Post on 06-Apr-2018
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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
composio mineralgica
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
composio mineralgica
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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Derrames piroclsticos
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).
Derrames piroclsticos
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Derrames piroclsticos
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).
Derrames piroclsticos
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Derrames piroclsticos
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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Tipos de intruses magmticas
Batlitos
Stocks
Diques
Chamins
Sillsou
soleirasxenlitos
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Tipos de intruses magmticas
Laclitos:corpos emforma dedomos comfundo planoformadosquando o
magmaconseguearquear osestratos
sobrejacentes.
Tipos de intruses magmticas
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Tipos de intruses magmticas
Laclitos: Gois
Ti d i t ti
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Tipos de intruses magmticas
Neckvulcnico ou chamin vulcnica:Chapelle Saint-Michel
Foto em Puy en Velais, Frana Central
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Tipos de intruses magmticas
Dique
Sill ou soleira
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Sill ou soleira: concordante
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Sill ou soleira: concordante
Tipos de intruses magmticas
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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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Tipos de intruses magmticas
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.