广西巴马玉的矿物学特征及其成因探讨  

Mineralogical characteristics and genesis of Bama nephrite

作　　者：黄倩心 王时麒[1] 梁国科 杨晓东[3] 吴祥珂 HUANG Qian-xin;WANG Shi-qi;LIANG Guo-ke;YANG Xiao-dong;WU Xiang-ke(School of Earth and Space Sciences,Peking University,Beijing 100871,China;Guangxi Institute of Geological Survey,Nanning 530023,China;Institute for Applied Physics,Guangxi Academy of Sciences,Nanning 530007,China)

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]广西地质调查院,广西南宁530023 [3]广西科学院应用物理所,广西南宁530007

出　　处：《岩石矿物学杂志》2021年第5期977-990,共14页Acta Petrologica et Mineralogica

摘　　要：继贵州罗甸、广西大化发现多个新型透闪石玉矿床之后,在同属黔桂地区的广西巴马亦发现了透闪石玉矿。通过偏光显微镜镜下观察、X射线衍射仪、电子探针及重砂分析等测试手段对广西巴马玉的宝玉石矿物学特征进行了研究,发现巴马玉主要由微晶透闪石组成,具毛毡状结构和束状结构,多见水草花结构,其主要矿物成分为微晶透闪石集合体,并含有滑石、褐铁矿、高岭石等次要矿物,Mg^(2+)/(Mg^(2+)+Fe^(2+))-Si投点显示数个巴马玉样品分别属于透闪石和阳起石,定名为闪石玉。巴马透闪石玉的密度为2.81~3.00 g/cm^(3),折射率为1.61,硬度为5.19~5.32,次要矿物滑石是导致其硬度低的原因。根据电子探针数据计算出巴马玉相关化学式并对比分析,发现巴马玉样品中C位Fe^(2+)的数量为0.08~0.67 a.p.f.u,随着样品颜色从淡紫到青灰到深青灰变化,C位Fe^(2+)的数量也相继增加,说明颜色的变青加深与巴马玉Fe元素的含量增加有关。X射线衍射分析结果显示水草花的矿物成分中有针铁矿的存在,说明巴马玉水草花为地表次生结构。通过野外观察,对其主要化学元素、稀有元素以及稀土元素等特征进行综合分析并与其它矿点的相关特征进行横向对比,基本确定了巴马玉矿床为辉绿岩侵入碳酸盐岩经过岩浆热液接触交代作用而形成的层控性接触交代型岩浆热液矿床,与之前发现的位于黔桂地区的贵州罗甸、广西大化闪石矿的成因一致,它们应属于同一矿带。Following the discovery of Luodian nephrite and Dahua nephrite,another nephrite mineral spot was also found in Bama,Guangxi,which also belongs to Qian-Gui area. Analysis methods,such as orthogonal polarization microscope,X-ray powder diffraction,electron probe microanalysis and artificial heavy concentrate,were employed to study petrographic characteristics,mineral composition,color-forming factors and the genesis. These studies show that the main mineral composition of Bama nephrite is microcrystalline tremolite or actinolite,and other minor minerals,such as talc,limonite,kaolinite,etc. Bama nephrite shows felty structure,bundle structure and structure of the pattern of aquatic plant. Spots of Mg/( Mg + Fe^(2+))-Si of Bama nephrite plot into tremolite or actinolite. The hardness of Bama nephrite is between 5.19 ~ 5.32,the denstity is between 2.81 ~ 3.00 g/cm^(3),the refractive index is about 1.61. Talc,auxiliary mineral of Bama nephrite,is the cause of lower hardness. According to the electron probe data,the relevant chemical formulas of Bama jade were calculated and compared and analyzed,we found that the green color of Bama nephrite is related to 0.08 ~ 0.67 a.p.f.u of Fe in C site in tremolite,which suggests that the increasing content of Fe in C site in Bama nephrite leads to change of the colors of nephrite from light purple to dark green. The data of X-ray powder diffraction show that goethite was in the structure of the pattern of aquatic plant,implying that the structure of the pattern of aquatic plant of Bama nephrite was formed on the surface of the earth.Through field observation,the comprehensively analysis of major elements,rare elements and rare earth elements,and comparison with related features of other mine point,the authors consider that the genetic type of Bama nephrite deposit is belongs to stratabound and contact metasomatic magmatic hydrothermal deposit,which is result-ed from the magmatic hydrothermal contact metasomatism induced by diabase intruding into carbonate rock. Bama nephrite is t

关 键 词：巴马玉 结构 成分 矿物学特征 矿床成因 

分 类 号：P578.955[天文地球—矿物学] P579[天文地球—地质学]