...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >~(226)Ra in marine barite: new constraints on supported ~(226)Ra
【24h】

~(226)Ra in marine barite: new constraints on supported ~(226)Ra

机译：海洋重晶石中的〜（226）Ra：支撑〜（226）Ra的新约束

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Following the pioneering work of Paytan et al. [A. Paytan et al., Geochim. Cosmochim. Acta 60 (1996) 4313-4319], new investigations have been undertaken on marine barite separated from central and western equatorial Pacific sediments. These investigations are designed to achieve a better quantification of supported ~(226)Ra activities in the separated samples, enabling the use of excess ~(226)Ra(~(226)Ra_(ex)) in marine barite as a tool for dating Holocene sediments. Instrumental neutron activation analysis allowed first to measure significant ~(238)U activities in the separated samples, attributable to highly insoluble minerals that, like barite, are resistant to the chemical treatment used in this study (TiO_2 minerals, zircon, monazite). Within these U-rich minerals. ~(226)Ra activities are in secular equilibrium with ~(238)U. Second, the study of the ~(226)Ra signal in old barite samples that do not contain any residual ~(226)Ra_(ex) activities provided accurate constraints on the amount of ~(226)Ra produced by unsupported ~(230)Th: the remaining ~(226)Ra activities (corrected for the ~(238)U contribution) appeared to decrease with depth with a slope comparable to that defined by the bulk ~(230)Th_(ex) activities. The consistency of this deep trend allowed its extrapolation upwards to the sediment top in order to obtain an estimate of the ~(226)Ra activities produced by unsupported ~(230)Th in the Holocene barite samples. The total correction for supported ~(226)Ra in the Holocene barite samples used in this study therefore consists of the sum of ~(226)Ra activities in secular equilibrium with ~(238)U within minerals and ~(226)Ra activities produced by unsupported ~(230)Th thus estimated. The resulting correction is low for samples separated from central equatorial Pacific sediments compared with both the total ~(226)Ra activities measured in barite and results of previous studies. The magnitude of the correction is nevertheless higher for samples from western equatorial Pacific sediments, which display a lower barite purity. The corrected ~(226)Ra-in barite profiles are in agreement with the general trend observed for long half-life radionuclides with a similar mixed layer in the sediment top, thus adding confidence in the use of this tool. Below the mixed layer, the exponential decay of ~(226)Ra_(ex) activities in barite allowed the determination of sedimentation rates that agree with the estimates for the two investigated sites. Ultimately, one of the main uses for the ~(226)Ra-in barite dating method will be its application to Holocene sediments from the Southern Ocean where dating is often problematic.
机译：继Paytan等人的开拓性工作之后。 [一种。 Paytan等，Geochim。宇宙猫Acta 60（1996）4313-4319]，对从赤道中部和西部赤道太平洋沉积物分离出的海洋重晶石进行了新的研究。这些研究旨在更好地量化分离样品中支持的〜（226）Ra活性，从而可以在海洋重晶石中使用过量的〜（226）Ra（〜（226）Ra_（ex））作为测年工具全新世沉积物。仪器中子活化分析首先允许测量分离样品中的〜（238）U活性，这归因于高度不溶的矿物（如重晶石）对本研究中使用的化学处理具有抵抗力（TiO_2矿物，锆石，独居石）。这些富含U的矿物质。 〜（226）Ra活性与〜（238）U处于长期平衡。其次，对不包含任何残留〜（226）Ra_（ex）活性的旧重晶石样品中〜（226）Ra信号的研究，对不受支持的〜（230）产生的〜（226）Ra的数量提供了准确的限制。 Th：剩余的〜（226）Ra活性（已校正〜（238）U的贡献）似乎随深度降低，其斜率与总体〜（230）Th_（ex）活性所定义的斜率相当。这种深部趋势的一致性使得其向上外推至沉积物顶部，从而获得了全新世重晶石样品中无支撑〜（230）Th产生的〜（226）Ra活性的估算值。因此，在这项研究中使用的全新世重晶石样品中支持的〜（226）Ra的总校正量包括长期平衡中〜（226）Ra活性与矿物中的〜（238）U和产生的〜（226）Ra活性之和。由不受支持的〜（230）Th估算。与重晶石中测得的总〜（226）Ra活度和先前研究的结果相比，从赤道中部太平洋赤道沉积物分离出的样品所得到的校正值较低。尽管如此，来自赤道西太平洋沉积物的样品的校正量更高，而重晶石的纯度较低。校正后的〜（226）Ra-In重晶石剖面与沉积物顶部具有相似混合层的长半衰期放射性核素的总体趋势一致，因此增加了使用此工具的信心。在混合层之下，重晶石中〜（226）Ra_（ex）活性的指数衰减允许确定沉降速率，该速率与两个调查地点的估计值一致。最终，〜（226）Ra-in重晶石测年法的主要用途之一是将其应用于来自南大洋的全新世沉积物中，那里的测年常常是有问题的。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号