Effects of pressure on the structure of lizardite-1T

The crystal structure of lizardite-1T has been studied in a range of P conditions, using crystals with different compositions. Two structure refinements have been performed, at 7 and 12.5 kbar. The highly anisotropic compressibility is determined by reductions in interlayer thickness. The tetrahedral sheet shows increasing ditrigonalization with increased P and the octahedral site becomes progressively more distorted. In particular the O(4) inner hydroxyl moves away from the coordinating Mg which results in asymmetrical deformation of the T-O layer. Such a modified bond pattern may be relevant in explaining the stability fields of lizardite, talc and chlorite, which are signicantly different in spite of similar compositions and related structures.