Preface to the special issue:'Protons in Minerals'

摘要

Many minerals contain water, primarily in the form of molecular H_2O or as hydroxyl OH groups. The bonding characteristics of H can influence properties, such as electrical conductivity, compressibility and, in a wider context, mineral stability as a function of pressure, temperature and composition. Of particular interest geologically is the ability of mantle minerals to act as a significant reservoir for water. Over the past three decades a new picture has emerged of the distribution of water (H_2O and OH) in the Earth. The main water budget is no longer found to be restricted to the oceans and atmosphere, but is likely to be concentrated in the Earth's mantle. Water is exchanged between the Earth's surface and deep interior via the formation and breakdown of hydrous minerals. Subduction zones are considered to be key sites in the global recycling of water. It has been found that nominally-anhydrous minerals (NAMs) such as garnet, ringwoodite and wadsleyite can also incorporate minor but potentially very significant amounts of water as structural OH defects. The characterization of these OH structural environments and recognition of the key factors controlling their occurrence continues to be an important research area in Earth sciences. This issue of Mineralogical Magazine arose from a meeting on 'Proton-mediated interactions in minerals' held by The Mineral Physics Group of the Mineralogical Society of Great Britain and Ireland at the University of Manchester in September 2004. The collection of ten papers provides a timely update on our current understanding of the crystal-chemical details of hydrogen incorporation into hydrous and nominally-anhydrous minerals and its influence on their physical and chemical properties. The experimental techniques used here to characterize H environments, behaviour and effects upon physical properties include infrared and Raman spectroscopy, neutron diffraction and X-ray diffraction.