I sopleth Temp 1* Mdt 80% An 20% Di 60% An 40% Di 51.5% An 48.5%Di Hint You will
ID: 287499 • Letter: I
Question
I sopleth Temp 1* Mdt 80% An 20% Di 60% An 40% Di 51.5% An 48.5%Di Hint You will need to apply the lever rule Thiswill require setting up the lever (i.e, What are the two ends? Where is the fulcrum? What line lengths do I measure? Etc) in an appropriate manner to answer this question E) Sourceregions for melts are typically heterogeneous and comprised of rocks for which the modal abundanoe of minerals can vary. Based on your results from part C what have you learmed regarding as to which bulk compositions in a source region are the most fertile (gener ate the most melt) with respect to melt production? F) "Migmatites" are "mixed" rocks which are transitional between igneous and metamorphic rocks. These rocks are interpreted to consist of domains called "eucosomes" and "melansomes". Leucosomes contain felsic minerals which crystalized from in-situ melt and melansomes consist of mafic minerals that did not melt. Migmatites may form from incomplete extraction of melt from the souroe region (some melt is left behind) or not enough melt was generated to achieve the critical melt fraction needed for the melt to collect and migrate upward. Which samples could form migmatites and why? What would you predict the mineralogy of the leucosome to consist of and why? What would you predict the mineralogy of the melanosome to consist of and why?Explanation / Answer
F. Migmatites are formed in high grade metamorphic terraines where prograde metamorphism is dominant. Extreme conditions envelop migmatisation. They are basically partially melt mixture of igneous and metamorphic rocks. The parent material is often metamorphic gneiss which undergoes partial melting or anatexis. The partial melt that is formed suffers crystallization to igneous rocks. Thus, there is coexistence of igneous and metamorphic rocks.
This is because granite and gneiss conforms to high grade prograde metamorphism.
Leucosomes are the lighter coloured parts of migmatites composed of quartz and feldspar. Mafic minerals form the portion between the leucosomes. The parent materials are pelitic and pssamatic rocks.
Melanosomes are the darker portion of the migmatites made of dark coloured materials like hornblende olivine and biotite. They form eutaxitic texture.