petrologi-11-metamorf

Temu ke sebelasTemu ke sebelasMetamorphism means "changed Metamorphism means "changed form (form (berubah bentukberubah bentuk))How do rocks change?How do rocks change?Metamorphism causes changes in: Metamorphism causes changes in: 11TextureTexture (definition:shape, size (definition:shape, size and orientation of mineral and orientation of mineral grainsin grainsin the rocks)the rocks)22MineralogyMineralogy (chemical (chemical composition)composition)METAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORP!"MMETAMORP!"M : process by hich : process by hich conditions ithin the !arth alter the mineral conditions ithin the !arth alter the mineral content and structure of any rock, igneous, content and structure of any rock, igneous, sedimentary or metamorphic, sedimentary or metamorphic, without melting without melting itit""Metamorphism occurs hen heat and pressure Metamorphism occurs hen heat and pressure exceed certain le#els, destabilizing the minerals exceed certain le#els, destabilizing the minerals in rocks"""but not enough to cause melting in rocks"""but not enough to cause melting $on%rich fluids circulating in and around rocks $on%rich fluids circulating in and around rocks also influences metamorphism also influences metamorphism PREEXISTING ROCKSBATUANMETAMORIKT! P! CHEMICA" "UI#SMETAMORISME METAMORISMECONTACT REGIONA"/#$NAMICCHANGESTEXTUREMINERA"OG$"INEATIONO"IATIONNONO"IATE#HO%%HEREHO%%HERE&ENIS BATUAN' CIRI KE&U(RUTERAANJENIS#ineation$#ineation$ hen hen prismatic or rod-like prismatic or rod-like mineralsminerals (eg" &ornblende, tourmaline etc") (eg" &ornblende, tourmaline etc") occurringinarockorientthemsel#es occurringinarockorientthemsel#es parallel to one anotherparallel to one another (perpendicular to (perpendicular to direction of maxi" 'ressure or stress)direction of maxi" 'ressure or stress)%oliation$%oliation$henhenplaty,lamellarorflaky platy,lamellarorflaky minerals (eg" sheet silicate minerals the micas: biotiteminerals (eg" sheet silicate minerals the micas: biotite andmusco#ite,chlorite,talc,andserpentine),andmusco#ite,chlorite,talc,andserpentine), occurringinrockorientthemsel#esoccurringinrockorientthemsel#esparalleltooneparalleltoone another another(i"e"perpendiculartothedirectionof(i"e"perpendiculartothedirectionof maximum pressure or stress)" maximum pressure or stress)"RandomRandom orientation orientationOf minerals Of mineralsPreferredPreferred orientation orientationOf minerals Of mineralsO"IATIONO"IATIONO"IATIONO"IATIONMe)a*or+h,c Rock P,c)-resMe)a*or+h,c Rock P,c)-resGran,)e! Gne,ss! Sha.e! S.a)e! Sands)one! and /-ar)0,)e are goodGran,)e! Gne,ss! Sha.e! S.a)e! Sands)one! and /-ar)0,)e are good e1a*+.es o2 *e)a*or+h,c rocks3 e1a*+.es o2 *e)a*or+h,c rocks3Metamorphic rocksMetamorphic rocks(henrocksarebakedbyheatofmoltenmagmaor(henrocksarebakedbyheatofmoltenmagmaor s)ueezed by the mo#ements of huge tectonic plates or bys)ueezed by the mo#ements of huge tectonic plates or by the pressure of o#erlying thick succession of rocks the pressure of o#erlying thick succession of rocksThey are altered or changed beyond their recognitioni.e. change in Chemical composition, texture and structureMe)a*or+h,c rocksMe)a*or+h,c rocksMetamorphismMetamorphism!s the process that occur !s the process that occur in rocks due to the in rocks due to the effects ofeffects ofHigh temperatureHigh temperatureHigh pressureHigh pressureChemically active fluidsChemically active fluidsThe source of temperature is either from magmaThe source of temperature is either from magma or due to the depth factor or due to the depth factorMetamorphism usuall& result into change in min'Metamorphism usuall& result into change in min' comp'andte(tureofrocks(!g'and"ed'))hichcomp'andte(tureofrocks(!g'and"ed'))hich aresub*ectedtotemp' aresub*ectedtotemp'>100 >1000 0Candpressure>Candpressure> 1000s Mpa. 1000s Mpa.#o)+grade metamorphism$#o)+grade metamorphism$ccurs at a!out 100 ccurs at a!out 1000 0 C to "00 C to "000 0 C. C.igh+grade metamorphism$igh+grade metamorphism$Occurs at , -.. Occurs at , -... . / /Te*+era)-reTe*+era)-re01!%ORM PRE""0RE 01!%ORM PRE""0REPress-rePress-re-increaseswithdepthdueto-increaseswithdepthdueto increase in overburden. increase in overburden.-actsverticallydownwardsand-actsverticallydownwardsand affectsthevolumeofbothaffectsthevolumeofboth liquid & solids. liquid & solids.--increaseswithdepthuptosomeincreaseswithdepthuptosome extent, effective in the upper partextent, effective in the upper part of the crust. of the crust.2!RE/T or 2ifferential 2!RE/T or 2ifferential PRE""0REPRE""0RE- acts in all direction and affects only- acts in all direction and affects only onsolidsresultingintoonsolidsresultinginto deformationofshapeandchangedeformationofshapeandchange in mineral composition in mineral composition-hightemperatureisalso-hightemperatureisalso associatedwithduetodepthassociatedwithduetodepth factor! factor!-hightemperatureisnotalways-hightemperatureisnotalways associated. to depth factor! associated. to depth factor!-"ithostaticpressure-dueto-"ithostaticpressure-dueto overburden overburden-#tress-dueto-#tress-duetotectonictectonic forces forcesSTRESSSTRESSUniform StressDifferential Stressminintermax$ranite $ranite $ranite-$neiss $ranite-$neissMETAMORPHISMMETAMORPHISMEAT$ TemperaturesEAT$ Temperatures needed to metamorphoseneeded to metamorphose rock (3.. rock (3.... / or 4... / or 4..... /)/) reached near 4. km (5reached near 4. km (5 miles) beneath themiles) beneath the surface' surface'PRE""0RE$ Re6uiresPRE""0RE$ Re6uires pressure , 4 bar or 4...pressure , 4 bar or 4... mb7 )hich is generall&mb7 )hich is generall& found 8 9 km (3 miles)found 8 9 km (3 miles) beneath the Earth:sbeneath the Earth:s surface surface %#0!2"$;ater is the%#0!2"$;ater is the usual fluid and comes fromusual fluid and comes from