ERS201H5 Lecture Notes - Lecture 8: Subduction, Xpl, Staurolite
Document Summary
Staurolite (one of those neither mafic nor felsic minerals) Staurolite under the microscope: ppl pleochroic yellow to light yellow hard to see if your microscope light is yellow rather than white! High relief, can have euhedral / subhedral shape, often with inclusions of other minerals, can show cleavage (though variable, and often fractured more than cleaved: xpl high 1storder yellow (plus greys). The mantle is solid it needs an external change in order to melt and form a liquid: add volatiles, add temperature, reduce pressure, by adding heat to the mantle, we drive the temperature of the rocks towards the solidus. How do we melt the mantle: decrease pressure. Adding volatiles shifts solidus -restricted to subduction zones: adding temperature shifts geothermal gradient, once a magma has been formed, it slowly rises upwards in the mantle and crust due to buoyancy.
