| 其他摘要 | Xuefeng district is an important Au-producer in Hunan Province, more than 80 percent gold deposits in this province occur in the Precambrian metamorphic rock series in the Xuefeng district. The Liulincha gold ore belt is located at northern of the central Xuefengshan, although this gold ore belt had been found and mined for a long time, the geological researches on these gold deposits are still rare. Based on systematic field investigation, our research team for the first time confirms that the gold depsoits in Liulincha are of typical albite-quartz vein type, and these gold deposits are significantly different from other quartz vein type gold deposits in the Xuefeng district. Based on systematic field investigation and sampling, this master’s dissertation placed emphasis on mineralogy, element geochemistry, isotope geochemistry, and fluid inclusion geochemistry of the four representative gold deposits in this area, and more details of mineralogy and geochemistry of albite as gold-bearing mineral had been discussed. Based on the above researches, this dissertation preliminary discussed the sources of ore-forming fluid and materials, the mineralization epoch and ore genesis of gold deposits in the Liulincha district. Some new conclusions are obtained in this dissertation as follows:
1.The feldspars in ore veins are pink in color in this area. Some characteristics of the studied feldspars under microscope can be listed as follows: the feldspars occur as lamellae and grains, weakened cleavage, polysynthetic twin, negative relief, grey to yellowish. It is shown for the first time that the feldspars in ore veins in the studied area are albites, these albites are cryogenic and high ordering degree. The gold deposits in this area are typical albite-quartz vein type ones.
2.The albites always contain high amount of Ab, and the amount of Or and An is lower, the albite is close to pure albite. The amount of Sr is higher than any other elements, and the LREE concentrations are usually relatively high, and no obvious Eu, Ce anomaly have been observed.
3.The oxygen isotopic compositions of albites separates vary in the range of 10.2‰~14.5‰, the δ18O‰ values of the corresponding fliud are 1.9‰~6.9‰. The ore-forming fluid is characterized by the hydrothermal fluid which was derived from the evolved meteoric water.
4.The liquid inclusions are dominatant in quartz co-existing with albite, its homogeneous temperatures vary in the range of 140~300℃, and its salinities fall in the range of 1~8 wt%NaCl, and the calculated densities of the ore-forming fluid range from 0.60 to 0.99g/cm3. The ore-forming fluids in the gold deposits of Liulincha gold ore belt is characterized by low-moderate temperature, low salinity and moderate density.
5.Combined with the previous researches in western Hunan, the origin of gold deposits of Liulincha ore belt were determined, that is, its ore-forming materials are derived from the Proterozoic Banxi group, and its mineralization epoch is Caledonian Period, the genetic type of gold deposits in the studied area is of hydrothermal-reworked stratabound origin.
Key words: Liulincha gold ore belt; albite; mineralogy; element geochemistry; fluid inclusions; ore genesis |
修改评论