Effects of pressure on the structure of lizardite-1T
Mellini, Marcello; Zanazzi, Pier Francesco
published: Mar 21, 1989
ArtNo. ESP147050101005, Price: 29.00 €
Abstract The crystal structure of lizardite-1T has been studied under a range of pressure conditions, using crystals with different compositions. The unit cell parameters range from a = 5.335(5), c = 7.243(5) A at 1 bar pressure up to a = 5.305(5), c = 7.045(5) Å at 19 kbar. The bulk modulus is 570 kbar. Two structure refinements have been performed, at 7 and 12.5 kbar, respectively. The highly anisotropic compressibility is determined by reductions in interlayer thickness. The tetrahedral sheet shows slightly increasing ditrigonalization with increased pressure and the octahedral site becomes progressively more distorted. In particular the O(4) inner hydroxyl moves away from the coordinating magnesium. This increasing distance 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 significantly different in spite of similar compositions and related structures.