States of Matter: Crystalline vs. Amorphous
Amorphous Solids
- No internal organization.
Crystalline Solids
- Possess internal organization.
- Cristalitzat (Crystallized): Internal order plus external geometry (minerals).
Crystalline Material (Crystal)
Frequency and Symmetry
- 3D Network: Repetition of the unit cell, characteristic of a crystal.
- Homogenous Symmetry: Occurs with extensive repetition.
- Anisotropy: Variation of certain properties within the crystal depending on the direction considered.
- Isotropy: Growth occurs equally in all directions (e.g., mineral formation in a fluid).
Crystallization Processes
- Fluid Origin: Evaporation of solvent, cooling magma, or vapor sublimation.
- Solid State Transfer: Minerals convert under ambient conditions (TIP) to new forms.
Magmatic Rocks
Magma
- Mixture of silicates, high temperature (700–1200°C), and a high proportion of gases.
- Source: Asthenosphere.
Rock Composition and Texture
- Composition:
- Acidic: High temperature (700–900°C), high silica (SiO2) content.
- Basic: Higher temperature (900–1200°C), lower silica content.
- Ore Types: Leucocratic (light-colored) vs. Melacratic (dark-colored).
- Texture:
- Phaneritic (PLU): Granular, homogeneous size, improved crystallization (Phase 1).
- Aphanitic (VOC): Porphyritic, heterogeneous size, poor crystallization (Phase 2).
Metamorphic Rocks
Metamorphism
- Increased pressure (factors vary) and temperature, causing solid-state reactions (a mineral transforms without melting).
- Changes: Mineralogical (new vs. old forms) and Textural (recrystallization and refocusing).
Foliation
- Textural characteristic where minerals align perpendicular to the direction of maximum stress.
Metamorphic Factors
- Pressure (?P): Confining pressure, tectonic forces, fluid pressure.
- Temperature (?T): Fault confinement, magmatic intrusions, radioactive decay.
Metamorphism Types
- Local (Contact, Cataclastic (Fault), Shock).
- Regional.
Metamorphic Indicators
- Mineral Index: Provides information on the conditions undergone.
- Paragenesis: The suite of minerals in a rock informs us about the pressure-temperature (P-T) conditions.
- Metamorphic Lines: The resulting rock depends on the grade of metamorphism and the original rock.
Sedimentary Rocks
Types
- Detrital (Physical Transport): Rudites, sandstones, lutites.
- Non-Detrital (Dissolved Ions): Carbonates, evaporites, siliceous, carbonaceous.
Carbonates (CARBO)
- Origin: Plant matter (C).
- Setting: Swamps, deltas, lagoons.
- Examples: Lignite, coal, anthracite, graphite.
Oil and Gas
- Origin: Unicellular algae (phytoplankton).
- Process: Decomposition + sapropel sediments $\rightarrow$ Diagenesis + reducing bacteria $\rightarrow$ Kerogen $\rightarrow$ Oil and natural gas.
- Conditions:
- Temperature 70–100°C (Oil).
- Above 250°C (Gas).
- Above 350°C (Degradation).
