Supplementary Material 1 Sources of data used in the figures

Data for some S-type rocks are derived from an unpublished compilation by various contributors at the University of Stellenbosch. To these have been added some analyses from Clemens (1981), Mikucki (1991), Elburg (1995), Helps (2009), Clemens et al. (2011), Clemens & Birch (2012), an unpublished BSc honours thesis by D. G. Cownley, University of Melbourne, Australia) and numerous secondary data sources referenced in these works.
	For the I-type rocks, data are from a compilation of analyses of rocks from the Cape Granite Suite (Scheepers, 1990), plutonic rocks from California (compiled from the EarthChem on-line database  at http://www.earthchem.org/), a general world-wide set of hornblende-bearing metaluminous felsic plutonic and volcanic rocks (also from EarthChem), analyses from Clemens et al. (2009), some unpublished data from the author, and Peruvian felsic rocks from a database compiled by Prof. N. Petford (Northampton University, UK).
	In all cases, the databases have been filtered to exclude metamorphosed, altered, trondhjemitic and peralkaline rocks, and to contain data only for truly felsic rocks (66 ≤ SiO2 ≤ 80 wt%) for which there are complete major-oxide analyses. Supplementary Materials 2 and 3 contain the data from EarthChem. Readers wishing to obtain copies of the compilations of worldwide S-type analyses and the I-type rocks of the Cape Granite Suite should write to Prof. G. Stevens at the University of Stellenbosch (gs@sun.ac.za). For access to the data on Peruvian felsic rocks, readers should contact Prof. Nick Petford of Northampton University (nick.petford@northampton.ac.uk). For other presently unpublished data, access cannot be granted for a variety of legal and proprietary reasons.

References
Clemens, J.D. 1981. Origin and Evolution of Some Peraluminous Acid Magmas. Unpub. PhD Thesis, Monash University, Australia.
Clemens, J.D. & Birch, W.D. 2012. Assembly of a zoned volcanic magma chamber from multiple magma batches: The Cerberean Cauldron, Marysville Igneous Complex, Australia. Lithos, 155, 272-288, DOI: 10.1016/j.lithos.2012.09.007.
Clemens, J.D., Birch, W.D. & Dudley, R.J. 2011. S-type ignimbrites with polybaric crystallisation histories: the Tolmie Igneous Complex, Central Victoria, Australia (and erratum). Contributions to Mineralogy and Petrology, 162(6), 1315-1337 and 1339, DOI: 10.1007/s00410-011-0652-1 and 10.1007/s00410-011-0666-8.
Clemens, J.D., Darbyshire, D.P.F. & Flinders, J. 2009. Sources of post-orogenic calcalkaline magmas: The Arrochar and Garabal Hill–Glen Fyne complexes, Scotland. Lithos, 112(3-4), 524-542, 10.1016/j.lithos.2009.03.026.
Elburg, M.A. 1995. Microgranitoid Enclaves in Three S-type Igneous Complexes, Lachlan Fold Belt, Australia. Unpub. unpublished Thesis, Monash University, Clayton.
Helps, P.A. 2009. Scales of Heterogeneities and Equilibration Volumes in Granitoid Magmas. Unpub. unpublished Thesis, Kingston University, Kingston-upon-Thames.
Mikucki, E. 1991. The evolution of Some S-type Magmatic Suites: Examples from the Southwestern Lachlan Foldbelt. Unpub. PhD Thesis, Monash University, Clayton.
Scheepers, R. 1990. Magmatic association and radio-element geochemistry of selected Cape Granites with special reference to subalkaline and leucogranitic phases (in Afrikaans). Unpub. PhD Thesis, University of Stellenbosch, Stellenbosch.