安徽亳县陨石中一颗斑状橄榄石球粒的凝聚和结晶作用

Condensation and Crystallization of a Porphyritic OlivineChondrule in Boxian Meteorite,Anhui Province

通过对亳县陨石中一颗斑状橄榄石球粒的分析，研究了该球粒的凝聚和结晶作用。结果表明这种球粒是由气体直接凝聚成超饱和的亚稳熔体液滴，而后熔体中结晶出成分较均一的橄榄石斑晶。由于温度迅速下降，残余熔体被“冻结”成为玻璃质。同时球粒熔质中橄榄石的结晶，导致残余熔体朝富Ｃａ、富Ａｌ方向演化，形成富Ｃａ、Ａｌ的球粒玻基。

By analysing a porphyritic olivine chondrule in Boxian chondrite and studying the condensation and crystallization of the chondrule, it is shown that this chondrule could have been produced by the direct condensation of a droplet of supersaturated metastable liquid silicates from gas, and followed by the crystallization of olivine with uniform composition. Due to the quick falling of temperature, the crystallization of the molten chondrule to solid silicates would be stopped,then the residual liquid would be frozen to hyaline. The crystallization of olivine in the chondrule led to the increase of Ca and Al in the residual liquid forming Ca,Alrich hyaline.