论文部分内容阅读
利用放射化学中子活化分析和仪器中于活化分析方法,测定了我国陕西段家坡黄土剖面第三系-第四系(2.48 Ma)沉积界线附近黄土样品中铱和一些其它微量元素的丰度.在古地磁倒转界线处发现了铱的丰度异常,其最高含量为 58.5×10~(12)g/g,比其背景含量至少富集了10倍.除了铱和金之外,其它元素,特别是与火山活动密切相关的As和Sb等亲硫元素在界线附近并无富集.因此,铱异常的火山成因基本上可以排除.铱异常的出现与古地磁倒转事件(M/G)具有等时性.这表明第三系-第四系之交的古地磁倒转事件以及全球性的气候突变可能与这次地外撞击事件有着密切的成因联系.
The abundances of iridium and some other trace elements in loess samples near the sedimentary boundary of Tertiary-Quaternary (2.48 Ma) in the section of Loess of Shaanxi Duanjiapo, Shaanxi Province, China were determined by using radioactive neutron activation analysis and activation analysis. The abundance anomaly of iridium was found at the paleomagnetic reversal boundary with a maximum content of 58.5 × 10-12 g / g, at least 10 times more than its background content.In addition to iridium and gold, the other elements , Especially the sulfur-related elements such as As and Sb, which are closely related to volcanic activities, are not enriched in the vicinity of the boundary line. Therefore, the volcanic origin of anomalous iridium can be basically ruled out. The occurrence of anomalies of iridium and paleomagnetic reversal event (M / G) Isochronous, suggesting that the paleomagnetic reversal and the global climate change at the turn of the Tertiary-Quaternary might have a close causal relationship with this extra-continental collision.