Understanding lower temperature natural systems using stable isotopes

氧、氢、碳和氮是构成地球大气、生物圈、水圈和岩石圈的最丰富的元素。每一种元素的原子都以两种或三种形式自然存在——被称为稳定同位素。它们在岩石、矿物、水、植物和动物中的相对丰度（例如，氧-18 vs氧-16、碳-13 vs碳-12、氮-15 vs氮-14、氢-2 vs氢-1）取决于元素的来源（淡水、海水、大气、生物圈、浅层或深层地球）和每种物质形成的条件（温度、干旱、光合作用途径、饮食）。我研究的目的是提高我们测量地球物质中稳定同位素组成的能力，并根据产生它们的过程来解释这些比率。你会问，目的是什么？一方面，我们正在利用岩石和矿物的稳定同位素组成来确定席卷地壳的流体的来源和类型，这些流体覆盖了一大片非常古老（7.6亿至5.1亿年）的岩石，现在包括新不伦瑞克、新斯科舍省大陆、布雷顿角岛、纽芬兰和马萨诸塞州的部分地区。我们的目标是了解岩石和热水之间这种大规模相互作用的原因和时间，以及它对经济矿床的创造或破坏的后果。另一方面，我们正在利用淡水、植物组织（有机物）、贝壳动物群、牙齿和骨骼（如猛犸象和乳齿象）的同位素组成中捕获的环境条件特征来跟踪气候/生态系统条件随时间的变化。古代土壤和沉积物中含有许多可以确定年代的代用物质。一个直接的目标是确定最后一个冰河时代末期五大湖地区冰川融水的路径。一个更长远的目标是增加我们对过去~ 15000年北美气候条件的了解。更好地了解这个现在人口稠密的大陆中部地区过去的气候变化速度，将有助于更好地预测其未来的行为。

Oxygen, hydrogen, carbon and nitrogen are among the most abundant elements making up Earth's atmosphere, biosphere, hydrosphere and lithosphere. The atoms of each of these elements occur naturally in two or three forms - known as stable isotopes. Their relative abundances (e.g., oxygen-18 vs. oxygen-16, carbon-13 vs. carbon-12, nitrogen-15 vs. nitrogen-14, and hydrogen-2 vs. hydrogen-1) in rocks, minerals, water, plants and animals are determined by the source of the element (freshwater, seawater, atmosphere, biosphere, shallow or deep Earth) and the conditions (temperature, aridity, photosynthetic pathway, diet) under which each substance developed. The objective of my research is to improve our ability to measure stable isotopic compositions in Earth materials, and to interpret these ratios in terms of the processes that created them. To what purpose, you ask? On one hand, we are using the stable isotopic compositions of rocks and minerals to identify the sources and types of fluids that swept through Earth's crust over a vast area of very old (760 - 510 million years) rocks now comprising parts of New Brunswick, mainland Nova Scotia, Cape Breton Island, Newfoundland and Massachusetts. Our goal is to learn the cause and timing of this large-scale interaction between rock and hot water, and its consequences for creation or destruction of economic mineral deposits. On the other hand, we are using the signatures of environmental conditions captured in the isotopic compositions of freshwater, plant tissues (organic matter), shelly fauna, and teeth and bones (e.g., mammoths and mastodons) to track changing climatic/ecosystem conditions over time. Ancient soils and sediments contain many such proxy materials, which can be dated. An immediate goal is to determine the pathways of glacial meltwater in the Great Lakes region at the end of the last Ice Age. A longer range objective is to increase our understanding of North American climatic conditions over the last ~15,000 years. Better understanding of the rate of past climate change in this now heavily populated mid-continental region should lead to better predictive capabilities for its future behaviour.