High pressure, down under: the first Australian high-pressure synchrotron facility for geoscience research

Abstract

Because the deep Earth is not directly accessible, geoscientists rely on laboratory experiments and computer models in order to understand the properties of minerals at the extreme pressure and temperature conditions of deep crust, the mantle and the core. In the field of high-pressure mineral physics and chemistry, we use our understanding of mineral properties, stress–strain relationships in multiphase rocks, and processes such as partial melting at high pressures and temperatures, to interpret geophysical observations of the deep Earth. Studies have constrained the pressure sensitivity of deformation of minerals such as olivine under subduction zone conditions, and the effect of pressure on slip systems in high-pressure minerals such as wadsleyite and perovskite. These results have important implications for the variation of mantle viscosity with depth, the geodynamic interpretation of seismic anisotropy, and changes in mantle rheology as a function of composition. However, the rheology and dynamics of the deep Earth are still poorly understood. Fortunately, technical development has been undertaken over the past 10 years in the USA, and scientific advances have been helped by the development of high-P–T deformation apparatus, such as the large volume multi-anvil deformation apparatus known as the D-DIA. This has opened up the possibility of determining physical and chemical processes in the upper mantle, and into the mantle transition zone. To participate in this exciting new area of research, we are now developing a high-pressure facility at the Australian Synchrotron. In this overview paper, we describe the background and current research that is being conducted in other synchrotron high-pressure facilities and what will now be possible for the Australian Synchrotron.

由于不能直接到达地球深部，地质学家依靠实验室实验和计算机模拟来了解地壳深部、地幔和地核极高温高压条件下的矿物性质。在高压矿物物理和化学领域，我们运用对矿物特征、多相岩石的应力应变关系以及诸如高压和高温部分熔融的过程的理解，来解释地球深部地球物理特征。研究制约了矿物质如俯冲带条件下橄榄石变形的压力敏感度，以及压力对高压矿物如瓦兹利石和钙钛矿的作用。这些结果对地幔粘度随深度的变化、地震各向异性的地球动力学解释和地幔流变性随组成的变化而变化具有重要的意义。然而，地球深部的流变性和动力学仍然知之甚少。幸运的是，近10年来在美国技术高度发展，研制出的高PT变形装置，如被称为D-DIA的大体积多砧变形装置，有助于科学的进步。这提供了确定上地幔中及地幔过渡带中的物理和化学作用的可能性。为了加入这个激动人心的新研究领域，我们现在正于澳大利亚同步加速器部开发高压设施。在这篇概述性文章中，我们描述了在其它同步高压设备处进行的研究和背景，以及澳大利亚同步加速器的未来。

KEY WORDS:

• Australian Synchrotron
• D-DIA
• high-pressure experiments
• rheology
• mineral physics
• upper mantle

ACKNOWLEDGEMENTS

This material is based upon work supported in part by the ARC Linkage Equipment and Infrastructure Facilities ARC Discovery Project 0986232 to Rushmer. All authors wish to acknowledge the support of Macquarie University DVCR Discretionary Funds.