Gurmeet Singh posted an Question
December 21, 2020 • 14:22 pm 30 points
  • IIT JAM
  • Geology (GG)

Why island arc is felsic. why not basic as it is made from asthenosphere.

why island arc is felsic why not basic as it is made from asthenosphere

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    Rahul kumar best-answer

    Magmatic differentiation processes shift the composition of upcoming magma from basic to felsic. So, even after island arcs magma source is of basic composition, crustal melting and differentiation processes change the final upcoming magma composition to felsic. That's why we get felsic rocks in island arcs.

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    do the island arc forms similarly as other basaltic magma comes up...

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    then it became felsic

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    Sajan sarthak best-answer

    Island arcs are neither felsic nor mafic it has an intermediate compostion as it is formed by melting of basaltic oceanic crust and when that magma comes up it assimilates the continental felsic rocks so producing mixture of both. Andesite and Basaltic.trachy andesite is the major rock. Extra info:- Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries (such as the Ring of Fire). Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone. They are the principal way by which continental growth is achieved.

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    i ll send you a picture..aftr somtime

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    Ask questions after 9pm ...I will not be available in the day time from today.

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    And do remember to mark answers....I am not supposed to tell you everytime...

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    sir you can answer anytime, no problem. ...

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    late chlege but comment pakka krdena.

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    the last line in picture.

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    i have send you the pictures...can u explain sir

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    thoda galat likha hua he....udhar

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    andesite composition is intermediate

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