橄榄石腐蚀像立体模型构建及其岩石组构研究之启示

利用20% 浓度的氢氟酸（HF）对橄榄石晶体不同方向之切面进行了腐蚀实验，以期建立三维立体构型。在晶体上选取垂直任一结晶轴的单形，如（100），（010），（001）等平行双面，（110），（011），（101）等菱方柱和（111）菱方双锥进行了腐蚀实验，由原子力显微镜记录各个切面腐蚀像。结果显示，相同切面上的腐蚀像具有固定的几何形状及角度，且在晶面上的结晶学方向固定。各腐蚀像形状具有共性，即长轴为[010] 方向，短轴为[100] 方向。由不同切面腐蚀像的变化规律，建立了橄榄石腐蚀像三维立体模型。相同腐蚀剂对不同晶面腐蚀的容易程度差异巨大，以蚀坑在DIC200× 下能清晰观察到腐蚀像形态为标准，橄榄石各切面的腐蚀速率为v（010）>v（110）>v（100）>v（111）>v（101）>v（001）>v（011）。由橄榄石晶体腐蚀像的唯一性及其结晶学定向，在橄榄岩切片中将橄榄石颗粒切面指数化，并获得其结晶学定向及结晶优选方向。由此，在大别山碧溪岭石榴子石二辉橄榄岩中推断橄榄石[100] 主极密垂直面理面，[010] 主极密平行于线理面。腐蚀像所确定的晶体结晶优选性为当地构造动力提供了一定有价值资料，开拓了腐蚀像的地质应用意义。

Three Dimensional Evolution of Etch Pits on Crystal Olivine and Insights into Understanding Petrofabrics

Chemical etching with 20% HF (HF+distilled water, volume rate) at room temperature was studied on seven sections
of olivine crystals, i.e., parallel twin (100), (010), (001), rhombic prism (110), (011), (101) and rhombic dipyramid (111) sections.
AFM (Atomic Force Microscopy) and DIC (Differential Interference Contrast Microscope) methods were used to analyze these
etched sections . With a fixed shape and angle, etch figures were different in each case, but all are elongated to [010] and
shortened to [100]. The face indices and the crystallographic orientation of a single crystal were only determined by the specific
etch figures, also in rocks. Meanwhile, the etch figure symmetry displayed the point group mmm of olivine. Measured by a
specific shape in DIC 200×, the reaction rate of the seven sections was v (010)>v (110)>v (100)>v (111)>v (101)>v (001)>v (011). Classified the
etched random grain section indices identified by typical etch figure, the crystallographic preferred orientation of olivine grains in
peridotites from Bixiling in Dabieshan areas, was defined as having strong maxima of [100]， subnormal to the foliation， and strong
maxima of [010]， subparallel to the lineation. These observations may suggest that specific tectonic events affected the peridotites
at the localities.