摘要
含水的枪晶石是十分罕见的交代矿物，发现于云南个旧锡矿打磨山地区燕山晚期花岗岩与三叠纪灰岩接触带夕卡岩中，它在我国是首次发现。作者对其矿物共生组合、物理性质、化学组成、光性特征、Ｘ射线粉晶衍射谱线、红外光谱和热分析曲线等特征作了较系统的研究。该矿物与钙铁榴石、透辉石、硅灰石、硅硼钙石和萤石等矿物伴生，以其明显的聚片双晶、折光率和光轴角的强烈色散以及有一定量ＯＨ替代Ｆ为特征。它形成于浅成的外夕卡岩带，是富Ｆ（Ｂ）高温流体作用下的接触交代产物。
Water_bearing cuspidine, a very rare mineral, was discovered by the authors in calcic skarn of the exocontact zone between Late Yanshanian granite and Triassic limestone in the Gejiu tin deposit, Yunnan Province. Its mineralogical characteristics, paragenesis, chemical composition, optical features, X_ray powder diffraction data, infrared absorption spectroscopy and thermal analysis were studied systematically. Associated with andradite, B_vesuvianite, diopside, datolite, fluorite, wollastonite and nordenskioldine, the mineral is characterized by clear polysynthetic twin, strong dispersion of refractive index and optic axial angle. Its optical properties are N g=1.604, N m=1.595, N p=1.592, N g- N p=0.012, (+)2 V =62°, c∧ N g=6.5° . Electron microprobe and chemical analyses of the mineral give SiO 2 30.64%, TiO 2 0.04% , Al 2O 3 0.01%, Cr 2O 3 0.06%, FeO 0.02%, CaO 55.61%, MgO 0.09%, MnO 0.14% , Na 2O 0.02%, H 2O + 4.55%, F 8.63%, B 2O 3 0.59%, and CO 2 1.43%, with the calculated empirical formula being (Ca 3.979 Mg 0.009 Mn 0.008 Na 0.003 Fe 2+ 0.001 ) 4(Si 2.046 B 0.068 Cr 0.003 Ti 0.002 Al 0.001 ) 2.120 O 7 (F 1.823 OH 0.322 ) 2.145 (CO 3) 0.130 · 0.854 H 2O. The unit cell parameters are a 0=10.94, b 0=10.50, c 0=7.623, β =110.42°. Infrared absorption spectral analysis suggests that there exists stretch_back vibration of OH at 3560cm -1 . Thermogravimetric analysis shows that the loss for H 2O is about 2.8% and about 1.6% for OH -. The authors consider that water_bearing cuspidine was formed in the hypabyssal exoskarn zone, being a product of contact metasomatism under the active role of F(B)_rich fluids. It was for the first time that water_bearing cuspidine was discovered in China.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
1999年第1期65-73,共9页
Acta Petrologica et Mineralogica
关键词
含水
枪晶石
矿物学特征
个旧锡矿
新矿物
water_bearing cuspidine
mineralogical characteristics
Gejiu tin deposit
