ERS120H5 Lecture Notes - Lecture 13: Metamorphism, Calcite, Mafic
Document Summary
Growth of porphyroblasts : large minerals that don"t have a preferred orientation. Same mineral but different size or shape. Solid state = no melting is involved (bonds are breaking very slowly and are rearranging) Solid state = no mineral! (heat and pressure is applies where bonds are reaaranged) Clay has lots of different elements in them but when heat and pressure is applied different rocks are created and seen. Alignment of tabular or elongate minerals: elongate minerals and tabular minerals align horizontally when heat and pressure is applied, with only tabular minerals, we get porphyroblasts. Composition: aluminous (rich in al, quartzo-feldspathic (rich in quartz and feldspar, calcareous (rich in calcite, mafic (rich in mafic minerals) When heat and pressure is applied to mudstone, it goes through all these rock stages where in the end migmatite, a metamorphic rock is made. Index minerals tell us what grade of metamorphism the rock is at.
