Earth General Science Notes A. Mineral Groups p. 42-43 1. Silicate minerals - all have the basic building block of a silica tetrahedron (SiO4) a. Isolated - held together by cation (+) 1. Olivine 2. Garnet b. Chains 1. Single -> pyroxenes 2. Double -> amphiboles (hornblende) c. Sheets 1. Biotite 2. Muscovite d. Framework - 3D arrangement 1. Quartz 2. Feldspars (Plagioclase & orthoclase)* 2. Non-silicate minerals a. Carbonates - all have the carbonate ion (CO3 -2) 1. Calcite 2. Dolomite b. Sulfates - have a sulfate ion (SO4 -2) 1. Gypsum -> sheetrock c. Sulfides - economically important minerals with a sulfide ion (S -2) 1. Galena -> lead 2. Sphalerite -> zinc 3. Pyrite -> iron d. Oxides 1. Magnetite 2. Hematite 3. Corundum A. Rock Cycle - shows rock types and the processes involved in forming these rocks a. WESL - Weathering, Erosion, Sedimentation, Lithification b. Igneous ->(WESL) -> Sedimentary ->(Heat/Pressure) -> Metamorphic ->(Melt & Crystallize) -> Igneous c. Igneous Rocks - form from magma either at the surface (volcano) or underground (pluton) i. Magma is produced by melting of existing rocks ii. Crystallization - rate influences the type of rock 1. Volcanic -> fast -> fine grain 2. Plutonic -> slower -> coarse grain d. Sedimentary rocks - particles of minerals or other rocks that become lithified i. Weathering - physical or chemical breakdown of rock ii. Erosion - moving the weathered material away from its original location 1. Water 2. Ice 3. Wind 4. Gravity
Sedimentation - sediment is deposited with change in energy *different environments have diff characteristics iv. Lithification - changes the sediment into rock by compaction or cementation e. Metamorphic rock - rocks that have had a change take place in the solid state i. Heat - most often generated by igneous activity close by. ii. Pressure - often related to depth & causes differences in the temperature B. Homework a. Granite, Diorite, Gabbro b. Rhyolite, Andesite, Basalt i. Where they form and why they're different Igneous A. Rocks a. Classification i. Texture - tells about cooling history 1. Coarse (phaneritic) cooled slowly 2. Fine (aphanitic) cooled quickly 3. Porphyritic - 2 distinct crystal sizes a. Phenocryst 4. Vesicular - generally from the release of gases (CO2, SO2, H2O, Cl2) -Holey 5. Glassy - cools extremely fast a. No crystals form ii. Composition - related to minerals that are present 1. Felsic - high in silica, low in magnesium & iron 2. Intermediate - moderate silica, iron and magnesium *minerals - feldspars (grey), hornblende (dark) 3. Mafic - High in magnesium and iron, low in silica *minerals - feldspars, pyroxene, hornblende, olivine 4. Ultramafic - Pyroxene, olivine b. Where do they occur? i. Extrusive -volcanic settings 1. Cool quickly 2. Glassy or fine grained, also porphrytic ii. Intrusive - in underground -- Plutonic settings 1. Slow cooling 2. Coarse A. Metamorphic Rocks 1. Agents of metamorphism a. Heat - generally comes from tectonic activity including volcanoes and plutons as well as mountain building 1. Temp range 250-1000 C 2. What it does -Facilitates chemical reactions -causes recrystallization & mineral growth b. Pressure - produces different textures 1. Range of kilobars (1000 bars) 2. Causes foliation if differential pressure
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3. Caused by -tectonic processes (mountain building) -depth c. Chemically active fluids 1. Hot water w/ ions dissolved in it 2. Allows exchange of cations to form new minerals 2. Where metamorphism occurs i. Contact metamorphism - around an igneous intrusion & it bakes the rock 1. Primary agent is heat 2. Relatively small portion of meta rocks ii. Regional meta. - rocks produced during mountain building due to pressure and heat (orogenesis) 1. Both heat and pressure and fluids 2. Large volumes of meta rock 3. Foliated rocks - slate, schist, gneiss, phyllite iii. Dynamic - along fault planes 1. Pressure is the primary agent 2. Produces pulverized rock (mylonite) 3. Foliation - allignment of minerals perpendicular to the of greatest pressure i. Slate foliation - clay minerals