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Chapter 30 to 35 - PowerPoint PPT Presentation

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Chapter 30 to 35

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  1. Applied mineralogy Chapter 30 to 35

  2. Introduction to applied mineralogy • Practical application of mineralogical knowledge • Mineralogy – major economic significance • Gemology (Ch 31), mineral prospecting, mineral extraction, chemical plants, cement industry (Ch 32), medicine & environmental mineralogy (Ch 33) • Growing field with developing needs – new branches of applied mineralogy develop • Indispensable in geology and petrology

  3. Chapter 30Metalliferous mineral deposits • Prospecting mineralogy • Economically important minerals • Geological setting of metal deposits • Convergent margins • Divergent margins • Precambrian shields • Sedimentary basins

  4. Chapter 30Prospecting mineralogy • Occurrence and identification of mineral deposits, determine mineralogical composition to classify and determine extractability • Traditionally rely on visual identification in field and sample collection for laboratory investigations • Mineralogical features primary criteria for prospecting • Currently more sophisticated analytical techniques • Mineralogy knowledge integrated with geochemistry, petrology and structural geology • Mineralogical prospecting partly replaced by remote sensing techniques • Use electromagnetic spectrum reflected from different type of minerals on earth surface • Spatial distribution of mineral types identified on large scale • Especially useful in iron and gold deposits

  5. Chapter 30Economically important minerals • Table 30.1 and 30.2 • Metalliferous minerals (Chapter 30) • Ferrous metals: Fe, Mn, Ni, Cr, Si, Mo, Co, W • Nonferrous base metals: Cu, Zn, Pb, Sn, Hg • Nonferrous light metals: Al, Mg, Ti, Be • Precious metals: Au, Pt, Ir, Ag • Gemstones (Chapter 31) • Diamond • Colour gems: Corundum, beryl, tourmaline, topaz • Cement minerals (Chapter 32) • Calcite, clay, gypsum

  6. Chapter 30Metal deposits • Many metal deposits are related to RECENT plate tectonic activity • Convergent margins • Melting of subducting sediments along continental shelf produce volcanism and batholithic intrusions • Igneous activity drives hydrothermal processes • Co and Mo, Hg • Divergent margins • Largest magma extrusions • Seawater penetrates seafloor, heat up, react with basalt and becomes acidic • Acidic water dissolves Cu, Pb, Zn, Co, Mn as trace elements from basalt, transport metals and concentrate them when precipitated as sulfides and oxides when in contact with cold seawater (VMS deposits)

  7. Chapter 30Metal deposits (cont) • Precambrian shields • Primary deposits of Cr, Ni, Pt much older • Orthogneisses and mafic to ultramaficvolcanics (greenstone belts) occur on these shields • Komatiites: ultramafic, very high T magma from great depths • Gold veins at contact with komatiites and surrounding granite – Witwatersrand (placer derived from above) • Layered chromite – Bushveld Complex: Cr, Pt, Cr-magnetitie, V • Sedimentary basins • BIFs: Algoma-type and Superior-type • Algoma: submarine hot springs release Fe-rich hydrothermal solutions in sedimentary basins alternated with Si-rich layers • Superior-type: no volcanism, associated with limestones, formed at shallow-water coastal environments, Fe and Si layers alternatively brought from deep ocean to coast by upwelling currents

  8. Chapter 30Metal deposits

  9. Chapter 31Gemstones Introduction Instruments used by gemologists Important gems Gemstone enhancements Crystal synthesis

  10. Chapter 31Introduction • Def: minerals highly valued for beauty, durability and rarity • Most precious gems exceed value of same mass of gold by 3000 times • Many gems artificially produced for a fraction of the price • Gems mostly permanent, BUT: some coloured gems could lose colour due to sunlight or heat exposure. • Small worldwide production in kg, but yearly value equals that of cement production.

  11. Chapter 31Gemology instruments • Similar to mineralogical instruments – but has to be non-destructive. • Energy dispersive X-ray fluorescence on gem surfaces • NB – binocular gemological microscope • Dark / light field illumination to check inclusions, growth features, treatment and synthesis • Gem refractometer, spectroscope, polariscope

  12. Chapter 31Important Gems • Diamonds – upper mantle, kimberlites • Emerald – hydrothermal systems • Ruby, sapphire – high T environments: alkaline magmas and aluminous metamorphic rocks • Aquamarine, topaz, tourmaline - pegmatites

  13. Chapter 31Gemstone enhancements • Improve appearance by: • Cutting • Heating to improve colour – often produce damage and often non-permanent • Filling cracks – can wear off, not as durable • Dying – not stable, do not penetrate entire crystal • Radiation to induce colour– also not always permanent

  14. Chapter 31Crystal synthesis • Large market for synthetic gems, also for industrial use • Different methods • Powder flame fusion: ruby and sapphire • Czochralski melt growth: rubies for lasers, silicon crystals, garnets • Flux growth: emeralds • Hydrothermal growth: quartz • Ultra-high pressure: diamond

  15. Chapter 32Cement minerals Significance of cement Some features of nonhydraulic cements Portland cement Some problems with concrete

  16. Chapter 32Significance of cement • Concrete is most widely used structural material in world today. • 1 billion tonnes of Portland cement converted into 11.5 billion tonnes of concrete • 5 x more than steel consumption • Much weaker than steel, but preferred • Resistance to water • Formed into many shapes and sizes • Cheapest and most readily available building material • Concrete: cement + aggregate ( sand, gravel and/or crushed rock)

  17. Chapter 32Types of cement • Non-hydraulic cements • Harden by calcination; not resistant to water • Minerals: Gypsym from anhydrite; calcite from lime • Hydraulic cements • Harden by reacting with water; water resistant • Portland cement: Ca-silicates and Ca-carbonates, with Al- and Fe-oxides

  18. Chapter 32Concrete problems • Sulfate attack • Sulfate in soil, seawater, acid rain • Cracking, permeability increase, loss of strength • Mainly when gypsum form when sulfate react with cement minerals and has a volume increase • Alkali-silica reaction • Siliceous minerals: opal, microcrystalline quartz, deformed quartz are open for this reaction with alkali ions in pore system of cement: destroys cement, increase permeability, swellling • Corrosion • Steel bars corroded when solution enters concrete; corrosion products have high volume – cause cracking around steel

  19. Chapter 33Minerals and human health • Mineral-like materials in human body • Apatite and other phosphate minerals • Mostly as important part of bones and teeth • Also occurs as abnormal growths as kidney, urinary, and gall stones; tumors; in lungs, glands, heart and arteries • Calcite, aragonite and vaterite • Constructive part of teeth • Abnormal growths in glands, tumors, kidneys and lungs • Magnetite, hematite, goethite, lepidocrocite • Urinary bladders • Also oxalates, urates and other organic compounds

  20. Chapter 33Minerals and human health • Minerals in nutrition • Halite – common mineral consciously ingested by humans • Also barite – filling in chocolate • Kaolinite – in ice creams – stabilize when melting

  21. Chapter 33Minerals and human health • Minerals in nutrition (continued) • Inorganic compounds known in market as ‘minerals’ – important as nutritional additives along with vitamins • Macrominerals: Ca, Cl, Mg, P, K, Na, S – needed in large quantities • Microminerals: Cr, Co, F, Fe, Mn, Mo, Zn – needed in trace quantities • Mostly derived from ‘real minerals’ • Deficiency as well as too high concentration of most of these can cause severe health effects

  22. Chapter 33Minerals and human health • Minerals as health hazards • Many minerals has been documented to cause pulmonary diseases: • Riebeckite – mesothelioma • Grunerite, actinolite, antophyllite, tremolite and chrysotile – asbestosis • Quartz – silicosis • Coal - emphysema (pneumoconiosis) • Chemical contamination by mining • Atmosphere, water (ground and surface)

  23. Chapter 34Minerals in the solar system • Current theory for universe: ‘Big Bang’ produce elements: • Firstly light elements: He and H • During cooling denser matter condense and collapse – nuclear fusion: up to Fe and Ni • Stellar explosions – supernovae: heavier elements • Meteorites • NB information on solar space mineralogy • Different types: chondrites, achondrites, iron and stony iron meteorites • Many unique meteorite minerals, but also minerals common to the earth

  24. Chapter 35Mineral composition of earth • Crust • Heterogenous: Sedimentary and igneous rocks; oceanic and continental crust • Feldspars, pyroxenes, quartz, olivine, amphiboles, micas > 80% of crust • Mantle • Uniform • Olivine, enstatite, Cr-diopside and augite, spinels, amphiboles, Ti-phlogopite, garnet, plagioclase, apatite, diamonds, chromite • Core • Heavy elements