云南鹤庆锰矿沉积环境研究

云南鹤庆锰矿床位于扬子地台西南缘,西近三江地槽,地处这两大构造单元的过渡地带。镜下观察,该矿床矿石矿物主要有硬锰矿、菱锰矿、水锰矿、黑锰矿,含有少量的软锰矿和恩苏塔矿。金属矿物在空间上存在明显的分带现象,主要表现在17线以西以硬锰矿和软锰矿为主,10～15线则以水锰矿和菱锰矿为主,而7～10线以黑锰矿和菱锰矿为主。灰岩样品的δ13C值变化范围为-3.0‰～2.9‰,平均值为0.6‰,其δ18O值变化范围为-9.9‰～-5.5‰,平均值为-7.7‰;而矿石样品的δ13C值变化范围为-46.3‰～-9.8‰,平均值为-24.2‰,其δ18O值变化范围为-16.5‰～-3.1‰,平均值为-8.6‰。综合研究认为鹤庆锰矿形成于浅海局限环境,介质性质由酸性向碱性、由还原性向氧化性转变的过渡带是矿物就位的主要空间,同位素研究认为可能有生物成因的甲烷参与成矿。

Study of the Sedimentary Environment of Heqing Manganese Deposit,Yunnan, China

Heqing manganese deposit in Yunnan is located in the southwestern margin of the Yangtze platform,adjoining the Sanjiang geosyncline in the west.The deposit formed in the transition zone of the two tectonic units.Ore minerals are mainly psilomelane,rhodochrosite,manganite and hausmannite,containing a small amount of pyrolusite and nsutite.There is metal mineral zonation in space:minerals from No.17 exploration line to the west are mainly psilomelane and pyrolusite,from No.10 to No.15 exploration lines are mainly manganite and rhodochrosite,and from No.7 to No.10 exploration lines are mainly hausmannite and rhodochrosite.The δ13C values of the limestone samples range from-3.0‰ to 2.9‰ with a mean value of 0.6‰ and the δ18O varies between-9.9‰ and-5.5‰,averaging at-7.7‰;the δ13C values of the ore samples range from-46.3‰ to-9.8‰ with a mean value of-24.2‰ and the δ18O values vary from-16.5‰ to-3.1‰,averaging at-8.6‰.Comprehensive studies support that Heqing manganese deposit formed in a restricted shallow water environment.Ore minerals deposited in media property zone(from acid to alkaline and from reduction to oxidation),and isotope studies support that the biogenic methane might participate in mineralization.