Mineralisation is anomalous, and anomalous structures are common around mineralisation. Our aim is to provide structural competence for the field or underground geologist plus sufficient theoretical background to be able to understand and deal effectively with unexpected structures that don't follow 'textbook' rules. The key concepts are time (generations of structures) and strain (bulk distortion pattern). Although one mode of deformation such as folding, cleavage or thrust faulting might dominate to produce the distortion (strain) in a deformation event, all other deformation modes can locally link up to accommodate irregularities at all scales.
Basic structure modules
- Why structure is important in mining and exploration. Types of structural 'control'. Dilatancy, accommodation, relay structures and strain incompatibility - the importance of interpreting 'unexpected' structures
- Deformation modes: contraction, extension, and shear in brittle, semibrittle, and ductile terranes
- Basic fold and fault geometry (NB, the terrane specific modules are more detailed)
- Strain - the best framework for understanding linked structures and interpreting unexpected structures
- Linked structures: folds; extensional, contractional and strike slip faults; transfer, tear, and detachment faults
- Accommodation structures: accommodation faults; gash veins; local cleavage; boudinage
- Dilatancy and deformation: rheology vs strain rate; fluid transfer during deformation; strain fringes to ore bodies
- Field mapping. The importance of mapping contacts and form lines versus transect or point data collection.
- Scale considerations. Keeping an eye on the big picture.
- Basic map preparation. Interpretation maps vs fact maps - the importance of continuous interpretation.
- Form line mapping and monotonous lithologies
- Making topography work for you. Three-point plane solutions; structure contours. Sparse dip problems and pseudo structure contours
- Cross-section techniques: freeform; buskian/tangent arc; kink; axial plane projection; fold axis projection. (Note that the terrane-specific modules include more deatils on the cross-section techniques appropriate to specific situations)
- Stereographic projection fundamentals and interpretation
- Oriented core procedures. Manual (stereographic) and computer solutions to oriented core data
- Obtaining orientations from unoriented core using local cleavages ('partially oriented' core procedures)
- Database and GIS fundamentals. Spreadsheets used as database
