Structural geology

Structural geology is a branch that explores how rocks deform in reaction to stresses within the earth’s interior. Rocks and their forming minerals accommodate and record the pressures on them by generating cracks, faults, and folds, which are sometimes quite stunning geological structures.

Structural geology, tectonics, and geodynamics are a cohesive and interrelated group of sub-disciplines whose goal is to learn how minerals, rocks, rock formations, and Earth systems deform and how they do so. Geology is frequently discussed in Geosciences, a collection of disciplines dedicated to learning about the interactions between Earth processes, the environment, and human societies.

Structural geology in geosciences

Structural geology aims to characterize deformation structures, characterize particle flow routes during deformation, and infer the direction and magnitude of the forces that drive deformation. Structural geology is a field-based profession that works at scales ranging from 100 microns to 100 meters.

The goal of tectonics is to understand the geological setting in which deformation occurs. It entails combining structural geology data with data from other Geoscience disciplines such as sedimentology, petrology, geochronology, geochemistry, and geophysics in maps, cross-sections, and 3D block diagrams. Tectonics is concerned with continental rifting and basin creation, subduction, collisional processes, and mountain development ranging from 100 m to 1000 km.

Geodynamics studies the forces that cause mantle convection, plate motion, and material deformation on earth. Deep mantle processes such as, cold drips, hot plumes, and their linkages to plate motion, including dynamic plate subsidence and uplift, and plate tectonic processes, are studied in geodynamics. Geodynamics entails working at scales greater than 100 kilometers. Modern geodynamics relies heavily on numerical modeling.

Importance of structural geology

Economic geology, including petroleum geology and mining geology, premium structural geology research. The fundamental goal of structural geology is to understand the stress field that caused the observed strain and geometry by using measurements. Plate tectonics also allows us to comprehend the structural evolution of a specific area (e.g., mountain building, rifting).

The knowledge of places with folds and faults is critical in structural geology because they can generate traps in which fluids such as oil and natural gas can accumulate and concentrate.

Types of geological structures based on orientation 

Planar structure geology or lines are geological formations that can be measured.

•  Planar structure geology geometries include geological structures such as beds, faults, joints, and axial planes.

• Linear geometries are found in geological features such as fold hinges, elongated minerals, and cleavage/bedding junctions.

Planar attitude

The attitude of a plane in 3D space is calculated by measuring two nonparallel lines within the aircraft.

•  Strike and Dip: The tendency of the horizontal line in the geological plane is called strike. This trend is always noted in the north quadrant by convention.

• The dip is the highest angle of inclination of the plane, and it can be in azimuth format. Because the dip trend is always perpendicular to the strike, the dip requires the quadrant direction (NE, SE, NW, SW).

• Because the striking of a plane always has a trend 90 degrees from the dip trend, the dip trend and dip angle of an aircraft may be quickly recorded. The strike is always calculated as a line parallel to the dip trend.

Linear attitude

• A bearing (trend) and plunge measurement define linear attitudes. Because no quadrant direction is required, two numbers are sufficient to describe the attitude.

Basic branches

The study of geology can be divided into three elements, all of which are tightly intertwined:

• The lithosphere’s notions of stress, strain, and rheology.

•  Formations are described from the grain scale through the outcrop scale to the mountain and tectonic scale.

• Interpreting geological maps and detecting features such as folds and faults on them.

Stress fields

Geologists can translate observed patterns of rock deformation into a stress field by understanding the relationships between stress and strain in rocks. To derive stress fields from deformational structures, the following characteristics are used:

•  Faulting at 30° to the highest compressional stress is completely brittle rocks.

•  Fold axial planes experience the most compressive stress.

Scales of structures

Structural geologists study phenomena with at least 14 orders of magnitude. Even if we confine our research to macroscopic structures by using the outcrop-scale as a lower limit, Ramsay and Lisle’s scale divide spans magnitudes ranging from millimeters to tens of thousands of kilometers.

Geological maps interpretation

A geological map is a form of communication that depicts spatial relationships between geographical and geological features using visual symbols. Interpreting geological maps entails more than just identifying the specific elements depicted on the map. Interpreting geological maps is an attempt to perceive and comprehend the complicated shapes of subterranean rock units.

Who needs structural geology

Structural geology is at the heart of hydrocarbon and mineral exploration because structures control the migration, trapping, and escape of hydrocarbon fluids. Any regional geophysical and geochemical surveys to locate new mineralized provinces begin with structural geology. It’s also necessary for deciphering geophysical, geochemical, and geochronological data. The mining process is guided by structural geology at the mine camp scale.

•  Structural geology is at the heart of geotechnical site assessment for bridges, dams, tunnels, nuclear reactors, and waste disposals, among other things. Because faults and earthquakes are inextricably linked, structural geology is at the heart of earthquake prevention and seismology.

•  Any study of historical and present mountain belts and sedimentary basins must include structural geology. Structural geology is required for any geological, geochemical, or geophysical analysis.

Conclusion

Structural geology is one of the most significant subjects for geoscientists working in the petroleum business, since it allows them to locate traps such as folds and faults that are conducive to the accumulation of oil and natural gas.