Development of the Radiogenic Helium Thermochronometer for Study of Landscape Evolution and Geomorphic Process in Active and Extinct Mountain Systems

9906357 Spotila这笔赠款为弗吉尼亚理工大学地质科学系购买和建造一个测量放射性成因氦年龄(U-Th/He)的设施提供匹配支持。氦热计时是一种新开发的强大工具，当冷却岩石在地壳上部几公里处上升时，它会限制它们的体验。年龄是通过测量小等分磷灰石上的放射性成因氦和铀/钍母体同位素来确定的。由于氦在磷灰石中的高扩散性，该热计时仪对温度比其他技术(如磷灰石裂变径迹测年)更低，并提供了对岩石抬升和折返的速度和幅度的定量控制。因此，它对地形演变、造山和其他地表过程的问题提供了有价值的约束。氦测年可能成为新构造学家和地貌学家的首要工具，氦年龄将成为任何与剥蚀和地形构造有关的研究的标准。这笔赠款将用于建造一条带有四极质谱仪的高真空萃取线，用于分析矿物分离物中的氦含量。由于这项技术相对较新，这样的设施不能直接购买，必须定制。用同位素稀释法测量母体同位素(U，Th)已经可以用弗吉尼亚理工大学的现有设施进行。氦测年技术将是弗吉尼亚理工大学新增加的P.I.Spotila应用的主要活动之一。它将在未来几年应用于地貌演化的三个主要项目，包括阿拉斯加的丘加赫/圣伊利亚斯山脉(活动造山带)和阿巴拉契亚山脉(灭绝的造山带)的研究。该约会设施将是该国为数不多的几个约会设施之一，将促进地区和国际层面的合作。它也将成为众多研究生和本科生研究项目的基础。***

9906357SpotilaThis grant provides matching support for acquisition and construction of a facility for measuring radiogenic helium ages (U-Th/He) in the Department of Geological Sciences at Virginia Tech. Helium thermochronometry is a powerful, newly-developed tool that constrains the cooling rocks experience as they rise through the upper few kilometers of crust. Ages are determined by measuring radiogenic helium and uranium/thorium parent isotopes on small aliquots of apatite. Because of the high diffusivity of helium in apatite, this thermochronometer is sensitive to temperatures lower than other techniques (e.g. apatite fission track dating) and provides quantitative control on rates and magnitude of rock uplift and exhumation. It is thus provides valuable constraints on problems of landform evolution, mountain building, and other surface processes. Helium dating may become the premier tool of the neotectonicist and geomorphologist, with helium ages becoming standard for any study to which denudation and topographic construction relate. The grant will enable construction of a high-vacuum extraction line with a quadrupole mass spectrometer for the analysis of helium content in mineral separates. Because this technique is relatively new, such a facility cannot be directly purchased and must be custom built. Measurement of parent isotopes (U, Th) by isotope dilution can already be made with existing facilities at Virginia Tech. The helium dating technique will be one of the main activities applied by the P.I., J.A. Spotila, a new addition to the faculty at Virginia Tech. It will be applied to three major projects of landform evolution in the next several years, including studies of the Chugach/St. Elias Range in Alaska (active orogen) and the Appalachians (extinct orogen). The dating facility will be one of only a few in the nation and will stimulate collaboration at both the regional and international level. It will also be the basis of numerous graduate and undergraduate research projects. ***