Acquisition of a Helix SFT Noble Gas Mass Spectrometer

这笔赠款支持继续创新和应用氦同位素地球化学技术，以解决地球科学问题。这笔赠款将用于购买一台新的氦同位素质谱仪，即使在非常少量的氦上也能进行精确和准确的氦同位素丰度测量。该仪器取代了已有数十年历史的前身，不需要对现有的从岩石和矿物中提取气体进行分析的硬件进行修改。该仪器将用于支持许多地球科学分支学科，并将成为多名本科生、研究生和博士后研究人员的主要工具。氦的两个同位素3He和4He提供了丰富的陆地岩石起源和历史信息。岩石中的氦几乎完全来自U和Th元素的衰变。4He在矿物中的积累允许一种独特的计时形式。由于他在埋藏到地壳几公里深的高温下从矿物中扩散出来，矿物中积累的4He可以用来确定岩石是何时被侵蚀或断层带到地球表面的。这些数据为关键的地质过程提供了重要的见解，例如造山的时间和原因。3岩石和矿物中的氦可能来自更不寻常的来源。例如，当宇宙射线与地壳最高约2米处组成矿物的元素相互作用时，就会产生3He。这也是一个计时器，但也是一个计时器，可以用来测量侵蚀速度，也可以确定岩石第一次暴露在地表的时间。后一种技术是建立冰川历史和米兰科维奇驱动的过去数万年气候变化的核心工具之一。在海洋沉积物中，3He来自宇宙尘埃的积累。通过测量海洋沉积物序列中的3He浓度，有可能确定沉积速率(时间的另一个关键指标)，在某些情况下，还可以识别产生宇宙尘埃的重大事件，如许多公里大小的小行星罕见的破坏性碰撞。这一奖项反映了美国国家科学基金会的法定任务，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This grant supports continued innovation and application of techniques of He isotope geochemistry to address Earth science problems. The grant will be used to purchase a new He isotope mass spectrometer capable of making precise and accurate He isotope abundance measurements even on very small quantities of helium. The instrument replaces a decades-old predecessor and requires no modification to the existing hardware for extracting gases from rocks and minerals for analysis. This instrument will be used in support of many Earth science subdisciplines and will be the main tool used by multiple undergraduate and graduate students and postdoctoral investigators in their studies.The two isotopes of He, 3He and 4He, provide a wealth of information on the origin and history of terrestrial rocks. 4He in rocks is almost exclusively derived from α-decay of the elements U and Th. Accumulation of 4He in minerals allows a unique form of chronometry. Because He diffuses out of minerals at elevated temperatures characteristic of burial to a few km depth in the crust, the accumulated 4He in minerals can be used to determine when rocks were brought to the Earth's surface by erosion or faulting. Such data provide important insights to key geologic processes such as the timing and causes of mountain building. 3He in rocks and minerals can come from more unusual sources. For example, 3He is produced when cosmic rays interact with the elements that make up minerals in the uppermost ~ 2 meters of the crust. This too acts as a chronometer, but a chronometer that can be used to measure erosion rates and also to establish when rocks first became exposed at the surface. The latter technique is one of the central tools in establishing the glaciation history and Milankovitch-driven climate change over the last few tens of thousands of years. In marine sediments, 3He is derived from the accumulation of cosmic dust. By measuring 3He concentrations in sequences of marine sediments it is possible to establish sedimentation rates (another key indicator of time) and, in some cases, to identify major cosmic-dust producing events such as the rare destructive collision of many-km-sized asteroids.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.