Evaluating pluton-volcano relationships: an example from the Mount Givens Granodiorite

Zircon U-Pb geochronology indicates that the Mount Givens Granodiorite (MGG) of the Sierra Nevada batholith, California, was constructed over at least 7 Ma from 98-91 Ma. Chemical and volumetric similarities between homogenous ignimbrites (monotonous intermediates; MIs) and plutons such as the MGG led some to suggest a genetic relationship between the two. However, there are three issues regarding this link: 1) large plutons like the MGG accumulated at estimated rates of 0.001 km3/a, 1-2 orders of magnitude less than fluxes calculated for MIs; 2) zircon dissolution modeling indicates that rejuvenation events thought to affect MIs would not sufficiently dissolve zircon that should record multi-Ma growth of a crystal-rich mush 3) the Sierra Nevada batholith apparently lacks mafic plutons large enough to initiate MI eruptions. I suggest that MI eruptions are caused by high flux events, leaving little behind in the intrusive rock record, whereas low fluxes favor pluton growth.