IntroductionThis paper focuses on the behavior of base metals during partial melting in the upper mantle and fractional crystallization in crustal magma. A base metal is a metal that oxidizes easily and reacts with dilute hydrochloric acid (HCL) to form hydrogen. Examples of base metals include iron, nickel, copper, zinc, and lead. The behavior of these metals in terms of partial melting and fractional crystallization is discussed using their partition coefficients. The partition coefficient is the ratio of the concentration of an element in a mixture of one phase compared to another phase. Furthermore, the partition coefficient depends on pressure, solid composition, melt composition and temperature (Hall, 1987). Furthermore, the behavior of these metals during fractional crystallization is discussed based on the results obtained from the Okataina Volcanic Center study on the behavior of metals (Zn, Pb, Cu, Mo) during crystallization and degassing of rhyolites. Subsequently, their behavior during partial melting is discussed based on the results obtained from experiments conducted at 1.5-2.0 GPa and 1300-1500ᵒC for divalent metals (Zn, Fe, Mn, Co and Ni). Behavior of metals during partial melting and crystallization by fractionationFirst, crystal fractionation is a chemical process by which the composition of magma changes due to crystallization. This is because the crystals within the magma have different compositions than the magma, which therefore leads to the separation of the crystals from the magma; resulting in a change in the composition of the remaining melt. Thus partial melting is a process by which a rock subjected to high pressure and temperature is melted into a small...... paper medium ......the presence of both elements in the expelled vapor and a phase steam determines the ability of metals to break down after melting. Conclusion The partition coefficient of metals with the melt determines which element will prefer to remain in the melt or move from the melt. Therefore, this describes the behavior of metals during partial melting and fractionation crystallization. The partition coefficient depends on the pressure, the composition of the solid, the composition of the melt and the temperature. The results discussed above indicate that melts of clinopyroxene-rich rocks are expected to have low Mn/Fe, Co/Fe, Ni/Co, Mn/Zn, and high Zn/Fe values ​​compared to partial peridotite melts (olivine + otopyroxene ). Throughout the fractional crystallization process the metals (Pb, Zn and Mo) divide into crystallizing minerals or remain dissolved in the molten mass.