摘要
大洋中脊的海底块状硫化物矿床是当前地球科学的一个热点。因为他不仅具有经济效益,而且可以直接观测到这些矿床的形成过程。这些矿床均有许多黑烟囱和白烟囱。在这些烟囱中成矿流体不断地流过,并同时沉淀出Cu,Pb,Zn硫化物和脉石矿物。本研究的样品是取自北纬21°N的太平洋洋脊中现代大洋海底的Zn(Cu)型硫化物烟囱。对这些烟囱的矿物共生组合进行研究发现其矿物组合相当简单,分硫化物和脉石矿物两种。硫化物中以其含量多少排列为闪锌矿,黄铁矿,黄铜矿和磁黄铁矿。脉石矿物以硬石膏为主,见少量重晶石。在烟囱中这些硫化物和脉石矿物的分布是有分带性的。从外到内为硬石膏带,黄铁矿带,闪锌矿带。闪锌矿带向里可见到少量黄铜矿和磁黄铜矿,及硬石膏,但它们尚未构成一个带。烟囱的中心常常是空的,因为是原来的热液通道。 发现两类流体包裹体:一类为水溶液相包裹体。另一类为CH_4的包裹体。其均一温度是从180～265℃。最外面的硬石膏带,均一温度从180～245℃(平均212℃)。黄铁矿带均一温度从185～260℃(平均218℃)。闪锌矿带均一温度从190～265℃(平均229℃)。从平均的均一温度看似乎从边上到中心从212—218—229℃向上升,说明一个趋势,中间的温度较高,边上的较低。成矿溶液的盐度与海水相差不大。
Petrographic and fluid inclusion studies of 8 samples from a recent ocean ridge sea floor mineralization at 21°N Pacific Ocean have been carried out. Total 24 polished thin sections, 14-microprobe analyses, and the composition of 30 fluid inclusions have been determined by GC-MS method. The explorer ridge samples are relatively simple mineralogy from petrographic and microprobe analysis. They are consisted of sulfides and anhydrite. The major sulfide is sphalerite, and other includes chalcopyrite and minor galena. Besides anhydrite, amorphous silica and barite are present too. The sulfides, barite and anhydrite are growth together. Liquid (H2O) and organic (CH4)-rich inclusions have been found in barite and anhydrite. The homogenization temperatures of fluid inclusions range from 185 to 265 and the composition of fluids in fluid inclusions are mainly H2O (from 79 to 97%), and CH4 (from 0 to 7. 3%) with minor amounts of C2 H6, CO or N2 and CO2. Besides that, H2 S is presented in several tests. The salinity of the fluid inclusions is slightly higher than that of seawater. Comparison to the homogenization temperatures, there is no big differences between the data from fluid inclusions and the results of in situ measurement, but the composition of the fluids is quite different with the sea water. The hydrothermal fluids formed the mineralization may come from a deep sources and mixture with seawater.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第2期235-241,共7页
Acta Petrologica Sinica
基金
国家自然科学基金
中国科协和中国科学院出版基金
关键词
黑烟囱
热液
流体包裹体
热液与海水相混
Black smoker, Hydrothermal fluid, Fluid inclusion, Mixture of hydrothermal fluid and seawater
