Effects of Precooling Thermal History and Cooling Rate on the Texture of Chondrules: a Preliminary Report

Effect of precooling thermal history of chondrules on the textures of chondrules was examined by crystallizing melts of chondrule compositions with or without relict crystals at cooling rates of about 50℃/min. Textures formed from super-liquidus temperatures (radial or barred olivine texture) were strikingly different from those formed from sub-liquidus temperatures (porphyritic or microporphyritic texture). Effect of cooling rate was also examined with cooling rates ranging from 500 to 5.3℃/hr. The cooling rate for producing radial or barred pyroxene texture ranges from about 200 to less than 5℃/hr, whereas radial or barred olivine texture was produced with cooling rates greater than about 100℃/hr.