metamorphism &amp rocks - kean university：变质&amp；岩-基恩大学

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1、METAMORPHISM&ROCKS©MarciaAndersonMetamorphicRocksMetamorphicrocksarehighlydeformed.Usuallycausedbyintrudedigneousmasses.Metamorphism:Transformationofrocksbyheat,pressure&chemicallyactivefluids.Changeistexturalandmineralogical.Alwaysoccursdeepwithintheearth.Providesc

2、lues@geologicprocessesw/inearth'scrustMustremainsolid,otherwisebecomesigneous.Rockbecomesunstableunderheat&pressure&graduallychanges.Calif..SinNombre;ancientschist&gneissMetamorphism:Occursduringmountainbuilding;intensestress&temperaturesassociatedwithlargescaledefo

3、rmation.ThisLargescaledeformationisregionalmetamorphism.RegionalMetamorphismOccursduringmountainbuilding.Crustissqueezedanddeformed,shortenedandthickened.Thickeningformsmountains.Coresofmanymountainsconsistofintrusiveigneousbodiessurroundedbyhigh-grademetamorphicroc

4、ks.AlaskaCopperMountainRegionalMetamorphismSincetheyareformedunderdirectstress,metamorphicrocksareusuallyfoliated.Shaleslatemicaschistfeldspar/hornblendegneissAppalachianMts.:Ohio-->Cent.Pa-->E.Pa.-->NY-->Vt../N.H.Metamorphism&PlateTectonicsMostmetamorphismoccur

5、satconvergentzones.Compressionalforcessqueeze&deformtheconvergingplates&accumulatedsedimentsalongthecontinentalmargins.Aslithospheredescends,pressureincreasesfasterthantemp.Materialiscontinuallytransportedtogreatdepthsatconvergentplateboundaries.Atonlyafewkm.,claybe

6、comesunstable,itrecrystallizesintominerals:(muscovite).ShieldsExtensiveareasofmetamorphicrocks&igneousplutonsoneverycontinent.Canadianshieldsformsthebedrockovermuchofno.CanadafromHudsonBaytoNo.Minnesota.Amongoldestrocksonearth.Remnantsofearliermountainbuilding.Conta

7、ctMetamorphismMoltenrockcomesincontactwithcountryrockZoneofalteration;aureole,orhaloforms@themagmabodyNearthemagmabody,hightempmineralsform.le:garnet.Furtheraway:low-grademineralslikechloriteareformed.Mineralcompositionandamountofwaterwillaffectthesizeoftheaureolepr

8、oduced.ContactMetamorphismClaymineralsare'baked'formingfine-grained,dense&hardrock.Sincedirectpressureisnotafactor:usuallynotfoliated.Hard