rochas Ígneas.

Click here to load reader

Post on 07-Apr-2016

217 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Rochas gneas

  • http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks8.html

  • Outra verso do Ciclo de Rocha http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html

  • Fuso Parcial e MagmaE.g., fuso parcial resulta enriquecimento em Slica

    Fuso Parcial MagmaEnriquecido: O, Si, Al, Na, K, Empobrecido: Ca, Fe, Mg Pobre em: O, Si, Al, Na, K, (< 50%) Rico em: Ca, Fe, Mg (> 50%)

  • Formao de MagmaComo so as rochas fundidas? 1. Aquecimento 2. Reduo de presso3. Aumento do contedo de gua4. Increased silica contentOnde as rochas fundem?Zonas de subduco (Silicosos e intermedirios) Plumas Mantlicas (Hot Spots) no somente em limites divergentes (Mficos)

    Hot andHigh PressureHot andLow Pressure

  • Intrusivo vs. Extrusivo (Rochas silicosas)Silicoso (flsico) MagmasFrio (
  • Rocha gnea IntrusivaE.x., Granito (cido):

    Pobre em: Fe, Mg, Ca, (70%)

  • VulcanismocidoMagma cidoAlta viscosidadeGasosoErupso explosiva Inclinao abrupta, vulces em forma de cone

  • Extrusive vs. Intrusive (Mafic Rocks)Mafic MagmasHot (>1000oC)Non-Viscous (runny, flows easily)Dry (no H2O or C02)Mafic RocksUsually Extrusive, Fine-grained, Mafic (Basalt) rock forms oceanic crust, Shield Volcanoes and Basalt FloodsIf Intrusive, course-grained mafic rocks are formed Gabbro. If intrusive, Dikes and Sills more common

    See Kehew, Fig 3-40

  • E.g., Vulcanismo Mfico, HawaiVulces Hot Spot

  • Hawaii 10.3 12.0 20.6 Midway 27.2 19.9 43.4 42.4 48.1 55.2 56.2 59.6 0-5 Current PlateMotionHawaiUma longa cadeia de vulces inativas Idade das ilhas, em milhes de anos

  • Tipos de Erupo (Mafic Volc.)Tipos de ErupoFluxo de lavaFontes de lava Erupo em fissuraTextura da rochaAfanticaPorfirtica VesicularVidro (Obsidiana)

  • Textura (Extrusiva, Rochas mficasAhah (Rubbley)Maior parte slida quando fluiPahoehoe (Ropey)Maior parte lquida quando flui

  • Desastre associado a rochas vulcnicos Baseado em Tipo de vulcanismoTerremotosHistria dos fluxosZonas de riftInclinao

  • Sill Mfico: Intrudido entre camadasMagma mfico menos viscoso e mais quente No forma plutons mas Corta ao longo de camadas (Sills) ou mesmo cortar camadas (Diques)

  • Classificao de rochas gneas cido Intermedirio Mfico

    Granito Diorito Gabro Riolito Andesito Basalto

    (Porphyritic)IntrusiveExtrusive

  • Intrusiva (Plutonica)Extrusiva (Volcanica)

    Mineral PercentageContinental Crust Oceanic Mantle CrustClassificao de rochas gneas

  • Igneous Rocks and Silicates The Igneous Rock Classification parallels the systematicSilicate Mineral Classification

    Frame- Double Single Iso. work Sheet Chain ChainFig. 3-6Mineral Percentage

  • GranitoCores claras, gro grosseira, sem padresQuartzo, feldspato, mica e hornblendaFrequentemente usada em edifcios e monumentos

  • BasaltoCores escuras, gro fina, extrusivoFormeda onde a lava alcana a superfcieMais abrangente das rochas gneasFrequentemente usada em edifcios e monumentos

  • GabbroDark-colored, coarse- grained intrusiveSimilar composition to basaltplagioclase feldspar with some pyroxene and olivinehttp://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock8.html

  • ObsidianNatural volcanic glassForms when lava cools very quicklyUsually dark, but small pieces may be clearFractures along curved (conchoidal) surfaceUsed as spear and arrow points, kniveshttp://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock7.html

  • Pumice and other igneous rocksLight colored, frothy (many air spaces)Same minerals as in granite, but finer in grain sizeFor more about igneous rocks: http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Igrocks/Igrocks1.html

    *************************