利用LIBS原位测定熔/流体系在地幔部分熔融条件下的元素分配

Mantle geochemistry is a interdiscipline discussing Earth's deep structure, composition and dynamic, studying the elements cycling in crust and mantle. Elemental behavior in melt/fluid coexisting system is an important object of mantle geochemistry studying. In-situ geochemical experiment is the most direct research approach. The results of in-situ experiments can be used to build the geochemical models which could be applied to explain the variety of igneous rocks and inclusions. However, so far there is no satisfactory test approach . This project arises a new method to combine Laser-induced breakdown spectroscopy (LIBS) with Diamond anvil cell (cell). The method could realize low cost, in-situ , quickly and accuratly testing of multiple elements in the condition of high temperature and high pressure. The results of fixed point, one-dimensional points and two-dimentional points could reveal elemental partitioning, transporting and exchanging in melt/fluid system. Elemental behaviour in the condition of high temperature and high pressure could be built as a model. The combination of LIBS and DAC could promote the development of experimental geochemistry under extreme environment, especially in the realms of subduction zone geochemistry, oceanic rocks cycling, metamorphic rock evolutions.

地幔地球化学是探讨地球深部化学结构、组成及动力学，反映壳-幔旋回的交叉学科，其中熔/流共存体系中的元素分配行为是地幔地球化学的重要研究对象。原位地球化学实验是最直观的研究手段，其观察结果可以用来构建地球化学模型，并用来解释观察到的地表岩石和各种包裹体。但是，至今为止尚没有令人满意的测试手段。本项目提出并发展一种将激光诱导击穿光谱（LIBS）与金刚石压腔（DAC）技术相结合的新方法，在实验室中实现原位对高温高压环境中样品的低成本、原位、快速、准确的多种元素检测。元素的定点分析、一维扩散研究和二维空间分布将揭示熔/流共存体系中元素的分配、输送和交换行为。实验结果将用于构建高温高压环境下的元素的化学行为模型。LIBS与金刚石压腔的联用，将会推动极端环境实验地球化学的发展，在俯冲带地球化学研究、大洋岩石旋回、高温高压变质岩演化等领域具有重要的应用前景。

为了实现可用于DAC高温高压系统原位检测元素和化合物含量的系统，本研究设计了部分重叠的双纳秒激光束实现光路，通过实验和数值模拟结果，证明了新型光路可以有效的缩小激光烧蚀面积。实验证明，该新型光路可以与密闭腔体耦合使用，有效提高元素检测的空间分辨率，在DAC等极小密闭腔体内，有利于获得一维、甚至是二维的元素空间分布。搭建了LIBS与拉曼复合二维扫描检测系统，可将其与部分重叠的双纳秒激光束实现光路耦合，达到高温高压下同时开展矿物与元素检测的目的。项目研究过程中拓展了LIBS元素检测的应用场景，如获得了微量纳米量子点中卤素阴离子的含量、光热治疗后生物体内残留纳米粒子含量、远程获取岩石矿物类型和微量元素分布。以上实验结果，证明了本项目光学系统可以用于进行熔/流共存体系中阴、阳离子和化合物的复合检测。