01 rochas igneas

8/3/2019 01 Rochas Igneas

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Rochas gneas

Vulcanismo e Plutonismo


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Rochas gneas: origem

registros da histria trmica daTerra.

origem associada com o movimentodas placas tectnicas,

possuem um papel importante nestamovimentao, origem dasmontanhas e evoluo doscontinentes.


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Rochas gneas: Fuso

Fuso parcial do manto produz magmasmficos (baslticos ou pobres em Si)

Fuso parcial na zona de subducoproduz rochas intermedirias(andesito)

Fuso parcial da crosta, em geralprofunda e continental, produzmagmas flsicos (granticos, ricos Si)


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O padro de fuso em bordas de gros de um protlitoarentico rico em feldspato (arcsio) submetido a T =700 800C em PH2O = 1kbar

Qzo isolado Tf >1170C

Qzo e albita em contato Tf= 790C

Qzo+alb+ortoc. Tf = 720C

Sem fuso

Fuso parcialAnatexia de ummetassedimento


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Magma o material fundido no interior da Terra,

ao sair na superfcie chamado de lava. (foto Hawai)


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Kilaweua Hawai


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Temperaturas do magma

prximas superfcie da Terravariam de

700C (composies flsicas Si-Al) a1200C (composies mficas Fe-Mg).

lavas mais raras (carbonatticas)temperatura pode ser em torno de

600C.


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Composio do magmamistura de fases lquidas, slidas e

gasosas.

Em geral O, Si e Al (lquido silictico).Pode ter tambm Ca, H, Na, K, Fe, Mg

entre outros.

Esses tomos so ligados emextensas redes (polimerizados)conforme a composio do magma.


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Composio do magmaBaixa razo O:Si (magmas granticos

ou flsicos) forma mais ligaes Si-O

e redes polimerizadas mais longas.magma flui lentamente, no perde

gases e produz erupes explosivas e

rochas piroclsticas.


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Cristalizao do magma processo de congelamento do

magma.

Conforme cai a temperatura soproduzidos minerais diferentesem uma ordem de cristalizaodeterminada experimentalmentee bem conhecida.


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Rochas gneas: classificaoconforme relaes de campo

Erupes vulcnicas: atividade gneaem vulces e fissuras, formando as

rochas vulcnicas com granulao fina.Enormes volumes de rocha lquida

que nunca chegam na superfcie,

esfriam lentamente em profundidadee formam as rochas plutnicas comgranulao grosseira.


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Cristalizao produz Minerais

Quartzo SiO2Feldspato potssico MAl(Al,Si)3O8 M=K

Feldspato plagioclsio MAl(Al,Si)3O8 M=Na-Ca

Mica biotita (K,Na,Ca)(Mg,Fe,Li,Al)2-3(Al,Si)4O10(OH,F)2AnfiblioA2-3 B5(Si,Al8)O22(OH)2 A=Mg,Fe, Ca

ou Na B = Mg, Fe, Al

PiroxnioABSi2O6 A= Ca, Na, Mg,Fe B = Mg,Fe,Cr,Mn,Al

Olivina (Mg,Fe)2SiO4


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Tipos derochas gneas:

composio mineralgica Granito e Riolito

(Quartzo, feldspato K,plagioclsio Na, micabiotita)

>68% slica


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Tipos de rochasgneas

composio mineralgica

Granito(Quartzo,feldspato K,

plagioclsio Na, micabiotita)

Egito, 323-317 a.C.

Transporte das

embarcaes sagradas


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Tipos derochas gneas

Riolito(Quartzo,feldspat

o K, plagioclsioNa, mica biotita)


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Riolito vesicular eamigdaloidal


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Tipos de rochas gneas: composio mineralgica

Diorito e andesito porfirtico (anfiblio,plagioclsio Na e Ca, pode ter quartzo e feldspatoK)

52-63% slica


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Tipos derochas gneas


Diorito (anfiblio,plagioclsio Na e Ca,pode ter quartzo e

feldspato K)

Fara, Tutms II,XVIII dinastia, 1479-

1425a.C.


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Tipos de rochas gneascomposio mineralgica

Gabro e basalto porfirtico (Piroxnio eplagioclsio Ca, pode ter olivina)

48-52% slica


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Tipos de rochas gneascomposio mineralgica

Gabro e Basalto (Piroxnio e plagioclsio Ca,pode ter olivina) fotomicrografia

B lt d B i d P


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Basalto da Bacia do Paran

Basalto (Piroxnio eplagioclsio Ca)

Estrada do Rio doRastro, SC


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Basalto

Pedra de Roseta

Museu Britnico

Londres

Ti d h


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Tipos de rochasgneas


Peridotito:predomina olivinapode ter piroxnio

Komatiito: piroxnios esqueletais


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Komatiito

Classificao de rochas gneas

Classificao

Textural

Composio Mineralgica

cidas Intermedirias Bsicas Ultrabsicas


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Srie de Bowen

Cl ifi


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ClassificaoModal

Feldspatide

Classificao de rochas

magmticas flsicas

fanerticas com mais de

10% de Q (quartzo) +A (Feldspato Alcalino)

+ P (plagioclsio) + F

(Feldspatide)

Foids = Feldspatoid


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Classificao de rochas ultramficas


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Principais elementos qumicosformadores de rochas gneas


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Fi f


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Fissura em formao

On August 16, 1975, a new fissure opened along the south rift zone of Tolbachik volcano

during the "Great Tolbachik Fissure Eruption" of 1975-76. The following day formation of

the third of a group of new cinder cones at the northern end of the rift zone began.

Formation of the first cone began on July 6 and ended on August 9, the day that the second

cone began erupting. The eruption occurred along a fissure system that extends 70 km SSW

of Plosky Tolbachik volcano. Photo by Yuri Doubik, 1975 (Institute of Volcanology,Petropavlovsk).

Tipos de V lces


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Tipos de Vulces De fissura, o tipo de erupo vulcnica mais comum na Terra. A lava sai

por fissuras na crosta. Domina nas dorsais.

Incandescent lava fountains play above an eruptive fissure at Krafla volcano in NE Iceland

on September 6, 1984. After a quiet interval of 33 months, an eruption began on September

4 along a fissure extending from Leirhnjkur 8.5 km to the north. Initially, the fissure was

active along its entire length, but later lava production was highest at the northern end ofthe fissure.Photo by Michael Ryan, 1984 (U.S. Geological Survey).


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Tipos de vulces: estratovulco

Vulcescompostos soconstrudos por

alternncia decamadas decinzas e

derrames de

lavas formandocones.


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Plumes of steam, gas, and ash often occurred at Mount St. Helens in the early 1980s. On clear days

they could be seen from Portland, Oregon, 81 kilometers to the south. The plume rose nearly1,000 m above the volcano's rim. The view is from Harrys Ridge, 8 km north of the mountain.


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Ilha vulcnica de Tenerife


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Vulco em Ol Doinyio Lengai, fricaLavas carbonticas


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Tipos de vulces: escudo

Mauna Kea (left) and Mauna Loa (right), both over 4000 m above sea level, are the world's largest

active volcanoes, rising nearly 9 km above the sea floor around the island of Hawaii. This aerial view

from the NW shows the contrasting morphologies of these two shield volcanoes. In contrast to the

smooth profile of Mauna Loa, Mauna Kea's early shield volcano morphology is modified by the late-stage products of explosive eruptions. Photo by Lee Siebert, 1987 (Smithsonian Institution).


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Evoluo de uma caldeira vulcnica


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Ti d d


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Tipos de derrames A superfcie de um derrame AA uma massa amontoada de blocos

angulares, que se forma quando a crosta solidificada quebrada pelo lento

movimento da lava mais viscosa e espessa do que o tipo Pahoehoe.

An aa lava flow, with a characteristic hackly surface, advances across a smooth-textured pahoehoe lava

flow. The front of this June 3, 1994, aa flow at Laeapuki, near the Puna coast of Kilauea volcano, is

about 1 m high. Aa flows are produced by eruptions with high lava fountains of gas-rich magma.

Eruptions producing aa lava commonly evolve into sustained eruptions of gas-poor pahoehoe.Photo by

Paul Kimberly, 1994 (Smithsonian Institution)


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Ti d d


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Tipos de derramesDisjuno colunar:

Forma-se por contrao da lava durante oresfriamento.

Spectacular curved columnar joints

in the Bishop Tuff are exposed in

Owens River Gorge SW of LongValley caldera in California. The 5-

6-sided columns are about 1-3 m

wide and curve downward to a

common point, forming a feature

known as a joint rosette. The

rosettes are the site of large fossil

fumaroles and often are overlain by

fumarole mounds. These moundsare close to the Owens River Gorge,

suggesting that they were formed as

a result of volatiles produced when

the hot Bishop ash flows overran

and vaporized the ancestral Owens

River. Photo by R. V. Fisher, 1984

(University of California SantaBarbara).

O eixo mais longo da coluna aproximadamente perpendicular superfcie de resfriamento.

Tipos de derrames


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Tipos de derrames

Tubos de lava seformam quando as

margens dos derramesse resfriam esolidificam e o materialmole do interior

continua a fluir.

Ti d d


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Tipos de derrames Submarine extrusion of magma produces a characteristic

"pillow lava" morphology, as seen here on Loihi seamountSE of the island ofHawaii. Thin streams of molten lava

are extruded in a form that resembles toothpaste

squeezed out of a tube. The outer surface of the moltenlava is quickly chilled by the water and solidifies, while theinterior remains molten and continues to flow, lengtheningthe tubes. Lava flows with similar textures on land can be

recognized as being uplifted submarine (or sublacustral)lavas. Photo by the Hawaii Undersea Research Laboratory (Univ. Hawaii).

Pillow

lavas Ti d d


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Tipos de derrames Pillowlavas ou lavas em almofadas se formam quando a

extruso do basalto ocorre em baixo dgua e o resfriamento rpido formando uma srie de massas elipsoidais. Foto abaixoa direita mostra pillowlavas formadas no assoalho ocenicoatual na Nova Zelndia.


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Fluxo decinzas

Derrames piroclsticos


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Pyroclastic flows are hot avalanches of rock, ash, and gas that sweep down the flanks of volcanoes at

high velocities. This photo shows a relatively small pyroclastic flow at Mayon volcano in the Philippines

on September 23, 1984. These hot, ground-hugging flows can travel at velocities to about 100 km/hr

and reach areas well beyond the flanks of a volcano. Their high temperatures make them lethal to

anything in their path. Billowing ash clouds rise above the denser basal portion, which can consist ofvesiculated umice or dense lava clasts. Photo by Chris Newhall, 1984 (U.S. Geological Survey).



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The powerful lateral blast from Mount St. Helens on May 18, 1980 swept 30 km away

from the volcano, blowing down giant trees like matchsticks. The blast, traveling at

velocities up to 1100 km per hour, devastated 600 sq km over a broad area nearly 180

degrees wide north of the volcano. Photo by John Dvorak, 1980 (U.S. Geological Survey).



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Voluminous pyroclastic flows on June 15, 1991, from Mount Pinatubo in the Philippines, swept all sides of

the volcano. The flat, light-colored areas in the foreground are pyroclastic-flow deposits that filled the

Marella River valley on Pinatubo's SW flank to a depth of 200 m, more than the height of the Washington

Monument. The dark hill at the center was completely surrounded by pyroclastic flows, which traveled 14km down this valley. Photo by Rick Hoblitt, 1991 (U.S. Geological Survey).

Derrames piroclsticos: estruturas sedimentares


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p

Pyroclastic surges originating from secondary phreatic explosions at Mount St. Helens in 1980 produced

thesecross-bedded layers. They were deposited from successive, rapidly moving horizontal clouds of gas,

ash, and rock fragments that resulted from the interaction of still-hot pyroclastic-flow deposits from the

May 18 eruption with groundwater and fragments of Mount St. Helens glaciers carried down by thecollapse of the summit. Photo by Norm Banks, 1980 (U.S. Geological Survey).

Rochas


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Rochasvulcnicas

Pmice

Escria

Tufo

LAHAR: derrames vulcnicos de lama


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LAHAR: derrames vulcnicos de lama

Volcanic mudflows, also known by their Indonesian name, "lahars," are water-saturated mixtures of volcanic

debris that sweep down volcanoes and valley floors far beyond. These lahars from the 1982 eruption of Galunggung

volcano on the Indonesian island of Java caused extensive damage to houses and croplands. Unlike pyroclastic

flows, mudflows are generally low temperature, and these houses were not ignited. Mudflows can remain a hazard

long after an eruption ends as heavy rainfall redistributes tephra produced by the eruption.Photo by Robin Holcomb, 1983(U.S. Geological Survey).

Tipos de intruses magmticas


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Batlitos

Stocks

Diques

Chamins

Sillsou

soleirasxenlitos


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Laclitos:corpos emforma dedomos comfundo planoformadosquando o

magmaconseguearquear osestratos

sobrejacentes.



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Laclitos: Gois

Ti d i t ti


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Neckvulcnico ou chamin vulcnica:Chapelle Saint-Michel

Foto em Puy en Velais, Frana Central


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Dique

Sill ou soleira


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Sill ou soleira: concordante


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Sill ou soleira: concordante



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Tipos de intruses magmticasBatlito, visto do espao,

Egito


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Tipos de


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Tipos deintruses

magmticas

Batlito, visto

do espao,Perfil da

figura anterior


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Relaes entre rochas encaixantessedimentares e metamrficas com os batlitos

Magma basltico gerado por fuso parcial do mantoi d l di t


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superior em margens de placas divergentes.

O magma grantico gerado em zonas de subducopor fuso de uma placa ocenica e da crosta continental


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por fuso de uma placa ocenica e da crosta continentalinferior.


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Referncias Bibliogrficas

Best, M. G. & Christiansen, E. H. 2001.Igneous petrology. Blackwell, Malden,USA. 458 p.

Press, F.; Siever, R.; Grotzinger, J.; Jordan,T.H. 2006. Para Entender a Terra. ArtmedEditora, So Paulo, 656 p.

Winter, J. D. 2001. An introduction toigneous and metamorphic petrology.Prentice Hall, Upper Saddle River, USA.697 p.

01 rochas igneas

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