北京石花洞“石花”的晶体结构、矿物组成及形态发育模拟分析

Analysis of the crystal structure,mineral component and simulated evolution of the cave flower from Beijing Shihua cave

以北京石花洞的石花为研究对象,将其分为基底、根部、冠部三个部分。通过实地观察监测、显微镜和扫描电镜观察、X射线粉晶衍射以及模拟石花生长实验,分析并确定石花的矿物组成,讨论其形成条件和造貌水动力特征,结果表明:(1)石花晶体呈树枝状结构,其附生基底的矿物几乎全部为方解石,仅含极少微量的杂质;石花根部方解石含量>90%,文石及少量杂质含量<5%;石花冠部文石含量>90%,方解石及杂质含量<5%;而就石花整体而言,其矿物组成为文石含量>90%,方解石及杂质含量<5%。(2)形成石花的环境条件为较封闭、气温稍低但较稳定、洞内湿度较低且气流扰动小。(3)形成石花的造貌水动力为来自基底内部渗出孔隙水的毛细作用。

This paper focuses on the study of a cave flower from Beijing Shihua cave. This cave flower can be divided into three parts here： the base, the root and the crown part. By means of microscope observations, x-ray power diffraction analysis, scan electron microscope analysis and the simulated experiment, the authors attempt to determine the mineral composition, to analyze the conditions under which the cave flower formed and the hydrologic dynamics which create this unique cave flower. The results show that： （1） The crystal possesses spatial distribution pattern of arborization. The speleothem base part on which the cave flower grows is almost composed of calcite with a little impurity. The root part of the cave flower contains more than 90% calcite and less than 5% aragonite as well as trace impurity. Whereas, the crown part contains more than 90% aragonite with needle-like crystal shape and less than 5% calcite as well as trace impurity. Therefore, the total of the cave flower contains more than 90% aragonite and less than 5% calcite and trace impurity. （2） The cave flower formed in low and stable temperature and a rather dry condition. （3） The shaping dynamics originating from capillary action, which drives the water seeping from the base, could be mainly responsible for the formation of the cave flower.