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Some Aspects of Rocks and Isotopes

Some Aspects of Rocks and Isotopes. Christopher Chui, PhD Acknowledgment: I am indebted to numerous sources in the Internet, and the Trilinear Chart of the Nuclides published by Mallinckrodt Nuclear. http://ChristCenterGospel.org ckchui1@yahoo.com. 10/22/2014. 1. Melting Points of Rocks.

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Some Aspects of Rocks and Isotopes

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  1. Some Aspects of Rocks and Isotopes Christopher Chui, PhD Acknowledgment: I am indebted to numerous sources in the Internet, and the Trilinear Chart of the Nuclides published by Mallinckrodt Nuclear. http://ChristCenterGospel.org ckchui1@yahoo.com 10/22/2014 1

  2. Melting Points of Rocks • Igneous rocks form through the crystallization of magma. There is a considerable range of melting temperatures for different compositions of magma. All the silicates are molten at about 1200°C and all are solid when cooled to about 600°C. Often the silicates are grouped as high, medium and low-melting point solids. • . 10/22/2014 2

  3. Melting Points of Rocks • .

  4. Bowen's Reaction Series

  5. Nature of Olivine • The composition of most olivines can be represented in the system Ca2SiO4-Mg2SiO4-Fe2SiO4 . The most abundant olivines occur in the system from forsterite (Mg2SiO4) to fayalite (Fe2SiO4). Most of the naturally occurring olivines are intermediate in composition to these two end-members and have the general formula (Mg, Fe)2SiO4. Members of the series monticellite (CaMgSiO4) to kirschsteinite (CaFeSiO4) are rare. Minor elements such as aluminum, nickel, chromium, and boron can substitute in olivine.

  6. Nature of Pyroxenes • The chemical composition of minerals of the pyroxene group can be expressed by the general formula XYZ2O6, in which X= Na+, Ca2+, Mn2+, Fe2+, Mg2+, Li+; Y= Mn2+, Fe2+, Mg2+, Fe3+, Al3+, Cr3+, Ti4+; and Z= Si4+, Al3+. The range of possible chemical substitutions in pyroxene is constrained by the sizes of the available sites in the structure and the charge of the substituting cations. The Xcation sites in general are larger than the Ycation sites. Extensive atomic substitution occurs between the ideal end-member compositions. Most pyroxenes have only limited substitution of aluminum for silicon in the Z(tetrahedral) site. When a substituting ion differs in charge, electrical neutrality is maintained by coupled substitutions.

  7. Chemical Divisions of Pyroxenes

  8. Chemical Formula: (Na,Ca)(Si,Al)4O8 Composition: Molecular Weight = 270.77 gm Sodium      4.25 %  Na     5.72 % Na2O Calcium     7.40 %  Ca    10.36 % CaO Aluminum   9.96 %  Al    18.83 % Al2O3 Silicon    31.12 %  Si    66.57 % SiO2 Oxygen     47.27 %  O           ______         ______             100.00 %       101.48 % = TOTAL OXIDE Empirical Formula: Na0.5Ca0.5Si3AlO8 Environment: Igneous and metamorphic rocks. Group name for Na, Ca feldspars. General Plagioclase Information

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