  Chondrites are the likely building blocks of Earth, and identifying the group
of chondrite that best represents Earth is a key to resolving the state of the
early Earth. The origin of chondrites, however, remains controversial partly
because of their puzzling major element compositions, some exhibiting depletion
in Al, Ca, and Mg. Based on a new thermochemical evolution model of
protoplanetary disks, we show that planetesimals with depletion patterns
similar to ordinary and enstatite chondrites can originate at 1-2 AU just
outside where enstatite evaporates. Around the "evaporation front" of
enstatite, the large inward flow of refractory minerals, including forsterite,
takes place with a high pebble concentration, and the loss of those minerals
result in depletion in Al, Ca, and Mg. When evaporated solid grains re-condense
onto pebbles, the concentration of pebbles is further enhanced, potentially
triggering the streaming instability. Planetesimals with the composition of
ordinary and enstatite chondrites can thus be naturally created in the
terrestrial region. The preferential loss of forsterite also creates an
enhancement of Mg/Si and heavy Si isotopes just inside the potential source
region for ordinary and enstatite chondrites. Earth, which shows both features,
may originate just inside where ordinary and enstatite chondrites were born.
