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Gurmeet Singh posted an Question
October 13, 2020 • 21:51 pm 30 points
  • IIT JAM
  • Geology (GG)

How the zones are formed by these facies in figure given below. sir.

A KIn a KIn, PrlaA +quartz +quartz +analcime or albite + albite Pmp Ep, Zo Prh Hul, Lmt Chl Chl F Act Cal, Ttn Cal Zeolite Facies Prehnite-Pumpellyite Facies

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    Rahul kumar

    Kindly mark the question as answered if you don't have any further queries related to this question

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    Rahul kumar

    Circles are showing bulk composition of the rock stable in that particular facies.

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    Rahul kumar

    Mineral phases that coexist with each other at given temperature and pressure are connected by lines, called tie lines. The tie lines divide the diagram into smaller compositional triangles, that tell us what minerals will coexist in a rock of any composition under the current temperature and pressure conditions. Formation (joining) of new lines indicate the formation of new minerals as a result of metamorphic reactions.

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    thank you sir. i got that zeolite facies - chl, cal, lmt coexist and we joined them to make tie lines but what is that great circle showing in fig.

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    Rahul kumar Best Answer

    Different zones are formed as a result of reactions between different minerals. Zeolite facies is low grade metamorphic facies contains mineral like zeolite, analcime, quartz etc. With increasing metamorphic grade, low grade minerals react to form assemblage stable in high metamorphic conditions. Minerals in zeolite facies will react with increasing P-T conditions to form new minerals like Prehnite-pumpellyite, Epidote, Zoisite etc. These new minerals (along with low grade minerals) form new facies known as Prehnite-pumpellyite facies. Similarly, with increasing P-T conditions different set of minerals form and characterizes different zones.

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    sir how this diagram formed.

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    why we have joined these tie lines.

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    Sajan sarthak best-answer

    Zeolite facies, one of the major divisions of the mineral facies. It represents the transition between the sedimentary processes of diagenesis and the distinct regional metamorphism exhibited by the greenschist facies. Minerals typically found under these conditions include the zeolites, albite, quartz, and prehnite. Volatile components are very important in the chemistry of this facies because, under zeolite facies, the temperature and pressure can change the chemical potentials of water and carbon dioxide so as to produce the mineralogy of the greenschist facies. 2. Prehnite-pumpellyite facies The facies is transitional, bridging the path to the blueschist facies or the greenschist facies. It is particularly well developed in graywacke-type sediments. The two minerals prehnite and pumpellyite replace the zeolite minerals of the zeolite facies and are themselves replaced by epidote minerals in the greenschist facies and by lawsonite and pyroxenes in the blueschist facies. Typical minerals in this facies are quartz, albite, prehnite, pumpellyite, chlorite, stilpnomelane, muscovite, and actinolite. Almost all the minerals are hydrated, and, except for chlorite, they bear little resemblance to the minerals of sediments. This facies has been most described from younger mountain

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