Core Orientation Overview
What is core orientation?
Core orientation is the process of marking the orientation of drill core sample with regard to its original position for analysis after it has been removed from the ground. Depth and azimuth are rightly regarded as important indicators of core position. These on their own, however, are generally inadequate to determine the original aspect of faults, cleavages, joints, schistosity, mineral lineations, slickenslides and lithological contacts. The orientation of the core, that is, which side of the core was facing the bottom (or top) of hole will enable the Geologist to establish these details. (Core orientation is most effective on non-vertical holes.)
Core orientation must be recorded during the drilling process. The analysis is then undertaken during normal core logging. The core logging process requires the use of an instrument to measure the angles of the geological features such as a goniometer or a more comprehensive integrated core logging system such as the StereoCore™ .
Why is recording & interpreting core orientation important?
It allows Exploration Geologists and Geophysical Engineers to understand the geology of an area & make decisions about the future of the site based on the results of the exploration. In the mining industry, this can impact a range of issues, from overall economic feasibility, ore body volume, to mine design & layout. In the construction industry, core orientation can reveal important information about the geology that will impact on the design of foundations for buildings and other structures; for example the World Trade Centre reconstruction site in New York.
How is core orientation achieved?
Various systems have been, and are currently, available to record core orientation. These include traditional systems such as the Spear and Clay Impression, and more recent systems such as the Ezy-Mark™.
Who uses core orientation tools?
Drill rig operators generally use the tools as part of their drilling tasks.
What are key considerations for core orientation systems?
- No interruption of the drilling cycle
- Cost effective
- Regular readings
- Accurate orientations
- Effective in a broad range of ground types and core breaks
- Orientation marks relate to the run of core drilled
- Can be used in up or down hole
- Single stage process to determine orientation position
- Option of an accurate, permanent record to be referred to at a later time