  Multiphase galactic outflows, generated by supernova feedback, are likely to
be more metal-rich than the interstellar media from which they are driven due
to incomplete mixing between supernova ejecta and the ambient ISM. This
enrichment is important for shaping galactic metallicities and metallicity
gradients, but measuring it quantitatively from simulations requires resolution
high enough to resolve mass, momentum and energy exchanges between the
different phases of the outflows. In this context, we present simulations of
outflows, driven by SN feedback, conducted using \textsc{Quokka}, a new
GPU-optimised AMR radiation-hydrodynamics code. This code allows us to reach
combinations of resolution, simulation volume, and simulation duration larger
than those that have previously been possible, and to resolve all gas phases
from cold neutral medium, $T \sim 100$ K, to hot ionised gas, $T \gtrsim 10^7$
K. In this, a first of a series of papers exploring generation and evolution of
multiphase outflows from a wide range of galactic environments and star
formation rates, we quantify the extent of selective metal loading in Solar
neighbourhood-like environments. We explain the selective metal loading we find
as a result of the transport of metals within and between phases, a phenomenon
we can study owing to the parsec-scale resolution that our simulations achieve.
We also quantify the sensitivity of metal loading studies to numerical
resolution, and present convergence criteria for future studies.
