Rate of construction of the Black Mesa bysmalith, Henry Mountains, Utah

Abstract: At shallow-crustal levels, the most efficient process for the accommodation f magma emplacement is roof lifting, which induces an upward vertical displacement of the Earth's surface. Estimates of the rate and duration of this process have rarely been pub-lished. One of the most spectacular places where plutons constructed by such mechanisms are exposed is the Henry Mountains in Utah. In this place, Pollard & Johnson (1973) derive a time of 'less than several weeks ' for the construction ofthe Black Mesa bysmalith (BMb), by coupling a mechanical pproach with a model for the flow rate of Bingham magma in a tabular conduit with a constant driving pressure at the feeder. The aim of this new study of the BMb is to evaluate the maximum duration of its emplacement and propose a feasible scenario for its construction. Our study of the pluton's internal structures suggest that the BMb is a multi-pulse pluton. We have constrained the duration of BMb emplacement by simulating the thermal evolution of the growing pluton and its wallrocks for different con-struction scenarios. We have adjusted the number, the t ickness and the frequency of the pulses with our textural 'time ' constraints, which are the absence of solid-state textures around internal contacts, which implies that a melted zone was maintained inthe intrusio