Many major orogenic gold and base metal deposits occur in complex multiply deformed structures. Such structures provide the greatest challenge to the structural specialist, let alone the average site geologist. A high level of theoretical understanding and observational skill is required to gather appropriate field data and to analyse the results. In most cases not only is the 3-D geometrical structural required, but also the relative mineralisation timing and genesis. The modules presented here cover both new tools appropriate for understanding and dealing with such structures, and at providing sufficient theoretical background to allow site geologists to engage and communicate effectively with structural specialists.
Key concepts are: fabric generations; overprinting criteria; fold superposition; outcrop interference patterns; fold facing; fabric generations and overprinting; vergence domains. Key tools are: microscopic and mesoscopic analysis; stereographic analysis and definition of structural domains; facing and vergence maps.
The following topics assume the Ductile Structures course as required background.
Advanced Analysis topics
- Introduction to multiple deformation and structural analysis: types of structural terranes and problems
- Introduction to the components of structural analysis: deformation analysis (understanding the processes), fabric analysis, and geometrical analysis
- Understanding the processes: the connection between physical flow (kinematics) and deformation processes that produce the structures and fabrics in shear zones and complexly deformed metamorphic rocks;
- Characterising and using strain (and flow) in real rocks;
- Techniques for analysing the geometry of complex structures;
- Interpreting shear zone fabrics: low strain and high strain shear zones; low-T; moderate-T and high-T shear zones;
- Working in non-plane strain shear zones: transpression and transtension
- Rheology, microscopic deformation mechanisms, and the inference of physical conditions (P, T, strain rate, fluids) from microstructures;