Orefind is commonly queried as to reference sources, software and equipment that we use, or that are available, for undertaking geological analysis at all scales. The items listed below are by no means exhaustive but they will serve as a starting point to cover most situations.
Structural analysis of diamond drill core
We use a combination of equipment and software to interrogate diamond drill core:
We use Leapfrog® Mining
(v.18.104.22.168) to quickly model structural data collected by the client in 3D (We are a little biased as Jun Cowan conceived and helped to design Leapfrog!). We do not use Leapfrog Geo, but we’ll comment on this in another blog post. We can very commonly identify issues before even getting to site viewing the drill core and this form of analysis allows us to target problem areas and to check for issues in the core orientation process.
We use GEOrient©
stereo and rose diagram plotting software to statistically check our data and visualise geometric relationships. This software has been written by Rod Holcombe, a structural geological consultant to the mining and exploration industry, and is very easy to use. In conjunction with this, we use GeoCalculator©
, another program written by Rod. In combination, these two, very affordable programs will cover most tasks. Details can be found on Rod’s website
. Spheristat version 3.1
is also used as it has what we consider to be the best stereoplot contouring routines. This software is older and less modern than Rod’s software products, so more difficult to use in comparison, but the technical capabilities is nevertheless very good. Written by Bob Stetsky , formerly of University of Toronto.
We also us a proprietary software to analyse structural data and deposit geometries in spatial coordinates.
The above programs are used by Orefind in conjunction with the standard Microsoft Office program suite, Mapinfo®+Discover, CorelDRAW®, Snagit v.10, Adobe® CS5.5 Illustrator and Photoshop. Autopano Pro
is used to create photo panoramas.
Hardware for orienting core at the rig
As noted in previous blogs, there are several widely used methods, all of which can give good results. The choice depends on cost, driller experience, ground conditions etc. Keep in mind that bad drillers and inexperienced geologists can achieve core that is unusable for orientation data regardless of method.
Currently, the down-hole spear is still widely used. The mechanical Ezy-MarkTM tool can give great data as can the electronic ReflexTM tool. However, the experience and capability of the drillers and geologists are much more important considerations than the method of orientation.
Hardware for interrogating core
Orefind advocates the use of equipment to measure alpha and beta data in tandem with a core orienting frame. The simplest and best equipment for taking alpha and beta angles is the Kenometer. These readings should be converted to true dip and dip direction (using software such as Geocalculator©) and then compared with that obtained by physically measuring structures in diamond core in a core orienting frame with a compass.
The style of core orienting frame can vary widely, as can the prices for commercially produced ones. Some, such as the one manufactured by James Cook University and the one designed by Roger Marjoribanks, are very portable and therefore useful if working across more than one project. If manufacturing your own, make sure that no steel is used in the construction.
Measurement of structures in a core frame is best done with a compass that can measure strike and dip in the one action. The Clar, Frieberg, and Brunton compasses will all do this and none of these are cheap. However, the Brunton is the cheapest and I find it is the best because it has an internal clinometer, several bubbles for levelling, and a plastic extension that is great for lining up lineations.
Orefind uses much of the same software and mapping equipment for mapping as we do for structural analysis of core, in addition to a GPS handset. One thing that we commonly do is to take oriented samples (refer to one of our previous blogs for the methodology). In this case, the humble bucket of non-magnetic sand is also important for reorienting samples.
As mentioned at the start of this post, the list below is by no means exhaustive and there are many good references available in addition to these general ones.
A recent text, Structural Geology, by Haakon Fossen is very good and the figures are excellent.
Fossen, H., 2010. Structural geology. Cambridge University Press. ISBN: 978-0-521-51664-8.
Twiss and Moores published a good text, Structural Geology, in 1992. It has a very good companion volume, Tectonics, by the same authors that was published in 1995.
Twiss, R.J. and Moores, E.M., 1992. Structural geology. W.H. Freeman and Company. ISBN: 0-7167-2252-6.
Moores, E.M. and Twiss, R.J., 1995. Tectonics. W.H. Freeman and Company. ISBN: 0-7167-2437-5.
In addition to these modern texts, we still use older texts and couple of oldies but goodies we refer to are Folding and Fracturing of Rocks, by John Ramsay, and An Outline of Structural Geology by Hobbs, Means and Williams.
Ramsay, J.G., 1967. Folding and Fracturing of Rocks. The Blackburn Press. ISBN-10: 1-930665-89-X.
Hobbs, B.E., Means, W.D., and Williams, P.F., 1976, An Outline of Structural Geology. John Wiley & Sons. ISBN: 0-471-40156-0.
Passchier and Trouw published a book, Microtectonics, in 1996 that is very good in terms of describing deformation processes and textures. Despite the title, it is applicable to many of the textures seen in hand-specimen.
Passchier, C.W. and Trouw, R.A.J., 1996. Springer-Verlag. ISBN: 3-540-58713-6
Texts on the structural controls of mineralisation are scarce. A thin volume was published by the Society of Economic Geologists in 2001 and comprised six papers by experts in the fields of fluid flow, deformation, and various styles of mineralisation.
Richards, J.P. and Tosdal, R.M., eds, 2001. Structural controls on ore genesis. Society of Economic Geologists, Inc. ISBN: 1-887483-58-6.
As with any books, the reference lists in these books can be almost as important as the text. The Society of Economic Geologists has many good publications on mineralisation in general, and in recent times has made available most of the papers published in Economic Geology for purchase in digital format. Membership to societies such as Society of Economic Geologists can be extremely useful.