Modulation of zircon solubility by crystal-melt dynamics

Abstract

Zircon dating is commonly used to quantify timescales of magmatic processes, but our appreciation of the consequences of internal magma body dynamics lags behind ever-increasing analytical capabilities. In particular, it has been shown that crystal accumulation and melting of cumulates by recharge-delivered heat may affect melt chemistry within magma bodies. We considered the effect of such processes on zircon solubility in highly evolved silicate melts of diverse chemical affinities. Our modeling shows that in most cases cumulate melting perpetuates the zircon saturation behavior of the first melts emplaced at shallow storage levels. Once cumulate melting is established, the ease of saturating in zircon is controlled by cumulate mineralogy, with a particular effect of the amount of cumulate zircon and its availability for resorption. The fidelity of zircon as a recorder of magma system history thus depends on both the system's chemical affinity and mineralogy, and the history itself.