Destruction of massive fragments in protostellar disks and crystalline
  silicate production
  We present a mechanism for the crystalline silicate production associated
with the formation and subsequent destruction of massive fragments in young
protostellar disks. The fragments form in the embedded phase of star formation
via disk fragmentation at radial distances \ga 50-100 AU and anneal small
amorphous grains in their interior when the gas temperature exceeds the
crystallization threshold of ~ 800 K. We demonstrate that fragments that form
in the early embedded phase can be destroyed before they either form solid
cores or vaporize dust grains, thus releasing the processed crystalline dust
into various radial distances from sub-AU to hundred-AU scales. Two possible
mechanisms for the destruction of fragments are the tidal disruption and
photoevaporation as fragments migrate radially inward and approach the central
star and also dispersal by tidal torques exerted by spiral arms. As a result,
most of the crystalline dust concentrates to the disk inner regions and spiral
arms, which are the likely sites of fragment destruction.
