西藏羌塘盆地及其东南周边地区放射性特征

Investigation of Radioactivity in Qiangtang Basin and Its Southeast Outside Area,Tibet

羌塘盆地地处青藏高原腹地,气候条件恶劣,是我国铀矿地质工作非常薄弱的地区。以野外放射性能谱测量数据和部分化学分析数据为基础,结合其他部门在该区的汽车能谱测量数据和少量区调数据,对羌塘盆地出露地层及其东南外围地区花岗岩的放射性特征进行了初步分析。分析结果表明:羌塘盆地中—上侏罗统雪山组、雀莫错组和夏里组铀含量较高,在盆地的东北斜坡带,它们的平均铀含量分别为4.12×10-6、4.06×10-6和3.68×10-6;在北羌塘坳陷,夏里组(J2x)的平均铀含量为7.75×10-6,索瓦组—雪山组(J3s-x)为5.93×10-6;北羌塘坳陷南部地层的平均U含量总体上要比北部地区高,而东北斜坡带的平均铀含量具有中北部偏高、南侧偏低的特点。这些信息为羌塘盆地铀成矿地质条件分析提供了重要的放射性依据。

Qiangtang basin is located in the middle of Qinghai-Tibet Plateau, where the weather is atrocious and the uranium geologic research was little. This paper primarily presented the radioactive characteristics about the strata in Qiangtang basin and the granite in southeast outside of basin based on the following data, radioactivity gamma-ray spectrum survey in field, some chemical analysis data of granite, car-borne gamma-ray spectrometry made by other geological department, and a few regional investigation material so on. Studies show that the Mid- dle and Upper Jurassic Xueshan Formation, Quemocuo Formation and Xiali Formation have fairly high uranium content, their average uranium content in the northeast slope zone are 4. 12 × 10^-6, 4. 06 × 10^-6 and 3.68 × 10^-6, respectively. In the northern Qiangtang depression, the average uranium content for Xiali Formation is 7.75 × 10 ^-6, and 5.93 × 10^- 6 for Suowa-Xueshan Formation. From the viewpoint of spatial variation, the average uranium content of strata in the south of northern Qiangtang depression is higher than that in the north. While in northeast slope zone, the average uranium content is characterized by high in the middle and the north, and low in the south. These data and analysis results in this paper can be served as the significant radioactive basis for analyzing the geological condition of uranium ore-formation in Qiangtang basin.