Image-furnace experiments on the differentiation process of basaltic achondites

在0.1MPa总压下，在浮区成像炉中对玄武质无球粒陨石的合成模拟物进行了动态结晶实验。人造玄武岩的生长条件为：移动速度0.5-3.0mm/h，转速0- 30 rpm，气体流量CO_2：300，H_2：15，N_2：400 ml/min。所产生的结构是次蛇绿到变绿，这是在eucrites中观察到的代表性结构。在11 ~ 84 GPa的压力下，对合成的硬硅钙石进行了冲击恢复实验，研究了玄武质陨石的残余冲击效应。岩石学检查的实验冲击玄武岩显示固态效应的形式增加解聚和变形的组分矿物和熔融增加冲击压力。在11 GPa时，只观察到不规则的晶粒破裂。钙斜长石的Maskelynization作用开始于27 GPa。在46 GPa下，奇诺-辉石的镶嵌现象很广泛。熔融发生沿着微断层在27和46 GPa。在84 GPa下观察到广泛的整体熔化。冲击变质玄武岩可分为4类，其特征为：第1类（P<20 GPa），颗粒破碎不规则;第2类（20<P<40 GPa）斜长石转变为各向同性的镁铝榴石。第3类（40<P<60 GPa），单斜辉石表现为镶嵌消光。第4类（P>60 GPa），斜长石和单斜辉石发生熔融。

Dynamic crystallization experiments have been performed on a synthetic analog of basaltic achondrite at 0.1 MPa total pressure in a floating-zone image fumace. The growth conditions of artificial basalts are as follows : travel rate 0.5-3.0mm/h, rotation 0-30rpm, gas flow CO_2 : 300 ; H_2 : 15 ; N_2 : 400ml/min. The synthetic basalts are cylindrical (6-8mm diam.by50-80mm length), and dark in color. Textures produced are subophitic to varioritic, which are representative textures observed in eucrites. Chemical compositions of pigeonite and plagioclase are very similar to those of the Pasamonte eucrite which is one of the most representative unequilibrated basaltic achondrite.Shock recovery experiments between 11 and 84 GPa were performed on the synthetic eucrites to elucidate the residual shock effects on basaltic meteorites. Petrographic examination of experimetally shocked basalts showed solid-state effects in the form of increasing disaggregation and deformation of component minerals and melting with increasing shock pressure. Only irregular grain fracturing was observed at 11 GPa. Maskelynization of calcic plagioclase begins at 27GPa. Mosaicism of chino-pyroxene was extensive at 46 GPa. Melting occurred along microfaults at 27 and 46 GPa. Extensive overall melting was observed at 84 GPa. The shock-metamorphosed basalts can be divided into four classes whose distinctive features are : Class 1 (P<20 GPa) , grains are irregularly fractured. Class 2 (20<P<40 GPa) plagioclase is converted to isotropic maskelynite. Class 3 (40<P<60 GPa) , clinopyroxene show mosaic extinction. Class 4 (P>60 GPa) , plagioclase and clinopyroxene have been melted.