PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Structure and chemistry of the EarthToday’s topic:The chemistry of Earth’s mantle and crustIron meteoriteChondrite meteoriteMeteorite compositiontells us about the chemistry of the earlyuniverse and Earth’score and mantle Most meteoriteoriginate from asteroidbelt, but many are beingidentified from the Moon and MarsMohoCore-mantle boundary(Gutenberg discontinuity)Inner core-outer core boundary(Lehmann discontinuity)Moho-discovery published c. 1910-12 by a Yugoslavian after a 1906? quake in EuropeCore-mantle boundary- discovered by Oldham after M8 in 1896 in Assam, IndiaInner core-outer core boundary- discovered in the 1930s by a Dane• Crust synonymous with lithosphere until the 1950s• 440 km discontinuity = change in olivine structure (spinel or ringwoodite phase) • 660 km discontinuity = transform all minerals into perovskite and minor Fe-Mg oxide (Mg-wustite) Upper mantle-lower mantle boundaryMantle plumes thought tooriginate at D” layer (otherwisecalled a ‘mantle upwelling’)New science! The inner core rotates faster than the earthMantle compositionEstimated from ultramafic xenoliths and stony meteorites, geophysical requirements for density and seismic velocities,heat production from decay of U, Th, and K, and basaltic magmasmust be able to form from partialmelting under mantle P-T conditionsSome mantle rocks have been recovered from deep ocean trenchesand by dredgingPyrolite(3 peridotites:1 basalt)Element Weight %O 45.5Si 26.8Al 8.4Fe 7.06Ca 5.3Mg 3.2Na 2.3K 0.90Ti 0.5Most abundant elements in the continental crustThe andesite model for continental crust:1 mafic:5 felsicresults in a chemical composition similar todiorite or
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