Study on the physical properties and genesis of borate minerals in skarns.

本研究旨在厘清冈山县福冈地区高温交代产物矽卡岩中硼酸盐矿物的物理性质及成因。硼酸矿物赋存状态：矽卡岩矿物如辉长岩、刺长岩等主要为高温交代产物。在变质后阶段，矽卡岩被大量由水合硅酸钙、含氟矿物和含硼矿物组成的脉切割。由硼酸盐矿物组成的矿脉，沿着结晶石灰岩和夕卡岩之间的边界发育。静脉的厚度约为10厘米，其中一部分扩张至3米。在扩大区域的中心，发生了地震。膨胀区周边发育厚20 ~ 50 cm的水合硼酸盐，如奥尔山云母、绢云母、矽云母、硼云母、寄生云母等。硼酸盐矿物的物理性质：通过研究揭示了多种硼酸盐矿物的光学性质、硬度、密度、x射线衍射性质、化学组成、热性质和红外吸收光谱等矿物学性质。硼酸矿物的成因：从赋存方式、硫化物矿物资料和Schafer（1968）报道的资料来看，这些矿物的形成可以认为：(1)含硼流体与石灰石反应形成；(2)绢云母矿和寄生云母矿为热液蚀变形成；(3)后期水热溶液将矽钛矿和寄生矽钛矿转化为橄榄云母、绢云母等。

The present study aims at claryfing the physical properties and genesis of borate minerals in skarns, which are formed as high-temperature metasomatic products at Fuka, Okayama Prefecture.1. Occurrence of borate minerals : Skarn minerals such as gehlenite and spurrite were primarily formed as high-temperature metasomatic products. During the post-metassomatic stage, the skarns were cut by numerous veins which consist of hydrated calcium silicates, fluoline-bearing minerals, and boron-bearing minerals. A vein consisting of borate minerals developed along the boundary between crystalline limestone and the skarns. The vein was approximately 10 cm in thickness, although in one part expanded to 3m. At the center of the expanded area, takedaite occurred. At the circumference of the expanded area, hydrous borates such as olshankyite, frolovite, sibirskite, borcarite and parasibirskite occurred 20 cm to 50 cm in thickness.2. physical properties of borate minerals : The mineralogical propertes such as optical properties, hardness, density, X-ray diffraction properties, chemical composition, thermal properties and Infrared absorption spectrum of many borate mineals, were revealed through this study.3. Genesis of borate minerals : From the mode of occurrence, the data on the sulphide minerals and the data reported by Schafer (1968), the formation of these minerals may be considered as follows : (1) takedaite was formed by reaction of boron-bearing fluids with limestone ; (2) sibirskite and parasibirskite were formed by hydrothermal alteration of takedaite ; (3) the late-hydrothemal solution converted sibirskite and parasibirskite to olshanskyite, frolovite, etc.