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Geology lecture Notes Summary

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Carleton University
Earth Sciences
ERTH 2404
Jason Mah

Nick Zrinyi 100812147 ERTH2404 – Engineering Geoscience Minerals • have an orderly internal structure – regular, and repeating • Classified according to: chemical composition, internal structure • Inorganic, homogeneous solid Polymorphs: Minerals with the same chemical composition, but different crystalline structure, i.e. Carbon – Diamond/Graphite Rock: a Solid aggregate of one or more minerals Monomineralic: composed of one mineral Polymineralic: composed of several minerals Crystals • macroscopic expression of the crystalline structure • Atoms arranged in different crystal lattic arrangements, different arrangements = different name Bonds and Forces • Covalent: sharing electrons between atoms • Ionic: two oppositely charged ions share electron(s) • Van der Walls: weak electrostatic attraction between layers Mineral Groups Group Group Formula Example 4- Silicates (SiO4) Quartz 2- Oxides O Magnetite 1- Sulfides S Pyrite Contain sulfur and one or more metals, source of metallic ore Sulfates (SO 42- Gypsum Nick Zrinyi 100812147 1- Halides (Cl, F) Halite Carbonates (CO 3 2- Calcite Hydroxides (OH) 1- Iron ore Phosphates (PO 4 3- Apatite One of very few minerals produced and used biologically Native Copper, Elements Gold Mineral Identification Lustre: the way light is reflected from mineral surface • Greasy: resemble fat or grease • Dull or Earthy: no lustre due to coarse granulations which scatter light • Adamantine: transparent or translucent and highly refractive • Metallic: Polished metal, reflective surface • Pearly: Thin, transparent, co-planar sheets • Vitreous or Glassy: transparent or translucent with low refractivity Color • Can be caused by impurities • Streak: Colour of the mineral in powder form o Non-metallic minerals streak white o Metallic minerals vary, but are diagnostic Habit • The way the crystal form of the mineral grows o Twinning: mineral grows as a cross. i.e. Staurolite o Polysynthetic Twinning: alternating 90 degree shifts in growth pattern. i.e. Plagioclase Nick Zrinyi 100812147 Hardness • Related to strength of atomic bonds, controlled by the weakest bond. • Function of the size and charge of ions in crystal structure • Moh’s Hardness Scale: Talc Gypsum Calcit Fluorit Apatit Orthoclas Quart Topa Corundu Diamon e e e e z z m d 1 2 3 4 5 6 7 8 9 10 Fingernail Penny Knife - Glass - Ceramic Cleavage • Breakage of surface along planes of weakness in the crystalline lattice o Cubic - Galena o Prismatic – Amphibole • Fracture is breakage that does not follow a plane of weakness o Quartz has no planar weakness Other • Magnetism • Density – Specific gravity • Taste – Halite • Reaction with acid – calcite Igneous Rocks Igneous: Form by cooling and solidification of magma. Crystallization: process of mineral formation in cooling magma • Extrusive/ Volcanic: Cooling at surface -> small grains Nick Zrinyi 100812147 • Intrusive/Plutonic: Cooling at depth -> large grains Magma is partially molten rock below the earth’s surface Lava is magma that reaches the surface Three main components: • Melt: Liquid portion – melted upper mantle of continental crust • Pyroclastics (Solids): ash, cinders, bombs, minerals – which crystallize from the melt • Gases (Volatiles): water vapour, carbon dioxide, sulfur dioxide Mantle • Liquidus: Temperature above which all is liquid • Solidus: Temperature below which all is solid • Mantle rises vertically due to change in depth and pressure – crosses solidus and become partially molten • Mantle melts due to: o Low pressure: Decompression melting o Volatile compounds: Dehydration melting o Hot mantle plume (both) Igneous Rock Classification Texture • Size, shape and arrangement of mineral grains • Cooling rate controls grain size o Extrusive -> small grains o Intrusive -> large grains o Or, two-phase cooling, one at depth and remainer at surface -> large and small crystals Igneous Rock SiO 2 Minerals Mnemonic Colour Temp Type Content Ultramafic <45% Olivine, Pyroxene Dark High Nick Zrinyi 100812147 Mafic 45-57% Olivine, Pyroxene, Ca- Magnesium + High Feldspar Ferric Intermediate 57-65% Na-Feldspar, Med Amphibole Felsic >65% Biotite, K-Feldspar, Feldspar + Pale Low Quartz Silica % SiO 2ontrols magma viscosity and therefore behavior and eruption style • High % SiO 2 o Viscous magma – Low temp o Large plutonic bodies, or explosive eruptions • Low % SiO 2 o Fluid magma – High temp o Large, peaceful outpourings at surface • Sedimentary Rocks Comprise 5% total rocks, but 75% of surface rocks Types of Sedimentary rock formation: • Detrital: Formed by: o Erosion: Detachment and transport o Weathering: Breakdown into fragments o Deposition: Deposits by natural processes o Lithification: Reduces voids – porosity and permeability, increases density  Compaction: By weight of overlying material  Cementation: Filling of voids by chemical precipitation (quartz (stronger) and calcite)  Crystallization: Additional growth of original crystal into voids Nick Zrinyi 100812147 • Chemical: Formed by precipitation Texture: • Clastic: Aggregates of individual fragments • Non-clastic: Pattern of interlocking crystals – chemical formation only η= Volof Voids Porosity: TotalVolof Earth Volof Voids Voids: e= Volof Particles Permeability: Qualitative term describing ability to transmit fluids • Water infiltrates porous/permeable rocks -> cracks open after freeze/thaw cycles Detrital Rocks Shale, siltstone, sandstone, breccia (angular), conglomerate (rounded – often weak) – classified according to size (clay->silt->sand->gravel) • Commonly contain: quartz, feldspar, clay • Grain size: Based on grain diameter • Roundness: Rounded vs. angular • Sorting: Grain size distribution within a rock Far from source: Smaller, rounded, better sorted Sediment maturity: Mature – well sorted, fine-grained, rounded, mostly quartz Chemical Sedimentary Rocks • Limestone and dolostone – best sedimentary aggregates, beds may dissolve • Inorganic: Crystallize from supersaturated water o SiO 2ased: Limestone, dolostone, chert, rock salt, gypsum • Biochemical: Organisms extract compounds from seawater, then die o Limestone, chert Sedimentary Structures Nick Zrinyi 100812147 • Bedding plane: surface the seperates each successive layer o
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