Sometimes as a geologist you get to travel and work in some pretty extreme locations. So how did I end up in a caravan halfway up a mountain over 300 km north of the Arctic Circle in Northern Norway, in a place only accessible by helicopter? Well, the most interesting rocks can often be in the hardest places to reach!
My research is on a magma chamber formed deep down in the Earth’s crust 560 million years ago. As the magma crystallized, crystals settled and formed a series of layers that recorded the evolution within that magma chamber. Understanding these processes is central to my current research project. It just so happens that this fossil magma chamber is somewhere quite hard to reach.
The rocks that I am working on range from dunite to gabbro and these rocks also host ore deposits of nickel, copper and platinum group elements that are being explored by Nordic Mining AS. To get a better understanding of the magma chamber and its link with the ore deposits, two drill sites were chosen with the aim of drilling to 400 meters depth.
At around 70°N and over 600 meters above sea level, the winter is long and the field location is almost entirely covered by snow for most of the year. This gives us only a short two month window from August to September to work there.
In the summer, the area is also home to a large herd of reindeer. To make sure that we disturbed the reindeer as little as possible, an agreement was made with the local herder that we would not begin the drilling program until after they had been herded off the mountains for winter. This meant that we could not start the drill until October. In northern Norway, the weather becomes much harsher in October, and the days rapidly become shorter.
The drilling equipment, along with a small caravan, were air-lifted up to the mountain by helicopter, where two Swedish drillers set up the drill site. On the first night the weather turned to a chilly -10°C, the winds rose to gale force and over a meter of snow fell. This made the conditions challenging for the drillers and some equipment was buried under the snow before preparation was finished.
I arrived a week later and it was my job to monitor the progress of the drilling. It was also essential that I deliver a satellite phone to the drillers. Phone reception is extremely poor in the area as the site is surrounded by high peaks that block the signal. Smart phones also struggle in cold weather conditions. Without the satellite phone it was almost impossible for the drillers to keep in contact with the outside world.
The conditions made it tough to take a look at the drill cores that had already been collected, with many boxes frozen shut. The drilling equipment also required some maintenance so I helped the drillers make repairs.
After several weeks of hard work, the drillers managed to complete all 800 meters of the drill core. The core was then sent to the drill core storage facility at Løkken, a one hour drive south of Trondheim. Every scientific drill core taken from onshore sites in Norway is stored here. That represents approximately 700,000 meters of rock! The facility was originally a copper mine but became a drill core storage site after mining activities stopped and is now owned by the Norwegian geological survey.
The next stage of the process was to log the drill core. Drill core logging involved making detailed observations and notes on how the rock types, mineral abundances and features vary with depth in each core section. The resulting log then allows us to easily visualize changes in the rock types with depth. From the log, we chose the best locations to take samples for laboratory work and analyses. In total over 150 samples were collected.
The drill core was sampled approximately every five meters. The samples are marked so that we know their orientation. This is particularly important for geophysical analysis because measurements of the magnetic properties are done with a reference to the 3D orientation of the sample in the core. Other geophysical methods involve measuring the density of different rock types so that field data can be compared to airborne gravity measurements of the region taken by the geological survey of Norway (NGU).
The geophysical data can then be modelled using sophisticated computer programs to help build a picture of the sub-surface geometry of the magmatic intrusion. Additionally, samples from every five meters of drill core were analyzed for the chemical composition in nearly 80 elements. This data is then used to help us understand the geochemical evolution of the magmas within the intrusion. Geologists often work in very varied locations. We can find ourselves in extreme and remote locations but we can also work on collecting very precise data in high-tech laboratories.
Written by Tom Grant