Polar Podcasts

23: Bjørn Thomassen: Vertical fieldwork – exploring the niobium-tantalum-enriched Motzfeldt Intrusion

December 01, 2020 Julie Hollis Season 1 Episode 23
23: Bjørn Thomassen: Vertical fieldwork – exploring the niobium-tantalum-enriched Motzfeldt Intrusion
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Polar Podcasts
23: Bjørn Thomassen: Vertical fieldwork – exploring the niobium-tantalum-enriched Motzfeldt Intrusion
Dec 01, 2020 Season 1 Episode 23
Julie Hollis

In this episode we hear more from Bjørn Thomassen, emeritus senior scientist, about his first job working for the Geological Survey of Denmark and Greenland, running a field program to study the niobium- and tantalum-enriched Motzfeldt Intrusion in South Greenland.

Show Notes Transcript

In this episode we hear more from Bjørn Thomassen, emeritus senior scientist, about his first job working for the Geological Survey of Denmark and Greenland, running a field program to study the niobium- and tantalum-enriched Motzfeldt Intrusion in South Greenland.


23: Bjørn Thomassen: Vertical fieldwork – exploring the niobium-tantalum-enriched Motzfeldt Intrusion

Based on interviews held on September 30 – October 2, 2019 in Copenhagen, Denmark            

Note: Polar Podcasts are designed to be heard. If you are able, please listen to the audio, which includes emotion and emphasis that is not evident in the transcript.


Bjørn 0:01

The problem is that the mineralization was situated in vertical mountainsides. So they had hired six Swiss mountaineers and the idea was that they should operate in teams of two, rappelling their way down and on the way collecting samples.

Julie 0:20

Welcome to Polar Podcasts, where you’ll hear stories from geologists who’ve spent their careers, their lives, exploring and studying the remarkable and remote geology of Greenland. Why did they become fascinated with Greenland? What were the problems and the discoveries that drove them? And what was it like working in these remote places, where few people venture, even now? I’m Julie Hollis.

In this episode we hear more from Bjørn Thomassen, Emeritus senior scientist, about his first job working for the Geological Survey of Denmark and Greenland, running a field program to study the niobium- and tantalum-enriched Motzfeldt Intrusion in South Greenland.

Bjørn 1:05

In er 1988, I was working at the Black Angel as a mine geologist and then the director of the Geological Survey of Greenland, Martin Ghisler,phoned me and offered me a job on short notice in South Greenland. And I accepted. So, and that was sometime in May. So er, one and a half months later, I was standing on this er, glacier in the Motzfeldt Intrusion some twenty-five kilometres er, north of Narsarsuaq airfield.

And the story is this that for some time, I think five years, a uranium exploration program supported by the Danish er, State and the European Commission, whatever they were called at that time, they supported er, uranium exploration. So the previous summers er, the teams had focused in on one of the Gardar intrusions in south Greenland called the Motzfeldt Intrusion. And er, they had er, found a large diffuse er, occurrence of minerals containing rare earth er, and uranium and thorium er, hosted in a mineral called er, pyrochlore.

So er, the survey, Geological Survey of Greenland had got a grant of four and a half million, a lot of money in those days, to investigate. And the problem is that the outcropping pyrochlore mineralization was situated in er, vertical mountainsides. So what they had done until then was a geologist had er, gone at the foot of the cliffs, collecting loose blocks, boulders, coming up from higher up and er, identified the pyrochlore. And they also walked on the top of the cliffs. But er, no normal geologists had been able to assess the proper mineralization. So they had hired six Swiss mountaineers and the idea was that they should er, operate in teams of two rappelling down from the top of the cliffs, rappelling their way down and on the way collecting samples from the mineralized zone, which was more or less in the middle of the cliffs.

So we set out and, at the same time we were going to fly a radiometric survey with helicopter in this alpine region, so in combination that would, should, the detailed sampling and mapping and radiometric survey, should give a much better understanding of the size and especially the grades of the mineralization. And to access the grade, you had to have samples, many samples. So we ended up with, with er, one thousand samples. And that’s a lot. And quite relatively large samples, at least one kilo, one to two kilos, a sample bag full was my instruction to the mountaineers.

So we operated in that way that we flew out, the seven of us, six mountaineers and me. And they were all German speaking. And it was my luck that I could speak German. And I learned my German the previous years in central East Greenland, where I worked as the only Dane among Austrian er, mining engineers. So I had to adapt in those days. So, for me, the German language is associated with fieldwork in Greenland. And I know a lot of, you know, special Austrian dialect expressions for various things like tent poles and things like that. And there’s still a language problem with, with the Swiss because er, the mountaineers, they were hand-picked. So they didn’t know each other beforehand. And that’s not the best thing when you are putting up a team for fieldwork. It’s much better that people know each other beforehand because, you know, all sort of small frictions you can, there should be taken away before you go into the field. But er, it worked out ok. But they spoke dialects. Every valley apparently in Switzerland has a dialect. And so when they spoke to me they, I said please, Hochdeutsch, that’s the official German. But between themselves they were joking and shouting in their, their funny dialects. They even couldn’t understand each other (what people) from the various valleys.

So we operated in that way that we put up camp. I remember the first cliff, there were two glaciers and my friend Tapsa, who’s worked there before, he’d er christened them Horror and Terror because those glaciers, they were so steep and when the sun was shining in, they were melting and by melting they released er, rock samples and they were coming fast down. So you shouldn’t be in the middle of the day in front of those glaciers. They were pretty dangerous. So we put our camp in between and the camp consisted of caravans and, two caravans and then this old metal container called Solvognen

Julie 6:08

The sun wagon.

Bjørn 6:09

which had been used by other scientists er, nearby. And Solvognen, it was so heavy, it had to be lifted er, inside by a Sikorsky 61, and they had to go in three tries to get it lifted. In the end they threw everything out of the helicopter, seats and and all those things to reduce their weight and then there had to be a slight wind to get a lift. And so they managed to put that container in, Solvognen, but then it was very stable standing there. And then we have the two er, two er, er campers. So a good camp. And then the daily routine was that er, in the morning the helicopter came up from Narsarsuaq and landed and took the teams on board, two each time, and put them on top of the cliff. And er, yeah and then they worked their way down.

I had, my job, I had um a binocular magnifying seventeen times. So I, in the morning, I walked out in the middle of the glacier, and was looking in at that cliff, was it thousand metre or five hundred metre? – it was at least five hundred metres (high), (between five). There were different, of course, four different cliffs, five different cliffs. But the first one, between Terror and Horror, was pretty high. So I was standing there and they were rappelling down and then I had this er, walkie talkie and I could direct them because beforehand I had er, photos taken the previous year of, of that steep slope, magnified. And there I had drawn in lines, parallel lines, and designed a sampling program and er, there was line A, B, C, D, and so on er, with a distance of 50 metres. So one team of two going down in each line. And they were under instructions to er, collect samples at some places with er, vertical distance of 25 metres, other at 50 metres. And at each sample site, they were supposed to spray paint a cross, 2m by 2m, and then fill up the sample bag, 1-2 kilos er, of chip samples. And they should take them from each quarter of the sample sites hanging in the ropes, standing on a small shelf. So, chip, chip, chip, chip, and in the bag and you can imagine the bag got heavier and heavier going down. At one locality, locality number 3, they started from the foot and worked their way up. But er, they were quite tough people. Also they had, from the start, a lot of equipment, mainly rope, and also those crampons to er, secure the line, hammer into the wall and secure the lines. And they also carried a scintillometer,

Julie 8:53

A scintillometer is a hand-held instrument used to measure gamma radiation, in this case radiation emitted from the mineralised rocks.

Bjørn 9:02

also weighed a couple of kilos. So they had spray paint er, scintillometer, sample bags, chip sample hammer, and their mountaineering gear. So they had good heavy rucksacks. But they were strong and and very fit. So I was standing there er, with my binoculars, directing them, so I said, “Ja, gruppe nummer drei, bitten links. Ja, ja, gut,gut,  nein, bitte rechts,” and so on. And then they spray painted their cross. And I had my, my enlarged photo and, and from that we later on produced a beautiful er, digital map. And when we got the er, analytical results, we could do er, data handling and plot in the analytical results and do contours, everything on computers. And that was the state of the art in those days. So we got very beautiful maps but the way we did the sampling was very primitive and old fashioned with me standing there and, and sketching in the sample points.

So that worked out er, ok. And I’m very impressed by those er, Swiss guys. And that said, I know nothing about mountaineering. I like to walk and, and er, scramble in the mountains, but I never do climbing, real climbing. But those guys, they told me they hated er, the thing because as a mountaineer, you’ll always look for fresh rocks, where you can put in your crampons, secure your lines, and avoid rotten rock. But what we have here, because um, it’s a syenitic intrusion and syenite, that’s a quartz-poor granite, in principle, and it has been heavily hydrothermally altered. That means er, the minerals, they’ve been er, broken down by, by hot solutions, which at the same time have precipitated ore minerals, something like that. We call it hydrothermal alteration and that’s not stable rock. That’s rotten rock, as I called it. So they didn’t like that.

And they also told me that the biggest danger by this rappelling was actually when there are two, one is on top and the other further down the line. And they said they were afraid that moving the line they would loosen a rock, which would fall and hit the companion further down. And they couldn’t see each other because it was a vertical cliff. So I heard on the, on the intercom er, walkie talkie, they were asking all the time, “Wo bist du? Wo bist du?” “Where are you?” So, a man, you could imagine he was passing through rotten rocks and he was afraid was his friend just below or was he down to the side? So things like that. So it was a quite unusual project and also because we had a lot of money for that project, we could set up a field laboratory in Narsarssuaq. So the samples, they were flown in on a daily basis to the field lab in er, Narsarsuaq airfield and there we had also, we had bought a, a crusher and, and a mill, so we could actually pulverize the samples and took out a split – 50 or 100 grams – that we send to commercial laboratories in Canada. All samples went to one laboratory and every tenth to another laboratory, as a check. And so they were shipped crushed, and the sample powder was sent directly from Narsarsuaq in, in end of August, also on a weekly basis.

So it all worked smoothly. We had one accident.

As I told you, on a daily basis the mountaineers were flown up and put on top of the cliffs and er, sometimes it involved quite difficult landings. I mean the rotor was running when the two guys were jumping out. So the pilot, he wanted er, a counter-weight, so to speak. So he used me. So I was sitting, you had the pilot and then the co-pilot seat. I was sitting weighting the machine down because in the back seat he had the two mountaineers. So he put one ski on, on er, on the slope, typically. One ski on the slope. And then he could balance the machine and said over the intercom to the two passengers on the backseat, please step out very carefully, because he should keep the machine in er, horizontal status because if it was tipping, the rotor would hit into the, the wall. And that should be avoiding at every cost. So I was sitting there, I didn’t like it, sitting weighting down as counterweight to, to help stabilize that process. But um, that was part of the job.

Bjørn 13:57

But then one day I remember we had, we had visitors coming in and I was discussing with, with er, my friend John Petersen, another geologist, came visiting. And they were flying up without me er, putting the mountaineers on location in the morning. It was a Jetranger, a Jetranger is not so powerful engine. So there wasn’t so much leverage for, for the pilot.

Er suddenly we heard the helicopter, “Mmmmmrrr,” and then ‘Clang, Clang’. That was the rotor that hit the mountain two times. And then he came back. And we were so afraid. We said, ‘He’ll come down in flame with three bodies on board.’ But he managed to land that helicopter. And it appears that both rotor blades had been shortened the same. And you know, rotor blades, they’re very stable. They should be absolutely balanced. It’s very much about balance. So apparently he cut the same amount off the end of each rotor blade, so he managed to land it. 

 I have a fantastic picture, they send out a Sikorsky 61 to pick up the helicopter. And it did that er. It took it in a sling load because the, the below the big Sikorsky. So I have a fantastic photo of the two helicopters, one flying away with, with a sling load of a smaller helicopter.

The project ended up and we did a lot of plotting and we analyse for 12 elements. The main elements were niobium, tantalum, thorium, and uranium. Thorium and uranium, they were just a pain in the arse because they created problems, all sorts of environmental problems, but the paying metals especially tantalum er, and also niobium er, and but they’re hosted in the same mineral. So er, to process that you have to, to separate out the pyrochlore and er. So, and, and the other elements which could be of interest – tin and moly and tungsten – so we analyse for 12 er, elements and I got the results. And, and then in the autumn we er, I did the final report and there’s a beautiful report with a lot of colour plots.

It was intended you know, I think that er, ten classes, when you do your contouring you er, make anomaly maps with gradients and you can take the most red part of the, the map is where the highest tantalum values are. That’s that’s common. And I remember we had a final meeting at the, with the bureaucrats in the mineral administration. And I said, “Well how many issues, how large, how many volumes should we print of that report?” And er, there were these er, nice fold-out maps, colour maps, twenty five or something. And that would cost so and so much. And, and these type in from the Ministry, “Oh, that’ll be too expensive. You’ll have to print those maps in black and white.” And I protested. I said, “You can’t distinguish when you have ten classes, they must be (in) colour. If not, they’re useless.”  And they said, “Well that’s not our problem, that’s a problem for the survey and if you want them in colour you can pay for, for it yourself.” So that report came out with, I think there were four, four copies with er, colour maps in. I have one here. And, and the rest which went out to institutions and industries were with useless maps. Of course there was the text and (made up,) I made up tables with, with tonnage estimates and er, you know, it’s very difficult to estimate tonnage when you don’t have (drill cores), but you have to come up with a guess. And I think I said something er, half a billion tonnes with er, a few hundred ppm tantalum. And then the high grade zones. Something like that. And then nothing happened.

Julie 17:48

I’m Julie Hollis and you’ve been listening to Polar Podcasts.

Julie 18:00

In the next episode, we hear more from Professor Allen Nutman about dating some of the oldest rocks in the world, from the Nuuk region.