Geological Exploration Methods

Vocabulary practice flashcards covering Chapter 1 of the Engineering Geology lecture on Geological Exploration Methods, including fundamental principles, exploration scales, drilling types, geophysical and geochemical methods, uncertainty management, and real-world case studies.

Geological Exploration

The comprehensive set of methods and techniques applied to investigate, detect, and characterize subsurface rock formations and natural resources, revealing rock distribution, structure, geometry, and mineralization.

Principle of Observation

A foundational rule of geological investigation requiring the direct examination and structural measurement of rock outcrops, lithologies, and geological features in the field.

Principle of Progression

The exploration guideline dictating that investigations begin with broad, inexpensive regional-scale methods before advancing systematically to finer, more expensive, and localized techniques.

Principle of Complementarity

The multi-disciplinary approach of integrating various complementary survey methods—including geology, geochemistry, geophysics, and drilling—to improve the accuracy of subsurface interpretation.

Principle of Sampling

The exploration requirement to collect representative materials (such as rocks, soils, and sediments) while strictly maintaining analytical quality and chain-of-custody traceability.

Principle of Uncertainty Reduction

The concept stating that each subsequent phase of exploration must contribute new, reliable information to progressively diminish geological and economic uncertainty about a deposit.

Regional Exploration

The preliminary reconnaissance phase conducted at a vast scale ($\text{km}$ scale) over large basins or territories using satellite imagery, regional maps, and broad geophysical and geochemical surveys to identify prospective corridors.

Semi-Detailed Exploration

An intermediate exploration stage carried out across selected sectors of interest ($\text{km}$ scale) to define specific geochemical or geophysical anomalies and detect mineral showings.

Detailed Exploration

A focused survey phase restricted to a localized anomaly or showing ($\text{m}$ scale), using detailed mapping, trenching, ground geophysics, and sampling to establish mineral geometry and continuity.

Advanced Exploration

The highly localized exploration stage ($\text{m}$ scale) characterized by intensive drilling, 3D geological modeling, geostatistical resource estimation, geotechnical testing, and feasibility studies.

Exploration Permit

A legal and regulatory mining authorization granting exclusive rights to conduct prospecting, surveying, and drilling activities over a defined area before an exploitation permit is granted.

Exploitation Permit

A formal mining concession license obtained after confirming feasibility (typically $6$ to $12\text{ years}$ into a project) that authorizes commercial ore extraction and processing.

Geochemical Exploration

An exploration method that systematically measures the concentrations and distributions of chemical elements in rocks, soils, stream sediments, or water to locate dispersion halos and mineralization anomalies.

Geophysical Exploration

An indirect subsurface investigation method that detects geological structures, water tables, lithological boundaries, or ore bodies by measuring physical property contrasts (such as magnetic field, density, resistivity, or seismic velocity).

Induced Polarization (IP)

An electrical geophysical method that measures subsurface chargeability ($\text{mV/V}$), widely used in mineral exploration to detect disseminated metallic sulfide bodies.

Bouguer Anomaly

A gravity anomaly measured in milligals ($\text{mGal}$) that corrects for elevation and surrounding rock mass, highlighting subsurface density variations caused by structural features, intrusives, or ore bodies.

Remote Sensing (Télédétection)

The acquisition and computational analysis of satellite or aerial sensor data (including multispectral band ratios and digital elevation models) to map lithologies, alteration zones, faults, and environmental changes without direct physical contact.

Rotary Drilling

A drilling method that employs a rotating bit to grind rock while circulating drilling fluids (mud or compressed air) down the drill pipe and up the annular space to flush cuttings to the surface.

Percussion Drilling

A penetration method utilizing a down-the-hole pneumatic or mechanical hammer that breaks hard rock through repeated, rapid impacts.

Rotary-Percussion Drilling

A hybrid drilling technique that merges rotational torque with high-frequency percussive hammering to achieve superior penetration in variable rock formations.

Diamond Core Drill Bit

An annular cutting tool set with industrial diamonds that cuts a cylindrical groove into the formation to recover continuous, intact core samples for laboratory and geological analysis.

Core Sample (Carotte)

A solid, continuous cylinder of rock recovered from depth during diamond core drilling, preserved in core boxes for lithological logging, structural analysis, and chemical assaying.

Porphyry Copper Deposit

A high-tonnage, disseminated hydrothermal mineral deposit associated with felsic-to-intermediate intrusions, exemplified by the Pebble deposit in Alaska ($5.942\text{ billion tonnes}$ at $0.42\text{ percent}$ Cu, $0.35\text{ g/t}$ Au, and $250\text{ ppm}$ Mo).

Geological Uncertainty

The inherent risk and lack of full knowledge regarding the 3D geometry, structural continuity, depth, and lithological variability of subsurface rock bodies and mineral zones.

Feasibility Study

A rigorous technical, financial, environmental, and regulatory assessment conducted toward the end of an exploration campaign to determine whether an orebody can be developed economically.

Adaptive Decision Making

A flexible, iterative management strategy where exploration outcomes continually update the geological model, prompting geologists to pursue a target, modify parameters, increase data density, or abandon unpromising zones.