ERTH 3207 Lecture Notes - Lecture 2: Pure Phase, Staurolite, Pseudomorph
9 Dec 2016
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Stable phase assemblage- must reduce g of the system the most. Rock in which qtz,ky, sil,and, cor may form depending on p-t. Quartz and corundum are fixed chemical composition therefore it is a pure phase. Garnet & biotite coexist well together because sharp interfaces. Staurolite (st) & biotite coexist well (sharp faces) Bt and chl does not form equilibrium assemblage because chl tries to change bt. Cluster of white mica grains: mu pseudomorphs after st. Metamorphic reactions: net transfer r. discontinuous r & continuous r, dissolution of reactant, growth of products, ion exchange r. continuous r, exchange of ions between reactants and product through chemical diffusion, no dissolution or growth. Continuous reactions (divariant; involve solution phases) most common reactions. Metamorphism of pelites what are rock forming phases in meta-pelite? staurolite corderite( fine grained) Chloritoid fluid, k-feldspar kyanite andalusite sillimanite quartz use tetrahedron. + h20 assumed present in excessive amounts in metapellites. Most minerals plot in mgo, feo and al2o3 phase.
