Analytical Suite Metadata

SIGÉOM lithogeochemical major oxides



SIGÉOM lithogeochemical major oxides – SiO 2, TiO 2, Al 2O 3, Fe 2O 3t, Fe 2O 3v, FeO, CaO, MgO, Na 2O, K 2O, MnO, P 2O 5, H 2O, LOI

General Methodology:

The SIGEOM database includes a very large number of lithogeochemical analyses.  These analyses are occasionally retrieved and re-published, possibly alongside re-analyses of the same samples, or data from other sources (GSC, universities, etc.).  Analytical techniques varied over the years.  Original publications should be consulted to determine analytical details.

Fe is expressed in different formats.  Many analytical techniques cannot distinguish between Fe 2+ and Fe 3+.  In XRF analysis, Fe is conventionally reported as Fe 2O 3 (or Fe2O3T, for total).  Fe 2+ can be measured by titration, and may then be reported as FeO.  This then allows one to calculate a “true” value for Fe 3+, or Fe 2O 3 (or Fe2O3V, for vrai (true in French)).  Sometimes, Fe is reported as FeOT rather than Fe2O3T.  Note that the different conventions for reporting Fe will have an effect on the total sum of the major oxides.  Theoretically, this sum should be slightly less than 100.  But reporting Fe entirely as Fe 2O 3 rather than a mix of Fe 2O 3 and FeO may lead to sums of greater than 100.

Fe calculations

Using atomic weights of Fe = 55.845(2) and O = 15.9994(3), we obtain molecular weights for Fe 2O 3 = 159.688 and 2(FeO) = 143.689.  This gives a conversion factor of 159.688 / 143.689 = 1.1113.

We can then use the expressions:

  • Fe2O3T – FeO * 1.1113 = Fe2O3V
  • Fe2O3T = FeOT * 1.1113

 

Instrument: unstated

Sample material: solid

Sample weight: unstated


Analytical Technique:

Hierarchical classification

Technique >> Other >> Multiple

Children

None


Analytical Decomposition:

Hierarchical classification

Decomposition >> Multiple

Children

None


Analytical Methods:

Index Method Order Method ID Quantity Detection Limit
1  5371     SiO2  
2  5372     TiO2  
3  5373     Al2O3  
4  5374     Fe2O3T  
5  5375     Fe2O3V  
6  5376     FeO  
7  5378     MnO  
8  5379     MgO  
9  5380     CaO  
10  10  5381     Na2O  
11  11  5382     K2O  
12  12  5383     P2O5  
13  13  5388     H2O  
14  14  5389     LOI  

Associated Analytical Packages:

Index Package ID Package Name
1  258     SIGÉOM lithogeochemical major oxides
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