Petrologi 4-rfm

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    01-Jul-2015
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Transcript of Petrologi 4-rfm

  • 1. Melting Rocks Question Doesa rocks melt like an ice cube, all at the same time?

2. Melting Rocks Rocksmelt according to their melting points. Example: Which ThisIce cube with waxwould melt first ice or wax?example is known as partial melting. PartialMelting: some minerals melt at lower temperatures and other minerals remain solid Think of stew 3. Fractional Crystallization Oppositeof Partial Melting Last to melt are first to solidify (crystallize) 4. Bowens Reaction Series N.L.Bowen Canadian 1900s Statedthat as magma cools, minerals form in predictable patterns Known as Bowens Reaction Series 5. Bowens Reaction Series TwoBranches Feldspars Continuous,gradual change of mineral compositions Iron-Rich AnMineralsabrupt change of mineral type 6. Bowens Reaction Series 7. Feldspars ContinuousChange First Feldspars are rich in Calcium (Ca) Sodium (Na) increases as cooling continues Last Feldspars to form are Sodium rich (Na) 8. Iron Rich Minerals Discontinuous Change Magnesium (Mg) cools around 18000C, when olivine crystallizes, this continous up to 15570C. NowPyroxene begins to form. All olivine that was formed is now turned to pyroxene Quartz is the last to form, because silica and oxygen are the last to crystallize 9. Why do we find Olivine? 10. Amongst the common rock forming minerals Felspathoid minerals containing less % of silica are also present which are usually allied with Feldspars Nepheline (Silicate of sodium and aluminium=>Albite Leucite (Silicate of potassium and aluminium=>Orthoclase