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Topic: Felsic


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In the News (Mon 22 Jul 19)

  
  Bloglines | Search: felsic
...conformity of the felsic and basaltic dikes, K-Ar ages and trace element considerations, a previous study concluded that the felsic rocks are...
The magmatic evolution of the Midcontinent rift: New geochronologic...
The magmatic evolution of the Midcontinent rift: New geochronologic and geochemical evidence from felsic magmatism.
www.bloglines.com /search?t=1&q=felsic   (288 words)

  
  NationMaster - Encyclopedia: Felsic
Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium.
Common felsic minerals are quartz, feldspar, and the feldspathoids, and common felsic rocks (i.e., rocks high in felsic minerals) are granite and rhyolite.
Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica and oxygen, aluminum, and potassium.
www.nationmaster.com /encyclopedia/Felsic   (1864 words)

  
 MYRMEKITE 51 OF 51
This K was then precipitated as K-feldspar (microcline) that replaced deformed plagioclase crystals, (a) in xenocrysts in the mafic tonalite, (b) in patches of coarse-grained felsic tonalite in agmatite, and (c) in the larger mass of coarse-grained felsic tonalite that enclosed the large enclaves.
In the following sections, evidence in photomicrographs for K-metasomatism is examined (1) in the felsic tonalite in the agmatite, (2) in the mafic tonalite in the large enclaves, and (3) in the large mass of coarse-grained felsic tonalite surrounding the large enclaves.
The absence of microcline and myrmekite in the coarse-grained felsic tonalite in the agmatite (Fig.
www.csun.edu /~vcgeo005/ChiefLake.htm   (5436 words)

  
 Igneous Rocks
Felsic minerals (quartz, K feldspar, etc) are light colored while mafic minerals (hornblende, pyroxenes) are normally dark colored.
Felsic minerals have the lowest melting points (600 to 750 °C) and mafic minerals have higher melting points (1000 to 1200 °C).
Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic, and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained (microscopic crystals) or glass (no crystalline structure; i.e., no minerals).
www.columbia.edu /~vjd1/igneous.htm   (558 words)

  
 Felsic Summary
Felsic minerals are usually higher in silica (SO) and aluminum and of lower density than mafic minerals.
Mafic minerals are usually higher high in iron and magnesium than felsic minerals; common mafic minerals are pyroxene, amphibole, olivine, mica, and biotite, and common mafic rocks are basalt and gabbro.
It is considered archaic as the terms acidic and basic rock were based on an incorrect idea dating from the 1800's that silicic acid was the chief form of silicon occurring in rocks.
www.bookrags.com /Felsic   (657 words)

  
 "V22A-06" in fm06
This early felsic phase of activity is cross-cut by basic and ultrabasic layered intrusions that comprise the Layered Suite (stage 2, [1]).
In contrast, the more voluminous felsic phase shows a strong involvement of crustal material with isotopic data implying 60-80% contamination of mantle-derived magmas by upper crustal Lewisian amphibolite gneiss.
The combined evidence from the early gabbro intrusions, basaltic margins and the felsic rocks lead us to a model for felsic magma generation in which basic and ultrabasic intrusions at depth, migrating towards the surface, heat and partially melt the surrounding crust, giving rise to a voluminous, but ultimately short-lived episode of felsic magmatism.
www.agu.org /cgi-bin/wais?hh=V22A-06   (410 words)

  
 7a. Igneous Rocks: Forged by Fire [Beyond Books - Earth Science: Part 2]
But rhyolite is a felsic extrusive rock, because its main mineral constituents are quartz, feldspar, and light-colored micas.
The best known of the igneous rocks is granite, an intrusive rock that forms from the same type of magma as rhyolite.
Like rhyolite, granite is a felsic rock, and is composed almost entirely of feldspar and quartz.
www.beyondbooks.com /ear82/7a.asp   (886 words)

  
 Definition of felsic - Merriam-Webster Online Dictionary
Learn more about "felsic" and related topics at Britannica.com
Find more about "felsic" instantly with Live Search
See a map of "felsic" in the Visual Thesaurus
www.merriam-webster.com /dictionary/felsic   (38 words)

  
 Vic Camp - controls on eruption style
Mafic magma will cool and crystallize to produce the volcanic rock basalt, whereas felsic magma will crystallize to produce dacite and rhyolite.
Intermediate-composition magmas will crystallize to produce the rock andesite.
Because the mafic rocks are enriched in Fe and Mg, they tend to be darker colored than the felsic rock types.
www.geology.sdsu.edu /how_volcanoes_work/Controls.html   (1263 words)

  
 Felsic: World of Earth Science
Because color is sensitive to minor chemical differences it is not a very reliable index to the history or composition of any given rock; however, it has the merit of being obvious at a glance, making color classification an indispensable aid to describing rocks in the field.
Felsic minerals are usually higher in silica (SO) and aluminum and of lower density than mafic minerals.
Mafic minerals are usually higher high in iron and magnesium than felsic minerals; common mafic minerals are pyroxene, amphibole, olivine, mica, and biotite, and common mafic rocks are basalt and gabbro.
science.enotes.com /earth-science/felsic   (262 words)

  
 Felsic - Biocrawler   (Site not responding. Last check: )
Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica, oxygen, aluminium, sodium, and potassium.
Felsic minerals are usually light in color and have specific gravities less than 3.
On the opposite side of rock spectrum are the iron and magnesium rich "mafic" rocks.
www.biocrawler.com /encyclopedia/Felsic   (179 words)

  
 felsic - Search Results - MSN Encarta
Felsic (rhyolitic) magmas are so viscous that they do not flow very far at all; instead, they form a dome above their central vent.
Silicon : rocks and minerals composed of silicon and silicates: felsic rocks
The most felsic, or silicon-rich, mineral is quartz.
encarta.msn.com /felsic.html   (106 words)

  
 Felsic
Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica and oxygen, aluminum, and potassium.
Felsic minerals are usually light in color and have specific gravities less than 3.
Common felsic minerals include quartz, biotite, muscovite mica, hornblende and the orthoclase feldspars.
www.askfactmaster.com /Felsic   (85 words)

  
 Nilanjan Chatterjee's professional and research interests   (Site not responding. Last check: )
Felsic rocks: Felsic igneous rocks in minor amounts are commonly associated with basalts in many of the major continental flood basalts of the world.
In the Deccan flood basalt province, felsic igneous rocks occur along the western coast of India at Mumbai (formerly Bombay), in the Saurashtra region of Gujarat and on the Narmada-Tapti rift at Rajpipla.
The Mumbai felsic rocks have been interpreted as partial melts of basalts underplating the lower crust, and their eruptions have been associated with the final stages of continental rifting.
web.mit.edu /nchat/www/research2a.html   (981 words)

  
 Granite [Athro, Limited: Earth Science]
Properly, a granite is a felsic rock of which between 10 and 50 percent of the felsic minerals are quartz and between 65 and 90 percent of the feldspars are rich in sodium or potasium.
Felsic magmas that are extruded and rapidly cooled form rhyolites.
Thus we can deduce that it has a felsic composition, and it cooled very rapidly in an eruption of a felsic melt that contained lots of dissolved gasses.
www.athro.com /earth_science/rocks/granite.html   (300 words)

  
 Historical Geology - Part III
Felsic rocks form from reworking and recycling of primarily continental sedimentary material.
The intrusive igneous rocks are gabbro (mafic), diorite/diabase (intermediate) and granite (felsic).
Felsic rocks contain fewer iron magnesium minerals but are high in aluminosilicate Sodium Feldspar/Albite and Potassium Feldspar/Orthoclase, as well as sheet silicates/Biotite and Muscovite Micas and pure silica tetrahedrons/Quartz.
ebeltz.net /classes/histgeo3.html   (1857 words)

  
 220Lec5
Felsic rocks are rich in the silicon, oxygen and sodium.
That is, felsic igneous rocks tend to solidify from relatively cool and water-rich lavas and magmas (around 650-1000oC) that are associated with the melting of the lower continental crust.
In comparison, felsic magmas and lavas are relatively cool and may contain partially solidified quartz and feldspars.
www.uky.edu /AS/Geology/henke/220/220Lec5.html   (1282 words)

  
 Structural Models
All of the felsic hypabyssal rocks are considered as part of a single hypabyssal dike swarm.
The composition of the microgranites falls between the felsic porphyries and the granitic rocks or composition diagrams.
Like the microgranites, these dikes are believed to be part of the felsic porphyry complex, because they are not found in the metarhyolite tuff, the metasediments or the granites.
www.angelfire.com /extreme4/lkrwork/c356.htm   (797 words)

  
 * Felsic - (GIS): Definition
felsic -- Term used to describe the amount of light-colored feldspar and silica minerals in an igneous rock.
This detailed view spans parts of the Bear and Slave geological provinces, N.W.T. A field term for a medium-grained porphyritic igneous rock of felsic but unspecified composition occurring normally as minor stock or dike intrusions, and carrying prominent phenocrysts of quartz.
Several felsic volcanic centres and widespread seafloor hydrothermal activity are known from this time interval, e.g.
en.mimi.hu /gis/felsic.html   (179 words)

  
 Mafic vs. Felsic   (Site not responding. Last check: )
Felsic, on the other hand, is used for silicate minerals, magmas, and rocks which have a lower percentage of the heavier elements, and are correspondingly enriched in the lighter elements, such as silica and oxygen, aluminum, and potassium.
Felsic minerals are usually light in color and have specific gravities less than 3.0.
The most common felsic rock is granite, which represents the purified end product of the earth's internal differentiation process.
jersey.uoregon.edu /~mstrick/AskGeoMan/geoQuerry11.html   (308 words)

  
 Tanzanian Royalty Exploration Corporation - Itetemia Property - Geology - Mon Apr 9, 2007
The fourth cycle crystal tuff is a crystal lapilli tuff and is separated from the third by a carbonatized basaltic sequence; the matrix appears to have the same composition as the second and third quartz crystal tuff.
Weakto strong sericitization affects the felsic volcanic rocks intersected in the drill holes drilled in the southwest corner of the Itetemia prospecting licence.
Five to twenty percent of felsic material (ash tuff/quartz) and less than 3% argillite are associated with and brecciated by the sulphides.
www.tanrange.com /s/Itetemia.asp?ReportID=27231&_Title=Geology   (1609 words)

  
 Reference.com/Encyclopedia/Craton
A craton (kratos; Greek for strength) is an old and stable part of the continental crust that has survived the merging and splitting of continents and supercontinents for at least 500 million years.
Cratons are generally found in the interiors of continents and are characteristically composed of ancient crystalline basement crust of lightweight felsic igneous rock such as granite.
These felsic protocontinents (cratons) probably formed at hot spots from a variety of sources: mafic magma melting more felsic rocks, partial melting of mafic rock, and from the metamorphic alteration of felsic sedimentary rocks.
www.reference.com /browse/wiki/Craton   (1224 words)

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