贵州松桃锰矿沉积有机质特征研究

Characteristics of Sedimentary Organic Matter in Songtao Manganese Deposits,Guizhou

松桃锰矿矿石氯仿沥青“Ａ”、饱和烃和芳烃含量高，非烃含量低，围岩泥岩则与此相反。正构烷烃、类异戊二烯烷烃、甾烷和萜烷等生物标志物的特征表明，贵州震旦松桃锰矿热水沉积体系中微生物主要为藻类生物和细菌类微生物，其生存环境为水温达１７０℃～１９５℃。

Songtao manganese deposits in Guizhou province,developed in the fine clastic sediments of Datangpo Formation of Sinian,belonging to marine sedimentary manganese-carbonate type,have the following characteristics. 1.n-Alkanes distribution curves derived from gas chromatograms show that the n-alkanes in the ores and the host rocks are dominated by medium and lower molecular weght alkanes with C 14 ～C 21 range,that the peaks are C 17 n-alkanes,and that the n-alkanes do not show marked odd or even predominance.All these characteristics indicate that organic matter in the manganese deposits originate from algae and microbes. 2.Some acyclic isoprenoids,such as isohexadecane,norpristane,pristane and phytant,are detected in the ores and the host rocks.The highly remarkable phytants predominance in the samples and ratio of Pr/Ph between 071 and 0.83 indicate the reducing environment. 3.The contents of chloroform bitumen A,alkanes and aromatic hydrocarbon in the ores are relatively higher,with an average of 93×10 -6 ,34% to 38% and 31% to 35% respectively,and the contents of nonhydrocarbon or lower,with 31% to 32%.However,the host rocks are characterized by lower contents of chloroform bitumen A(45×10 -6 averagely),alkanes(under 20%),aromatic hydrocarbon(70% to 15%)and higher contents of nonhydrocarbon (above 60%). 4.Triterpanes and hopane-type pentacyclic triterpanes are abundant in the samples,which demonstrate that organic matter in the manganese deposits originate from algae and microbes. 5.Homogenization temperature of primary quartz inclusions in the ores is 194℃,while the temperature deduced by the bitumen reflectance (2.5% to 4.0%)is 170 to 195℃,which indicate that the living temperature of microbes in the hydrothermal system of Songtao manganese deposits is higher than that of contemporary geothermal field,and lower than that of contemporary sea floor hydrothermal system.