Mineral Resources: Formation, Use, and Exploitation

Posted on Dec 5, 2024 in Geology

Magmatic Mineral Resources

Magmatic processes, both internal (plutonic) and external (volcanic), form magmatic rocks through crystallization. Fractional crystallization and magma consolidation involve:

  1. Initial crystallization of iron and magnesium-rich minerals, resulting in dark-colored rocks.
  2. Depletion of silica, calcium, aluminum, and sodium in the magma.
  3. Crystallization of the remaining water-rich magma, forming hydrothermal water that carries dissolved metals, filling rock cracks and crystallizing.

Types of Magmatic Mineral Deposits:

  • Mafic rocks (basaltic, rich in iron and magnesium): Deposits of platinum, copper, nickel, chrome, and tin.
  • Felsic rocks (rich in quartz and feldspar): Lithium pegmatite, iron, tin, and granite deposits.
  • Volcanic rocks: Gold and silver deposits formed by hydrothermal processes.

Metamorphic Mineral Deposits

Metamorphic mineral deposits form due to changes in temperature, pressure, or the action of water at high temperatures. Regional metamorphism involving trapped water can lead to dissolution, transport, and precipitation of minerals like gold, silver, and mercury.

Mineral Resources from Exogenous Processes

Weathering-Related Resources

Chemical Weathering: Residual deposits form when chemical weathering transforms original rock minerals, creating an altered surface layer. Rainwater dissolves minerals, concentrating metal oxides and compounds like nickel, iron, and bauxite in lower layers.

Physical/Mechanical Weathering: Fragmentation of rocks creates concentration fields. Arenization, followed by rain washing, concentrates heavier minerals like gold, zircon, and diamonds.

Transport and Sedimentation Resources

  1. Granoselection: Transport processes separate materials based on size, density, and resistance, forming banded deposits, placer nodules, gold, and diamonds.
  2. Chemical Sedimentation: In shallow waters, specific physicochemical conditions lead to the formation of layers or nodules rich in substances like banded iron and manganese nodules.

Diagenesis Resources

Diagenesis in sedimentary basins enriches sediments with minerals. This includes coal and oil. PET or ECT (tonne of oil or coal equivalent) refers to the heat energy released by burning one tonne of coal or oil.

Principal Uses of Mineral Resources

  • Ornamental: Stone quarries produce polished marble (calcite and dolomite rocks) and slate (metamorphic rock with foliation) for global trade. Granite, an igneous rock, is also used.
  • Industrial: Cement, aggregates, concrete, plaster, and ceramics.

Exploitation of Mineral Resources

Depletion of easily accessible deposits coincides with increasing demand. Deposit Search:

  1. General Data: Identify the sought-after minerals.
  2. Particular Phase: Specify the prospecting area by studying geological structures indicating mineral presence.
  3. Concretion Phase: Delimit the reservoir through drilling and geophysical surveys, evaluating mineral content.

    Mining Methods

    • Open-Pit Mines: Large excavations to reach the reservoir, with steps for mineral evacuation. Challenges include water evacuation and slope stability.
    • Underground Mines: Wells and galleries for mineral extraction, requiring ventilation, reinforcement, and utilities.

    The feasibility of mining depends on ore value, operating costs, and environmental impact.

    Environmental Impact of Mining

    • Increased erosion and landscape impact.
    • Waste generation (tailings).
    • Noise and vibration pollution.
    • Environmental pollution.
    • Social impacts (socio-economic changes, potential poverty after closure).

    Prevention and Correction of Impacts

    Prevention:

    1. Actions to prevent erosion (surface condition, vegetation preservation).
    2. Landscape protection (tree screens, vegetation regeneration, prohibiting mining in high-interest areas).
    3. Protection of natural resources and pollution prevention (impermeabilized channels, methods for eliminating toxic elements in drainage water).

    Correction:

    Spanish law mandates mine restoration projects, including:

    1. Land use definition after exploitation.
    2. Waste management plan.
    3. Drainage system design and anti-erosion measures.
    4. Interventions to restore vegetation.

    Complete restoration is often impossible. Recovery aims for a similar composition and density of organisms as the original. Rehabilitation focuses on making the area productive according to a plan, considering aesthetic values.

    Notable Mineral Deposits in Spain:

    • Huelva (Rio Tinto): Iron, pyrite, copper, salt.
    • Cordoba: Feldspar, barite, fluorite.
    • Linares: Lead.
    • Almeria (Macael): Marble.
    • Granada (Alquife): Strontium and iron.
    • S. Brown: Iron, feldspar, barite, lead, salt.