Applications of geochemistry to igneous petrology

我们所有人都感兴趣和重要的问题是海洋、大陆、大气和地球内部是如何形成的，以及这些地球系统今天是如何运作和相互作用的。答案影响着我们对当今气候、人类对大气和海洋的影响以及在哪里寻找维持社会的资源的理解。一个问题是，地球最大的部分，地幔(地球内部)，是无法到达的，我们对它的了解很差。我的研究使用玄武岩熔岩流来研究地球内部。玄武岩是地球上最常见的岩石，它们是由于地幔熔融而形成的。对大洋盆地玄武岩的研究告诉我们，有不同类型的地幔。例如，其中一种显然含有从其中提取的钾和硅等元素，形成了数十亿年前的大陆。其他类型的岩石可能含有曾经在地球表面的“回收”岩石。大陆之下的地幔岩石似乎具有不同寻常的成分，使它们成为大多数钻石的来源。一个重要的问题是，地幔的类型是如何形成的，因为它们将包含地球海洋、大陆和大气如何演化的记录。通过比较来自大洋盆地和大陆的不同“玄武岩”中元素的浓度，就有可能回答这些问题。然而，这种比较并不容易。例如，当熔融的玄武岩结晶形成矿物时，不同的元素进入不同的矿物。有些矿物形成得早，有些形成得晚。结果是玄武岩的成分随着元素的耗尽而发生变化。这个过程被称为“分化”。尽管这使地球内部的研究变得复杂，但这些过程可能会导致矿藏，因为形成的一些矿物含有丰富的镍、铬、铂和其他有价值的元素。总而言之，这项研究对人类有很大的兴趣，因为玄武岩对于理解地球的演化很重要。然而，这项工作也具有经济意义。这可能有助于解释为什么一些矿藏(例如钻石和铂)会出现在它们所在的地方，或者指向有助于发现新矿藏的化学测试。

Questions of interest and importance to us all are how did the oceans, continents, atmosphere and interior of the Earth form, and how do these Earth systems operate and interact today. Answers affect our understanding of present-day climate, human impacts on the atmosphere and ocean, and where to look for resources that sustain society. A problem is that the largest part of the Earth, the mantle (interior of Earth), is inaccessible and our understanding of it is poor. My research uses basalt lava flows to study the interior of the Earth. Basalts are the most common rocks on Earth and they form due to melting of the mantle. Studies of basalts from the ocean basins tell us that there are different types of mantle. For example, one type apparently had elements such as potassium and silicon extracted from it to form the continents billions of years ago. Other types may contain "recycled" rocks that were once at the Earth's surface. Mantle rocks beneath the continents appear to have unusual compositions that make them the source of most diamonds. An important question is how the types of mantle formed because they will contain a record of how the planet's oceans, continents and atmosphere evolved. By comparing the concentrations of elements in different "basalts" from the ocean basins and continents, it will be possible to answer these questions. However, the comparisons are not easy. For example, when molten basalt crystallizes to form minerals, different elements enter different minerals. Some minerals form early and some form late. The result is that the composition of a basalt changes as elements get used up. This process is called "differentiation". Although this complicates studying the interior of the Earth, these processes can lead to ore deposits because some minerals that form are rich in nickel, chromium, platinum and other valuable elements. In summary, the research is of substantial human interest because basalts are important to understanding the evolution of the Earth. However, the work also has economic implications. It may help explain why some ore deposits (e.g. diamonds and platinum) occur where they do, or point to chemical tests that assist in discovering new deposits.