The composition in zone1 grades continuously away from center of crystal from an70 to an50.zone 2 had uniform composition of an17.

Normal discontinuous zoning: zoning in which the outer portions of the crystal have a lower-temperature composition than the core. Usually reflects progressive change of melt compo...

The shown zoning is normal dis-continuous zoning because the core is more anorthitic and the rim is less anorthitic. The term discontinuous is used because of Sharpe change in comp...