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Chile Expedition Summer 2009 We are a group of 5 geology undergraduate students. Over the summer we spent 6 weeks in Chile making geological maps which will count towards 20% of our third year grades. We mapped areas covering the El Tesoro Mine, a copper mine, and part of the Limon Verde mountain formations in the Atacama Desert located 60km SSW of Calama, II Region, northern Chile. Location of the El Tesoro Mine, Northern Chile Map showing the distribution of major copper mines in Northern Chile including El Tesoro Geology of Chile The Andean Mountain Range which runs the length of Chile provided us with a unique opportunity to study the subduction zone setting that led to this mountain range’s formation. Having studied the theory behind such settings in lectures we were all keen to observe it firsthand. Most aspects of the geology of the areas we mapped can be linked back to the formation of the mountains, from the presence of ammonites (marine fossils) which have been uplifted to our mapping area over 2km above sea level, and extensive faulting due to tensions created by the colliding tectonic plates off the coast of Chile. The geology is very different to that in the UK and therefore any area in which we have previously carried out fieldwork. The rocks we observed in Chile are generally much younger than those in the UK and have been formed by very different processes. Not only did we improve on mapping skills, we also learnt an invaluabe amount on the fascinating geology of Chile and the Andes. We look forward to applying our new knowledge to nearly every aspect of our future studies in Geology. We have all gained a strong personal interest in it and will continue to research it now we are back in Cambridge. El Tesoro, We were very lucky to be able to be accommodated on the El Tesoro site itself. This proved a very enjoyable time for us and an invaluable chance to be in direct contact with the everyday lives of the geologists and miners working there. All the facilities were open to us, and we had several occasions of experiencing the local culture directly through festivities such as the miner’s day celebrations. Residing on site meant we were able to be in contact with the geologists throughout our stay, exchanging ideas, and receiving invaluable help for our mapping work. We were required to take at least one day off work every week, and so we decided to use the opportunity to visit Chile (see later section). Limon Verde – Victoria Stevens, Marie Cavitte, Harriet Rawson Our mapping area consisted of old uplifted basement rocks, and rose 700m above the surrounding desert, so commanded fantastic views of almost the entire width of Chile. The Sierra de Limon Verde has been little studied before which made it quite exciting for us to be the first ones to ever map the area in detail. It is good to now that our map may be useful in the future for other geologists who want to find out more about the history of the area. The rocks in our area were predominantly igneous, with some metamorphics, and this meant we learnt a lot as previously we have not had much experience of mapping these types of rocks in the field. We also learnt about initially mapping from an aerial photo, as often the colour changes of the rocks on the ground can be seen. This is not possible in Britain due to the dense vegetation. El Tesoro – Dominic White and Hannah Wood The area we mapped is situated on several strands of the regionally extensive Domeyko Fault System which runs north-south for 100s kms through the centre of Northern Chile and is a strike-slip system (same type as the San Andreas Fault) with displacements of up to 80km across it. The fault system ran through the centre of our mapping area which linked it well with the regional geology. The presence of 2 mines in our mapping area provided an interesting insight into the link between geology and the economy. Northern Chile produces more copper than any other region of the world and its economy relies heavily on it. Copper mines run in a north-south band along the Domeyko Fault System and their distribution is shown in the map above. The presence of copper in this region is attributed to the subduction zone off the west coast of South America. The mines situated within our mapping area also provided lots of information on the subsurface geology which helped in compiling lithological logs and detailed cross sections of the area. We were also fortunate to be given the opportunity to study boreholes of the area which provided further information on the subsurface. Our mapping area included both igneous (andesites) and sedimentary (conglomerates) rocks. This is perfect for a mapping project as it provides information on the volcanic history of the area (igneous) and the environmental history (sediments). We analysed rocks and structures in detail in order to piece together the series of events that led to the formation of the current geology. We found that either a series of volcanic eruptions, shallow intrusions of magma in the crust, or both predated a desert environment in which much sediment was transported in flash flood events (known as an alluvial fan). Weekend Adventures We took one day off each weekend in which we travelled to San Pedro de Atacama, a scenic town in the centre of the Atacama Desert surrounded by a plethora of extraordinary otherworldly landscapes. For example, we visited the Valley of the Moon, which, as its name suggests, resembles the surface of the moon, formed of strongly weathered salt deposits. The El Tatio Geyser Field, the highest geyser field in the world, was also nearby and equally impressive. We reached the geysers at sunrise and swam in their thermal warm waters despite an air temperature of -22°C. On our final weekend we climbed to the summit of the Lascar Volcano which is currently active. Yellow sulphurous steam billowed from its crater and the views from the top were truly spectacular and well worth the gruelling climb to 5600m in freezing temperatures and very thin air. Our weekend adventures linked well with geology. It is the geology that makes the scenery of Chile so stunning and we are all truly inspired by it. We also spent a few days in Antofagasta, mostly to visit our local contact, Professor Guillermo Chong Diaz in order to prepare ourselves for our work, as well as visiting this impressive coastal town. Personal Benefits Although the expedition was dedicated to furthering our academic understanding, we all learnt a lot personally by travelling to South America and experiencing Chilean culture. For example, the feast day of Saint Laurence, the patron saint of miners, happened whilst we were staying at the mine and there were lots of celebrations including traditional Chilean dancing. We all improved are Spanish enormously whilst there; the four of us who spoke no Spanish initially can now have moderately fluent conversations, especially if they involve technical geological terms! Having planned this trip successfully we have learnt organisational skills, and about the benefits of teamwork. The people we met…. We were fortunate in having the benefit of a specialist on the geology of the region. Professor Guillermo Chong Diaz is a leading Chilean Geologist at the Universidad Catolica del Norte in Antofagasta, Northern Chile, who helped us to organise and carry out our project. He has worked successfully with a similar project group from Cambridge University in the past and I hope that this trip has helped to strengthen a link between the universities which students may use in the future. We will forward all of our data and conclusions both to our contact and the mine to aid research into and understanding of the area. We feel that we have all gained a lot from this fieldtrip. We will undoubtedly use the many skills we have learnt in the future. Academically, we seized the exceptional opportunity to make geological maps in an area unlike anywhere else in the world. Our university degree does not cover economic geology, it was thus a precious opportunity to be able to study this side of or subject. And as for the numerous personal skills that we were able to acquire, these range from travel and organisation skills, developing our Spanish knowledge, to developing invaluable contacts in our field of study as well as the unique opportunity to meet Professor Constantino Mpodozis, and Richard Silllitoe, a renowned geologist and consultant respectively in Chile and worldwide. We are all very grateful to have been awarded the travel grant. None of this would have been possible without your generous and precious support. Budget Breakdown We were extremely fortunate to have received free accommodation and food whilst at El Tesoro mine due to the generosity of the owning company, Antofagasta PLC. We had no idea of this in advance, so have spent less than previously budgeted for. Pre-expedition costs (£200) Geological maps, Base maps, Aerial photographs: £100 First aid training: £100 (Emergency and basic first aid: www.sja.org) International Travel (£5,000) Flights and transport to mapping location: £1,000 (x5), Total = £5,000 (flights £680) Subsistence (£1,750) Food, accommodation and water: £25 each (x5) per day (x14), Total = £1,750 Local Travel (£350) Local buses from mine to Antofagasta and San Pedro de Atacama on weekends: £70 each (x5) over whole trip, Total = £350 Local counterparts/ guides (£100) Field Equipment (£980) GPS receivers: £80 each (x2), Total £160 Geological Hammers: £20 each (x5), Total = £100 Notebooks: £10 (x5) each (x5), Total = £250, Pens/stationary: £150 Notebook laptop: £320 Insurance (£280) Insurance: £56 each (x5), Total = £280 Medical Health and Safety (£468) Hard hats: £3 each (x5), Total = £18 First aid kits and medication: £20 each (x5), Total = £100 Vaccinations: £70 each, Total = £350 Expedition report (£150) Unforseen costs (£370) Camera memory card = £20 Camera (damaged due to dust) = £150 Clothing (footwear needed to be replaced due to harsh terrain underfoot) = £100 (x2) = £200 TOTAL: £9648