EARTH221 Lecture Notes - Lecture 14: Continental Crust, Oceanic Crust, Sedimentary Rock
26 Aug 2016
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Incompatible elements: do not fit w/ fe mg silicates. Compatible cations have the same radius and charge as fe/mg. Reason for oceanic lithosphere to sink: becomes dense over time and more dense than the underlying asthenosphere. Sinks as a result: same reason for continental crust, continental lithosphere is primarily silica rich so it floats compared with the denser oceanic crust. Subduction zones: as oceanic crust subducts, a dehydration rxn occurs and the released water lowers melting temperatures. Triggers partial melting and produces magma: multistage process produced magma heats up surrounding rocks and causes more melting. Sedimentary geochemistry: shale is the most common type of sedimentary rock. Oxidation-reduction: oxidation of fe (lost electrons), reduction of o2 (gained electrons) Increased susceptibility to weathering: follows brs, olivine is the first to form, it is the most susceptible to weathering, same with continuous series. Why is k feldspar greater in the rock: losing plagioclase and biotite, only parts left is k feldspar and quartz.
