Lateral magma propagation during the emplacement of La Gloria Pluton, central Chile.

La Gloria Pluton (LGP) in central Chile is a shallow, north-northwest- elongated granitoid body of 18 km length and 4-6 km width, belonging to a regional north-south trend of Miocene plutons, from the San Francisco Batholith and porphyries in the north, to Mesón Alto, and San Gabriel in the south. New U-Pb zircon ages of the LGP indicate that crystallization occurred mostly within an interval between 11.3-10.2 Ma, with a pattern of decreasing ages along the pluton axis from south to north. The progression of zircon ages can be explained either by gradual northwestward migration of the feeder zone that supplied magma to the shallow pluton or, more likely, by shallow lateral magma propagation southeastward from a fixed feeder zone located beneath the northern margin of the pluton. The age progression, together with existing data of subhorizontal mineral and magnetic lineations in the LGP 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 possible volcanic output, such 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 magmatic-hydrothermal ore formation above laterally emplaced laccoliths in the shallow crust. [ABSTRACT FROM AUTHOR]