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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Ishita Das posted an Question
November 25, 2020 • 03:02 am
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30 points
30 points
- IIT JAM
- Geology (GG)
112. which of the following stalements is/are true for the zoned plagioclase ka sodic core and calcic shell in metamorphic rocks (b) calcic core and sodic shell
112. Which of the following Stalements is/are true for the zoned plagioclase a Sodic core and calcic shell in metamorphic rocks (b) Calcic core and sodic shell in metamorphic rocks c Calcic core and sodic shell in volcanic rocks Sodic core and calcic shell in volcanic rocks (d) sodic core and calcic shell in plagioclase (e) Both 'a' and 'c'
2 Answer(s)
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Rahul kumar Best Answer
Answer (e) Both a and c Metamorphic rocks exhibit reverse zoning (sodic core and calcic rim) whereas volcanic rocks exhibit normal zoning (calcic core and sodic rim). It happens because in case of volcanic plagioclase, the temperature is maximum at centre and decreases towards the rim whereas during any Metamorphic transformation, temperature is maximum at the rim and decreases towards the core. High temperature favours the formation of Calcic plagioclase and low temperature favours the formation of sodic plagioclase.
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Sajan sarthak![best-answer]()
In zoned plagioclase Calcic core Sodic rim is the Igneous case in solidsolution. But in metamorphic it's reverse case Sodic core and Calcic rim because due to replacement. so option e is the answer.