granitos classificacao petrogenesis tectonica

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    GRANITESClassification, Petrogenesis and

    Tectonic Discriminations

    Presented By:

    Samir Kumar ari!

    "#$Sc % IIT om&a'(Pro)ect *ello+

    Geocronolog' Di-$

    CSIR.NGRI, /'dera&ad

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    Granite

    #ineralogicall'0Essential minerals - Quartz , Feldspar

    Accessor' minerals Biotite, muscovite , amphibole.Other accessories are 1ircon, a2atite, ilmenite, magnetite, s2ene,

    2'riteetc.

    Te3turall'0

    Medium to coarse grained crystalline rock generally ehibiting/'2idiomor2ic te3ture and Intergro+t te3tures !perthite,

    "ntiperthite, Myrmekite, #raphic, #ranophyric, rapakivi$.

    %he term 4Granite4 is derived &rom latin 'ord "Granummeaning (grain( because o& its granular nature.

    Cemicall' 0 )iO* - + , !other oides vary$

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    Classification of Granitoids0

    #ineralogical classifications !/0#) classi&ication$

    Cemical classification !alumina saturation, )-/-"-M

    classi&ication etc.$

    Tectonic classification !Based on plate tectonic setting$

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    5.A.P classification of Granitoids

    " a 2art of 5AP* classification(

    Fig.1. "&ter /0#) !1234$

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    Granite classification &ased on alumina

    Saturation "&' Sand(0

    Fig *. "lumina saturation classes based on the molarproportions o& "l*O

    45!6aO78a

    *O79

    *O$ !:"5689;$

    a&ter )hand !12*3$.

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    Al2a&etic "S.I.A.#( Classification of

    Granitoids0

    ' Ca22ell and 6ite "789:(

    S.t'2e Granitoid "sedimentary protolith$

    I.t'2e Granitoid!igneous protolith$#.t'2e Granitoid !direct mantle source$

    ' ;oiselle and 6ones "7898(

    A.t'2e Granitoid !anorogenic type$

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    S.T'2e Granitoids0

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    I.T'2e Granitoids0

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    #.T'2e Granitoids0

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    A.T'2e Granitoids0

    "-type granites are emplaced in either 'ithin plate anorogenic

    settings or in the &inal stages o& an orogenic event.

    Caracterised &'0

    ?igh )iO* "7?(?igh F contents "@ to > 22m(Cresence o& fluorite is an important characteristic o&

    "-type granites.

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    S.I.A. # Classification of Granitoids0

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    Classification of Granitoid Rroc!s

    &ased on Tectonic Setting0

    BRBGENIC0Mountain building resulting &rom compressive stresses

    associated 'ith subduction.

    e$g$ 6ontinental collision granites- ?imalayas.

    Fig.E. " 6lassi&ication o& #ranitoid ocks Based on %ectonic )etting. "&ter Citcher !124$ in 9. G. ?sH !ed.$, Mountain

    Building Processes, "cademic Cress, IondonJ Citcher !1224$, The Nature and Origin of Granite, Blackie, IondonJ and

    Barbarin !122K$ Geol. Journal, *, **3-*4. Linter !*KK1$ "n /ntroduction to /gneous and Metamorphic Cetrology.

    Crentice ?all.

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    Classification of Granitoid Rroc!s

    &ased on Tectonic Setting0

    Fig.. " 6lassi&ication o& #ranitoid ocks Based on %ectonic )etting. "&ter Citcher !124$ in 9. G. ?sH !ed.$, Mountain

    Building Processes, "cademic Cress, IondonJ Citcher !1224$, The Nature and Origin of Granite, Blackie, IondonJ and

    Barbarin !122K$ Geol. Journal, *, **3-*4. Linter !*KK1$ "n /ntroduction to /gneous and Metamorphic Cetrology.

    Crentice ?all.

    ANBRBGENIC0Magmatism 'ithin plate or at a spreading plate margin.?ere magmatism occurs in settings that are not genetically

    related 'ith compressive orogeny.

    e.g. ello'stone-snake river plain in 0)"

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    TRANSITIBNA; PBST.BRBGENIC 0Magmatism takes place a&ter the main orogenic event. ! because it

    needs a precursor orogeny t'o diverse groups eist 'hether they are

    orogenic or anorogenic$.

    e.g. Iate 6aledonian plutons o& Britain

    Classification of Granitoid Rroc!s

    &ased on Tectonic Setting0

    Fig.. " 6lassi&ication o& #ranitoid ocks Based on %ectonic )etting. "&ter Citcher !124$ in 9. G. ?sH !ed.$, Mountain

    Building Processes, "cademic Cress, IondonJ Citcher !1224$, The Nature and Origin of Granite, Blackie, IondonJ and

    Barbarin !122K$ Geol. Journal, *, **3-*4. Linter !*KK1$ "n /ntroduction to /gneous and Metamorphic Cetrology.

    Crentice ?all.

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    Geocemical "trace element(

    Discrimination Plots of Granitoids0

    Fig. 3. %ectonic discrimination plots o& b!8b7$ and 8b !Cearce et al.12E$. Fields &or

    syn-collision !6OI#$, volcanic arc !N"#$, 'ithin plate !LC#$ and ocean ridge !O#$ granites.

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    Petrogenesis0

    Magmatic Origin

    Metasomatic %rans&ormation !#ranitisation$

    o+ensstudies sho'ed that a basaltic magma can give rise toacid magma !granitic$ due to di&&erentiation.

    tensive &ield studies , in high grade terranes, sho'ed that

    etensive metasomatic trans&ormation 'as capable o& bringingabout compositional changes insitu o& a variety o& pre-eisting

    rocks to create granites "/$/$Read($

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    Most granitoids o& signi&icant volume occur in areas 'here the

    continental crust has been tic!ened by orogeny, eithercontinental arc subduction or collision.

    Because the crust is solid in its normal state, some termaldistur&anceis reDuired to &orm granitoids.

    Most 'orkers are o& the opinion that the ma@ority o& granitoidsare derived by crustal anate3is, but that the mantle ma' also&e in-ol-ed. %he mantle contribution may range &rom that o& asource of eat &or crustal anateis, or it may be the source of

    material as +ell$

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    Many 'orkers believed there are

    more than one origin &or granites P the

    term GRANITES F GRANITES

    'as coined.

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    *uture 6or!0

    )tudy about #ranite #eochemistry 'ith special re&erence to

    Larangal and 8algonda

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    THANK YOU