MAGMA AND SPREADING CENTERS Partial melting of upper melting peridotite forms

Magma and spreading centers partial melting of upper

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MAGMA AND SPREADING CENTERS Partial melting of upper melting (peridotite ) forms mafic magma. Rises and forms layer of GABBRO, with DIKES above and lavas of BASALT on sea floor. These layers capped by sediments laid down later-5 sequences form OPHIOLITIC SUITE Later may be scraped upon onto continents near subduction areas. Are totally anomalous here-generally expect felsic rocks/sediments on continents. MAGMA (ROCKS) NEAR SUBDUCTION ZONES. Wet, mafic ocean floor, capped by (wet) sediments under go subduction. Partial melting relatively easily-giving magma that is intermediate in composition. Magma may be gassy (water+ carbon dioxide from melting carbonate sediments). May form both intrusive and extrusive rocks-islands/mtn chains. INTRA-PLATE VOLCANISM Many mafic case thought to be caused by narrow HOT SPOT (PLUMES) of molton material rising from deep (~2900 km?) within the earth. Lecture 2-7-07 Wednesday Review for exam on Friday Things to know: Know cation and anion Esp what atoms substitute for what Types of bonding Properties of each General comments on each type of bonding Will not be asked about valence e- Know diagrams
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