SOTA 7, San Pedro de Atacama

GeoExpedition participated in the SOTA 7 ‘Stateof the Arc Meeting’ between September 1th and 8^th in San Pedro deAtacama, Chile. This conference is supported financially by the International Union of Geodesy and Geophysics (IUGG) trough the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI). The main organizerwas Gerhard Wörner from Georg-August-Universität Göttingen, Germany, who made this conference something scientifically very high, but at the same time, very entertaining and cordial.

The meeting program contemplated in 4-days of talks and discussions, and 2-days of spectacular field work: the first was on Purico ignimbrite shield and La Pacana Caldera (led by Shan de Silva) and the second one was on Lascar Volcano (led by Felipe Aguilera).  There were thirty-two attendees from the USA, UK, Switzerland, Australia, Germany, France and Chile, so there was a lot of scientific interaction and discussion. The general focus of this conference is arc magmatism, arc and subduction physics and modelling, and the role of arcs in the formation and evolution of planet Earth and its continents. The specific focus of SOTA 7 was silicic magmatism that produced the Altiplano-Puna Volcanic Complex of the Northern Volcanic Zone (NVZ) with emphasis on the spectacular high-volume magmatic events termed “flare-ups” between 9 to 3 Ma. The resulting explosive volcanism give place to an ignimbrite and caldera plateau that that constituted the Altiplano today, from where new volcanism had been formed.  The biggest example is Atana Ignimbrite an example of crystal-rich ‘monotonous intermediate’ type that erupted about 4 Ma ago, evacuating 2,500 km³ of dry rock equivalent (one of the largest described ignimbrite of the world), and leaving the La Pacana Caldera, a depression of 80 km².

We presented a talk entitled ‘Lateral magma propagation during the emplacement of La Gloria Pluton, central Chile’, based on the research in Central Chile that is currently developed by GeoExpedition. On the case of La Gloria Pluton the age progression, together with existing data of subhorizontal mineral and magnetic lineations parallel to the pluton axis, indicate lateral propagation of magma during reservoir construction along the hinge of an anticline of the volcanic host sequences. In addition to controlling the position of volcanic output, this horizontal migration of silicic magmas in the upper crust significantly increases the surface footprint over which fluids are exsolved and outgas, strongly decreasing the potential for ore formation above such laterally-emplaced laccoliths in the shallow crust.