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11.
在一定量的[F eC l4]-的存在下,以磷酸三丁酯(俗名TBP)萃取,然后用K I—HC l反萃取,进行富集分离铱(Ir)的实验研究。确定了萃取和反萃取的条件,考查了多种共存元素的分离情况,并在此基础上,制定了岩石矿物中超微量铱的简便、快速的测定方法。在拟定的条件下,铱的检测下限为0.005ng/mL。并对两个w(Ir)值分别为0.27×1-0 6和0.05×10-6的标准地质样品进行了9次测定。其相对标准偏差(R.S.D)为9.4%和7.5%。因此,该方法适用于岩石矿物中超微量铱的测定。 相似文献
12.
Two large asteroids struck Earth at almost the same time, 65 million years ago, causing the major extinctions recognized as ending the Mesozoic Era. Although occurring close together in time, the Earth's magnetic pole had moved from the South Pole to the North Pole in between, allowing a time difference between the impacts to be calculated. The first strike produced a ∼180 km diameter crater named Chicxulub on the Yucatan shelf of southern Mexico. The second hit the shelf of the northward drifting Indian continent in the southern Indian Ocean, producing a crater ∼450 × 600 km named Shiva. Hitherto, the main obstacle to verifying this scenario has been the paucity of geological sections containing evidence of both impacts. Here, we present such evidence, and conclude that the two impacts were separated by about 40,000 years. 相似文献