Comprehensive Study Notes on Mineral and Rock Resources, Ore Genesis, and Mining Systems

Course Announcements & Administrative Deadlines

• Week 3 Quiz: Due today at $5:00\text{ PM}$ on Brightspace.

• Homework Assignment: Due Sunday at $11:59\text{ PM}$ on Brightspace.

• Going Global Project:

  • The last written component (edited version) is due next Friday.

  • Submission format: Word document (.docx) uploaded to the Brightspace discussion board to facilitate peer review and editing.

  • Next week schedule: Dedicated to the Going Global project week. No standard homework assignment will be assigned, but a quiz will still be administered.

  • Step-by-step instructions for submission are located under the "Going Global" tab within the "project instructions" section on Brightspace.

• Reading Alignment: Content corresponds to Chapter 13 of the course textbook.

Foundations of Mineral & Rock Resources

• Resource Definition:

  • Broadly defined as all materials necessary or important for human life, civilization, or items holding individual value to people or societies.

  • Basic necessities include water, food, and shelter.

  • Resource definitions evolve over time based on social context (e.g., a stable Wi-Fi internet connection is now categorized as a necessary resource).

  • Modern high-value resources include fuels, building materials, and metals required for infrastructure and technology development.

  • Encompasses reserves as well as known and unknown mineral deposits that may possess economic value in the future.

• Reserve Definition:

  • Identified, known deposits currently legally extracted because extraction carries intrinsic economic value and profitability.

  • Represents a small subset (one quadrant) of estimated total global resources.

• Resource Classification Hierarchy:

  • Identified / Presently Economic: Reserves.

  • Identified / Sub-economic (Conditional): Known deposits that are currently not profitable or economically viable to extract.

  • Undiscovered / Hypothetical Resources: Unfound deposits that may exist near known, existing resource deposits.

  • Undiscovered / Speculative Resources: Unfound deposits hypothesized to exist in unexplored or unknown geographic regions.

Historical and Contemporary Mineral Utilization

• Historical Timeline:

  • Metal usage dates back over $17{,}000\text{ years}$, verified via archaeological artifacts, written records, historical paintings, art, and museum collections.

  • Precious metals such as gold, silver, and copper historically held intrinsic value and functioned as social status symbols.

• Common Industrial & Building Minerals:

  • Copper, lead, tin, and zinc: Standard construction materials used in plumbing pipes, electrical wiring, and electronics.

  • Gypsum: Key mineral component used in manufacturing drywall.

  • Clays: Processed for various construction and ceramic applications.

• Agricultural Mineral Exports:

  • Calcium carbonate ($\text{CaCO}_3$), sodium nitrate ($\text{NaNO}_3$), and calcium phosphate ($\text{Ca}_3(\text{PO}_4)_2$) are extracted and sold directly to the agricultural sector for fertilizers.

• Hard Abrasive Minerals:

  • Diamonds and garnets are extracted for industrial cutting/grinding abrasives and gemstones.

• United States Mineral Consumption (2021 Data):

  • Measures per capita annual consumption ($1\text{ kg} \text{ is approximately } 2.2\text{ lbs}$).

  • Per capita consumption of traditional materials like gypsum has decreased relative to the 1990s.

  • Consumption of rare earth elements (REEs) is rapidly increasing due to technological growth.

Rare Earth Elements & Global Resource Dependency

• Characteristics of Rare Earth Elements (REEs):

  • Highlighted in orange on the periodic table.

  • Not physically scarce in Earth's crust, but occur in very low concentrations and abundances within rock deposits.

  • Essential components in computer microchips, batteries, electric vehicles, hybrid vehicles, lighting, and renewable energy technology.

• US Reserve Deficit & Import Reliance:

  • No single nation is completely self-sufficient in non-fuel mineral resources; global trade is required.

  • The US possesses only a minor fraction of global REE reserves (represented as a small pink slice in global reserve charts).

  • The US produces $0\text{\%}$ of its domestic supply for several critical metals such as manganese, relying entirely ($100\text{\%}$ import reliance) on foreign imports.

  • Specialized doctoral research (e.g., Coralie's PhD research) investigates alternative REE sources such as marine ferromanganese crusts.

Economics of Ore Deposits & Grade Factors

• Ore Definition:

  • An economic term defining a naturally occurring mineral aggregate from which one or more valuable minerals can be extracted at a profit.

• Grade:

  • The minimum threshold concentration of a metal in an ore below which extraction is not economically viable.

  • Determined by:

  1. Market price of the target metal (e.g., high-value metals like gold maintain low grade thresholds because small amounts yield high returns).

  2. Mining extraction costs.

  3. Transportation and logistics costs.

• Historical Concentration Example:

  • California Gold Rush sluice boxes utilized density differences to isolate high-density gold from lower-density gravel via flowing water.

• Concentration Factor:

  • A metric quantifying metal enrichment relative to average continental crustal abundance:     $\text{Concentration Factor} = \frac{\text{Percent Metal in Ore}}{\text{Average Percent Metal in Continental Crust}}$

  • Iron has a low required concentration factor due to high crustal abundance.

  • Mercury requires an extremely high concentration factor to be viable; cinnabar (bright red, toxic mercury sulfide, $\text{HgS}$) serves as a primary high-concentration mercury ore.

• Gangue & Tailings:

  • Gangue: Non-valuable minerals intermixed within an ore rock (e.g., non-lead minerals in a galena/lead sulfide matrix).

  • Tailings: Waste residue and gangue discarded into tailings piles during processing.

Tectonic Drivers of Ore Formation

• Plate Tectonic Controls:

  • Ore deposits are unevenly distributed and tied directly to tectonic boundaries:

  • Subduction Zones / Magmatic Arcs (e.g., Western North America): Form copper, lead, gold, silver, molybdenum, zinc, and tin deposits.

  • Divergent Boundaries / Mid-Ocean Ridges: Form hydrothermal deposits of iron, copper, and zinc.

  • Abyssal Plains: Host manganese nodules and ferromanganese crusts.

  • Forearc Basins: Host lead, zinc, and copper deposits.

  • Pacific Rim Porphyry Deposits: Major copper porphyry deposits align precisely with subduction zones surrounding the Pacific Ocean.

The Five Primary Types of Mineral Deposits

• 1. Magmatic / Igneous Deposits:

  • Concentrated via partial melting and fractional crystallization in cooling magmas.

  • Partial Melting: Minerals possess distinct melting points; partial melting creates separation between liquid melt and solid crystals.

  • Crystal Settling: Dense minerals (e.g., chromite in basaltic magma) crystallize early and settle to the magma chamber floor under gravity, forming dense mineral layers extracted for chromium.

  • Pegmatites: Igneous plutonic rock (granite) featuring exceptionally large crystals (e.g., feldspar crystals up to $1.5\text{ ft}$ in diameter) formed over extended cooling periods, concentrating rare elements.

  • Kimberlites: Ultramafic rocks formed under extreme pressure at great mantle depths; transported rapidly to the surface via volcanic pipe structures; primary source of diamonds.

• 2. Hydrothermal Deposits:

  • The most common deposit type; formed by mineral precipitation from circulating hot, ion-rich groundwater heated by cooling magma bodies.

  • As fluids migrate through rock fractures away from the heat source, cooling causes dissolved ions to precipitate as mineral veins (e.g., calcite veins).

  • Seafloor Hydrothermal Vents (Black & White Smokers):

  • Located at mid-ocean ridge spreading centers where seawater infiltrates crustal faults, heats near shallow magma chambers, and rises buoyantly.

  • Black Smokers: Expel hot water rich in dissolved metal sulfides, forming dark mineral chimneys.

  • White Smokers: Expel cooler fluids rich in barium, calcium, and carbonate ions.

• 3. Sedimentary Deposits:

  • Formed via chemical precipitation of dissolved substances in aqueous environments.

  • Banded Iron Formations (BIFs):

  • Alternating layers of oxidized red iron minerals and gray chert deposited during early Earth's atmospheric transition.

  • Early oxygen-poor oceans contained dissolved, unoxidized iron; photosynthetic organisms introduced free oxygen ($\text{O}_2$), oxidizing dissolved iron into insoluble iron oxide layers.

  • Historically mined in Michigan and Minnesota for US steel production; current US operations have ceased in favor of imports.

  • Evaporites: Formed by the evaporation of saline water bodies, leaving behind precipitated salts such as halite ($\text{NaCl}$).

• 4. Low-Temperature Deposits (Placer & Chemical Weathering):

  • Placer Deposits:

  • Heavy, high-density minerals settle out of moving water in point bar regions where water flow velocity decelerates.

  • Slowing water drops heavy minerals (gold, platinum, diamonds) while carrying lighter sediment downstream.

  • Found in river point bars, behind rock ledges, in deep river holes, below waterfalls, inside meander loops, and on the seafloor.

  • Historical impact: Driven by discoveries in the Sierra Nevada Mountains and Sacramento River, triggering the California Gold Rush and westward US migration.

  • Chemical Weathering (Residual) Deposits:

  • Intense weathering dissolves and leaches away soluble minerals, leaving behind an insoluble, highly concentrated metal residue.

  • Bauxite: An aluminum-rich residual soil formed in tropical regions with intense rainfall and high temperatures; primary global source of aluminum, mined heavily in Australia, Guyana, Jamaica, and Guinea.

• 5. Metamorphic Deposits:

  • Heat and pressure recrystallize existing minerals into valuable deposit types.

  • Organic Carbon Sequence: Coal subjected to heat and pressure converts to graphite; extreme heat and pressure convert graphite to diamond.

  • Asbestos: Spindly, fibrous mineral family produced by metamorphic alteration of volcanic rocks in the presence of heat, pressure, and water; historically used for heat-resistant building materials, though usage is now curtailed due to carcinogenic health risks.

  • Local Example: Coal and graphite mining in Rhode Island began in 1808 and ceased in 1959; the area was subsequently redeveloped into the Garden City shopping complex.

Mining Methods and Environmental Consequences

• Extraction Method Selection:

  • Governed by depth, geometry, and grade of the ore body relative to the Earth's surface.

• Underground Mining:

  • Utilized for deep ore deposits via vertical shafts, horizontal tunnels, elevators, and hoist systems.

  • Hazards: Structural mine collapses, worker fatalities, and surface land subsidence (ground collapse creating uneven terrain unusable for agriculture or building).

  • Example: Collapsed coal mine in Acme, Wyoming (mining continued for over 40 years post-collapse prior to abandonment).

• Strip Mining:

  • Surface mining technique for shallow, horizontal ore beds (e.g., coal, South African manganese).

  • Soil overburden is removed to extract the ore strip, and overburden is continuously backfilled behind advancing machinery.

• Open-Pit Mining:

  • Massive, terraced circular surface excavations used for shallow-to-moderate depth high-tonnage ores (e.g., copper).

  • Pit voids are typically not refilled, resulting in permanent land surface modification, ecosystem loss, and dust emission.

  • Examples: MacIntyre Mine (Tahawus) in the Adirondack Mountains (1960s–1970s titanium mine, now flooded); Bingham Canyon Mine in Utah (largest open-pit mine in the world).

Case Study: Kennecott Bingham Canyon Copper Mine & Industrial Metallurgy

• Step-by-Step Mine Operation Process:

  1. Core Drilling & Modeling: Exploratory cores drilled hundreds of feet deep; geologists assess mineralogy; engineers build 3D computer models of ore grade versus waste rock.

  2. Blasting: Benches drilled with $55\text{ ft}$ deep holes filled with $\approx 1000\text{ lbs}$ of explosives; single blast fractures $\approx 180{,}000\text{ tons}$ of rock.

  3. Excavation: Electric/hydraulic shovels (6 stories tall) scoop up to $98\text{ tons}$ ($40\text{ pickup trucks}$ equivalent) per pass.

  4. Haulage: House-sized haul trucks ($250\text{ to } 320\text{ tons}$ capacity) move rock; daily throughput is $\approx 450{,}000\text{ tons}$ of ore/waste ($160{,}000{,}000\text{ tons/year}$). Operations are monitored by centralized computer traffic dispatch.

  5. Primary Crushing: In-pit gyratory crusher reduces rock to fragments less than $10\text{ inches}$ in size; moved $5\text{ miles}$ via conveyor belt (including a $3\text{ mile}$ tunnel) to the Coperton Concentrator.

  6. Milling & Concentration: Raw ore containing less than $1\text{\%}\text{ Cu}$ is ground and processed into liquid concentrate containing $28\text{\%}\text{ Cu}$.

  7. Tailings Management: Waste slurry (tailings) is piped $13\text{ miles}$ to an impoundment near the Great Salt Lake designed with dust suppression technology.

  8. Smelting: Concentrate is piped $17\text{ miles}$ to the smelter near the Oquirrh Mountains, dried in rotating dryers, and flash-smelted with oxygen at temperatures exceeding $2400^\circ\text{F}$.

  9. Output Products:

  • Gases: Captured and converted to sulfuric acid ($\text{H}_2\text{SO}_4$) for commercial fertilizer and industrial sales.

  • Slag: Waste material composed of silica and iron.

  • Matte: Concentrated copper-sulfide fluid containing $70\text{\%}\text{ Cu}$.

Environmental Pollution & Future Resource Outlook

• Acid Mine Drainage (AMD):

  • Caused when uncaptured sulfide minerals in mining tailings/waste rock interact with infiltrating groundwater and oxygen.

  • Produces sulfuric acid ($\text{H}_2\text{SO}_4$) runoff that contaminates groundwater aquifers, surface streams, soils, and wildlife habitats.

• Economic Significance of US Mining:

  • The US is the 2nd largest global producer of copper and gold.

  • US mineral exports equal approximately $\$26\text{ billion}$ annually, employing $\approx 3{,}000{,}000$ workers.

• Resource Lifespans & Depletion Horizons:

  • At projected exponential growth rates, domestic reserves for numerous critical non-fuel minerals will be completely exhausted by 2050.

  • Static consumption rate models extend reserve lifespans further into the 21st and 22nd centuries.

• Future Horizons:

  • Deep-sea mineral exploration targeting seafloor deposits (e.g., abyssal manganese nodules and ferromanganese crusts) driven by advanced ocean mapping technology.

Audience Interaction & Questions

• Question on Rare Earth Elements:

  • Question: Is the rarity of rare earth elements due to difficulty in creating them, or difficulty in finding them?

  • Answer: Rare earth elements are actually widely distributed in many rock types across the crust; however, they occur in such extremely small concentrations that finding deposits where extraction is economically viable and profitable is difficult.

• Question on Placer Deposits in Swamps:

  • Question: Can placer deposits form in swamp environments?

  • Answer: Placer deposits require flowing water with an active current to sort dense minerals. In a stagnant swamp lacking inflow/outflow currents from tributaries, placer formation is unlikely; however, if an active current exists within the swamp system, placer deposition can occur.