白云鄂博群同位素地质年代学研究

A STUDY ON ISOTOPE CHRONOLOGY OF THE BAYAN OBO GROUP

铅同位素分析结果表明,白云鄂博群的物质来源始于1310Ma,矿化时间为665Ma。底部尖山组Rb—sr等时年龄为749.6±62.11Ma、753.99±42.28Ma、685.91±24.12Ma。其上比鲁特组K—Ar年龄为607.9Ma,以上可划归震旦纪地层。胡吉尔图组及上部地层具有353±30Ma的Rb—Sr等时年龄、200Ma左右的K—Ar年龄,应划归古生代。白云鄂博群之上的志留纪地屠Rb—Sr等时年龄分别为327±36Ma、314.29±28Ma及260±11Ma。

The results of lead isotope analysis indicate that the materials of the Bayan Obo Group originated at 1314 Ma B. P. and that the mineralization occurred at 6650 Ma B.P. The Jianshan Formation at the base of the group has Rb-Sr isochron ages of 749.6±62.11 Ma, 753.99±42.28 Ma and 685.91± 24.12 Ma. The Bilute Formation above it has a K-Ar age of 607.9 Ma. The two Formations may be assigned ot the Sinian. The Hujiltu Formation and the strataabove it have a Rb-Sr isochron age of 353±30 Ma and a K-Ar age of about200 Ma, so should be assigned to the pateozoic. The Pb-Sr isochron ages of the Silurian strata overlying the Bayan Obo Group are 327±36Ma, 314.29±28Ma and 260±11 Ma respectively.