and run Theriak.exe randomly to check the output results, it seems everything goes well and i havn't find a 'K' phase as you said.


With best regards,
Blakelee
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WillM
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Joined: 03 Nov 2015, 09:27

Re: Floating 'K' in assemblage

Post by WillM »

Hi Blakelee,

Thanks for trying and I am glad that you were successful with it. I noticed that you used a O(?) in the input. I have never understood why a question mark is used rather than calculating out the O. Could you explain this for me? And if it has to do with never knowing the exact 'O' content, how does this value affect the additional H2O and SiO2 inputs as fixed values (e.g., H(60)O(30))? The help is much appreciated.

Cheers,
Will
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Blakelee
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Re: Floating 'K' in assemblage

Post by Blakelee »

Hi Will,
I have checked further and now i am sure that the right O vaule should be 163.6655, not 163.665, and i guess K is adjacent to O in your input file, if so, that means the excess K would leave alone after all O have been assigned to the other cations. A question mark O(?) allows the system to automatch the numbers of O each cation acquires, and thus this method as well as yours should give the identical results (please see the screenshots below).
2021-07-02_234839.jpg
2021-07-02_234839.jpg (90.34 KiB) Viewed 987 times
PS: The left input is 0 MN(0.116)NA(3.914)CA(1.358)K(4.952)FE(5.769)MG(3.373)AL(24.839)SI(55.019)TI(0.660)H(60)SI(30)O(?) *
while the right is 0 MN(0.116)NA(3.914)CA(1.358)FE(5.769)MG(3.373)AL(24.839)SI(55.019)TI(0.660)K(4.952)O(163.6655)H(60)O(30)SI(30)O(60) *

Kind regards,
Blakelee
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WillM
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Joined: 03 Nov 2015, 09:27

Re: Floating 'K' in assemblage

Post by WillM »

Hi Blakelee,

Thanks again for all the help. I wasn't aware that the order of the elements on the THERIN input affected the outcome of the results. I tried the first input you listed (0 MN(0.116)NA(3.914)CA(1.358)K(4.952)FE(5.769)MG(3.373)AL(24.839)SI(55.019)TI(0.660)H(60)SI(30)O(?) *) and unfortunately got the diagram attached, which is a very common result of mine. I will try it again with a specified 'O' input of 163.6655. Thanks again for all the help.

All the best,
William
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Screen Shot 2021-07-04 at 10.28.02 AM.png
Screen Shot 2021-07-04 at 10.28.02 AM.png (413.47 KiB) Viewed 967 times
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