Chapter 3a - Earth Materials

Chapter 3a - Earth Materials - Grotzinger • Jordan...

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Unformatted text preview: Grotzinger • Jordan Understanding Earth Sixth Edition Chapter 3: EARTH MATERIALS Minerals and Rocks © 2011 by W. H. Freeman and Company Chapter 3: Chapter Earth Materials: Materials: Minerals and Minerals Rocks Rocks About Earth Materials About • All Earth materials are composed of All atoms bound together. atoms • Minerals are composed of atoms bonded Minerals together and are the building blocks of rocks. • Rocks are composed of minerals and Rocks they record various geologic processes. they Lecture Outline Lecture 1. What are minerals? What 2. The structure of matter 3. The formation of minerals 4. Classes of rock-forming minerals 5. Physical properties of minerals 6. What are rocks? Lecture Outline Lecture 7. The rock cycle: interactions between 7. the plate tectonic and climate systems the 8. Concentrations of valuable mineral 8. resources resources 1. What Are Minerals? 1. Minerals are the building Minerals blocks of rocks. 1. What Are Minerals? What Geologists define mineral as a Geologists naturally occurring, solid, crystalline substance, usually inorganic, with a specific chemical composition. 1. What Are Minerals? What Naturally occurring = found in nature Solid, crystalline substance = atoms are arranged in orderly patterns are Usually inorganic = not a product of living tissue living With a specific chemical formula = unique chemical composition unique Thought questions for this chapter Thought Coal, a natural organic substance that forms from Coal, decaying vegetation, is not considered to be a mineral. However, when coal is heated to high temperatures and buried under high pressures, it is transformed into the mineral graphite. Why is it, then, that coal is not considered a mineral, but graphite is? Explain your reasoning. reasoning. 2. The Structure of Matter 2. The atom is the smallest unit The of an element that retains the physical and chemical properties of that element. 2. The Structure of Matter Atomic nucleus: protons and Atomic protons neutrons. Electrons: cloud of moving Electrons cloud particles surrounding the nucleus. nucleus. Example: the carbon atom (C) The Carbon Atom electron cloud atomic nucleus The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons… The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons… electron (–) proton (+) neutron The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons… …and a nucleus of 6 protons … electron (–) proton (+) neutron The Carbon Atom electron cloud atomic nucleus Carbon has 6 electrons… …and a nucleus of 6 protons … …and 6 neutrons having no charge. electron (–) proton (+) neutron 2. The Structure of Matter Isotopes – atoms of the same Isotopes element with different numbers of neutrons. This was wrongly neutrons termed protons in previous version of slides version Example: the carbon atom (C) Example: typically has 6 neutrons and 6 protons (called C12), but there are protons ), 13 13 14 2. The Structure of Matter Chemical reactions – interactions of the atoms of two or more elements in certain fixed proportions. Example: H + H + O = H2O Example: Example: Na + Cl = NaCl 2. The Structure of Matter Chemical compounds that are minerals form by: electron sharing electron or electron transfer Electron Sharing: Electron Carbon atoms in a diamond Electron Transfer: Electron Sodium (Na) + chlorine (Cl) = Sodium NaCl (halite) NaCl Electron Transfer: Electron Sodium (Na) + chlorine (Cl) = Sodium NaCl (halite) NaCl sodium ion (circled in red) rounded by 6 chloride ions d in yellow), and vice versa. in 3. The Structure of Minerals 3. How do minerals form? Crystallization – atoms come together in the proper proportion and proper arrangement 3. The Structure of Minerals Electrical charges of atomic ions Electrical Cation – positively charged Anion – negatively charged Atomic ions arrange themselves Atomic according to charge and size. according 3. The Structure of Minerals The forces of electrical attraction between protons (+) and electrons (-) that hold minerals and other chemical compounds together covalent bonds covalent ionic bonds metallic bonds 3. The Structure of Minerals 3. 3. The Structure of Minerals When do minerals form? When • During cooling of molten rock • During evaporation of water • Upon changes in temperature Upon and pressure on existing minerals minerals 4. Classes of Rock-forming Minerals Chemical classes of minerals: Chemical • • • Silicates – contain O and Si Carbonates – contain C and O Oxides – contain O and Oxides metallic cations metallic • Sulfides – contain S and metallic Sulfides cations cations • Sulfates – contain SO4 and metallic cations cations 4. Classes of Rock-forming Minerals Chemical classes (cont.): Chemical • • • Halides – contain Cl, F, I, or Br Hydroxides – contain OH Native elements – masses of all Native the same element metallically bonded bonded 4. Classes of Rock-forming Minerals Formation of silicate minerals Silicate ion (SiO44–) Oxygen ions (O2–) Silicon ion (Si4+) Silicate ion (SiO44–) The silicate ion forms tetrahedra. Oxygen ions (O2–) Silicon ion (Si4+) Quartz structure Silicate ion (SiO44–) The silicate ion forms tetrahedra. Oxygen ions (O2–) Silicon ion (Si4+) Quartz structure Silicate ion (SiO4 ) 4– The silicate ion forms tetrahedra. Oxygen ions (O2–) Silicon ion (Si4+) Quartz is a silicate polymorph. Quartz structure Silicate ion (SiO44–) The silicate ion forms tetrahedra. Oxygen ions (O2–) Silicon ion (Si4+) Tetrahedra are the basic building blocks of all silicate minerals. About 95% of Earth’s minerals are silicates. Thought questions for this chapter Thought Draw a simple diagram to show how silicon and oxygen in Draw silicate minerals share electrons. silicate 4. Classes of Rock-forming Minerals Types of silicate minerals: Types Isolated silica tetrahedra Single-chain linkages Double-chain linkages Sheet linkages Frameworks Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Olivine (Mg, Fe)2SiO4 Silicate structure Isolated tetrahedra Specimen Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Olivine Isolated tetrahedra (Mg, Fe)2SiO4 2 planes at 90° Pyroxene Silicate structure (Mg, Fe)SiO3 Single chains Specimen Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Olivine Single chains (Mg, Fe)SiO3 2 planes at 60° and 120° Amphibole Isolated tetrahedra (Mg, Fe)2SiO4 2 planes at 90° Pyroxene Silicate structure Ca2(Mg, Fe)5Si8O22(OH)2 Double chains Specimen Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Olivine Isolated tetrahedra (Mg, Fe)2SiO4 2 planes at 90° Pyroxene Silicate structure Single chains (Mg, Fe)SiO3 2 planes at 60° and 120° 1 plane Amphibole Micas Double chains Sheets Ca2(Mg, Fe)5Si8O22(OH)2 Muscovite: KAl2(AlSi3O10)(OH)2 Biotite: K(Mg, Fe)3AlSi3O10(OH)2 Specimen Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Olivine Isolated tetrahedra (Mg, Fe)2SiO4 2 planes at 90° Pyroxene Silicate structure Single chains (Mg, Fe)SiO3 2 planes at 60° and 120° 1 plane Micas Sheets 2 planes at 90° Amphibole Double chains Three­dimensional framework Ca2(Mg, Fe)5Si8O22(OH)2 Muscovite: KAl2(AlSi3O10)(OH)2 Biotite: K(Mg, Fe)3AlSi3O10(OH)2 Feldspars Orthoclase feldspar: KAlSi3O8 Plagioclase feldspar: (Ca, Na) AlSi3O8 Specimen Thought questions for this chapter Thought Diopside, a pyroxene, has the formula (Ca, Mg)2Si2O6. What does that tell you about its crystal structure and cation substitution? cation What physical properties of sheet silicates are related to their crystal structure? 5. Physical Properties of Minerals 5. Hardness Cleavage Fracture Fracture Luster Luster Color Streak Density Crystal habit 5. Physical Properties of Minerals 5. Uses of physical properties: Mineral identification Industrial application of Industrial minerals minerals 5. Physical Properties of Minerals 5. Mica and its cleavage 5. Physical Properties of Minerals 5. Pyrite and its crystal habit 5. Physical Properties of Minerals 5. Calcite and its cleavage 5. Physical Properties of Minerals 5. 5. Physical Properties of Minerals 5. Hematite and Hematite its streak its Thought questions for this chapter Thought Aragonite, with a density of 2.9 g/cm3, has exactly the has same chemical composition as calcite, which has a density of 2.7 g/cm3. Other things being equal, which of density Other these two minerals is more likely to have formed under high pressure? high There are at least seven physical properties one can There use to identify an unknown mineral. Which ones are most useful in discriminating between minerals that look similar? Describe a strategy that would allow you to prove that an unknown clear calcite crystal is not the same mineral as a known clear crystal of quartz. same Thought questions for this chapter Thought Choose two minerals from Appendix 4 that you think Choose might make good abrasive or grinding stones for sharpening steel, and describe the physical properties that cause you to believe they would be suitable for that that purpose. 6. What Are Rocks? 6. Rocks are naturally occurring solid aggregates of minerals, or in some cases, non-mineral solid matter. cases, Identity is determined by: texture composition 6. What Are Rocks? 6. Rocks are classified into three groups: groups: Igneous Sedimentary Metamorphic 6. What Are Rocks? 6. Igneous Rocks Igneous Sedimentary Rocks Sedimentary Metamorphic Rocks Metamorphic Thought questions for this chapter Thought In some bodies of granite, we can find very large crystals, In some as much as a meter across, yet these crystals tend to have few crystal faces. What can you deduce about the conditions under which these large crystals grew? conditions Which igneous intrusion would you expect to have a wider Which contact metamorphic zone: one intruded by a very hot magma or one intruded by a cooler magma? magma Where are igneous rocks most likely to be found? How Where could you be certain that the rocks were igneous and not sedimentary or metamorphic? sedimentary 7. The Rock Cycle 7. Interactions between the plate Interactions tectonic and climate systems tectonic 7. The Rock Cycle 7. 7. The Rock Cycle 7. 7. The Rock Cycle 7. 7. The Rock Cycle 7. 7. The Rock Cycle 7. 7. The Rock Cycle 7. Igneous Rocks in North America Sedimentary Rocks in North America Metamorphic Rocks in North America Thought questions for this chapter Thought What geologic processes transform a sedimentary rock What into an igneous rock? into Describe the geologic processes by which an igneous Describe rock is transformed into a metamorphic rock and then exposed to erosion. exposed Using the rock cycle, trace the path from a magma to a Using granitic intrusion to a metamorphic gneiss to a sandstone. Be sure to include the roles of the plate tectonics climate systems and the specific processes that create rocks. systems 8. Concentrations of Valuable Mineral Resources Mineral Types of ore minerals: Vein deposits Disseminated deposits Igneous deposits Sedimentary deposits 8. Concentrations of Valuable 8. Mineral Resources Mineral Deformed country rock Geysers and hot springs Groundwater Magma Plutonic intrusion Origin of vein Origin deposits deposits Groundwater dissolves metal oxides and sulfides. Heated by the magma, it rises, precipitating metal ores in joints. Deformed country rock Geysers and hot springs Groundwater Magma Plutonic intrusion Groundwater dissolves metal oxides and sulfides. Heated by the magma, it rises, precipitating metal ores in joints. Deformed country rock Geysers and hot springs Groundwater Magma Plutonic intrusion Vein deposit 8. Concentrations of Valuable 8. Mineral Resources Mineral Typical sulfide minerals from vein deposits Typical 8. Concentrations of Valuable 8. Mineral Resources Mineral Open-pit mine for disseminated deposits of copper-bearing minerals. deposits 8. Concentrations of Valuable 8. Mineral Resources Mineral Igneous deposits Igneous Chromite layers (dark) in layered igneous rock 8. Concentrations of Valuable 8. Mineral Resources Mineral Sedimentary deposits: Sedimentary Copper, iron, other metals Gold, diamonds, other Gold, heavy minerals (placers) heavy Kaolinite (clay) Kaolinite Salts Underground halite (salt) mine Lake Magadi, Kenya + = Thought questions for this chapter Thought Back in the late 1800s, gold miners used to pan for gold Back by placing sediment from rivers in a pan and filtering water through the pan while swirling the pan’s contents. The miners wanted to be certain that they had found real gold and not pyrite (“fool’s gold”). Why did this method work? What mineral property does the process of panning for gold use? What is another possible method for distinguishing between gold and pyrite? for Key terms and concepts Anion Anion Atomic mass Atomic number Bedding Biological sediment Carbonate Cation Chemical sediments Cleavage Color Contact metamorphism Covalent bond Crystal Crystal habit Key terms and concepts Density Density Disseminated deposit Electron sharing Electron transfer Erosion Fracture Grain Hardness Hydrothermal solution Igneous rock Ion Ionic bond Isotope Lithification Key terms and concepts Luster Luster Magma Metallic bond Metamorphic rock Mineral Mineralogy Mohs scale of hardness Ore Oxides Polymorph Precipitate Regional metamorphism Rock Rock cycle Key terms and concepts Sediment Sediment Sedimentary rock Silicate Siliclastic sediments Specific gravity Streak Sulfate Sulfide Texture Trace element Vein Weathering ...
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This note was uploaded on 07/12/2011 for the course EAS 2600 taught by Professor Ingalls during the Summer '08 term at Georgia Institute of Technology.

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