Geometry, scaling relationships and emplacement dynamics of a ca. 6 Ma shallow felsic sill complex, Calamita Peninsula, Elba Island, Italy

7 Conclusions The Calamita sills exhibit similar geometric scaling to other felsic sills, once sampling bias is considered. For the Elba data unrealistically high magma viscosities and or volumetric flow rates are required to fit the viscosity dominated regime. However, the fracture-toughness dominated regime brackets the data well if field-scale fracture toughness values exceed laboratory values by one to two orders of magnitude. Such high effective fracture toughness values are feasible if there is extensive interaction and branching between growing sills and or if magma freezing at sill extremities leads to armoring of the crack tip process zone. Similar mechanical questions arise for the scaling of other felsic sills as well as mafic dykes. References Bunger, A.P. , and E. Detournay (2005), Asymptotic solution for a penny-shaped near-surface hydraulic fracture. Engineering fracture mechanics, 72(16):2468-2486. Cruden, A., and K. McCaffrey (2006), Dimensional scaling relationships of tabular igneous intrusions and their implications for a size, depth, and compositionally dependent spectrum of emplacement processes in the crust. EOS Trans. AGU, 87, Abstract V12B-06. Mazzarin, F., and Musemeci, G. (2008), Hydrofracturing-related sill and dyke emplacement at shallow crustal levels: the Eastern Elba Dyke Complex, Italy. Geol. Soc. London, Sp. Publ. 320, 121-129. 1 Dimensional Scaling of Tabular Intrusions