Abstract
We here propose a new calculation method for estimation of primary basalt magmas from mid ocean ridges (MOR) and island arcs (tholeiite to mildly alkalic basalt with various H2O). The calculation model uses a thermodynamic crystallization model of COMAGMAT 3.72 (COM3) which runs with an Excel spreadsheet calculator PRIMACALC 2.00 (PMC2) for mantle equilibrium and trace element back calculations of primary basalt.