Continued Development and Application of 40Ar/39Ar Dating for Archaeometric Research

考古研究中 40Ar/39Ar 测年的持续开发和应用

• 批准号: 0211172
• 负责人: Alan Deino
• 金额: $ 26.95万
• 依托单位: Berkeley Geochronology Center
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0211172&HistoricalAwards=false
• 关键词: Continued; Development; Application; 40Ar; 39Ar

Argon dating is extremely important to paleoanthropologists because it can be used over almost the entire last 6 million years; this is the period when hominids emerged and developed. Many significant archaeological and paleontological sites are located in volcanic regions such as Eastern Africa and contain strata which can be dated by this technique. With National Science Foundation support the Berkeley Geochronology Center (BGC) will continue to develop the technique of 40Ar/39Ar dating and apply this technique to a series of significant paleoanthropological sites. The BGC has collaborated with researchers at a number of sites in Africa, Europe and Asia, and with NSF support such projects will be continued and expanded.The 40Ar/39Ar dating method is based on the radiometric decay of a fraction of natural potassium in geologic materials over time. The products of the decay include 40Ar, which remains trapped in certain types of geologic materials, such as crystals within volcanic rocks. Measurement of the amount of 40Ar that has accumulated in a rock or mineral, combined with knowledge of the material's potassium content, yields the age of crystallization. In 40Ar/39Ar dating, the material to be dated is irradiated in the core of a nuclear reactor for minutes to days, in order to transmute some of the potassium to an artificial isotope of argon. Then, both the artificial isotope, which stands in for potassium, and the radiogenically produced argon, can be measured at the same time in a highly sensitive and accurate mass spectrometer.The facilities at BGC include three fully automated dating systems, each of which is capable of dating anywhere from a single small crystal of geological material weighing less than a milligram, to hundreds of milligrams, by the 40Ar/39Ar method.As in the past, Archaeometry support will be vital both to maintaining routine availability of 40Ar/39Ar dating for the archeological and paleoanthropological communities, as well as advancing the capabilities of 40Ar/39Ar dating methods. Though routine in many regards, evolving technology permits continued improvements in the method's capabilities,. Such improvements pay large scientific dividends by expanding the scope of problems that can be solved. The principal motivations for this development effort are to: 1) sustain routine access to high-quality 40Ar/39Ar data for archeological and paleoanthropological research worldwide; 2) continue refinement of 40Ar/39Ar methods to improve precision and accuracy, particularly in dating younger, smaller, or less potassic materials, and 3) replace or augment old equipment to maintain high levels of productivity and scientific excellence.Grant funding will be focused primarily in three areas: 1) replacement of a Nd-YAG with a CO2 laser for heating geological materials on one of our Argon extraction lines, 2) installation of a robust UPS power supply that will permit uninterrupted lab operation in the face of increasingly frequent power outages, and 3) modernization of the computer control systems on our automated extraction line/mass spectrometer combinations. The benefits of converting to a CO2-laser based heating system are derived primarily from an ability to incrementally heat large amounts of feldspar with a broad laser beam with uniform energy profile, while accruing the benefits of extraction-line blanks that are many times lower than the conventional resistance-furnace heating device currently in use. Enabling the laboratory to weather short power outages ( 1hr in duration) will provide for continued efficient operation of three extraction lines while protecting equipment from the occasionally devastating effects of sudden power loss. Modernization of the computer control systems is necessitated by obsolescence of software and hardware components, and is essential if innovation is to continue.

对于古人类学家而言，氩约会非常重要，因为它可以在过去的600万年中使用。这是人类出现和发展的时期。许多重要的考古和古生物学地点位于东非东部等火山区域，并包含该技术日期的地层。借助国家科学基金会支持伯克利年代学中心（BGC）将继续开发40AR/39AR约会的技术，并将此技术应用于一系列重要的古人类学遗址。 BGC已与非洲，欧洲和亚洲的许多地点的研究人员合作，并在NSF支持的情况下继续进行和扩展。40AR/39AR约会方法基于随着时间的推移，地质材料中天然钾的一小部分的放射测定衰减。衰减的产物包括40AR，它仍然被困在某些类型的地质材料中，例如火山岩中的晶体。在岩石或矿物质中积累的40AR量的测量，结合材料的钾含量的知识，得出结晶的年龄。在40AR/39AR约会中，要注明日期的材料在核反应堆的核心中被照射几分钟到几天，以将一些钾转移到人工同位素上。然后，可以同时在高度敏感和准确的质谱仪中同时测量钾的人造同位素和放射原生成的氩的生产。BGC的设施包括三个完全自动化的约会系统，每种设施都可以通过少于30毫克的地质材料来约会的任何一种，每种材料都可以约会到任何地方。过去，考古学支持对于维持考古和古人类学社区的40AR/39AR约会的常规可用性至关重要，并且可以推进40AR/39AR约会方法的能力。尽管在许多方面是常规的，但不断发展的技术允许该方法的能力持续改进。 这样的改进通过扩大可以解决的问题范围来支付大量科学股息。这项发展工作的主要动机是：1）常规获取全球考古和古人类学研究的高质量40AR/39AR数据； 2) continue refinement of 40Ar/39Ar methods to improve precision and accuracy, particularly in dating younger, smaller, or less potassic materials, and 3) replace or augment old equipment to maintain high levels of productivity and scientific excellence.Grant funding will be focused primarily in three areas: 1) replacement of a Nd-YAG with a CO2 laser for heating geological materials on one of our Argon extraction lines, 2) installation of a robust UPS面对越来越频繁的停电，将允许不间断的实验室操作，以及3）在自动提取线/质谱仪组合中对计算机控制系统的现代化。转换为基于CO2激光的加热系统的好处主要来自具有具有均匀能量曲线的宽宽激光束的逐步加热大量长石的能力，同时又具有比当前使用的常规抵抗力燃料供暖设备低很多倍的萃取线空白的好处。使实验室能够到达短暂的停电（持续时间为1小时），将提供三个提取线的持续有效操作，同时保护设备免受偶尔突然损失的毁灭性影响。计算机控制系统的现代化是必须通过软件和硬件组件的过时来实现的，如果要继续创新，则至关重要。