Exploring Plutonic Rocks: Crystal Growth and Mineral
School
Stony Brook University**We aren't endorsed by this school
Course
GEO 407
Subject
Geology
Date
Dec 10, 2024
Pages
9
Uploaded by SuperResolve14279
204003a) - The main minerals include Plagioclase Feldspar,Pyroxenes, Magnetite, and Biotite.b)–The plagioclase crystals show evidence of at least three stage crystal growth i.e. growth at different points in the melt. Evidences are growth at corners and twinning.BiotiteMagnetitePlagioclase Feldspar
208a) Thin section 208 is plutonic based off the sizes of the crystals.As we already know plutonic rocks have a characteristic of having large crystals due to a slower cooling that occurs within the magma before reaching the surface.Also the presence of certain crystals supports the rock being plutonic which includes..•- Apatite crystals are found in igneous rocks but its presence in this plutonic thin section may indicate that it was present during the first crystallization of the magma.•- Pyroxene reacting to form biotite definitely supports the the thin section rock is plutonic because these rocks tend to seep through cracks and crevices within the magma chamber.•When this happens, the decrease in temperature as well as the presence of the liquid phase decreases , leading to the formation of various minerals - We have seen in architectural tables that a crystal like pyroxene can interact with SiO2 present in the molten liquid, as well as temperature.•changes in biotite formation
b)
200520a) The most abundant feldspars found in this thin section are clinopyroxene and alkali feldspar.Its diagnostic characteristics include brown and green color, moderate to high relief, especially when surrounded by minerals such as alkali feldspar, as well as moderate birefringence in light cross polar .As for alkali feldspar, the gray color as well as the sheet/streaky texture proves it.b) C) The rock name is Ribeckite Granite.
202510Triple Junction
a)The primary mineral here is pyroxene.b) This appears to be an orthocumulate as the crystals are roughly equidistant and show equal proportion of crystalline and solid phases.c) A triple junction is formed when three crystals intersect at roughly 120 degrees, showing adjustment during crystallizationd) The bulk composition will show the overall chemical composition of the rock because different minerals crystallize at different temperatures.e) The rock maybe Gabbro or Peridotite.
221005 a)b) The way we distinguish between plag and quartz is •Quartz has undulating extinction•Quartz is uniaxial and plag is biaxial MagnetiteBiotiteQuartzK-Feldspar
200506 a)b) The rock maybe Pyroxenite.(or diorite or Gabbro)c) This was a Dry Magma mineral because no water is present in any of the mineral phases. d) The presence of Olivine within a pyroxene is odd, especially the small size of the crystals this shows that the rock may have gone through various stages of pounding (or a peritectic). Also Olivine is present within Pyroxene shows that olivine crystallized first and then was overgrown by pyroxene
OLIVINEPyroxene204001a) Main original minerals are plagioclase andolivine,.b) Hypabyssal mineralc) Rapid heating of water underground mat have caused the alterations visible.d) The name of this rock Basalt