Earth Rocks! Lab Exam #2 notes.docx

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Earth Sciences
Earth Sciences 1022A/B
Stephen R Hicock

Earth Rocks! Lab Exam #2 Notes Hardness of Minerals: Metals extracted from ore minerals:  Pyrite – an ore mineral of iron  Chalcopyrite – an ore mineral of copper (wire)  Galena – an ore mineral of lead (car batteries)  Sphalerite – an ore mineral of zinc  Magnetite – an ore mineral of iron (steel) Igneous Rocks – rock that has solidified from mainly molten material (magma)  Orthoclase, plagioclase, olivine, pyroxenes, amphiboles, quartz, and mica constitute over 95% of all igneous rocks (they crystallize according to Bowen’s Reaction Series) Parent Magma Composition:  Felsic – magmas rich in SILICON and ALUMINUM, produce more quartz, orthoclase and Na-plagioclase minerals – tend to produce light coloured rocks (granite and rhyolite)  Intermediate – magma composition between felsic and mafic (diorite and andesite)  Mafic – magmas rich in IRON, MAGNESIUM, and CALCIUM produce more olivine, pyroxene, amphibole, Ca-plagioclase, and tend to produce darker rocks (gabbro and basalt)  Ultramafic – magma produces only ferromagnesian (Mg, Fe-rich) minerals like pyroxene and olivine (dunite, peridotite, pyroxenite) Textures of Igneous Rocks:  Phaneritic – interlocking crystals of about equal size that are plainly visible to the unaided eye  Aphantic – interlocking crystals are too small to see without a microscope (rocks appear structureless)  Porphyritic - >10% of the rock volume comprises large crystals (phenocrysts) surrounded by a matrix of smaller crystals (groundmass) which may be phaneritic or aphantic  Glassy – non crystalline (amorphous) structure like glass – formed from rapid cooling  Pyroclastic (fragmental) – broken, angular volcanic fragments which may be fused (welded) together Origin of Igneous Rocks:  Intrusive (plutonic) – magma crystallizes slowly, deep below ground surface (rocks tend to be phaneritic)  Extrusive (volcanic) – magma is extruded onto the ground surface where it becomes lava (rocks tend to be glassy or aphantic)  Hypabyssal – magma forms intrusions at shallow depths (rocks tend to be porphyritic) Sedimentary Rock – particles of other preexisting rock material from erosion, transportation, deposition, compaction, cementation etc.  Hold lots of fossils, oils, gas and coal  Valuable as construction material/ornamental facing stone Composition: 1. Quartz 2. Carbonate – calcite/dolomite 3. Clay (weathered feldspar) 4. Rock fragments 5. Evaporates – halite/gypsum 6. Decayed plant material (forms coal) Textures of Sedimentary Rocks:  Clastic – rock composed of the individual particles that were transported and deposited mechanically (flowing water, wind, gravity, glacial ice) o Coarse Grain (conglomerate, breccia) o Medium Grain (sandstone, arkose) o Fine Grain (siltstone) o Very fine Grain (shale, mudstone) o Well Sorted – all grains about equal in size o Poorly Sorted – wide range of grain sizes  Non Clastic Texture – pertains to chemical and organic rocks o Crystalline – minerals precipitated from sea water as a network of interlocking crystals o Fossiliferous/skeletal – CaCO 3xtracted from sea water by organisms – die and their shell fragments form clastic looking rock Sedimentary Environments:  Alluvial Fans – stream deposits near the base of a mountains – usually poorly sorted and angular (breccia, arkose)  Fluvial Environments – river deposits of well sorted, rounded sediments (ex. sandstone in channels and bars, shale on floodplains)  Eolian Environments – wind deposits which are well rounded, very well sorted and normally cross bedded (sandstone)  Glacial Environments – sediments are very poorly sorted with subangular to subrounded grains (tillite)  Deltas – complex environment where thick accumulations of siltstone, sandstone and shale may be deposited  Karst Environment – carbonates are extracted from groundwater in limestone caves to form new carbonate deposits (travertine)  Shoreline Environment – sediment deposited in beaches, bars, spits, lagoons, are clean, well sorted (siltstone, sandstone, shale)  Organic Reefs – solid structures composed of shells and secretions of marine organisms (highly fosilliferous limestone)  Shallow Marine Environment – cyclic sequences including sandstone, shale, and limestone layers representing changes in sea level  Deep Ocean Environment – turbidity currents form fining upward, graded deposits of well sorted angular grains (greywacke) also thi
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