Domain structures in rutile in ultrahigh-pressure metamorphic rocks from Dabie Mountains, China

According to the HRTEM study, the UHP jadeite-quartzite mineral (Rutile, TiO2) in Anhui Province, Dabie Mountains, China, has ultrastructures such as <011> two-dimensional commensurable modulated structures or superstructures, {011} twin domain structures, dislocations and crystal deformations. The SAED patterns and HRTEM images indicate the existence of the deformations and stacking faults on the interface of {011} twin crystal of rutile and its two-dimensional commensurate modulated structures with repetition period 0.753 nm (3d(011)) has tetragonal symmetry, cell parameters a = 3a(0) = 1.377 nm (a(0) = 0.459 nm), c = c(0) = 0.3 nm. The modulated structures of rutile were probably caused by the isomorphic replacement of Ti4+ and position modulation or occupation modulation of oxygen atoms in different degree; the deformation structures reveal that during the process of crystallization and mineralization, this mineral may be affected by the geological environment (such as temperature, pressure and stress), metamorphism and deformation. (C) 2004 Elsevier Ltd. All rights reserved.