Abstract:

Wulagen zinclead deposit in Xinjiang Province is located in north margin of Kashi sag. Large quantity of organic matter exists in the mining area and the periphery of Wulagen zinclead deposit, and the relationship between organic matter and zinclead mineralization has attracted the attention. By the organic extraction, family components separation and quantitative, saturated hydrocarbons chromatogrammass spectrum, the chloroform bitumen “A” and biomarkers were analyzed, and the characteristics of the organic matter and its geological significances and the relationship between organic matter and zinclead mineralization were discussed. The chloroform bitumen“A” family components and main eigenvalues of biomarkers in the wallrocks and the periphery of Wulagen zinclead deposit have a similar and smaller variational range (CPI=1.111.17; Pr/Ph=0.681.08; C27, C28 and C29 sterane has a pattern of C27>C28<C29; steranes/17α(H)hopanes=0.550.93; C29/C30 hopanes=0.360.52), indicating that the organic matter have the same nature and origin, and the organic matter were derived mainly from continental shale. The features of biomarkers (OEP=1.011.15; C31αβhopane 22S/(22S+22R)=0.560.58; βαMO alkyl/αβhopane=0.130.21) show a high maturity of the organic matter in the mining area and the periphery of Wulagen zinclead deposit. The Pr/Ph ratio of the samples were low (<0.85) and all samples were detected having a certain amount of gammacerane, indicating that organic matter has undergone a high salinity and reduction conditions. The “hump” phenomenon of gas chromatography baseline of saturated hydrocarbons is not obvious, suggesting that the organic matter biodegradation effect was weaker. Combining these with the characteristics of geology, petrography, mineragraphy and geochemistry of the mining area, it is suggested that the oreforming fluids was the basin oilfield brine, which contained organic matter with reduction fluid and thus made the fifth member of LowerCretaceous Kezilesu Group purple rock faded. Because the hydrocarbons of organic matter in oreforming fluids reacted with SO2-4 to produce H2S, the H2S generation was the main cause of the lead and zinc precipitation and mineralization.

Key words:  biomarkers, chloroform bitumen “A”, organic matter, Wulagen zinclead deposit, Kashi sag, Xinjiang