What is this layer?
Locations, calculated Mg number and geochemistry for mafic–ultramafic intrusive rocks Geochemical data are derived from the Geological Survey of Western Australia geochemistry database (WACHEM) via the Geochemistry — RECALC and Geochemistry — mafic–ultramafic intrusion layers. Mg# values are calculated using the recommended method of Rollinson (1993): 100 × (MgO%/(MgO% + Fe2O3T%)). The Mg number can be used to interpret the degree of fractionation in a melt (Barnes et al., 2012).
Legend
|
Legend |
Range |
Classification |
Description |
Reference |
|---|---|---|---|---|
|
Mg# mafic–ultramafic intrusion SOURCE |
>75 |
Manual |
A higher degree of fractionation in a melt |
Barnes et al. (2012) Hayman et al. (2015) |
|
30–75 |
Manual |
Mg# >65 likely represents komatiitic basalts and komatiites |
Hayman et al. (2015) |
|
|
0–30 |
Manual |
A lower degree of fractionation in a melt |
Barnes et al. (2012)
|
Model logic and recipe
|
Operation |
Expression |
Operation |
Expression |
|---|---|---|---|
|
Add Field |
Mg_number |
Calculate Field |
100 * (!MnO_pct! / (!MnO_pct! + !Fe2O3T_pct!)) |
References
Barnes, SJ, Van Kranendonk, MJ and Sonntag, I 2012, Geochemistry and tectonic setting of basalts from the Eastern Goldfields Superterrane: Australian Journal of Earth Sciences, v. 59, no. 5, p. 707–735.
Hayman, PC, Thébaud, N, Pawley, MJ, Barnes, SJ, Cas, RAF, Amelin, Y, Sapkota, J, Squire, RJ, Campbell, IH and Pegg, I 2015, Evolution of a ~2.7 Ga large igneous province: a volcanological, geochemical and geochronological study of the Agnew Greenstone Belt, and new regional correlations for the Kalgoorlie Terrane (Yilgarn Craton, Western Australia): Precambrian Research, v. 270, p. 334–368.
Rollinson, HR 1993, Using geochemical data: evaluation, presentation, interpretation: Pearson Education Ltd, Harlow, England, 352p.