内蒙古黄岗梁水晶的成因:来自包裹体的证据

Genesis of quartz crystal in Huanggangliang,Inner Mongolia:evidence from inclusions

利用光学显微镜、电子探针、激光拉曼光谱仪、X射线衍射仪、冷热台等仪器,对产自内蒙古黄岗梁水晶中的包裹体成因进行了研究。样品有绿色和烟色两种类型,晶体生长环带明显,核部较洁净,只有零星分布的气液两相包裹体,其中绿色水晶外层环带杂乱分布大量针状铁阳起石包裹体,烟色水晶的中、外层环带中可见大量富含CO_(2)和N_(2)的气液两相包裹体。绿色水晶从核部→中间环带→外层环带的均一温度分别为300、330和260℃,盐度w(NaCl_(eq))在0.18%-5.71%;烟色水晶从核部→中外层环带的均一温度分别为260和350℃,盐度为18.22%-23.18%。黄岗梁水晶的形成环境复杂,具有多期活动性,包裹体温度和盐度的变化表明烟色水晶结晶早于绿色水晶。烟色水晶生长初期处于稳定的中温热液条件,热液的侵入和少量大气降水的混入导致成矿流体温度升高并发生不混溶作用,富含CO_(2)、N_(2)的流体被正在生长的水晶捕获并包裹在其中。绿色水晶早期处于较稳定的高温热液环境,后期大气降水的加入导致流体的温度降低,针状铁阳起石混杂在流体中,并被后期生长的水晶包裹,形成子矿物包裹体。

The inclusions of Huanggangliang quartz crystal in Inner Mongolia were observed and tested by mi-croscope,electron probe,laser Raman spectrometer,hot and cold stage,etc.The genesis of the crystal was preliminarily discussed.There are two types of quartz crystals:green and smokey crystal.The growth annulus in the crystal is obvious.The core of the crystal is relatively clean,with only sporadic gas-liquid two-phase inclu-sions.A large number of acicular ferroactinolite inclusions are scattered in the outer ring of the green crystal,and another number of gas-liquid inclusions rich in CO_(2) and N_(2) can be seen in the middle and outer ring of the smokey crystal.The homogenization temperatures of the green crystal from the core,middle ring to outer ring are 300,330 and 260℃,respectively.The salinity(w(NaCl_(eq)))is 0.18%-5.71%.The homogenization tem-perature of the smokey crystal from the core to the middle and outer rings is about 260 and 350℃,respective-ly,and the salinity is 18.22%-23.18%.The growth environment of Huanggangliang quartz crystal is complex and multi-stage.According to the change of inclusion temperature and salinity,the crystallization of smokey crystal is earlier than that of green crystal.At the initial stage,the smokey crystal grew under relatively stable mesothermal hydrothermal conditions.The intrusion of magmatic hydrothermal solution and the mixing of a small amount of atmospheric precipitation increased the temperature rise of the ore-forming fluid and immiscibility.The fluid rich in CO_(2) and N_(2) was wrapped by the growing crystal.The green crystal grew in a relatively stable high-temperature hydrothermal solution,in the early stage.The addition of atmospheric precipitation in the later stage decreased the temperature of the fluid.The acicular ferroactinolite was mixed in the fluid and wrapped by the later growing crystal.