Mapping with drones
Intro: An exciting part of being a PhD student is being surrounded by new ideas and technology that pushes forward your field of study. On an undergraduate geology field trip to Freycinet National Park, Tasmania, I was part of a team in conjunction with our new TMVC hub (i.e. ARC Industrial Transformation Research Hub, Transforming the Mining Value Chain) at the University of Tasmania, to teach the undergraduate students geological mapping. What was different about this was that we integrated high-resolution photographs taken from an aerial drone with a mapping technique used in mineral exploration and ore deposit studies. Are exercise took place on a beautiful outcrop near Bluestone Bay, Freycinet Peninsula, Tasmania, Australia.
Science Spiel: Mapping and drones
Geology is very much an observational-based science. While many branches of the science focus on observation on a microscopic scale, it is critical to first understand what the bigger picture is. The best way to record these observations is by creating a geological map of the rocks you are interested in. In fact, it was just the 200th anniversary of the first ever geological map by William Smith in 1815. The technique of geological mapping hasn’t changed a whole lot since then, but new technologies like Unmanned Aerial Vehicles (UAVs; i.e. drones) are being used to create the most detailed 3-D photos of the outcrops ever.
On a recent field trip for the 2nd year geology undergraduate students, we went to Freycinet Peninsula, on the east coast of Tasmania, to teach them about the rocks that make up the peninsula, and how to do geological mapping. One of the professors in the Geology department at the University of Tasmania, Dr. Michael Roach, has been very active with capturing 3-D spatially referenced geological outcrops. The main purpose is to have a representation of key geological outcrops for teaching to students (check out www.AusGeol.org for a virtual library of Australia’s geology). The UAV was flown over the area ahead of time so we had the high-resolution maps ready to deploy.
Bridging the Old with the New
A small area was chosen for detailed mapping, with a high-resolution photograph as a base layer. Instead of just mapping the usual rock units (lithotypes) and structures (…which are beautiful, note the fault offsetting the pink dyke in the centre of the photo…), we also mapped hydrothermal alteration and mineralization. This is very important when it comes to mineral exploration, as the hydrothermal fluids that create veins and alter rocks over a wide area are usually associated with (or are the same) hydrothermal fluids that cause mineralization and ore deposition (i.e. gold, copper). A colour-coated mapping style was used, known as “Anaconda” mapping, which basically is mapping of different alteration assemblages (Einaudi, 1997).
That is, if a hydrothermal fluid passed through or nearby a rock, the original minerals will because altered with depletion or addition of different elements. These are visible in the rocks, as when you look at primary minerals their properties (i.e. colour, hardness, appearance, etc.), differ from what they originally were.
Final Thoughts: For the interest of future students doing this exercise I shouldn’t reveal the final geological map, but there were some good-looking maps by the students and lots of enthusiasm to go around (a good chunk coming from us, the demonstrators…). The aid of a high-resolution base layer makes mapping prominent geological features fantastic, and it allows you to keep thinking about the big picture while you take your hand lens, hammer and notebook out to understand the details. Mapping alteration and veins systematically in the field allows you to start to see the more prospective areas on the map while you are still on the ground, and have a better understanding of the prospective areas associated with hydrothermal fluid flow. Overall it was a successful exercise in integrating an old technique with new technology, something that will no doubt be used going forward!
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