  Volatile compositions of asteroids provide information on the Solar System
history and the origins of Earth's volatiles. Visible to near-infrared
observations at wavelengths of $<2.5\ {\rm \mu m}$ have suggested a genetic
link between outer main belt asteroids located at $2.5$-$4\ {\rm au}$ and
carbonaceous chondrite meteorites (CCs) that show isotopic similarities to
volatile elements on Earth. However, recent longer wavelength data for large
outer main belt asteroids show $3.1\ {\rm \mu m}$ absorption features of
ammoniated phyllosilicates that are absent in CCs and cannot easily form from
materials stable at those present distances. Here, by combining data collected
by the AKARI space telescope and hydrological, geochemical, and spectral models
of water-rock reactions, we show that the surface materials of asteroids having
$3.1\ {\rm \mu m}$ absorption features and CCs can originate from different
regions of a single, water-rock-differentiated parent body. Ammoniated
phyllosilicates form within the water-rich mantles of the differentiated bodies
containing NH$_3$ and CO$_2$ under high water-rock ratios ($>4$) and low
temperatures ($<70^\circ$C). CCs can originate from the rock-dominated cores,
that are likely to be preferentially sampled as meteorites by disruption and
transport processes. Our results suggest that multiple large main belt
asteroids formed beyond the NH$_3$ and CO$_2$ snow lines (currently $>10$ au)
and could be transported to their current locations. Earth's high hydrogen to
carbon ratio may be explained by accretion of these water-rich progenitors.
