2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 25
Presentation Time: 1:30 PM-5:30 PM


WHALEY, Peter W., Department of Geosciences, Murray State Univ, Wilson Hall, Murray, KY 42071-3047, peter.whaley@murraystate.edu

Memory experts recognize diagrams as superior to lists in committing information to memory. Bowen's Reaction diagram contains minerals arranged to form a Y. The Y shaped diagram can be used as a memory device for geologic information. Using a Y diagram: 1.Temperature - pressure under which the igneous rock silicate minerals form decreases as one goes down the Y. 2. Left branch minerals contain Fe and Mg, the remainder do not. 3. The specific tetrahedral structures from single, single and double chain, sheet and three dimensional silicates can be noted. 4.The four igneous rock families relate to the Y. Orthoclase & Quartz, are the two key minerals in Granite. The upper two minerals on the Y's left branch are key minerals in Peridotite. At the junction of the Y's arms, Biotite, Hornblende, Na Plagioclase & Orthoclase are Diorite's key minerals. Across the arms of the Y, Ca Plagioclase, Hornblende & Biotite are Gabbro's key minerals. 5. Stability of minerals to chemical weathering increases as one goes down the Y. 6. Why these minerals produce the chemical weathering products they do can be deduced if the chemistry of the Y minerals is shown. All minerals on the Y weather to form amorphous silica. All minerals on the Y except Quartz and Olivine weather to form clay minerals. All Fe/Mg silicates weather to form oxides and hydroxides of Fe and Mg. None of the nonFe/Mg minerals form oxides or hydroxides of Fe or Mg. All minerals on the Y except Quartz weather to form a soluble carbonate. 7. Quartz, Orthoclase, Clays and Calcite, a soluble carbonate, are major minerals in Sedimentary Rocks. 8. Metamorphic Rocks are formed by all minerals on the Y below Hornblende plus Clays & Calcite. 9. For physical properties, all Y minerals have a bright but nonmetallic luster and none have a definite streak. All Y minerals are harder than glass except Muscovite and Biotite which are softer than glass but harder than a fingernail. Quartz & Olivine break with a conchoidal fracture, the remaining Y minerals all exhibit cleavage. Biotite & Muscovite cleave in one direction, the remainder cleave in two directions. Hornblende's two cleavage directions do not meet at 90 degrees, the remaining Y minerals do. Only the Plagioclase Feldspars exhibit twining striations.