On October 19th I had the chance to visit the Los Pelambres Mine near Salamanca, Chile. It is a giant porphyry copper-molybdenum mine about 5 hours north of Santiago. It is one of the biggest copper mines in the world and is a typical Cu-porphyry deposit in that tonalite and quartz diorite stocks intruded the local host andesite and then underwent hydrothermal and/or magmatic-hydrothermal alteration 12-10 million years ago. The hydrothermal fluids deposited chalcopyrite, bornite, pyrite, molybdenite, and some gold. The mine is a huge open-pit mine that is at a very high altitude (+3,000 m; +9,800 feet) close to the Argentinian border. The principle ores are copper and molybdenum but they also mine smaller quantities of gold, arsenic, and silver depending on the economy. First the rock is crushed, then molybdenum is chemically separated from the ore and then the copper-containing chalcopyrite is polverized into dust and transported in a pipeline to the coast where it is loaded onto a ship and transported to the refining factories.
We went on the mine tour as a trip funded by the Society of Economic Geologists (SEG) chapter at the University of Chile. SEG is a worldwide organization that sponsors chapters all over the world to go on trips, to conferences, or to host speakers in order to give students the opportunity to learn more about economic geology and industry. There were 14 students and 2 professors in our group. We left Santiago the day before the visit in the afternoon to get to our hotel for the night and got to the mine entrance at 8:30am the next day. At the entrance we had to give them all our personal information and sign a waiver for safety and then loaded on the bus for our trip up to the sites of main operations. It was such a huge place that started near the bottom of the Andes and went all the way up into the cordillera! First we arrived at the “base camp” where we put on sunscreen and had a quick medical checkup to make sure we were all fit to ascend the extreme elevations. Then we met the head geologists and they gave a presentation on the history, geology, and specs of the mine. Last year the Los Pelambres Mine produced 363 kilotons of Cu and 10.1 kilotons of Mo concentrate.
After the presentation we got back on the bus and drove for another hour to the very top of the mine to the viewing deck. We saw some of their huge Komatsu 930E trucks carting rock from the mine to the crushers driving around and felt extremely small in our bus. The drive offered stunning views of the landscape and mountains and we even saw some animals: snakes, rabbits, and vicunas. But the view of the huge mine pit was something else entirely. It was such a giant hole that I wondered how humans could possibly engineer equipment to move that much rock. The lookout at the top was at an elevation of 3,600 m (11,800 ft) and the cold wind was blowing so hard that I was reminded of ND! There we talked to a few more geologists who told us the details of the different roles geologists have. There are only 5-6 dedicated geologists working at Los Pelambres! Afterwards we drove back down partway and had lunch at the cafeteria before going to look at rock cores. They have all the representative rocks on display and it was really cool to see the different mineralization styles and ore minerals.
We also just celebrated Halloween! Last Friday I showed my friends how to carve a pumpkin since they’ve never done it! But since they don’t have pumpkins here (it is spring, after all) we had to carve a squash instead. Everyone loved the end result and took tons of pictures of our happy squash. We also ate some candy and listened to Halloween music. We got a long weekend because Oct 31 and Nov 1 are holidays so we had an asado one night and took a day trip to a reserve about an hour from Santiago to get away from the city and relax. I also introduced my friends to popcorn balls, which were very well received. I really want to make a pumpkin pie but don’t know where I will be able to find pumpkin puree. Other than that I have been busy working on getting everything ready to submit my paper but am still waiting for some feedback. I have just a month to go before I’ll be back in the US!