PRIMARY ENVIRONMENT OF MOST IGNEOUS ROCKS FORMED BY A DIFFERENTIATION PROCESS

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This starts with a parent magma,often of basaltic composition, and as cooling proceeds,early-crystallizing minerals are separated to form cumulate rocks.The remaining melt,have lost elements that are concentrated in the early minerals,becomes changed in composition. Through such a process the magma may pass through a differentiation series,such as gabbro-diorite granodiorite granite-pegmatite,in which each point has a distinctive  composition of both major and minor chemical elements.
This figure below shows use of surface rock chip sampling to detect leakage anomalies that reflect concealed zinc mineralization. Horizontal distance 1km(0.6mi),vertical distance 200m(650).Ore bodies have formed in a porous limestone bed capped by an impermeable shale;some mineralization fluid has escaped upward along preexisting faults.