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Motivazione «Medaglia Capellini» 2010


James Quick, Professor of Geology, at Southern Methodist University, began his research activity in Italy about 20 years ago as a research scientist with the US Geological Survey, working in the deep crust of the Ivrea Zone. His collaboration with the Italian team of Trieste was immediately fruitful and friendly, especially after preliminary field work discovered that the Ivrea Mafic Complex was characterized by a megascopic arcuate structure defined by layering and foliation. The geometry of this structure and the distribution of strain defined by high temperature foliation and hypersolidus deformation structures are similar to those observed in gabbros of ophiolites on which James worked in the previous years, and for which he developed the "gabbro glacier" model. The "gabbro glacier" fits perfectly the structural pattern of the Ivrea Mafic Complex, resolving a long lasting controversy between research groups on the metamorphic versus igneous nature of the gabbroic body. Pushed by these results, James Quick and his Italian collaborators completed not only the geological map of the southern Ivrea Zone, which was published in 2003, but also a number of papers on the igneous evolution of the Mafic Complex. Most recently, James and his Italian colleagues identified a large fossil caldera within Permian volcanic rocks cropping out in Val Sesia. Field evidence indicates that this caldera was a minimum of 13 km in diameter. Age determinations on the volcanic rocks and field relations demonstrate that volcanism was tightly correlated in space and time with intrusion of the Mafic Complex in the deep crust and the onset of granitic plutonism in the middle to upper crust, leading to the conclusion that 

the Sesia Valley exposes a virtually complete plumbing system beneath a Permian caldera to a depth of about 25 km. The Sesia Magmatic System is as an unprecedented analogue of igneous systems triggering explosive volcanism. Remarkably, these results would never have been attained without the fundamental input from James Quick.

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