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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
- IIT JAM
- Geology (GG)
The composition in zone1 grades continuously away from center of crystal from an70 to an50.zone 2 had uniform composition of an17.
what kind of zoning is displayed by plagioclase grain? a-normal continuous b-reverse continuous c-normal discontinuous d-reverse discontinuous
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Rahul kumar
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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 composition is demarcated by boundary between zone 1 and zone 2. Normal zoning is characterized by anorthite rich core and Albite rich (anorthite poor) rim.
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Sajan sarthak Best Answer
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 composition during growth of the crystal. Plagioclases are normally zoned from calcic cores to more sodic rims. Because of sharp change what actually that sharp change reflects Temperature fall in a short span Here the core is more anorthitic and it's zoning is dicontinuous and getting riched to albitic so it's progressive one.