ppp1 Introduction.- Part I RGCDkit at work.- 2 Data manipulation and simple calculations.- 3 Classical plots.- 4 Specialized plots.- 5 Radiogenic isotopes.- Part II Modelling major elements.- 6 Direct models.- 7 Reverse models.- 8 Forward modelling in R.- 9 Reverse modelling in R.- Part III Modelling trace elements.- 10 Dilute trace elements partition coefficients.- 11 Direct dilute trace-element models.- 12 Reverse dilute trace-element models.- 13 Trace elements as essential structural constituents of accessory minerals the solubility concept.- 14 Forward modelling in R.- 15 Reverse modelling in R.- Part IV Radiogenic isotopes.- 16 Direct models.- 17 Reverse models.- 18 Forward modelling in R.- 19 Reverse modelling in R.- Part V Practical modelling.- 20 Choosing an appropriate model.- 21 Semi-quantitative geochemical approach.- 22 Constraining a model.- 23 Numerical tips and tricks.- 24 Common sense in action.- Part VI Worked examples.- 25 Differentiation of a calc-alkaline volcanic s